WO2018049422A1

WO2018049422A1 - Pilot actuator for deluge and pre-action fire protection systems

Info

Publication number: WO2018049422A1
Application number: PCT/US2017/051230
Authority: WO
Inventors: Thomas Edwin ARCHIBALD
Original assignee: Globe Fire Sprinkler Corp
Current assignee: Globe Fire Sprinkler Corp
Priority date: 2016-09-12
Filing date: 2017-09-12
Publication date: 2018-03-15
Anticipated expiration: 2019-03-12

Abstract

A pilot actuator for activating a deluge or pre-action fire suppression system when pressure in a pilot line drops is disclosed. Aspects comprise utilizing an opening spring to bias the pilot pressure operating point, resulting in faster activation, large pilot sensing area to control fluid sealing area ratio, for higher reliability and reduced actuation slope, and acceleration surfaces about opposing surfaces about the sealing port. Actuators embodying one or more of the above features are considered. Deluge or pre-action firefighting systems utilizing one or more of the aspects described above, and methods for activation of such firefighting systems are also disclosed.

Description

PILOT ACTUATOR FOR DELUGE AND PRE ACTION FIRE PROTECTION SYSTEMS

Related applications

[0001] This patent application claims priority to US Provisional patent application No. 62/393,584, filed

September 12, 2016. This patent application is incorporated herein by reference in its entirety.

Field of the invention

[0002] The present invention is directed generally to improvements in pilot actuators for fire protection systems, and more particularly to an actuator coupled to hydraulically controlled valves.

Background of the Invention

[0003] The field of fire protection is of extreme importance to life and property. Firefighting system design presents many challenges to the designer including a need to optimize the effectiveness of the fire protection equipment while at the same time minimizing the cost of installation. One method for improving fire protection calls for rapid delivery of fire suppression fluid, to overcome fires. Fires grow rapidly and thus methods to achieve early fire suppression can significantly reduce overall installation costs by minimizing the scale of the system needed to suppress the fire. Rapid delivery design requirements can drive a need for large pipe and valve diameters, and/or a need for high operating pressures to accelerate fluid delivery. Clearly, high reliability is of-course desired.

[0004] Sprinkler systems are standardized nowadays to deliver the fire suppression fluid to the needed sites.

Sprinkler systems comprise fluid distribution systems having pipes that communicates a primary fire suppression fluid to a plurality of individual nozzles or sprinklers. Common types of such systems include, inter alia, wet pipe systems and various dry type sprinkler systems, which include deluge systems and preaction systems. In 'dry' type firefighting systems fire suppressant is not introduced into the distribution system piping until a fire detection event has occurred. Many aspects of these specifications relate primarily to dry type systems, and more specifically to deluge and pre-action type systems.

[0005] Multiple regulatory and private standards define differing types of firefighting systems. By way of

example Underwriter Laboratories© of Northbrook IL, USA, commonly known as UL, publishes UL 260, "Standard for Safety" which relates to dry pipe and deluge valves and provides examples of standardization to the differing types of firefighting systems. By way of example a deluge and pre-action type systems are defined in section 5.5. Similarly, FM Approvals© of Thomaston RI, USA publishes "Approval standards for deluge and preaction sprinkler systems" commonly known as FM classes 1011, 1012, 1013 which provides the definition of such systems in section 1.9. Further explanation relating to the nature of this types of firefighting systems is provided throughout the UL 260 and FM Approvals "Approval standards for deluge and preaction sprinkler systems" for classes 1011, 1012, and 1013, which are incorporated herein by reference in their entirety. Such differing standards differ not only by their intended use, but also by their modes of operation and by the requirements which they must meet. Design of those systems present different requirements to the designer, as well as different methods and modes to achieve the requirements, and oftentimes solutions designed for system type would fail to meet the requirements in another system type. Therefore despite the different systems being aimed at firefighting, clear and distinct differentiation must be drawn between the different types as separate fields, and differing standards or differing standard definitions should be consulted as indicative of significant differences between differing firefighting system types.

[0006] Deluge systems commonly comprise of open nozzles or open sprinklers where flooding of an area

proximal to the nozzles or sprinklers is accomplished by distributing fluid through a piping system to the open nozzles. This distribution of fluid through the deluge piping system is initiated after a fire detection event has occurred, and the distribution results in releasing fluid into the distribution system. In preaction sprinkler systems fluid communicates through distribution piping to closed sprinklers or nozzles. These preaction distribution systems are commonly used in fire protection applications where inadvertent discharge of the primary fire suppression fluid such as water, will result in damage to property or other disruption of commerce thus special precautions are warranted to prevent such inadvertent discharge.

[0007] Accelerated actuation of the fire suppression system is desired in order to speed up fire suppressant

delivery. Deluge and pre-action system utilize a deluge control valve which is an automatic control valve that is intended to be operated by mechanical, electrical, hydraulic, pneumatic, or thermal fire detection system installed at least partially in the same area of the sprinklers, by manual actuation, or by a combination of those methods. To that end hydraulic control valves were designed, to transition a control valve from a closed to open state (and in certain cases from open to closed state). In a hydraulic valve, fluid pressure is applied to a control chamber, and the resulting force is transmitted to a waterway sealing member, either directly for effecting water seal in the waterway, or via a trip mechanism that holds the waterway sealing member closed against the incoming fire suppressant. After a fire detection event occurs there is actuation reduction of the pressure in the control chamber. The pressure reduction allows the sealing member to open, and allows distribution of the primary firefighting fluid into the firefighting system. Thus the control valve may be in a "closed",

(equivalently known as "standby") state where the valve sealing member impedes flow of fluid between the inlet and outlet, and an "opened", (equivalently known as "activated", or "actuated') state in which sufficient pressure is released from the control chamber and primary firefighting fluid is allowed to flow between the inlet and the outlet.

[0008] Hydraulic control valves should be differentiated from differential dry pipe type control valves, which are defined for example by UL 260 in section 5.7. In a differential type control valve pressure exists in both sides of the sealing member such as a clapper, usually over a larger area on the outlet side and a smaller area on the inlet side and there is no need for a control chamber - in closed state the pressure in the outlet side of the sealing member imparts a greater force thereupon then the force imparted by the inlet side, and the valve stays closed. When pressure is released from the outlet side, the sealing member opens and primary firefighting fluid is allowed to the outlet side. While simple in principle, purely differential valves are large, heavy, slow, subject to premature operation due to inlet side pressure surges, and oftentimes less dependable than the hydraulic control valve.

[0009] The terms 'hydraulic valve', 'hydraulic control valve', or 'control valve' shall be utilized interchangeably henceforth, and represent any type of valve which controllably in response to pressure in the valve control chamber, holds the primary firefighting fluid from entering the primary distribution system, regardless of the specific type of systems, such as deluge or pre-action. Those terms extend to valve types such as a diaphragm or a clapper valve, among others, and to hydraulic stop valves, deluge reducing valves and on/off valves.

[0010] Controlling the control valve is done with additional devices generally known as 'trim'. The control valve trim comprises external connections and accessory equipment, and includes an actuation device colloquially known as 'actuator', that when actuated releases the pressure in the control chamber of the control valve, causing the sealing member to open, in effect transitioning the control valve from the closed to open state and releasing the primary fluid from the valve inlet to its outlet and thus to the distribution piping which then distributing fluid to effect fire suppression in the protected area.

[0011] Various methods are employed for automatic actuation of the deluge/pre-action fire suppression system.

The speed of activation of the actuator and subsequent activation of the control valve is critical to achieve efficient control of a fire. Slow activation of a trim device or control valve can result in increased fire damages, or even failure to control a fire.

[0012] A common type of firefighting system actuation method is known as a pilot system. In a pilot system pressurized pipe lines are distributed throughout the area to be protected, and one or more sensors such as sprinklers, electrical valves, or other sensors vent the pilot lines pressure in response to a fire detection event. The resulting pressure drop in the pilot lines causes actuation of the firefighting system and primary firefighting fluid is distributed through the primary distribution system. The pilot line system may be a dedicated set of pipes extending through the area to be protected from fire, or in certain systems may utilize the primary fluid distribution system itself. When the distribution system or a portion thereof are utilized to embody a pilot line or a portion thereof, the pilot line and distribution line are considered to be integrated. Combinations of the separate pilot and distribution systems also exist. Several types of pilot fluids are known, ranging from 'wet' pilot systems containing liquid such as water or anti-freeze, to 'dry' pilot fluid systems which commonly contain gaseous pilot fluid such as air, nitrogen, and the like. In the deluge type firefighting systems, the pressure drop in the pilot line results in actuation of the pilot actuator, which in turn releases pressure in the control valve control chamber. In pre-action systems at least one more condition is required prior to release of primary firefighting fluid into the area protected by the system.

[0013] For brevity the present specifications including the claims will describe a deluge or pre-action type

firefighting system where the primary firefighting fluid is water, and a dry pilot type containing air. The use of the terms water and air should be construed as a shorthand notation for any type of primary firefighting fluid and pilot fluid respectively, within the context of the pilot, distribution, and trim and control system. The term 'water' is used interchangeably to a primary fluid, and the term 'air' to a pilot fluid.

[0014] Generally, in a deluge type system the pilot line is separate from the primary distribution system, which utilize open sprinklers or nozzles. In preaction systems the pilot line may be a separate line as in a deluge system, it may be embodied in the primary distribution piping, or it may utilize a combination of the separate pilot line and primary distribution system, or portions thereof, as the pilot line.

[0015] Detection events can take several forms such as electronic detection of heat or smoke, infrared and other image processing, and other events would result in discharging pressure from the pilot line. A particular type of detection event is activation of the heat sensitive elements of closed nozzles or sprinklers that holds the air from discharging from the pressurized distribution or pilot piping.

[0016] A pilot actuator is a type of actuation device that is subject to pressure from a pressurized fire sensing pilot line that is located in the area to be protected. The pilot actuator has a pressure sensing member in communication with pressure from the fire sensing line. This pressure on the pilot actuator sensing member is translated to a sensed force which is mechanically transferred to a pilot actuator sealing member. The pilot actuator sealing member is in fluid communications with a vent line from the control valve control chamber, and may controllably hold the vent line closed, or vent the content thereof to the atmosphere. The sensed force resulting from pressure in the pressurized pilot line maintains the control valve control chamber vent line in a closed state by being applied to the pilot actuator sealing member. Upon sufficient pilot line pressure drop, as will be caused by a fire and subsequent venting of the pilot line, the pilot actuator sealing member moves from the closed state to an open state, allowing the control valve control chamber to vent to atmosphere, resulting in actuation of the control valve, thus delivering fire suppression fluid to the sprinklers via the distribution system.

