JP2766256B2 - Mandrel load measurement system - Google Patents

Abstract

A stem load determining system comprises a method and apparatus for determining the load developed on a threaded stem, including a valve stem (15) driven by a valve operator (16). An integral component of the apparatus is a stem strain transducer (24) uniquely designed to grip a threaded stem to define a gauge length on the threaded stem and to detect and measure deformation of the stem at the gauge length when subjected to a compressive or tensile load.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates generally to the field of strain and stress measurement devices, and more particularly to a device for measuring the strain and stress of a threaded bearing mandrel in a flow control valve system.

[0002]

BACKGROUND OF THE INVENTION The ability to measure thrust in a valve actuation device has become increasingly important since the advent of Charbonneau et al., Disclosed in U.S. Pat. No. 4,542,649. More importantly, the need to measure the thrust of the operating device while the operating device is mounted on the valve has been identified.

[0003]

In Charbonneau and other prior art, a load cell mounted on an upper bearing housing is utilized, wherein the valve stem is raised from a closed to an open position and the mounted load cell is mounted. The mandrel load is measured when colliding with the ground. Load cell techniques for measuring mandrel loads may not always work. This is because many valve operating devices are not designed with an upper bearing housing to which a load cell can be mounted.

[0004]

SUMMARY OF THE INVENTION A strain monitoring apparatus for monitoring deformation in a threaded mandrel under load according to the present invention grips the thread of the threaded mandrel, and A first defining a first reference point along the longitudinal direction of the mandrel;
Screw gripping means for gripping a screw of the threaded mandrel and defining a second reference point along a longitudinal direction of the mandrel, a second reference point located axially away from the first reference point;
Screw gripping means for gripping a screw of the threaded mandrel and defining a third reference point along the longitudinal direction of the mandrel, a third reference point located 180 ° circumferentially away from the first reference point; Screw grip means for gripping the thread of the threaded mandrel and defining a fourth reference point along the mandrel, located circumferentially 180 ° from the first reference point and further comprising the third reference point Fourth screw grip means axially spaced from a point for detecting a relative change between the first and second reference points and for emitting a signal indicative of the relative change First change detecting means, a second change detecting means for detecting a relative change between the third reference point and the fourth reference point, and for emitting a signal representing the relative change, and The signals from the first and second change detecting means; Conditioning means for coupling the signals in a predetermined manner are provided for providing parameters representative of the deformation in the mandrel.

An apparatus for determining a load on a threaded mandrel according to the present invention comprises: first screw grip means for gripping a screw of the mandrel to define a first reference point along the mandrel; A second screw grip means for gripping a screw of the mandrel at a position axially distant from the first reference point, so as to define a third reference point along the mandrel; Third screw grip means for gripping a screw of the mandrel at a position circumferentially distant from the first reference point; circumferentially extending from the first reference point so as to define a fourth reference point along the mandrel; Fourth screw gripping means for gripping the mandrel screw at a position further axially away from the third reference point, measuring means for axially measuring a distance between the reference points in an unloaded state, To get the length change First motion detection means for detecting and measuring the relative motion between the first and second reference points during compression of the mandrel, during compression of the mandrel to determine a second length change Motion detecting means for detecting and measuring the relative motion between the third and fourth reference points, determining means for determining an average of the first and second length changes, and E as an elastic modulus and A Is the stress area based on the thread properties of the mandrel, the determined average length change (dL), the measured unloaded distance (L) and the formula F = dLE A /
A calculating means for calculating a load force applied to the mandrel using L, wherein the first motion detecting means and the second motion detecting means perform the first to fourth motions in a radial direction and an angular direction, respectively.
Independent relative movement of the first and second screw grip means, and between the first and third screw grip means and between the second and fourth screw grip means. Is provided with a degree of freedom of movement, wherein the degree of freedom of movement is at least some distance in each of the axial direction, the radial direction, and the angular direction. Allowing the distance between the gripping means and the distance between the second and fourth screw gripping means to be varied, and furthermore, the threaded mandrel is capable of all of the bending and torsion forces Alternatively, the deformation of the axis of the threaded mandrel can be measured while receiving a portion.

