GB2309765A - Float/gravity operated valve - Google Patents

Abstract

A float operated valve (10) comprises a body (12) and a closure member (13) for closing the valve (10) by occlusion of .apertures (17) in the valve body (12). The closure member (13) being acted upon by gravity to allow it to take up a lower position which allows liquid to flow through the apertures (17). A cam surface (25) connected to and rotatable by movement of a float (11) raises the closure member (13) against the force of gravity to close the valve (10) as the float (12) is raised. Pressure relief apertures (19, 28) allow the feed pressure to fall after the valve has closed.

Description

LIQUID STORAGE SYSTEMS AND VALVES FOR USE THEREIN This invention concerns liquid storage systems and valves for use therein.

Liquids of various types are frequently stored in holding tanks for use as required. For example, fuel oil for heating systems is usually stored in holding tanks which are located above ground, oil being taken from the tanks through a delivery pipe to a boiler where it is burnt as required. In order to enable the tanks to be refilled, these storage systems usually include an inlet pipe leading into the top of the tank, the end of the pipe remote from the tank usually including a hand operated gate valve which is opened to allow oil to be pumped from a road tanker, but is normally kept closed in order to minimise drips of oil from the inlet pipe and to prevent the ingress of foreign bodies.

In order to prevent a vacuum being produced when oil is withdrawn from the tanks or an increase in pressure within the tanks as the tanks are refilled, they are provided with an air vent in the head space above the oil which ensures that the pressure within the tanks is the same as that outside.

Such systems are very widely used, but they suffer from a serious disadvantage in that if they are overfilled, oil can be expelled through the air vent. Care in refilling these tanks can reduce the risk of over filling, but few are provided with gauges to indicate how much oil is present when filling commences, and even if such a gauge is provided there can be no guarantee that it is accurate let alone working. Dip sticks can be used to estimate the amount of oil remaining in the tanks, but these can be incorrectly used and the remaining volume underestimated, and furthermore the available space for new oil can be incorrectly calculated, resulting in too much oil being pumped from the road tanker used to refill the tanks. Even if the correct volume is calculated, it is possible for the operator of the pumps on the road tanker to attempt to pump into the storage tanks more oil than calculated. Oil spillages then result when overfilling occurs.

Oil spillages from overfilling storage tanks are a serious environmental problem, especially when the oil enters water courses. Containment devices such as walls built around the tanks are used, but they add to the costs of the system.

Furthermore, containment devices address the symptoms rather than cause of the problem.

Warning devices actuated by a float within the tanks can be used to provide an audible indication the oil within them has reached a predetermined level. However, there is no guarantee that such devices are in working order, or that even if they are, the pump sending oil to the tank will be turned off in time to prevent a spillage caused by overfilling.

Underground storage tanks for gasoline are provided with automatic shut off valves to prevent overfilling of the tanks.

These valves are actuated by a float which causes a valve closure member to snap shut and cut off the flow of gasoline to the tanks. Unlike above ground tanks, where refilling generally has to be carried out by pumping because of the outlet from the delivery tanker is generally below the inlet of the storage tank, underground tanks are usually filled by gravity flow, gasoline for example simply pouring out of the delivery tanker into the underground tank through a flexible hose.

A consequence is that rapid shut off valves, such as are used for gasoline, under gravity filling, are unsuitable for pumped systems since the high back pressures which are produced when they shut off the full flow of liquid, can lead to damage to delivery hoses and pumps, and even inaccurate metering of the amount of delivered liquid, apart from leaving the delivery hose under pressure when the flow of liquid into the tank is stopped by the valve.

The present invention seeks to provide an above ground liquid storage system which can be refilled by pumping whilst avoiding overfilling. In particular, it seeks to provide a cut off valve for effecting this.

According to the present invention there is provided a float operated valve for controlling the flow of a liquid therethrough, the valve comprising a valve body through which the liquid flows when the valve is open, a closure member for closing the valve by occlusion of apertures in the valve body as the closure member is moved relative to the valve body, the closure member in the operating position of the valve being acted upon by gravity to allow the closure member to take up a lower position which allows liquid to flow through said apertures in the valve body and through the closure member, a float for closing the valve in accordance with the level of liquid in which the float is placed, and a cam surface connected to and rotatable by movement of the float, the cam surface serving to raise the closure member against the force of gravity thereon, thereby to close the valve as the float is raised by a rising level of liquid and to allow the closure member to fall under the force of gravity as the float takes up a lower position as the level of liquid falls.