[0017] The system is exposed to pressure variations that can take many forms. The sensing member can be subjected to pressure variations due to temperature changes, pilot pressure control compensation, and the like. The pilot actuator sealing member can also be subject to pressure variations in the control chamber of the control valve. This control pressure can experience fluctuations for example from daily morning and evening cycles in public water supply pressures, from water hammer due to rapid activation of piping components on a shared piping system, from temperature variations of closed piping and due to other reasons. An important aspect of pilot actuator design is that increased speed of activation of the pilot actuator in turn accelerates the actuation of the control valve and increases the speed of delivery of the firefighting fluid.

[0018] The term 'pilot actuator', or equivalently 'dry pilot actuator' in these specifications relates to a device which when properly installed in a sprinkler based deluge or pre-action fire suppression system, acts in response to change in pressure in a piping system, to vent a control chamber of a hydraulic control valve of such system, thus allowing opening of the control valve and delivery of the fire suppression fluid to the sprinklers or nozzles.

[0019] Fig. 1 depicts a simplified schematic of an exemplary dry pilot sprinkler system. Primary fire suppression fluid is provided under pressure Pw to a main pipe 2, commonly referred to as a riser. By way of example such fluid may be water from a public water supply, a dedicated reservoir, a dedicated firefighting water supply, a gaseous fluid, foam system and the like. The fluid is piped to a shutoff valve 5 which is normally open except during maintenance, or after a system activation, in order to facilitate reset of the system. A control valve 10 is coupled to the fluid supply downstream from the shutoff valve 5. A fluid distribution system 15 is coupled to the outlet of control valve 10. Commonly fluid under pressure is also supplied to the control chamber 30 of control valve 10, via a check valve 24 and a flow restrictor 25 and control line 20. It is common to couple fluid from the primary fluid supply to the control chamber 30 as such arrangement simplifies the installation and mitigates pressure fluctuations. However the pressure P_c supplied to the control chamber may come from any desired source, and does not have to come from the fluid supply side of the firefighting system. The control fluid, supplied under pressure to the control chamber 30 maintains the valve 10 in closed state.

[0020] A pilot actuator 35 is coupled to the control line 20. The pilot actuator 35 is also coupled to a pilot line 45 which extends to the area to be protected, and which has at least one sensor 55 coupled thereto. Pilot line 45 contains a pilot fluid pressurized at pilot pressure Pp, and is commonly kept pressurized by a pressure source 50 such as gas or fluid supply, a compressor, release of gas from a pressurized gas reservoir, and the like. Pressure source 50 can pressurize the line initially and then compensate for pressure loses by minor leaks, temperature variations and the like. Oftentimes the pressure source is coupled to the pilot line only as required. The sensor 55 is constructed to vent the pressure from the pilot line upon at least one condition that is considered to be caused by a fire, such as heat. When sensing a fire, such as by being exposed to temperature exceeding a predetermined threshold, the sensor vents the pilot line at a higher rate than the rate that the pressure source 50 may replenish the pressure, if pressure source 50 is constantly active. The sensor 55 is commonly a sprinkler but may be another type of sensor such as an electrical valve and the like, and in most embodiments several sprinklers are utilized. In certain pre-action systems a detection of fire may cause venting of the pilot line in response to a fire detection event by a device other than a sprinkler, such as heat detector, smoke detector, infra-red detector and the like, which couple to an electrical valve coupled to the pilot line.

[0021] During the firefighting standby state, the actuator is in closed (also known equivalently sealed or standby) state, sealing the control fluid pressure in the vent line 20. Upon the resulting drop of pilot line pressure Pp, the pilot actuator 35 transitions to an open state, and provides a discharge fluid path which vents the control pressure P_c in the vent line 20 to the atmosphere via outlet 40. When fully open, the pilot actuator provides a less restrictive fluid path than the fluid path provided via the flow restrictor 25. As the rate of discharge of the pilot actuator is larger than the rate of replenishment via the flow restrictor 25, the pressure P_c in the control chamber 30 is reduced, and control valve 10 is opened. Decisive and fast opening of the control valve is desired for efficient fire suppression, and furthermore, in certain types of valves, repeated partial opening and closing of the control valve may cause a malfunction of the valve.

[0022] Pilot actuators are well known in the art. By way of example US Patent Publication No. 20140182865 to Ringer discloses a high liquid to gas trip ratio pilot actuator. Several models of a pilot actuator exist, such as by way of example the Model A manufactured by the Reliable Automatic Sprinkler Co., Inc. of Elmsford NY, U.S.A., model H-l 1 is supplied by HD Fire Protect PVT. LTD. Of Thane, India, and the Tyco (Lansdale PA, U.S.A.) model DP-1 are but few examples. Conceptually, pilot actuators are divided into two main categories, namely direct acting and indirect acting.

[0023] Generally, both actuator categories comprise a chamber exposed to the pressure of the pressurized pilot line or lines however while in a direct acting type pilot actuator the force exerted by the pilot fluid on the sensing surface is mechanically transferred to act against the force exerted by the control fluid invent line 20 on a seal surface, in indirect type pilot actuator an intermediate fluid is utilized to provide the force required for maintaining the pilot actuator in the closed state. The chamber exposed to the pilot pressure Pp in a direct acting pilot actuator is referred to as pilot chamber in these specifications.

[0024] A portion of the pilot chamber is formed by a pressure sensing member. Various embodiments of

pressure sensing members are known, such as a diaphragm or piston, by way of non-limiting example, however for clarity and brevity, these specifications shall use a diaphragm type pressure sensing member, and the term diaphragm shall be used as a generic term for a pressure sensing member in all its forms, unless specified or otherwise clear by the context. One of the diaphragm faces is at least partially exposed to the pilot chamber and the portion exposed to the pilot chamber and operative to translate pressure in the pilot chamber to a closing force directed to urge the actuator to the closed state is referred to as the 'sensing surface' of the diaphragm. The sensing surface area is sometimes denoted A_s for brevity.

[0025] The pilot actuator further has a vent port in fluid communication with a sealing port, and henceforth

controllably to a drain outlet 40. A sealing member is mechanically coupled, directly or indirectly, to the pressure sensing element, and is moveable thereby between at least the closed state and an open state, and commonly with a plurality of intermediate states. The sealing member has a seal which cooperates with the sealing port to seal fluid passage through the sealing port when the sealing port is in the closed state, and allows at least partial fluid communication between the vent port and the drain in other states. When the sealing member is in the closed state, the pilot actuator is also considered to be in a closed or sealed state. Conversely, when the sealing member allows fluid passage between the vent port and the drain, the pilot actuator is considered to be in open state, which may be fully open or partially open.

[0026] The sealing member has an area which is exposed to fluid pressure from the vent port when the pilot actuator is closed, and that area is termed the 'Sealing surface' in these specifications. Oftentimes the sealing area would be on one of the faces of the seal. In some embodiments the seal is embodied on the side of the diaphragm opposite the sensing area, or a portion thereof.

[0027] When configured in a firefighting system, the pilot actuator vent port is connected via a vent line 20 to the control chamber 30 of the control valve 10. The pilot chamber is in fluid communication with the pilot line or lines 45. The drain 40 is commonly at, or close to, ambient atmospheric pressure. When the firefighting system is in standby state, the pilot line, and thus the pilot chamber are pressurized by the pressure source 50, and the pressure Pp acts on the sensing surface which in turn urges the sealing member to the closed state. Control fluid under pressure P_c is communicated to the vent port from the control valve control chamber 30, and is sealed by the sealing port which cooperate with the seal.

[0028] In most embodiments the pressure Pp in the pilot chamber is lower than the control fluid pressure P_c in the vent line 20, when the pilot actuator is in closed state, the control fluid pressure in the vent line effects a sealed fluid opening force on the sealing member. In order to allow the pilot actuator to affect sealing of the vent line from the drain, the pilot pressure sensing surface of the diaphragm is larger than the sealing surface, and thus the diaphragm, sealing member, and seal may act to properly seal the sealing port. The ratio between the area of the sealing surface and the area of the sensing surface is referred to in these specifications as the advantage ratio, symbolized by the symbol Ra. In order to provide sealing, the total force imparted by the pilot fluid to the sensing surface must exceed the opposing opening force imparted by the control fluid on the sealing member.

[0029] In these specifications, the state at which the pilot actuator 35 begins its transition from closed to open is referred to as 'drip' state, and the state at which the pilot actuator is fully open, or at least sufficiently open to results in fast and full draining of the control chamber 30 to cause control valve actuation is referred to as 'trip' state. An infinite number of intermediate steps exist between the drip and trip states.

[0030] An important characteristic of pilot actuators is the pressure interval between the pilot pressure required to place the pilot actuator in drip state at pilot pressure Pd and the pilot pressure required to place the pilot actuator in a trip state at pilot line pressure Pt. This interval is referred to as the trip range. Pilot actuators are further characterized by the full open state at a pilot line pressure Pf where any further change in pilot line pressure has no incremental effect on the pilot actuator opening state. In some embodiments Pf=Pt.

[0031] It is desired to minimize the trip range since smaller intervals allow faster fire suppression system response to fire detection, and long interval or indecisive transition between closed to trip state may lengthen the firefighting system response time, and in certain cases may even lead to fire protection system failures.

[0032] An important consideration in the design of a pilot actuator hydraulic valve firefighting system is the requirement to have a nominal pilot set point pressure Ppn that is above the pilot actuator trip pressure Pt by a sufficient margin of safety pressure Ps (Ps = Ppn - Pt) to prevent fluctuations in control chamber pressure Pc or fluctuations in pilot pressure Pp from resulting in unwanted actuation of the hydraulic valve due to low Ppn. On the other hand, overly high Ps is also undesirable. An overly high Ps will result in delayed hydraulic valve actuation and delayed delivery of fire suppression fluid delivery to a fire. Overly large pressure difference Ps from nominal set pressure Ppn to trip pressure Pt delays the hydraulic valve actuation endangering life safety and resulting in increased property damage in a real fire event. And in cases where Ps is not sufficiently large the low margin of safety pressure Ps commonly results in unintended activations of fire dry pipe systems (both conventional differential types and hydraulic control types). Unintended activations are expensive where personal injury or property water damages result.