[0006] The present invention includes a method and related apparatus for measuring the load imposed on a valve stem driven by a valve operating device. The method of the present invention utilizes known principles and properties related to the stress and strain of metals, especially threaded shafts, and applies these principles and properties in combination with the unique apparatus of the present invention. . The method and apparatus of the present invention detects and measures deformation of a threaded portion of a valve stem when a load is applied to the stem. The measured deformation is recorded,
Input to a computing device for determining the load applied to the mandrel.

In a preferred embodiment, the compressive deformation and the compressive load are measured and determined, but the tension is also taken into account.

The device of the present invention has a unique screw grip assembly which is rigidly mounted on the thread of the valve stem for movement with the stem. The grip assembly has a plurality of spaced apart reference points that move relative to each other and are rigidly attached to the screw and further define a test segment (also referred to as a gauge length) of the thread.

As the metal body of the stem is deformed (ie, compressed or stretched) by the load, the reference points move relative to each other. Therefore, the deformation of the test segment is reflected by the movement of the reference point. With the device according to the invention, the relative movement of the reference point is detected, measured and recorded. The measured deformation is input to a computing device along with other material properties in a preferred embodiment and the load is calculated.

In a preferred embodiment of the present invention, the deformation of the strike segment is compensated for by bending the mandrel under load.
Measured at three locations. Furthermore, the device of the present invention has a tapered conical gripping member having a unique shape and, in combination with the fixing member, serves to provide the necessary tightening of the valve stem screw. This allows the reference point to move exactly as the mandrel deforms.

The method and apparatus of the present invention and the mandrel loads calculated thereby have, of course, applications in a wide variety of different industries, and the present invention is not limited to such applications, but is described in US Pat. Ch. 4,542,649
The invention of arbonneau et al., ie, an improvement over the disclosure of US Pat. No. 4,542,649, incorporated herein by reference, has application in the valve diagnostics industry.

It is therefore an object of the present invention to provide a method for measuring the load on a valve stem driven by an operating device as it moves from an open to a closed position.

It is another object of the present invention to provide a method and apparatus for measuring a valve stem load by attaching a measuring device to the threaded portion of the valve stem.

Yet another object of the present invention is to provide a method and apparatus for measuring the deformation of a loaded valve stem.

Yet another object of the present invention is to provide an apparatus for tightly tightening threads and detecting deformation of a threaded shaft under load.

[0016] Other objects, features, and advantages of the present invention will become apparent from reading and understanding the present specification with reference to the accompanying drawings.

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. Throughout the drawings, the same numerals indicate the same components. FIG. 1 (partial schematic) shows the device of the invention in a preferred operating environment. The process pipe 12 has a valve 13 shown as a gate valve. Valve 13 is a stem 15
Is moved vertically up and down with respect to the fluid flow in the pipe 12. The valve stem 15 is driven up and down by a gear device 16 known as a valve operating device 16. Operation device 16 is frame 17
Mounted on the valve 13. In the preferred embodiment, the operating device is operated manually by a steering wheel 18 or by a motor 19.

As shown in FIG. 1, a mandrel distortion transducer
24 is attached to the threaded portion 20 of the valve stem 15.

As shown in detail in FIGS. 2 and 3, the mandrel distortion transducer 24 has a left clamp half 25 and a right ramp half 26. Left clamp half 25
An upper grip plate 29 and a mounting plate 30 have a support plate 28 to which the mounting plate 30 is firmly attached. Lower grip plate 31 is bolted
It is detachably attached to the support plate 28 by 35.
Linear variable differential tr
ansducer ("LVDT")) 32 is attached to bracket 30 and L
The needle 33 (on the extension of the center) of the VDT touches the upper surface 34 of the lower grip plate 31. The right clamp half 26 has a support plate 38, on which an upper grip plate 39 and a mounting bracket 40 are firmly attached. Lower grip plate 41
Is detachably attached to the support plate 38 by bolts 45. LVDT42 is attached to the bracket 40, LV
The needle 43 (on the extension of the center) of the DT is in contact with the upper surface 44 of the lower grip plate 41. These LVDTs are of the type typical in the art and have a core that moves through a stationary base to enable a voltage output signal.