An embodiment of storage system and control valve for use therein will now be described, by way of example, with reference to the accompanying diagrammatic drawings in which:- Fig. 1 shows a part cut away view of a conventional above-ground oil storage system; Fig. 2 shows a part cut away view of a system in accordance with the present invention including a float valve in accordance with the invention; Fig. 3 is a partially cut away, vertical section through the valve in Fig. 2, to an enlarged scale; and Fig. 4 is a view of the valve as shown in Fig. 3 with the valve in its closed position.

Referring to Fig. 1, the oil system consists of an essentially cylindrical storage tank 1 located above ground on supports 2.

The tank 1 has an oil outlet pipe (not shown) through which oil 3 can be fed for a desired end use, for example to a central heating boiler. In order to prevent a vacuum forming when oil is removed from the tank 1, the tank 1 is provided with a vent tube 4 which causes equilibration of the pressure of the head space 5 above the oil 3 with that of the atmosphere outside the tank 1.

The tank 1 has a refilling pipe 6 with a gate valve 7 at its end remote from the tank 1, the opposite end 8 of pipe 6 opening into the head space 5.

Refilling of the tank 1 is effected by connecting a delivery tanker via a hose (not shown) to the end of the pipe 6 adjacent to the gate valve 7, opening the valve 7, and pumping the required volume of oil into the tank 1. An estimate of the volume of oil required to fill the tank 1 can be made by knowing how much oil has been used, or by the use of a dip stick inserted, for example, into an inspection hatch 9.

Once the desired amount of oil has been pumped into the tank 1, pumping is stopped, the gate valve 7 is closed, and the flexible hose is disconnected from the end of the pipe 6. The volume of oil present in the tank 1 can then be tested using a dipstick.

As will be appreciated, there is nothing to warn the operator of the pumps on the delivery tanker when the tank 1 is full, and the first that is known of the tank 1 having become full is the discharge of oil through the open end of the vent tube 4.

Fig 2 shows an oil storage system in accordance with the present invention which is substantially identical to that of Fig. 1 except that it includes a float actuated valve in accordance with the present invention shown generally at 10.

The valve 10 is situated between the end of the inlet pipe 6 and the tank 1, and in use it serves to cut off the flow of oil through the pipe 6 when the rising level of the oil 3 in the tank 1 as it is being filled causes a float 11 of the valve 10 to cut off the flow of oil.

As will be appreciated from the detailed description of the valve 10 which follows, the valve 10 gradually cuts off the flow of oil through the pipe 6 as the float 11 rises, thereby avoiding the sudden increase in pressure associated with rapid shut-off valves such as are used with underground storage tanks, for example for gasoline. The delivery hoses used to feed oil from the delivery tanker are normally capable of withstanding back pressure from the pumps which gradually builds up, and gradual pressure build up often provides the operator with an audible warning that this is taking place, since pumps often make a different noise as they attempt to pump against an increasing back pressure on their outlet side.

The embodiment of valve shown in Figs. 3 and 4 has the additional advantage, not only of shutting off gradually as the float 11 (partially cut away) rises, but of enabling pressure to be relieved in the delivery hose even after the valve 10 has cut off the main flow of oil. This facilitates disconnection of the delivery hose from the inlet pipe 6.

Fig. 3 is a partial vertical section through the valve 10 used in the system illustrated in Fig. 2, with the valve 10 in its open position so that oil can flow through the valve.

The valve 10 has a valve body shown generally at 12 and a valve closure member 13 operated by the float 11. The valve body 12 has an external thread 14 which enables it to be screwed into the top of a tank 1 in place of the pipe 6, the pipe 6 being screwed into an internal thread 15 within the body 12 to provide a fluid connection from the tap 7 to the tank 1. The valve body 12 can, for example, be of steel.

Located within the valve body 12 is a static valve seal member 16 which is essentially cup-shaped, and it is preferably made of brass. The static member 16 has two sets of four circumferential slotted apertures 17 therethrough which allow oil to flow through the valve body 12 into the tank 1 when the valve 10 is open.

The end face 18 of the static member 16 has fine bore holes 19 therethrough which enable pressure in the feed hose connected to the pipe 6 to be relieved after the valve 10 has been shut off by the float 11 and the pumps feeding oil to the delivery hose have been turned off. The functioning of the holes 11 will subsequently be described in more detail.