[0033] Hydraulic valves are subject to large fluctuations in the control fluid pressure Pc. Such control fluid fluctuations make selection of a margin of safety pressure Ps and nominal set point pressure Ppn in the pilot line an important design consideration. The margin of safety pressure Ps included in Ppn must be sufficiently high to offset the highest Pc fluctuations to fluctuation prevent unintended hydraulic valve actuation. Control fluid pressure Pc may vary significantly due to many factors. Water supply pressures vary due to high and low demand periods such as high demand morning shower and lawn sprinkler cycles, low demand early morning times, commercial user periods of high demand, during shutdowns due to piping system maintenance, from water hammer, and for many other reasons. Water hammer is a particularly onerous piping pressure fluctuation and has many causes such as when nearby equipment quickly open or turn off high water demand activities, or merely from common water system operations.

[0034] All dry pipe systems with hydraulic valves are required by NFPA regulation to have a supply line check valve 24 in the control chamber supply piping to retain supply pressure in the control chamber. The supply line check valve retains peak upward water supply pressure fluctuations in the control chamber. Even a Hydraulic valve with low nominal supply pressure (such as NFPA minimum 20 psi) often will have a control chamber pressure of 100, 200, or more PSI due to water supply pressure Pc upward fluctuations. As a result, pilot actuators for hydraulically controlled dry pipe systems must have pilot set pressure Ppn with sufficiently large safety margin Ps to offset all reasonably expected water supply pressure fluctuation factors.

[0035] When determining the magnitude of Ps and resulting nominal pilot set point Ppn it is important to consider the slope of the air/water pressure trip ratio of the actuator. A steeper slope Pt/Pc ratio results in a greater difference between Pt at low control chamber pressure Pc and Pt at high control chamber pressure Pc. A pilot actuator with steeper Pt/Pc ratio slope requires a higher margin of safety pressure Ps and higher Ppn over the range of control chamber pressures. Pilot actuators with shallower Pt/Pc ratio slope can have a lower margin of safety pressure Ps allowing lower Ppn. This lower margin of safety pressure for pilot actuators with shallower slope Pt/Pc ratio can be reduced by an amount greater than the necessary margin of safety pressure Ps for numerous other factors.

[0036] Another important consideration in the design of a pilot actuator triggered firefighting system are

fluctuations in the pilot fluid pressure Pp. Pilot fluid is often a gas such as air or nitrogen, and the pilot pressure Pp may vary significantly due to temperature changes alone. Other common factors that cause fluctuations in Pp are compressor on/off cycles and hysteresis in pressure regulators, and minor leaks. Such pilot fluid pressure fluctuations make selection of margin of safety pressure Ps and nominal pressure Ppn in the pilot line, an important design consideration. The safety factor included in Ppn must be high enough to compensate for low Pp fluctuations. Failure to have a large enough safety margin in pilot pressure commonly results in unintended activations of fire dry pipe systems which are a major cost where personal injury or property water damages result. [0037] Another important characteristic of direct acting pilot actuators is the pressure interval between the pilot pressure required to place the pilot actuator in drip state at pilot pressure Pd and the pilot pressure required to place the pilot actuator in a trip state at pilot line trip pressure Pt. This interval is referred to as the trip range Pd-Pt. Pilot actuators are further characterized by the full open state at a pilot line pressure Pfo where any further change in pilot line pressure has no incremental effect on pilot actuator opening state.

[0038] In case of a fire, the sensor 55 drains pilot fluid from the pilot line. The decay rate Dp/Dt of pressure in the pilot line, measured as change in pressure per unit of time such as PSI per second, is in direct relation to the rate of discharge affected by the sensor. For a sprinkler in a pilot line with fixed flow rate, the larger the volume of the pilot system the slower the decay rate Dp/Dt of the pilot pressure. However it is important to note that higher starting pilot pressure results in faster decay rate for any size pilot system. As a sensor drains fluid from the pilot line the pilot pressure is reduced and the force exerted thereby on the sensing surface is also reduced, until it falls below the force exerted by the control fluid on the sealing member, and the pilot actuator transitions to an open state. In a simple system the time for opening the pilot actuator may be approximated by Ta= (Pp - Pt)/(Dp/Dt)

where Ta is the elapsed time from beginning of venting of pressure from the pilot line until the pilot actuator reaches its trip point, and Pt is the pilot line pressure at which the actuator trips, so that the control valve may trip and fire protection fluid be freely discharged from the control valve into the primary distribution system piping.

[0039] For a given pilot line volume and sensor flow rate the pilot pressure decay rate Dp/Dt will be faster for a higher pilot line pressure and for a smaller pilot line volume. By way of example figure 9.1 of Underwriters Laboratories Standard 1486 graphically depicts the relationship of pilot system volume and Dp/Dt for a standard orifice sprinkler where smaller volumes have faster Dp/Dt, and higher starting pilot line pressures have higher Dp/Dt. Pilot setpoint pressure Ppn must be set above the drip pilot pressure required to overcome fluctuations in both the pilot Pp and control fluid P_c pressures, however in common pilot systems higher than necessary pilot setpoint pressure causes longer delay between the sensor fire detection and the pilot actuator tripping. The effect of longer delays are amplified when a pilot actuators trip pressure Pt is low due to lower Dp/Dt. When the pilot actuator trip pressure Pt is below the pilot actuator drip pressure Pd the difference between set pressure Pp and trip pressure Pt must be larger, again resulting in longer time between sensor actuation and control valve actuation.

[0040] It is seen that the design of any fire suppression system, and in particular the design of deluge and/or pre- action firefighting system presents a complex compromise between the requirements of high reliability, fast actuation, avoidance of nuisance actuation, and reducing costs and complexity. Various organizations invest significant efforts and resources into optimizing such compromises. There is therefore an ongoing need for optimizing the design of direct acting pilot actuators and of various components, settings and piping arrangements in fire suppression systems, to provide faster actuation, reduced drip/trip interval, and reduce dependency on pressure fluctuations in the control and pilot fluids.

Summary of the invention

[0041] Contrary to current wisdom in the art which generally touts the desirability of a low pilot pressure setpoint Ppn, certain aspects of the invention are based on the realization that with proper configurations, and by utilizing a pilot actuator, as disclosed by the present specifications, a larger pilot pressure setpoint Ppn increases the reliability and speed of operation of the system, and increases its resistance to false tripping. If the pressure range between a closed and tripped actuator is maintained, higher pilot pressure Pp shall result in actuator tripping in response to a smaller percentage drop in the pilot pressure than the percentage of a lower pilot pressure. . Stated differently, a smaller percentage of pilot pressure drop is required for a properly configured actuator to actuate, and since the rate of pressure decay is faster at higher pilot pressure operating, the system actuation is faster. Furthermore, reducing the gap between the drip point pressure Pd and the trip point pressure Pt provides faster system response and preserves reliable operation of the hydraulic control valve, and the reduced operating slope of the trip pressure offers higher resistance to pressure fluctuations. In general the above concepts are achieved by different and novel feature and feature combinations such as a spring to urge the actuator valve to an open state, which biases the actuator pilot pressure operating point towards higher pressures, high sealing area to sensing area ratio which provides flatter slope and shorter trip difference, and accelerating surfaces for reducing the Pd to Pt interval.

[0042] An aspect of the present invention is directed to providing a pilot actuator that couples the pilot line

pressure to the control valve control chamber vent and effects rapid actuation of control chamber venting while also reducing the dependence of the sensing line pressure setpoint on fluctuations in control chamber or pilot pressure, thus allowing safe utilization of lower safety margin of the pilot setpoint pressure. A further aspect of the invention relates to arrangements, and parameter settings that will allow fast fire suppression system response time to fire, while minimizing nuisance tripping.

[0043] Aspects of the invention provide large flow paths and component clearances for reduced likelihood of actuation failure, and small differences between pilot actuator drip pressure Pd and pilot actuator trip pressure Pt. Those small differences allow for a sharp transition from pilot actuator closed state to open state.

Furthermore, aspects of the invention allow raising the operating point of the pilot actuator, enabling smaller margins of safety in nominal pilot line pressure which increases system activation speed and improved simplicity of pilot line system design. Additionally, aspects of the present invention provide high resistance to false tripping stemming from low sensitivity to variations of control chamber supply pressure P_c, and mechanical coupling of the pilot sensing pressure to the control vent line seal, which eliminates components and flow path design complexity that can impede actuation.

[0044] To that end, in an aspect of the invention there is provided a direct-acting pilot actuator for deluge or pre- action type firefighting systems utilizing a pressurized sensing pilot line for sensing a fire, the actuator controllably venting a pressurized control line in response to drop in pilot pressure in the pilot line, the pilot actuator comprising a housing having an internal cavity, the housing having a pilot port, a vent port, and a drain controllably in fluid commumcation with the vent port via a sealing port, and a pressure sensing member which at least with a portion of the internal cavity defines a pilot chamber in fluid communications with the pilot port, the pressure sensing member having a pilot pressure sensing surface. A seat is disposed about the sealing port, the seat comprising a seat face circumscribing the sealing port. A sealing piston is coupled directly or indirectly to the pressure sensing member, the sealing piston having an active end portion movable between a closed state and at least one open state, the seat and the active end forming a sealing arrangement therebetween when the piston is in the closed state, for controllably sealing fluid communications between the vent port and the drain; the sealing arrangement defining a seal contact area circumscribing a sealing surface of the piston active end, the ratio of the area of the sealing surface and the area of the sensing surface defining an advantage ratio Ra of at least 1 : 15. A spring is disposed to directly or indirectly impart a spring force to the piston, the spring force acting against a force imparted to the pilot pressure sensing surface by pressure in the pilot chamber, the spring force urging the sealing piston away from the closed state, the spring force being an opening force greater or equal to an opposing force which would be imparted on the sensing surface by a pressure of 5 PSI.