FIG. 3 is a top view of the assembly of FIG. 2, with only two upper plates 29, 39 shown. However, the lower plates 31 and 41 have a similar structure and assembly. Each of the four grip plates 29, 31, 39 41 has a wedge-shaped concave surface 50 forming its front end 50, and rear ends for attaching the grip plates to the support plates 28, 38, respectively.
It has 51. The ends 52, 53 are provided with bolt grooves 54, 55. Two implant member receiving holes 58, 59
Opened at the front end 50 of 31, 39, 41. The holes are each oriented such that its center line 62 is perpendicular to one side of the wedge at the front end. Rear end 5 of the plates 29, 31, 39, 41
A passage is provided from 1 to each of the holes 58, 59 by screw grooves 60, 61. Implanted members 63 and 64 have thread grooves 60 and 61
Are held in each hole 58, 59 by screws. The implants 63, 64 can be adjusted to move in the rotational and axial directions within the holes 58, 59. 4 (a) and 4 (b),
As shown in more detail, each implantation member 63, 64 has a cylindrical body
65 and the conical head 66 form a unique shape. In a preferred embodiment, the conical shape of the head 66 defines an angle "a" of about 90 degrees as viewed from the side. The centerline 68 of the conical head 66 is offset from the centerline 69 of the body 65. In the preferred embodiment, the head centerline 68 is offset by a distance equal to about a half radius of the implant body 65. FIG. 4 (a)
Also shows a threaded groove 71 by which the screw holds the implant 63, 64 in the hole 58, 59. Key hole
72 is open at the end of the head of the implant members 63,64.

Referring to FIGS. 1 and 5, the electronics portion of the device of the present invention can be understood. This part has a power supply 74 that supplies power to the conditioning device 75. The conditioning device 74 has conditioning modules 77, 78 for each of the LVDTs 32, 42. Each conditioning module 77, 78 is an LVDT 32,
The excitation power (exitatio
n power) and receive the LVDT signal from wires 79 and 80. In a preferred embodiment, modules 77 and 78 demodulate and amplify the LVDT signal, filter the LVDT output, and convert it to a high level DC signal. Off-the-shelf modules can be used for such modules. The conditioning device 75 further comprises an addition module 81, which combines the output signals from the two conditioning modules 77, 78 into a single signal from the conditioning device. The adder is an amplifier
82, separate input resistors R1 and R2, feedback circuit 83 (resistor R3
And R4), and a bias current correction resistor R5. The values of these resistors can be varied by choice to provide the desired output. For example, in one embodiment, the output from the summing module 81 is the average of the two signals from the conditioning modules 77, 78 (in such a case, the values of the resistors would be R1 = R2 = 10Kohms, R3 = 4.5Kohms, R4 = 1Ko
hms, R3-R4 can be adjusted to 5Kohms in one set, R5 = 2.5kohms);
In another embodiment, the summing module output is the sum of the two conditioning modules. (R1 = R2 = 10k; R3 = 9.5
K, R4 = 1K, R5 = 4.3k). Each output is typically
It is in the form of a DC voltage.

An output signal from the conditioning device 75 is sent to a recording device 86 such as an oscilloscope through a cable 85.
Is transmitted to The signal value is recorded by the device, and the signal value can be visually observed. The voltage signal from the conditioning device 75 is associated with a corresponding distance measurement on the recording device 86. From the recording device 86, the distance value is the cable 88
Is sent electronically to the computer by
Alternatively, the data is transferred to the calculator 87 by manually transferring the data to a calculator by a keypad.