In sliding but fluid sealing engagement around the static valve seal member 16 is a movable valve seal member 20. The movable member 20 is of a mass such that with the valve 10 oriented substantially vertically in the tank 1 as illustrated in Fig. 2, the member 16 is urged to move vertically downwardly under its own weight. A set of four circumferential slotted apertures 21 in the movable member 20 are so positioned that with the movable member 20 in its most downward position, they are substantially in register with the lower set of four apertures 17 in the static member 16. In this position of the movable member 20, the upper set of four apertures 17 in the static member 16 are not occluded by the movable member 20, and oil can pass through them, the valve body 12, and also through the lower sets of apertures 17 and 21 in the static and movable valve members 16 and 20 respectively.

It should be noted that the static and movable valve members 16 and 20 respectively are not prevented from relative axial rotation, the movable member 20 being free to rotate about the static member 16. Whilst such rotation may cause some restriction in the flow of oil through the valve 10, this is generally insignificant bearing in mind that the apertures 17 and 21 are in the form of relatively long circumferential slots.

As a result, flow through the closure member is relatively unaffected by the relative rotational orientation of the members 16 and 20.

The movable valve member 20 is free to move in a vertical plane and rotationally on the exterior surface of the static member 16 on a cylindrical shaft 22 which depends axially downwardly from the static member 16.

The lower end 23 of the shaft 22 is pivotally connected to the float 11 which actuates the valve 10 via a valve closure device 24 which consists of a cam surface 25 against which rests a lower surface 26 of the movable member 20. When the float 11 rises in the tank 1 as oil 3 flows into it via the inlet pipe 6, the cam surface 25 moves relative to the movable member 20 and gradually raises the latter. As this occurs, the upper edge 27 of the movable member 20 moves upwardly, thereby gradually occluding the upper set of apertures 17 in the static member 16.

Simultaneously, the lower set of apertures 21 in the movable member 20 move upwardly and out of alignment with the lower set of apertures 17 in the static member 16. Eventually, the movable member 20 shuts off the flow of oil through the static member 16. However, since the shutting off of the oil flow is gradual, pressure shock is substantially reduced compared with snap action valves such as are used for gravity fed systems for underground storage tanks.

In order to relieve the pressure in the feed pipe 6 after the movable and static members 16 and 20 have shut off the main flow of oil through the valve 10, the members 16 and 20 have bore holes 19 and 28 respectively through their circular end faces.

The bore holes 19 in the static member 16 need not be of particularly large diameter to effect this, and indeed it is obviously desirable that they should be of small diameter in order to prevent significant flow through them when the movable member 20 has shut off oil flow through the apertures 17.

Typically, holes with diameters of less than 2 mm have been found to be satisfactory for the purpose with valves having internal diameters of valve body of approximately 8 cm. The bore holes 28 in the end face of the movable member 20 are of considerably larger diameter than those in the static member 16 in order to allow oil to flow freely out of the member 20 into the tank 1 as pressure is relieved through the bore holes 19 in the static member 16.

Claims (4)

Claims

1. A float operated valve for controlling the flow of a liquid therethrough, the valve comprising a valve body through which the liquid flows when the valve is open, a closure member for closing the valve by occlusion of apertures in the valve body as the closure member is moved relative to the valve body, the closure member in the operating position of the valve being acted upon by gravity to allow the closure member to take up a lower position which allows liquid to flow through said apertures in the valve body and through the closure member, a float for closing the valve in accordance with the level of liquid in which the float is placed, and a cam surface connected to and rotatable by the movement of the float, the cam surface serving to raise the closure member against the force of gravity thereon, thereby to close the valve as the float is raised by a rising level of liquid and to allow the closure member to fall under the force of gravity as the float takes up a lower position as the level of liquid falls.

2. A valve according to claim 1, wherein the valve closure member and the valve body include a plurality of circumferential apertures therethrough which are so positioned as to allow liquid therethrough when the valve is open but not when it is closed.

3. A valve according to either of the preceding claims, wherein the valve body includes at least one pressure relief aperture which allows pressure to fall in the feed side of the valve after the valve has been shut off by the closure member.

4. A liquid storage system comprising a storage tank for the liquid, an inlet conduit for feeding liquid to the tank, and an outlet conduit through which liquid can be fed from the tank, an air vent for venting the interior of the tank to atmospheric pressure, and a float operated valve according to any of the preceding claims for controlling the flow of liquid into the tank according to the level of liquid in the tank detected by the valve float.