[0045] The pilot actuator described above results in the actuator pressure sensing member and the sealing piston assembly being exposed to a first and a second opposing forces imparted thereupon, the first force being a closing force imparted by the pilot pressure and the second force being an opening force imparted by a combination of a pressure exerted by the control pressure and the spring. The ratio between the control pressure and the pilot pressure, also referred to above as Ra, is at least 1: 15, and the forces they impart on the pressure sensing member is a product of the respective pressure operating on the respective area. The spring imparts an opening force greater than a force equivalent to the force exerted by pilot pressure of 5 PSI. Thus in order to maintain the actuator in closed state, preventing venting of the control pressure, the pilot pressure must overcome the some of the force imparted by the control pressure in combination with the force imparted by the spring.

[0046] The rate of discharge of the pilot actuator is very important. For the system shown in Fig. 1 it must be larger than the rate of replenishment via the flow restrictor 25, but the skilled in the art would readily realize that the difference in flow rates must be sigmficant. Small open actuator flow rate would delay actuation of the control valve. Thus it is desired that the flow path would allow large flow rate. However, the larger flow rate implies larger flow paths and larger sealing area. Thus, while higher sealing to sensing area ratios, and the resulting control to pilot pressure ratios, and imparted opening and closing force ratios, may be utilized. Ratios greater than 1 :20, 1 :22 1 :25 or 1 :30 and even greater than 1 :50 are explicitly considered, with ratios as large as 1 :80 being acceptable, however larger ratios are considered to impose heavy dimensional penalty of the actuator, and larger ratios than 1 :80 are less desirable and ratios over 1 :95 or 1 : 100 are considered only in special circumstances.

[0047] Similarly, higher spring forces are also considered. While a spring force equivalent to the force imparted by pilot pressure of 5 PSI would raise the pilot actuator trip pressure point by 5PSI, higher spring forces, such as a force which would be equivalent to the force imparted to the sensing area by a pilot pressure of at least 8 PSI, 10 PSI, 20 PSI, and 30 PSI are considered. Even a spring force equivalent to the force imparted by 50 or 75 PSI are considered, but higher forces would result in costs on other portions of the system, such as larger compressors, heavier pipes, sensors able to withstand the pilot pressures, and the like.

[0048] In some embodiments the sealing piston is formed on or by the pressure sensing member or a portion thereof, and thus is considered to be integrated thereto. In certain other embodiments the sealing piston is formed separately than the pressure sensing member but is coupled thereto as is the case with the integrated piston, directly or indirectly, by one or more intermediate members. By way of example a single side of a diaphragm may act as a pressure sensing member, while the opposite of the diaphragm acts as a sealing piston, forming an example of an integrated piston, while in other cases the piston is a separate member coupled directly, or in certain embodiments may be coupled by levers and the like (Not shown).

[0049] In some embodiments the seat face have a seat acceleration surface extending from the seal contact area towards the seat edge, and the piston active end has a piston accelerating area extending from the seal contact area towards, or in certain embodiments to, the piston edge. The piston acceleration surface and the seat acceleration surfaces are at least in partial registration when the piston is in the closed state. Thus, when the piston begins to transition between the closed on open states the incoming control fluid operates on one or both accelerating surfaces for accelerating the transition from closed to open state.

[0050] In some embodiments the piston accelerating face and the seat accelerating face are flat. In other

embodiments the accelerating seat surface and the accelerating piston surface, or portions thereof, are angled relative to the sealing port plane. However optionally only portions of the accelerating surfaces are in registration with each other. The accelerating surfaces may be of any desired profile, and are optionally textured. In certain embodiments, when the piston is in closed state the piston accelerating face and the seat accelerating face, or portions thereof, are configured at spaced apart relationship, and in others they may contact each other when in the closed state. Recognizing that smaller spacing of the acceleration surfaces would create larger acceleration and higher initial flow resistance, and larger spacing would result in the opposite effect, it is recognized that when spacing is present, the space between accelerating faces is a matter of engineering choice, dictated by the desired characteristics, and determinable by common techniques such as calculations, simulations, and the like. By way of example any spacing smaller or equal to twice the size of a ridge extending between the seat and the seal is believed to provide satisfactory results, but larger spacing is explicitly considered.

[0051] Different sealing arrangements are considered. In some embodiments the seal is coupled to the piston active end/or is integral thereto, while in other arrangements the seal is coupled to the seat. Optionally a sealing ridge is utilized. The seal may comprise a sealing ridge extending away therefrom, or sealing ridge may be disposed on the member opposite the seal, where the ridge extends towards the seal. When used, the sealing ridge is disposed to engage the opposite member at the seal contact area circumscribing the sealing port when the piston is in the closed state, and thus the ridge defines the sealing surface. In certain other embodiments a ridge is not utilized and the seal contacts the seat surface directly, and the sealing surface is defined by the sealing port and/or the seat internal boundary. In some embodiments the surface area of the piston accelerating surface having at least twice the area of the sealing surface, and potentially the area ration may be significantly larger.

[0052] For brevity these specifications would be directed to a seal ridge extending towards the seat, by way of a convenient example. It is understood however that the above mentioned ridge or direct seal arrangement are a matter of technical choice and the skilled in the art would be able to practice the invention with equivalent arrangements in view of the specifications.

[0053] Optionally the pressure sensing member comprises a diaphragm, and at least a portion of one side off the diaphragm, comprises the sensing surface. As described above the skilled in the art would recognize that other embodiments, such as a piston or a clapper by way of example, may also be utilized, and such a piston or clapper would have a portion exposed to the pressure in the pilot chamber, and another side acting as a sealing member or piston. As described above, the sealing member and the pressure sensing member may be different portions of a single element, or distinct elements coupled directly or indirectly.

[0054] In certain aspect of the invention it is also a goal to provide an arrangement of a fire fighting system

utilizing a pilot actuator and having a reduced trip range. Fig. 2B provides an example chart showing recommended pilot line pressure at the Y axis versus vent line pressure at the X axis in a prior art actuator. The top curve SPl (Represented by a solid line) represents the recommended setpoint of pressure in the pilot line or lines. The intermediate curve DPI (represented by dash-dot-dot line) denotes drip point - the pilot pressure at which the actuator begins opening, while the lower curve TP (represented by a dashed line) represents the pilot pressure at the full trip point. As venting the pilot line or lines require time, smaller drip to trip interval allows faster actuator opening is desired, which in turn provides faster and more decisive control valve opening. Fig. 2A represents similar chart relating to a prior art actuator, and the difference in drip-trip interval is clear. The smaller drip-trip interval provide for more efficient firefighting.

[0055] It is further desired to reduce the dependency of the trip range on the control vent line 20 pressure, that as described supra is often the same as the primary fluid supply pressure. Fluctuations in supply pressure and fluctuations in pilot pressure necessitate higher pilot pressure setpoint, to mitigate the risk of false tripping due to fluctuations of high control fluid pressure and/or low pilot pressure. Higher pilot pressure setpoint requires in turn longer time of draining the pilot fluid, resulting in slower system response. Fig. 2B depict response curves showing characteristic opening of a pilot actuator according to an embodiment of the invention showing relation between pilot pressure and control vent line pressure. TPl represents the trip pressure, DPI represents the drip pressure, and SPl represents the required pilot pressure setpoint. As the importance here is of a ratio, specific pressure units are immaterial, but for convenience would be assumed to be denoted in Pounds per Square Inch (PSI).

[0056] A system design directed at accommodating control P_c and pilot Pp pressure fluctuations while avoiding nuisance tripping necessitates setting the pilot pressure setpoint to counter the highest expected vent line pressure and the lowest expected pilot line pressure during system standby. Increasing pilot pressure setpoint results in increased pilot line decay time which in turn delays primary fluid delivery. For applications having large variation invent and pilot line pressure, the pilot setpoint pressure Ppn should be increased as a function of the slope of the response curves, as depicted for example in Figs. 2A and 2B. It is clear therefore, that decreasing the slope of the pilot actuator opening curves reduces the sensitivity to pressure fluctuations, with the following advantage of reduced activation time. Such reduction of the slope may be achieved by increasing the advantage ratio Ra, as the effects of control pressure fluctuations are reduced substantially by the ratio Ra. However assuming a fixed control pressure Pp, merely increasing the ratio RA implies that the actuator will trip at a lower absolute pilot pressure, or stated differently at a larger pressure interval between the pilot setpoint Ppn and the actuator trip point Pt.

[0057] Fig 2C depicts pilot pressure decay time for various volumes of pilot line piping when pressure is vented through a single standard orifice sprinkler. The figure clearly shows that decay time required for the pressure to fall a fixed amount of pressure units is longer for a lower starting pressure. For example, time to decay 5 PSI from 40 PSI pilot pressure to 35 PSI is about 7 seconds for a 300 gallon system, and time to decay 5 PSI from 10 PSI to 5 PSI is about 25 seconds in the same system. It is clear therefore that, increased pilot setpoint pressure Ppn for a pilot actuator with a fixed pilot pressure margin of safety between set pressure and trip pressure will reduce the time from start of pilot pressure decay to venting of the control line pressure.

[0058] In an aspect of the invention directed at deluge and/or pre-action fire protection systems, there is provided embodiments of the direct acting dry pilot actuator as described above, with or without the acceleration surfaces. The opening spring force opposing the closing sensing force allows raising the pilot line setpoint pressure by an amount equal to the spring force divided by the sensing member area, with all other parameters being equal. This higher pilot pressure accelerates pressure decay during a pilot pressure venting sensor activation due to a fire, as it allows the trip interval to occupy a smaller percentage of the nominal pilot pressure.

[0059] In yet another aspect of the invention there is provided a deluge or pre-action type firefighting system comprising a control valve having an inlet coupled to a fire suppression fluid supply, and an outlet coupled to a distribution system, the control valve having a control chamber and control valve maintaining the system in a standby state when the control chamber is exposed to an operating control pressure, and transitioning to a deployed state in response to reduction of control pressure in the control chamber below a predetermined level, The firefighting system further comprises a pressurized sensing pilot line for sensing a fire and having a trim arrangement and parameter settings for at least the pilot pressure. The pilot line is internally exposed to a pilot pressure, and is coupled to at least one sensor capable of venting the pilot pressure upon activation thereof, such as in response to a fire detection event. The firefighting system further comprises a direct-acting pilot actuator having a pilot chamber coupled to the pilot line, a vent port in fluid communications with the control chamber of the control valve, and a drain port, the vent port being in controllable fluid communication with the drain port via a sealing port. The pilot actuator further has a pressure sensing member having a pilot pressure sensing area operatively exposed to the pilot pressure, the pressure sensing member is directly or indirectly mechanically coupled to a sealing piston having a sealing area operatively exposed to the control pressure, the ratio Ra between the sealing area and the pilot pressure sensing area being at least 1: 15. The pilot actuator further comprises a spring which directly or indirectly imparts to the sealing piston an opening force greater than a force equivalent to the force imparted to the pressure sensing area by pilot pressure of 5 PSI. The sealing piston is operative to impede fluid flow between the vent port and the drain when the pilot pressure applies to the pilot pressure sensing area imparts a closing force that is larger than an opening force comprising the spring force and a force resulting from the control pressure applied to the sealing area, and allow fluid flow between the vent port and the drain when the opening force is larger than the closing force.