Operation The device described above is connected to the valve stem 15 through an attached mandrel strain transducer 24. In practice, the valve stem is relaxed (pulling stress is not generated) by pulling the valve 13 and partially opening it to disengage from its valve seat
That is best. Next, the mandrel strain transducer 24 is attached to the threaded portion 20 of the valve stem 15 near the tip of the frame 17. in this way,
When the valve 13 is closed again, the strain transducer turns on the valve housing
It doesn't get stuck in contact with the top of 14. Valve stem
Before attaching the mandrel distortion transducer 54 to the clamp half 115, the clamp halves 25 and 26 are assembled as described above. The lower grip plates 31, 41 are bolted to the respective support plates 28, 38 so as not to move. When mounting on the support plates 28 and 38, the upper surfaces 34 and 44 of the lower grip plates 31 and 41 are attached to the LVDT mounting bracket.
Be careful to stay away from 30, 40. As shown in FIG. 2, two clamp halves 25 and 26 are provided on the threaded portion 20 of the valve stem 15, and one clamp half 25 and 26 are provided on both sides of the shaft surface 90 of the valve stem 15. Then, the installation of the converter 24 is completed. As shown in FIG. 3, the wedge-shaped concave surface 50 of each grip plate 29, 31, 39, 41 surrounds the valve stem 15. The implants 63, 64 of all grip plates 29, 31, 39, 41 are firmly pulled into the respective implant receiving holes 58, 59 by the screws in the thread grooves 60, 61. Since the clamp halves 25, 26 are arranged in the threaded portion 20, the tapered conical heads 66 of the respective implant members 63, 64 project into the threaded valleys 91 of the mandrel, and each head 66 has one valley. (See FIG. 6).

The conical shape of the head 66 helps the implant 63 to just fit the threads of the variously sized threads. The offset nature of the tip 67 helps to correct the corresponding screw pitch and lead in order to maintain a parallel arrangement of the pair of upper grip plates 29,39 and the pair of lower grip plates 31,41. The tapered conical head 66 of each implant rotates about the body centerline 69 so that it fits well within the thread root 91 and the mated grip plates are in a generally parallel arrangement. In the preferred embodiment, 2
When the two clamp halves 25, 26 are mounted in alignment with the mandrel 15, the four implant members of the two upper grip plates 29, 39
The body centerlines 69 of 63 and 64 are all in the same plane perpendicular to the axial surface 90 of the valve stem. Center line 68 of each implant member head 66
Is preferably as close as possible to the plane of each body centerline 69. The rotation of the implant members 63 and 64 about the main body center line 69 is facilitated by inserting a pin into the key hole 72 and using the pin as a lever. Implanted member
63, 64 are tightened by screws in thread grooves 60, 61 to prevent further movement in holes 58, 59. The pair of grip plates 29, 39 and 31, 41 are attracted to each other by bolts 56, 57 passing through the bolt grooves 54, 55 around the mandrel 15.

The head center line 68 of the implanted members 63, 64 functions as a reference point and marks the reference point on the mandrel 15. The reference point defines a test segment on the valve stem 15 or a gauge length ("L"). The axial distance between the corresponding reference points (center line of the head) 67 of the grip plates 29, 31, 39, 41 is measured. Thus, the distance between the head center line 68 of the implanted member 63 of the left half grip plate 29, 31 and the left half grip plate
29, 31 the distance between the head center line 68 of the implant 64, the right half grip plate 39, 41 the distance between the head center line 68 of the implant 63, and the right half grip plate 39, 41. Implanted members
Measure the distance between the 64 head centerlines 68. The average of these four distances is defined as the gauge length "L" and is input to the memory of the calculation device 87. The LVDTs 32, 42 are connected to a conditioning device 75 which is connected to a recording device 86 as shown above. In the preferred embodiment, each LDVT 32, 42 is mounted on a clamp half 25, 26, respectively, when the clamp half is mounted on the valve stem 15, the core of the LVDT 32, 42 (needle 33, 43). Are radially separated from the center line of the stem by approximately 180 ° and at equal distances from the center line of the stem. At this time, bolts 35, which hold the lower grip plates 31, 41 to the respective support plates 28, 38,
45 is removed and lower grip plates 31, 41 are bolts 56, 5
It is fixed to the valve stem 15 by 7, but can move freely relative to the LVDT mounting brackets 30, 40.