[0060] The pilot pressure setpoint is set above a pressure calculated by adding the opening force imparted on the sealing piston by the spring, and the force applied to the sealing area by the highest estimated control pressure during system standby mode, the sum of those forces being divided by the sensing surface, and preferably, further adding to the result of the division an estimate of pilot pressure fluctuation below the mean pilot pressure. Commonly a safety margin is also added.

[0061] Notably a high ratio Ra would lower the effects of fluctuations between the nominal control pressure and the highest control pressure caused by control pressure fluctuations. This reduction allows setting the pilot pressure with tighter safety margins. Thus a range of advantage ratios Ra of 1:20 and 1 :50, or 1:30 and 1 :40 provide significant advantages. However ranges of 1:40 to 1 :50 and even 1:50 to 1:80 and up to 1:95 are considered.

[0062] Thus in preferred embodiments, the advantage ratio Ra is at least a ratio selected from a list consisting of 1 : 15, 1 :20, 1:25, 1:30, 1 :35, 1 :40, 1 :50, 1 :60, 1 :70, 1 :80, 1 :85, 1 :90, and 1:95. The advantage ratio does not commonly exceed a ratio of 1:95 or 1 : 100. In some embodiment the spring is selected such that it imparts an opening force greater than a force equivalent to the force imparted to the pilot pressure sensing member by a pilot pressure of 8 PSI, 10 PSI, 20 PSI, 30 PSI, 65 PSI, and/or 75 PSI. [0063] The opening and closing forces may be imparted to the pressure sensing member and the sealing piston assembly directly or indirectly. The pilot line and the distribution system may be integrated or separated.

[0064] In some embodiments the pilot actuator comprises a seal and the piston having an active end, the seat and sealing piston forming a sealing arrangement therebetween when the pilot actuator is in a closed state, and defining a seal contact area where the seal and piston, or sealing portions thereof, interface. The seat has a seat acceleration surface extending from the seal contact area, towards the seat edge; and a piston accelerating area disposed at or about the piston active end and extending from the seal contact area towards the piston edge, the piston acceleration surface and the seat acceleration surfaces are at least in partial registration when the piston is in the closed state.

[0065] In some embodiments the surface area of the piston accelerating surface is at least twice the area of the sealing surface. Optionally the seat acceleration surface and the accelerating piston surface are angled relative to the sealing port. Further optionally the seat acceleration surface and/or the piston acceleration surface are textured.

[0066] There is further provided a method of operating a firefighting system, the method comprising of providing a deluge or a pre-action firefighting system as described above; pressurizing the pilot line to a pilot pressure; pressurizing the control chamber to a control pressure, providing a direct-acting pilot actuator having a pilot chamber coupled to the pilot line, a vent port in fluid communications with the control chamber of the control valve, and a drain port, the vent port being in controllable fluid communication with the drain port via a sealing port. The pilot actuator further has a pressure sensing member having a pilot pressure sensing area operatively exposed to the pilot pressure, the pressure sensing member is directly or indirectly mechanically coupled to a sealing piston having a sealing area operatively exposed to the control pressure, the ratio Ra between the sealing area and the pilot pressure sensing area being at least 1 : 15. The pilot actuator further comprises a spring which directly or indirectly imparts to the sealing piston an opening force greater than a force equivalent to the force imparted to the pressure sensing area by pilot pressure of 5 PSI; wherein the pilot setpoint pressure is set to a pressure at or above a pressure calculated by the sum of a) opening forces acting on the sealing member by the control pressure under the highest expect control pressure, and divided by the sensing surface, b) the difference between the mean pilot pressure and the lowest pilot pressure expected to be present in the pilot lines without the detection of a fire, and c) the pilot pressure required to counter the force imparted by the spring.

[0067] There is also provided a method of operating a deluge type firefighting system comprising the steps of providing a control valve having a control chamber, the control valve maintaining the system in standby state when the control chamber is exposed to an operating control pressure, and transitioning to the deployed state in response to reduction of control pressure in the control chamber; providing a firefighting fluid under pressure to the control valve; Providing a pilot line exposed to a pilot pressure, the pilot line coupled to at least one sensor capable of venting the pilot pressure upon activation thereof, responsive to fire detection event. The method further comprise providing a direct-acting pilot actuator for venting the pressurized control chamber in response to drop in pilot pressure in the pilot line, the pilot actuator comprising a housing having an internal cavity, the housing having a pilot port in fluid communication with the pilot line, a vent port in fluid communication with the control chamber, and a drain controllably in fluid communication with the vent port via a sealing port; a pressure sensing member having a pilot pressure sensing surface which at least with a portion of the internal cavity defines a pilot chamber in fluid communications with the pilot port; a seat disposed about the sealing port, comprises a seat face circumscribing the sealing port; a sealing piston is coupled directly or indirectly to the pressure sensing member, the sealing piston having an active end portion movable between a closed state and at least one open state, the seat and the active end form a sealing arrangement therebetween when the piston is in the closed state, for sealing fluid communications between the vent port and the drain. The sealing arrangement defines a seal contact area circumscribing a sealing surface of the piston active end, the ratio of the area of the sealing surface and the area of the sensing surface defining an advantage ratio Ra of at least 1: 15. The pilot actuator further comprises a spring disposed to directly or indirectly impart a spring force to the sealing piston, the spring force acting against a force imparted to the pilot pressure sensing surface by pressure in the pilot chamber, the spring force urging the sealing piston away from the closed state. The method also comprise setting the pilot pressure setpoint to a pressure above a pressure calculated by the sum of the opening forces imparted to the sealing surface by the highest expected control pressure, and divided by the sensing surface, and the spring force. Preferably the difference between the mean pilot pressure and the lowest pilot pressure expected to be present in the pilot lines without the detection of a fire is added to the pilot pressure setpoint. Responsive to fire detection by the at least one sensor and activation of the pilot actuator, the method comprises causing the control valve to allow flowing of the firefighting fluid to a distribution system having a plurality of outlet distribution ports.

[0068] As described above, in a pre-action type system the system further comprises at least a second sensor and the method provides for causing activation of the control valve in response to a fire detection event by the first sensor and the second sensor, at least one of which results in at least partial venting of the pilot line or a portion thereof, which in turn results in activation of the pilot actuator.

[0069] Optionally, in embodiments which use an actuator having a spring, the spring coefficient is linear along a portion of its travel between the drip and trip states. Providing large number of spring turns is one common way of achieving such linearity.

[0070] In yet another aspect of the invention there is provided A direct-acting pilot actuator for a firefighting systems utilizing a pressurized sensing pilot line for sensing a fire, the actuator venting a pressurized control line in response to drop in pilot pressure in the pilot line, the pilot actuator comprising a housing having an internal cavity, the housing having a pilot port, a vent port, and a drain controllably in fluid communication with the vent port via a sealing port, a pressure sensing member having a sensing surface which at least with a portion of the internal cavity defines a pilot chamber in fluid communications with the pilot port. A seat is disposed about the sealing port, the seat comprising a seat face circumscribing the sealing port. A sealing piston is coupled directly or indirectly to the pressure sensing member, the sealing piston has an active end portion movable between a closed state and at least one open state, the seat and the active end form a sealing arrangement therebetween when the piston is in the closed state, for sealing fluid communications between the vent port and the drain. The sealing arrangement defines a seal contact area circumscribing a sealing surface of the piston active end. The pilot actuator further has a seat acceleration surface extending from the seal contact area towards the seat edge, and a piston accelerating area disposed at or about the piston active end and extending from the seal contact area to the piston edge, the piston acceleration surface and the seat acceleration surfaces are at least in partial registration when the piston is in the closed state.

[0071] In some embodiments the surface area of the piston accelerating surface is at least twice the area of the sealing surface. Optionally the seat acceleration surface and the accelerating piston surface are angled relative to the sealing port. Further optionally the seat acceleration surface and/or the piston acceleration surface are textured.

Short description of drawings

[0072] The summary above, and the following detailed description will be better understood in view of the

enclosed drawings which depict details of preferred embodiments. It should however be noted that the invention is not limited to the precise arrangement shown in the drawings and that the drawings are provided merely as examples to facilitate understanding of different aspects of the invention.

[0073] Fig. 1 depicts a schematic representation of a simplified firefighting system in which aspects of the

invention may be deployed.

[0074] Fig 2A depicts an example activation graph of a prior art pilot actuator, and Fig. 2B depicts an example activation diagram of an embodiment of the present invention. Fig. 2C is a graph showing drainage rates of pilot fluid from pilot lines with an open standard sprinkler orifice coupled thereto.

[0075] Fig. 3 depicts a perspective view of an example pilot actuator.

[0076] Fig. 4 depicts a cross-section of a pilot actuator in a closed state.

[0077] Fig. 5 depicts a cross section of the pilot actuator of Fig 4 in an open state.

[0078] Fig. 6 depicts a detail view about the sealing port of a pilot actuator in a closed state.

[0079] Fig. 7 depicts a detail view about the sealing port of a pilot actuator as it begins to open.

[0080] Fig. 8 depicts a detail view about the sealing port of a pilot actuator in an open state.

[0081] Figs. 9 and 10 depict a detail view about the sealing port of a pilot actuator using different sealing

arrangements.

[0082] Fig. 11 depicts a detail view about the sealing port of a pilot actuator utilizing accelerating surfaces which are angled to the sealing port.

Detailed Description

[0083] Several aspects and embodiments of the invention are described herein to facilitate understanding of the invention and provide certain details thereof, but the description should not be construed as limiting the variations and equivalents enabled by this disclosure, and the invention is not limited by the example embodiments.