The valve stem 16 is driven downward to close the valve 13 manually or by motor operation of the valve operating device 16. valve
When 13 comes to the closed position, compressive load (“mandrel load”)
Occurs in the axle. The mandrel load continues to increase until the torque switch in the valve operating device is disengaged and the operating device is opened (or the manual operation is stopped).

[0027] Due to the compressive load received by the mandrel 15, compression of the distortable material in which the mandrel is formed occurs. When the mandrel 15 is compressed, the mandrel test segment (gauge distance) defined by the distance "L" is compressed proportionately. When the test segment is compressed, the lower grip plates 31, 41
Moves relative to the LDVT mounting brackets 30,40.
The reference planes 34,44 move the LDVT needles 33,43, which cause relative movement between the LDVT core and the base, as is known in the art, so that the length of the test section ( A signal is generated representing the change (".DELTA.L") in "L"). It can be seen that when the test segment is bent, the distance between the reference points of one clamp half increases and the distance between the reference points of the other clamp half decreases. Each LDVT 32, 42 detects this and sends a signal of ΔL indicating a relative increase or decrease. As described above, the signals from the LDVTs 32 and 42 are sent from the conditioning modules 77 and 78 to the adder 81, respectively.
The true values are added, averaged or otherwise adjusted in the adder 81 and sent to the recorder 86. The prepared signal is displayed on the recording device 86 and otherwise recorded. In the preferred embodiment, the time trajectory of the change (ΔL) in the test length “L” is recorded and displayed. A sample 93 of such a trajectory is shown in FIG.
Is shown in The value of the distance recorded by the recording device 86 is
As described above, it is then input to the computing device. It is understood that the recording and calculation steps can be combined.

The final determination of the actual value of the mandrel load is based on the principles of material strength and elasticity. The following formulas are known and used in the art.

Strain = ΔL / L Stress = (strain) × (elastic modulus) Force = (stress) × (stress area) The stress area of the threaded portion is the smallest pitch circle diameter (P) and the smallest tooth base circle. Based on the average of the diameter (K):

Stress area = π [(P + K) / 4] ² Therefore, the following calculation is performed by the calculation device 87.

F = π [ΔLE / L] × [(P + K) / 4] ² where F is a mandrel load.

ΔL is determined by the conditioning device 75. If the adder 81 produces an output that is different from the average ΔL, an appropriate correction must be made to the above equation.

E is the modulus of elasticity of the mandrel material.

L is the pre-measured mandrel test segment length.

P is the minimum pitch circle diameter of the threaded portion 20 based on the screw geometry.

K is the minimum tooth root circle diameter of the threaded portion 20 based on the thread geometry.

Although the mandrel transducer 24 is disclosed herein as part of a larger inventive system, the mandrel distortion transducer is novel in itself and can be used in other threaded mandrel applications. It is understood that it can be applied.

Although the preferred embodiment described herein discloses the use of an LVDT to detect and measure relative changes between two reference points, it has similar purposes. It is within the scope of the invention to use other devices to detect the change to achieve.

Although the preferred embodiment of the present invention discloses the use of the mandrel distortion transducer 2X to define test segments and to track reference points that delimit test segments, the present invention is disclosed. It is within the scope of the present invention to use other methods to achieve equivalent objectives within the more advanced apparatus and methods of the present invention.

Although the present invention has been described in detail with particular reference to preferred embodiments thereof, it will be understood that modifications and variations have been made within the spirit and scope of the invention as set forth above and as set forth in the appended claims. It is understood that modifications can be made.

[0041]

The present invention includes a method and related apparatus for measuring the load imposed on a valve stem driven by a valve actuation device. The method of the present invention utilizes known principles and properties related to the stress and strain of metals, especially threaded shafts, and applies these principles and properties in combination with the unique apparatus of the present invention. . The method and apparatus of the present invention detects and measures deformation of a threaded portion of a valve stem when a load is applied to the stem. The measured deformation is recorded,
Input to a computing device for determining the load applied to the mandrel. In a preferred embodiment, the compressive deformation and the compressive load are measured and determined, but the tension is also taken into account.

The device of the present invention has a unique screw grip assembly which is rigidly mounted on the thread of the valve stem for movement with the stem. The grip assembly has a plurality of spaced apart reference points that move relative to each other and are rigidly attached to the screw and further define a test segment (also referred to as a gauge length) of the thread.

As the metal body of the stem is deformed (ie, compressed or stretched) by a load, the reference points move relative to each other. Therefore, the deformation of the test segment is reflected by the movement of the reference point. With the device according to the invention, the relative movement of the reference point is detected, measured and recorded. The measured deformation is input to a computing device along with other material properties in a preferred embodiment and the load is calculated.

In a preferred embodiment of the present invention, the deformation of the strike segment is adjusted to compensate for the bending of the mandrel under load.
Measured at three locations. Furthermore, the device of the present invention has a tapered conical gripping member having a unique shape and, in combination with the fixing member, serves to provide the necessary tightening of the valve stem screw. This allows the reference point to move exactly as the mandrel deforms.

[Brief description of the drawings]

FIG. 1 is a sketch of the mandrel load measurement system of the present invention when used with a valve and valve operating device.

FIG. 2 is a side view showing only a mandrel distortion transducer of the mandrel load measuring device of FIG. 1;

FIG. 3 is a top view of FIG. 2;

FIG. 4 (a) is a side view of the implantable member of the present invention,
FIG. 4B is an end view of the implantable member of FIG.

FIG. 5 is a schematic view of an electronic device of the mandrel load measuring device of FIG. 1;

FIG. 6 is a diagram showing only threaded portions, showing engagement of the implantable member of the present invention.

[Explanation of symbols]

──────────────────────────────────────────────────続 き Continuation of the front page (73) Patentee 597028818 2999 Johnson Ferry Road, Marietta, Georgia 30062, U.S.A. S. A. (72) Inventor John A. McMenamy United States Georgia 30064 Marietta, Hayward Circle 534 (56) References Japanese Utility Model Showa 60-129655 (JP, U) Japanese Utility Model Showa 60-48108 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB) Name) G01L 5/00 013

Claims (1)

(57) [Claims] 1. An apparatus for determining a load on a threaded mandrel, said first mandrel gripping means gripping a screw of said mandrel so as to define a first reference point along said mandrel. Second screw grip means for gripping the mandrel screw at a position axially distant from the first reference point so as to define a second reference point along the mandrel; and defining a third reference point along the mandrel. Third screw gripping means for gripping the mandrel screw at a position circumferentially distant from the first reference point; and circumferentially from the first reference point so as to define a fourth reference point along the mandrel. Fourth screw grip means for gripping the mandrel screw at a position further in the axial direction and further away from the third reference point in the axial direction; measuring means for axially measuring the unloaded state between the reference points; 1 to change the length during compression of the mandrel. First motion detection means for detecting and measuring relative motion between first and second reference points; the third and fourth reference points during compression of the mandrel to determine a second length change Second movement detecting means for detecting and measuring a relative movement between; determining means for determining an average of the first and second length changes;
And E are the modulus of elasticity and A is the stress area based on the screw properties of the mandrel, the determined average length change (dL), the measured unloaded distance (L) and the formula F = dLE
Calculating means for calculating a load force applied to the mandrel using A / L, wherein the first motion detecting means and the second motion detecting means perform the first to fourth motions in a radial direction and an angular direction, respectively. Allowing independent relative movement of the screw gripping means, whereby between the first screw gripping means and the third screw gripping means and between the second screw gripping means and the fourth screw gripping means.
A degree of freedom of movement is provided between the first screw and the screw grip means, the degree of freedom of movement being at least some distance in each of the axial, radial and angular directions. Allowing the distance between the gripping means and the third screw gripping means and the distance between the second screwing gripping means and the fourth screw gripping means to be varied, Apparatus for determining the load on a threaded mandrel that can measure the deformation of the shaft of the threaded mandrel while undergoing all or part of the bending and torsion forces.