[0084] Fig. 3 depicts a general view of a pilot actuator 100 incorporating aspects of the invention. The pilot actuator comprises a housing 110 having body 115 and a cover 120 which cooperate to define an internal cavity 125 (fig. 4). In this embodiment a pilot port 130 is disposed on the cover 120. A drain port 135 is visible on the body. A vent port 140 is not visible in Fig 3. It is noted that location of the ports is a matter of design choice.

[0085] Fig. 4 depicts a cross-section of the pilot actuator of Fig. 3 in closed state, and Fig. 5 depicts a cross section of the pilot actuator in an open state. The body and the cover cooperate to define an internal cavity 125. Vent port 140 and drain port 135 are in controllable fluid coupling via sealing port 165. A seat 168 is disposed about the sealing port, the seat comprising a seat face 170 circumscribing the sealing port.

[0086] A pressure sensing member, embodied in the present embodiment as a diaphragm 145, divides the cavity 125 and in cooperation with portions of the housing define a pilot chamber 150 within the cavity 125. The pilot chamber is in fluid commumcation with the pilot port. Oftentimes of the diaphragm 145 is supported by having portions thereof mounted between the pilot actuator body and the cover 120 and the body 115. In some embodiments the diaphragm or another embodiment of the pressure sensing member is supported by lips or other structures. In the context of defining the pilot chamber the term diaphragm relates to any portion thereof exposed to the chamber, and the chamber may be defined by additional structures as well as the body and the pressure sensing member.

[0087] The surface of the diaphragm exposed to the pilot chamber is referred to hereinafter as the 'sensing

surface' 155 since it is exposed to the pressure Pp in the sensing pilot line when the firefighting system is operational in standby mode. It is noted however that other embodiments of a pressure sensing member are explicitly considered such as a piston with peripheral seal, a clapper, a gasket with peripheral seal, and the like. However it is noted that only the portion of the diaphragm which when acted upon by the pilot pressure may transfer a force to the sealing member 160 is considered to be included in the pressure sensing surface. There may exist areas of the diaphragm which are exposed to the pilot pressure but do not participate in the force transfer to the sealing member and such portions are excluded from the sensing surface.

[0088] In the depicted embodiment a sealing member 160 is mechanically coupled to the side of the diaphragm opposite the sensing surface. The sealing member is equivalently referred to as a piston. In certain embodiments the piston may comprise the actual opposite side of the pressure sensing member from the sensing surface. By way of example when the pressure sensing member 145 is embodied in a diaphragm with one side being the pressure sensing surface, the opposite side of the diaphragm may act as the piston, and similarly a clapper type pressure sensing member one side of the clapper would act as a sensing surface while the other may act as a sealing surface, or intermediate elements may couple between the sealing surface and the pressure sensing member. In the depicted embodiment a distinct piston 160 element may be observed, and such piston may comprise a separate element mechanically coupled directly or indirectly to the pressure sensing member 145, or be embodied in an integral element thereof, such as by being cast together, co-formed, and the like. By way of example the piston may be embodied on the surface of a membrane acting as a pressure sensing member, opposite the pressure sensing surface. The piston is moveable between a closed state a plurality of partially open states, and an open state.

[0089] The piston comprises an active end 175 facing the seat face 170. The pilot force, which is the force

summing the product of the pilot pressure Pp operating on the pressure sensing surface 155, and the size of the sensing area (by way of example pressure which is measured by Pounds per Square Inch - PSI, and the sensing surface in square inches) urges the sealing member and thus the active end 175 to the closed state. It is advantageous but not mandatory to arrange the active end such that the pilot force would operate at right angles thereto, to exert force concentric and perpendicular to the sealing port 165. The sealing face comprises a seal 180, commonly made of elastic material such as rubber, Teflon, nitrile, silicon and the like. The active end 175 is disposed such that when the piston is in the closed state, the seal contacts the seat face 170 at a seal contact area 195. The seal contact area 195 surrounds the sealing port 165 and thus in the closed state the seat face 170 cooperates with the seal 180 to impede fluid flow between the vent port 140 to the drain port 135.

[0090] In some embodiments, the seal 180 comprises a ridge 185 extending from the piston active end 175

towards seat face 170. In some such embodiments the ridge may define the seal contact area, however in certain embodiment the ridge may completely collapse when the pilot actuator is in the closed state, and the seal contact area includes larger portions of the seal, potentially to the edge of the sealing port. In other embodiments, such as depicted by way of example in Fig. 9, the seat face forms a ridge 185 A extending from the seat face towards the seal 180 on the piston active end 175. The sealing face in these embodiments may be flat. In certain of these embodiments the ridge may form a line upon first contact with the sealing face on the piston active end and as the ridge reaches the closed state the seal contact area includes larger portions of the sealing face. As described supra the ridge is optional as a whole, and in different embodiments may extend from the seat face towards the seal, or vice versa. A plurality of ridges may be utilized. In certain embodiments the seal 180 A is disposed on the seat, as shown for example in Fig. 10. Optionally a flat seal may be utilized and the seal ridge may extend from the piston active end (not shown). Selection of the sealing arrangement may be utilized with all the actuator embodiments disclosed herein. In summary the seal may be disposed on the seat or the active end, and one or more ridges are used, they too may reside on either the seat or the active end.

[0091] The seal portion in contact with the opposite face circumscribes and defines a sealing surface 190 on the piston active end. The sealing surface is the surface which is exposed to control line pressure P_c from the inlet and sealing port when the pilot actuator is operational in the closed state. The pressure P_c operating on the seal surface results in an opening force, acting to urge the pilot actuator into an open state. The sealing surface may include only the seal, or various portions of the piston active end 175, fasteners 192, intermediate parts, and the like.

[0092] While the pilot actuator is in standby state the pilot force is mechanically transferred to the piston active end and the seal. The pilot force acts to oppose the opening force, and is greater than the opening force, thus the pilot actuator is closed and no fluid communication exists between the vent port 140 and the drain port 135. When the pilot force is sufficiently reduced due to reduction in the pilot pressure, and the opening force is greater, the pilot actuator opens.

[0093] In certain embodiments of the invention the piston active end 175 extend outwardly from the seal contact area towards the peripheral edge of the piston active end edge, or completely thereto. The piston active edge surface extending from the seal contact area towards the edge is referred to herein as the piston accelerating surface 200 (Figs 7-11). As the piston moves from the drip state towards the open state, the fluid from the vent port 140 flows from the sealing port 165 and exerts a force on the piston sealing port 200, the force acting against the pilot force, and thus reducing the transition time from closed to open state. In some embodiments the piston accelerating surface is less than twice as large as the sealing surface, but in other embodiments the piston accelerating surface is twice as large as the sealing area and in some others it significantly larger, such as at least three, four, and five time and in certain cases even ten times, as large as the sealing surface.

[0094] In some embodiments, a cooperating surface referred to herein as the seat accelerating surface 205, further increases the accelerating effect on the piston accelerating surface. The seat accelerating surface extends outwardly on the seat face, from the seal contact area. The piston acceleration surface 200 and the seat acceleration surface 205 are in general parallel relationship to each other. As the pilot actuator opens fluid flow is confined between the two surfaces 200, 205 and thus exerts higher pressure on the piston accelerating surface, which results in additional force cooperating with the opening force, resulting in yet faster transition between closed an open state of the pilot actuator, and in reduced drip/trip interval, i.e. the trip range. It is noted that the piston and seat accelerating surfaces are most efficient when they cooperate in registration and in embodiments having both a seat and piston accelerating surface those surfaces may be considered to extend to the congruent accelerating surfaces. In certain embodiments one or both of the acceleration surfaces are textured to increase resistance to fluid flow at the initial operating stage and thus accelerate the opening. When the actuator is completely open the effect of such texture is negligible. Fig. 11 depicts an optional embodiment where the accelerating surfaces 200A and 205 A are angled relative to the sealing port 165 plane.

[0095] As commonly the pressure Pp in the pilot line is significantly lower than the pressure P_c operating on the seal surface, advantage is provided by having a sensing surface area larger than the seal surface area.

Hereinafter the mechanical advantage is considered as reflecting the ratio Ra between the seal surface area and the sensing surface area. Notably, higher Ra reduces the slope of the activation curves of the actuator.

[0096] It is noted that in certain embodiments additional mechanical advantage may be deployed between the pilot force as sensed by the pressure sensing surface and the sealing surface. Such mechanical advantage may be accomplished by levers, cams, gears, and the like (not shown). In these specifications however the pilot force is considered as the force directly opposing the opening force, regardless of any additional mechanical advantage in the transmittal of force imparted on the pressure sensing surface and transmitted to the seal surface.

[0097] A spring 300 is disposed to impart a spring force urging the pilot actuator into an open state, or more generally into any state away from the closed state. The spring force is additive to the opening force imparted by the control pressure. Different spring arrangements would be clear, and thus by way of example, the spring may be a compression spring pushing against the sealing member, or a tension spring pulling the sealing member, and the like. The spring 300 may be coupled directly or indirectly to the sealing surface. One side of the spring is anchored to any convenient support such as the actuator body, and the other side may be anchored to the piston, the pressure sensing member, or any intermediate parts. The spring force is considered to be the force component imparted by the spring in the direction of opening of the opemng force imparted by the control pressure acting on the sealing surface.

[0098] As described supra in many embodiments the spring imparts a force greater than an opposing force which would be exerted on the sensing area by a pressure of at least 5 PSI. Stated differently, a pilot fluid pressure of at least 8 PSI acting on the pressure sensing area in the pilot chamber 150 is required to counter the effect of the opening force imparted by the spring However differing spring forces may be utilized. Thus by way of example in certain embodiments the spring imparts an opening force greater than a force equivalent to the force exerted on the pressure sensing member by a pilot pressure of 8 PSI, 10 PSI, 20 PSI, 30 PSI, and/or 65 PSI, and/or 70 PSI. While generally spring force requiring more than 75 PSI to oppose are considered impractical for most systems, certain special embodiments may require such larger forces.

[0099] As shown above, the system time for opening the pilot actuator may be approximated by

Ta= (Pp - Pt)/(Dp/DT).

where Ta is the time to activate the pilot actuator from detection of a fire and beginning of venting pressure from the pilot line, Pp is the instantaneous pilot pressure at the time of fire detection, Pt is the pilot pressure at which the pilot actuator transitions to trip state and Dp/Dt is the rate of pilot pressure decay. As the spring force is added to the vent line 20 pressure P_c force operating on the seal surface, the actuator trip pressure point Pt raises. This allows higher pilot pressure set point Ppn, which biases the pilot system operating points to a higher pressure. Stated differently the pressure range Pp-Pt lies over higher absolute pressure. Higher pilot pressure causes a faster rate of decay Dp/Dt, however the range Pp-Pt stays constant. Therefore since the denominator Dp/Dt increases, the activation time Ta decreases.

[0100] Thus the spring raises the trip pressure of the actuator, and the pilot pressure setpoint required to maintain stable operation and avoid false tripping needs to be raised accordingly. Raising both the pilot pressure setpoint and the actuator drip pressure higher causes the operating pressures involved to be higher while maintaining the interval between the nominal pilot pressure and the trip point. As may be seen in Fig. 2C the higher operating pressure offers faster decay rate resulting from fire detection, thus resulting in faster actuation of the firefighting system.

[0101] By way of example, if fluctuations of the pilot pressure and control fluid pressure, and a desired safety margin are symbolized by X, in a firefighting system utilizing actuator without a spring the pilot pressure setpoint would be Ppn = X+Pd. However in a system utilizing a spring which imparts on the closing member a force requiring an opposing force which would be imparted on the sensing area by a pressure of Y PSI, the drip pressure Pd would be increased by Y, and the pilot pressure setpoint would be Ppn=X+Pd+Y. System activation would require releasing at least X PSI from the pilot line system in order to bring the actuator to at least a drip state. However as seen in Fig. 2C, the decay rate of X PSI is faster when the operating point is higher (by Y pounds provided by the spring force), which in turn results in faster system activation. At higher setpoint Ppn, the range between Ppn, or even Pp, and Pd occupies a smaller portion percentage-wise of the pilot pressure. Thus the actuator trips at a shorter time.

[0102] Figs. 6, 7, and 8 depict an enlarged view of the area about active end region, seal, and seat face, in closed, partially open, and open, respectively. The spring 300 is not shown in those drawings for clarity. Fig. 7 is shown in the drip state which is the state at which the pilot actuator merely begins to open and allow communication between the inlet and drain ports. Figs. 7 and 8 do not include optional fastener 192, and the seal surface is more clearly visible, however the details of the seal construction are a matter of technical choice, and different seal structure may be utilized on each aspect of the invention.

[0103] It is noted that various embodiments of the present invention may combine certain features in varied combinations. By way of example, each item of the list below describe by way of example a pilot actuator embodiment which may combine with any embodiment described above, and with any combination of listed features:

a. Advantage ratio Ra larger than 1 : 15 and preferably equal or larger than 1 :20, in combination with a spring 300 exerting directly or indirectly an opening force to the sealing member 170.

In such embodiments the spring force is equal or greater than a countering force imparted on the piton active end by 5 pounds per square inch, and up to 75 pounds per square inch, of the pressure acting on the sensing member 155;

b. A piston accelerating surface, potentially in combination with a seal ridge;

c. A piston accelerating surface in combination with a seat accelerating surface, and optionally with a seal ridge.

[0104] Thus by way of example a pilot actuator embodiment is envisioned that will include the features items a. and c. above, however varying subsets of above listed features are also considered as varied embodiments. Higher ratios such as higher spring forces may be utilized. Notably a pilot actuator utilizing only the feature accelerating surfaces and any Ra or even without any spring, is also considered a useful aspect of the invention. [0105] A non-limiting example is provided to demonstrated one method of selecting a pilot pressure setpoint. It is noted that the example is provided merely as guidance and while clearly sufficient for the skilled in the art, other parameters may be exercised.

[0106] In a pre-action or a deluge firefighting system having a pilot actuator as descried in any of the

embodiments described herein, where only the spring and control pressure impart an opening force on the actuator sealing member, the setpoint is calculated as at least

p ₌ ((Pc_max . _ p

rpn J ' ^r min ¹ mean) ^c

[0107] Where Ppn is the pilot pressure setpoint, Ppmax is the maximum pressure expected in the control vent line 20 at the seal, Fs being the force applied by the spring, Ac is the area of the sealing member acted upon by the control pressure Pc. As is the sensing surface, Ppmin is the minimal expected pilot pressure during system standby, and Ppmean is the mean actual pilot pressure, which in many cases is the setpoint pilot pressure. The term (P_pmtn— P_pmean) is directed to the amplitude of downward fluctuation in pilot pressure and the actual pressure is immaterial. In many embodiments a safety factor ε is added to the calculated result, as otherwise the actuator may be left at undetermined state in borderline pressures. Selecting a safety factor ε may be done to comply with an applicable standard, arbitrarily, according to common engineering standards, and the like. Optionally the pilot setpoint may be set as an engineering choice or by code requirements, to any value that would exceed Stated differently in general form the pilot pressure setpoint in PSI is set to a

pressure above a pressure calculated by the sum of the opening forces (pounds) imparted to the sealing surface of the pilot actuator by the highest expected control pressure, and the spring force, divided by the sensing surface area inches. Commonly a safety factor is added to the pilot pressure setpoint. In certain jurisdictions standards provide directions as to the estimated fluctuations to be expected in the control pressure and the pilot pressure, as well as for the additional safety margin. Otherwise the selection of those parameters are primarily an engineering choice befitting the firefighting system and its environment.

[0108] Fig 2 A depicts a schematic example actuation graph of a prior art pilot actuator, and Fig. 2B depicts a schematic example actuation diagram of an embodiment of the present invention. The graphs represent smoothed lines and approximated values. In Figs. 2A and 2B the vertical Y axis represents pilot pressure and the horizontal X axis represents control pressure. Graphs TP and TP 1 respectively (represented by dashed lines) represent the trip point at which the actuator is in tripped state, graphs DP and DPI respectively (represented by dash-dot-dot lines) represent the drip pilot pressure, or the point at which the actuator begins to open, and graphs SP and SP1 respectively (represented by solid lines) represent the recommended pilot pressure setpoint, all as a function of the control pressure. As seen in Fig. 2A and 2B generally higher control line pressure Pc in the control vent line 20 requires higher pilot pressure Pp to maintain the valve in closed state. An example of such correlation is shown by lines TP and TP1. It is desired to reduce that dependency, as the pilot pressure set point Ppn must be set higher than a point which will maintain the pilot actuator closed at the highest expected control line pressure Pc. Thus for any given control vent line pressure other than the highest expected, the pilot pressure set point Ppn is excessive. Excessive pilot pressure cause longer actuation times. It is therefore advantageous to maintain the slope of such trip or drip characteristics curve as low and close to flat as possible, as doing so allows reducing the nominal pilot pressure setpoint. Examination of Fig. 2B shows that as the shallower slopes of the drip and trip, pilot pressures pressure allow shallower slop of the recommended pilot pressure setpoint Ppn. Notably, the drip-trip interval is also smaller.

[0109] As seen in Fig. 2C the rate of pressure decay Dp/Dt in pilot piping systems is faster at higher pilot pressures.

[0110] Fig. 1 depicts a common dry pilot firefighting systems. However system which embodies any of the pilot actuator embodiments according to the present invention the system becomes an embodiment of a system acting in accordance with an aspect of the invention. Notably, the system aspect of the invention extends to pre-action systems where the pilot line system 45 includes the main distribution system 15 or portions thereof. Deluge systems are also considered.

[0111] In an aspect of the invention, there is provided a method for configuring a deluge or a pre-action

firefighting system in any of the configurations described above which comprises a pilot actuator having a spring imparting an opening force to a sealing member thereof, the method comprising setting the pilot pressure setpoint to a pressure equal to or higher than

P_pn = (^^{F max}^^{* +Fs}j -I- (P_pmln— P_pmean) + ε, where the spring force F_s in pounds is equal to or greater than a force exerted on the sensing surface of the pilot actuator by 8 pounds per square inch. Optionally the pilot i(P *A ) +Fs\

pressure setpoint is set to any value exceeding ( — ) as set by engineering choice or by code.

V A_s /

[0112] Additional trim components, such as accelerators, latches, alarm actuators, test and drain devices, and the like may be utilized in any of the systems described herein.

[0113] In a pre-action type firefighting system the system requires at least two conditions to be asserted prior to release of firefighting fluid into the area to be protected. Thus at least two sensors of differing types are commonly utilized.

[0114] The term 'line' in this context refers to a length of pipe or pipes, and is commonly referred to as the 'pilot line' for deluge systems or the preaction system piping for preaction systems. The present application uses the term 'pilot line' for all system types, including systems in which the distribution system pipes, or portions thereof, are used for fire sensing.

[0115] This firefighting systems disclosed herein may utilize any type of hydraulically controlled valve 10, such as a diaphragm valve, a clapper type valve, a gate type valve, and the like. Notably, an actuator having either a seat and/or a piston accelerating face is compatible with any type of firefighting system which may benefit from an accelerator valve, regardless of the biasing of the actuator valve operating parameters, or the system configuration such as deluge, or pre-action, and the like.

[0116] Oftentimes, the predetermined levels of pressure at which the control valve and/or the pilot actuator would actuate or prevent actuation, are relative to a respective opposing pressure. By way of example, a diaphragm valve would begin to open when the ratio between the pressure at its inlet reaches a certain predetermined ratio with the pressure in its control chamber. In contrast, the effect of inlet pressure on certain clapper type valves relative to the control chamber pressure are negligible while the control valve operates within its parameters. Thus a predetermined pressure in the control chamber required to keep the diaphragm valve closed would be expressed in percentage or ratio of inlet/control chamber pressures, while a clapper valve opening control pressure may be determined in absolute pressure. Similarly, a predetermined pressure drop required to transition a pilot actuator from close to open state relates to the interval between the actual pilot pressure prior to actuation, and the pressure required to maintain the actuator closed against the force exerted on the sealing surface by the control fluid at the time of actuation. As both the pilot pressure and the control pressures fluctuate, the term predetermined pressure drop should be construed as directed to a relative term, rather than to an absolute pressure level. Such predetermination is done by selection of area ratio, against nominal set points, as a percentage, and the like of an opposing or cooperating force at the time of operation. Such considerations would be clear to a person skilled in the art in view of the present specifications.

[0117] It is important to note that only the area of the pressure sensing member which is exposed to the pilot chamber and can translate pressure in the pilot chamber to a closing force which is transmitted to the piston is considered as the pressure sensing area.

[0118] Unless otherwise specified, relational terms used in these specifications should be construed to include certain tolerances that the skilled in the art would recognize as providing equivalent functionality. By way of example the term perpendicular is not necessarily limited to 90.0°, but also to any slight variation thereof that the skilled in the art would recognize as providing equivalent functionality for the purposes described for the relevant member or element. Terms such as "about" and "substantially" in the context of configuration relate generally to disposition, location, or configuration that is either exact or sufficiently close to the location, disposition, or configuration of the relevant element to preserve operability of the element within the invention which does not materially modifies the invention. Similarly, unless specifically specified or clear from its context, numerical values should be construed to include certain tolerances that the skilled in the art would recognize as having negligible importance as it does not materially change the operability of the invention.

[0119] In these specifications reference is often made to the accompanying drawings which form a part of the disclosure, and in which are shown by way of illustration and not of limitation, exemplary implementations and embodiments. Further, it should be noted that while the description provides various exemplary embodiments, as described below and as illustrated in the drawings, this disclosure is not limited to the implementations described and illustrated herein, but can extend to other embodiments as would be known or as would become known to those skilled in the art. Reference in the specification to "one embodiment", "this embodiment", "these embodiments", "several embodiments", "selected embodiments" or "some embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiment(s) may be included in one or more implementations, and the appearances of these phrases in various places in the specification are not necessarily all referring to the same embodiment(s). Additionally, in the description, numerous specific details are set forth in order to provide a thorough disclosure, guidance and/or to facilitate understanding of the invention or features thereof. However, it will be apparent to one of ordinary skill in the art that these specific details may not all be needed in each implementation. In certain embodiments, well-known structures, and materials, have not been described in detail, and/or may be illustrated schematically or in block diagram form, so as to not unnecessarily obscure the disclosure.

[0120] For clarity the directional terms such as 'up', 'down', 'left', 'right', and descriptive terms such as 'upper' and 'lower', 'above', 'below', 'sideways', ' inward', 'outward', and the like, are applied according to their ordinary and customary meaning, to describe relative disposition, locations, and orientations of various components. When relating to the drawings, such directional and descriptive terms and words relate to the drawings to which reference is made. Notably, the relative positions are descriptive and relative to the above described orientation and modifying the orientation would not change the disclosed relative structure.

[0121] It will be appreciated that the invention is not limited to what has been described hereinabove merely by way of example. While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various other embodiments, changes, and modifications may be made therein without departing from the spirit or scope of this invention and that it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention, for which letters patent is applied.

Claims

I Claim

1) A direct-acting pilot actuator for deluge or pre-action type firefighting systems utilizing a pressurized sensing pilot line for sensing a fire, the actuator venting a pressurized control line in response to drop in pilot pressure in the pilot line, the pilot actuator comprising:

a housing having an internal cavity, the housing having a pilot port, a vent port, and a drain controllably in fluid communication with the vent port via a sealing port;

a pressure sensing member which at least with a portion of the internal cavity defines a pilot chamber in fluid communications with the pilot port, the pressure sensing member having a pilot pressure sensing surface;

a seat disposed about the sealing port, the seat comprising a seat face circumscribing the sealing port; a sealing piston coupled directly or indirectly to the pressure sensing member, the sealing piston having an active end portion movable between a closed state and at least one open state, the seat and the active end forming a sealing arrangement therebetween when the piston is in the closed state, for sealing fluid communications between the vent port and the drain; the sealing arrangement defining a seal contact area circumscribing a sealing surface of the piston active end, the ratio of the area of the sealing surface and the area of the pilot pressure sensing surface defining an advantage ratio Ra of at least 1 : 15; and,

a spring disposed to directly or indirectly impart a spring force to the piston, the spring force acting against a force imparted to the sensing surface by pressure in the pilot chamber, the spring force urging the sealing piston away from the closed state, the spring force being greater or equal to an opposing force which would be imparted on the sensing surface by a pressure of 5 PSI.

2) A pilot actuator as claimed in claim 1, wherein the sealing piston is integral to the pressure sensing

member.

3) A pilot actuator as claimed in any of claims 1 or 2, further comprising:

a seat acceleration surface extending from the seal contact area towards the seat edge; and, a piston accelerating area disposed at or about the piston active end and extending from the seal contact area to the piston edge;

wherein the piston acceleration surface and the seat acceleration surfaces are at least in partial registration when the piston is in the closed state.

4) A pilot actuator as claimed in claim 3, wherein the surface area of the piston accelerating surface having at least twice the area of the sealing surface.

5) A pilot actuator as claimed in claim 3, wherein the piston accelerating surface or the seat accelerating surface, or a combination thereof, are textured.

6) A pilot actuator as claimed any preceding claim, wherein the pressure sensing member comprises a

diaphragm, and at least a portion of one side of the diaphragm comprises the sensing surface.

7) A pilot actuator as claimed in claim 5, wherein the piston is coupled to, or is embodied on, the second side of the diaphragm.

8) A deluge or pre-action type firefighting system comprising: a control valve having an inlet coupled to a fire suppression fluid supply, and an outlet coupled to a distribution system having a plurality of fluid distribution ports, the control valve having a control chamber for maintaining the system in a standby state when the control chamber is exposed to an operating control pressure, and transitioning to a deployed state in response to reduction of control pressure in the control chamber below a predetermined level;

a pressurized sensing pilot line for sensing a fire, the pilot line exposed to a pilot pressure, the pilot line coupled to at least one sensor capable of venting the pilot pressure upon activation thereof; a direct-acting pilot actuator having a pilot chamber being coupled to the distribution system via a pilot port, a vent port in fluid communications with the control chamber of the control valve, and a drain port, the vent port being in controllable fluid communication with the drain port via a sealing port;

the pilot actuator further having a pressure sensing member having a pilot pressure sensing area operatively exposed to the pilot pressure, the pressure sensing member being directly or indirectly mechanically coupled to a sealing piston having a sealing area operatively exposed to the control pressure, the ratio Ra between the sealing area and the pilot pressure sensing area being at least 1 : 15; the pilot actuator further comprises a spring directly or indirectly imparting to the sealing piston an opening spring force greater than a force equivalent to the force imparted to the pilot pressure sensing area by a pilot pressure of 5 PSI;

the sealing piston being operative to impede fluid flow between the vent port and the drain when the pilot pressure applied to the pilot pressure sensing area imparts a closing force that is larger than an opening force opening force comprising the spring force and a force resulting from the control pressure applied to the sealing area, and allow fluid flow between the vent port and the drain when the opening force is larger than the closing force.

9) A firefighting system as claimed in claim 8, wherein the pilot pressure having a pilot pressure setpoint, the setpoint being set above a pressure calculated by adding the opening force imparted to the sealing piston by the spring, and the force applied to the sealing area by the highest estimated control pressure during system standby mode, the sum of those forces being divided by the sensing surface, and further adding to the result of the division an estimate of pilot pressure fluctuation below the mean pilot pressure.

10) A firefighting system as claimed in claim 9 wherein an additional safety margin is added to the calculated pilot pressure setpoint.

11) A firefighting system as claimed in claim 10 wherein the safety margin equals the difference between a mean pilot pressure and the lowest pilot pressure expected to be present in the pilot lines without the detection of a fire.

12) A firefighting system as claimed in any of claims 8-11, wherein the pilot line and the distribution system are integrated.

13) A firefighting system as claimed in any of claims 8-12, wherein the pilot actuator further comprises a seal and the sealing piston having an active end, the seat and sealing piston forming a sealing arrangement therebetween when the pilot actuator is in a closed state, the seat having a seat acceleration surface extending from the seal sealing, towards the seat edge; and a piston accelerating area disposed at or about the piston active end and extending from the seal contact area to the piston edge, the piston acceleration surface and the seat acceleration surfaces are at least in partial registration when the piston is in the closed state.

14) A firefighting system as claimed in any of claims 8-13, wherein the ratio the ratio Ra between the sealing area and the pilot pressure sensing area is at least a ratio selected from a list consisting of 1:20, 1 :25, 1 :30, 1:35, 1 :40, 1 :50, 1:60, 1 :70, 1 :80, 1 :85, 1:90, and 1 :95.

15) A firefighting system as claimed in any of claims 8-14, wherein the ratio between the force imparted by the control pressure and the force imparted by the pilot pressure does not exceed a ratio of 1 :95 or 1 : 100.

16) A firefighting system as claimed in any of claims 8-15, wherein the spring imparts an opening force greater than a force equivalent to the force exerted on the pilot pressure sensing area by a pilot pressure of 8 PSI, 10 PSI, 20 PSI, 30 PSI, 65 PSI, and/or 75 PSI.

17) A firefighting system as claimed in any of claims 8-16, wherein the pilot line is integrated with the

distribution system.

18) A firefighting system as claimed in any of claims 8-17, wherein the system comprises at least two sensors of differing type.

19) A direct-acting pilot actuator for deluge or pre-action type firefighting systems utilizing a pressurized sensing pilot line for sensing a fire, the actuator venting a pressurized control line in response to drop in pilot pressure in the pilot line, the pilot actuator comprising:

a pressure sensing member having a pilot pressure sensing surface which at least with a portion of the internal cavity defines a pilot chamber in fluid communications with the pilot port;

a seat disposed about the sealing port, the seat comprising a seat face circumscribing the sealing port; a sealing piston coupled directly or indirectly to the pressure sensing member, the sealing piston having an active end portion movable between a closed state and at least one open state, the seat and the active end form a sealing arrangement therebetween when the piston is in the closed state, for sealing fluid communications between the vent port and the drain, the sealing arrangement defining a seal contact area circumscribing a sealing surface of the piston active end;

a seat acceleration surface extending from the seal contact area towards the seat edge; and, a piston accelerating area disposed at or about the piston active end and extending from the seal contact area to the piston edge, the piston acceleration surface and the seat acceleration surfaces being at least in partial registration when the piston is in the closed state.

20) A pilot actuator as claimed in claim 19, wherein the surface area of the piston acceleration surface having at least twice the area of the sealing surface.

21) A pilot actuator as claimed in any of claims 19 or 20, wherein the seat acceleration surface and the piston acceleration surface are angled relative to the sealing port.

22) A pilot actuator as claimed in any of claims 19-21, wherein the seat acceleration surface and/or the piston acceleration surface are textured.