WO1997017641A1

WO1997017641A1 - Fluid regulator over-pressure protection device

Info

Publication number: WO1997017641A1
Application number: PCT/US1996/017755
Authority: WO
Inventors: James C. Hawkins; Justin W. Hart
Original assignee: Fisher Controls International, Inc.
Priority date: 1995-11-09
Filing date: 1996-11-06
Publication date: 1997-05-15
Also published as: AU7554296A

Abstract

A fluid regulator includes a fluid inlet, a fluid outlet and a valve (105) disposed between the fluid inlet and the fluid outlet which allows fluid to flow therebetween at a rate related to the position of the valve. A loading element, such as a diaphragm (22), is coupled to the valve through valve linkage (106, 108) disposed on one side of the diaphragm (22) so that movement of the loading element causes movement of the valve (105). An overtravel spring (118) is disposed on the one side of the diaphragm (22) and is coupled between the loading element and the valve linkage (106). This overtravel spring (118) allows the loading element to move relative to the valve linkage (106) when the difference between a force applied to one surface of the loading element and a force applied to an opposite surface of the loasing element reaches a predetermined amount, i.e, in the presence of an over-pressure condition. A stop mechanism (106) stops movement of the loading element when the overtravel spring (118) has allowed the loading element to move a predetermined distance relative to the valve linkage (106).

Description

FLUID REGULATOR OVER-PRESSURE PROTECTION DEVICE

This invention relates generally to fluid pressure regulators and more particularly to an over-pressure protection device for use in a fluid pressure regulator.

BACKGROUND OF THE INVENTION

Fluid pressure regulators, such as gas pressure regulators, are commonly used in fluid pipeline systems to assist in maintaining system load pressures within acceptable limits. The primary function of a gas pressure regulator is to match the flow of gas through the regulator to the demand for gas placed on the system to keep the pressure of the gas downstream of the regulator at a constant pressure or, at least, within acceptable pressure limits.

Many known gas pressure regulators, such as the gas pressure regulator disclosed in Duffy et al. , U.S. Patent No. 5,402,820, include a diaphragm assembly having one side thereof exposed to the downstream gas pressure and having the other side thereof biased by a predetermined pressure produced by an adjustable control spring. In these systems, the diaphragm is coupled to a pivoting lever which, in turn, throttles a valve disk with respect to an orifice so as to communicate gas from a gas inlet of the regulator to a gas outlet of the regulator. In particular, movement of the diaphragm, which is caused by a force differential between pressure exerted by the control spring and pressure exerted by the sensed downstream gas, moves the valve disk with respect to a valve seat to control the amount of gas flow from the gas inlet to the gas outlet. In this manner, the valve disk and orifice operate to provide a variable restriction that modulates the flow of gas through the regulator in accordance with the sensed downstream pressure.

Other known gas regulators, such as pilot operated regulators, include a main actuator diaphragm coupled to valve linkage which opens and closes a main gas valve, wherein one side of the actuator diaphragm is exposed to the downstream gas pressure while the other side of the diaphragm is exposed to a loading pressure developed by a pilot valve assembly. The pilot valve assembly typically modulates the upstream gas pressure to develop the loading pressure. These gas pressure regulators are sensitive to, and can be damaged by, an over-pressure condition which results, for example, when the downstream gas pressure reaches a greater than expected value or becomes greater than the upstream gas pressure. Such an over- pressure condition may occur when the gas pressure regulator is installed incorrectly, e.gr. , backwards, or may occur during a pressure anomaly in the gas pipeline caused, for example, by the release of gas into the pipeline downstream of the pressure regulator. An over-pressure condition may also occur during installation or repair of a pilot operated regulator when the downstream gas pressure is applied or connected to the outlet of the regulator before the upstream gas pressure is applied or connected to the inlet of the regulator. During over-pressure conditions, the downstream pressure acts on the regulator diaphragm to close the regulator valve. However, once the valve has closed, the greater than expected downstream pressure continues to apply force to the diaphragm and, because the diaphragm is at its travel limit, this force is completely absorbed by the diaphragm, the valve linkage and the valve of the regulator. If the downstream gas pressure or the pressure differential between the downstream and upstream gas pressures is great enough, this applied force can bend or break the diaphragm, the valve linkage and/or other components of the valve. Thus, after an over-pressure condition is removed, the regulator must be examined for damage and may have to be replaced. This procedure is time consuming and expensive. Furthermore, if an installer or user is not aware that an over-pressure condition has occurred, continued installation or use of the damaged regulator may cause a safety hazard if the damaged regulator overpressurizes downstream components.

Some prior art pressure regulators include relief mechanisms which prevent damage to the diaphragm and/or valve linkage during an over-pressure condition. For example, Davis et al. , U.S. Patent No. 4,972,868, discloses a regulator relief spring which is disposed on the opposite side of a regulator diaphragm as the valve linkage to which the diaphragm is connected and which biases the diaphragm against a sealing surface of the valve linkage. The valve linkage is movable with respect to the diaphragm such that, during an over- pressure condition, the diaphragm compresses the relief spring and moves away from the sealing surface which, in turn, allows gas to escape from the high pressure side of the diaphragm to the low pressure or atmospheric side of the diaphragm. The gas traveling to the low pressure side of the diaphragm is typically vented to the atmosphere which can be dangerous, impractical or, due to environmental regulations, against the law. A gas pressure regulator manufactured by Fisher Controls International, Inc., identified as the Y690 regulator, and the regulator disclosed in Hughes, U.S. Patent No. 4,069,839, prevent damage to regulator components during an over-pressure condition without venting gas to the atmosphere. These regulators include a diaphragm which is biased against valve linkage by a spring disposed on the opposite side of the diaphragm as the valve linkage. During an over¬ pressure condition, the diaphragm compresses the spring and moves away from the valve linkage until the diaphragm comes into contact with a stop which, thereafter, absorbs the force exerted on the diaphragm. However, an O-ring or other sealing member must be disposed between the diaphragm and the valve linkage to prevent gas from escaping between the high pressure side of the diaphragm and the low pressure or atmospheric side of the diaphragm during the over¬ pressure condition. This O-ring or other sealing member wears with time, especially in the presence of gas, and, therefore, requires periodic replacement or shortens the useful life of the regulator.

SUMMARY OF THE INVENTION

The present invention is directed to an over- pressure protection mechanism for use in a fluid pressure regulator which does not require the venting of a fluid to the atmosphere or the use of 0-rings or other sealing members between the diaphragm and the valve linkage of the regulator. According to one aspect of the invention, a fluid regulator includes a fluid inlet, a fluid outlet and a moveable valve disposed between the fluid inlet and the fluid outlet which allows fluid to flow therebetween at a rate related to the position of the valve. A loading element, such as a diaphragm, is coupled to the valve through valve linkage so that movement of the loading element causes movement of the valve. An over-pressure protection spring disposed on the same side of the diaphragm as the valve linkage is coupled between the loading element and the valve linkage. This over¬ pressure protection spring allows the loading element to move relative to the valve linkage when the difference between a force applied to one side of the loading element and a force applied to the other side of the loading element reaches a predetermined amount, i.e., in the presence of an over-pressure condition. The fluid regulator may include a stop which stops movement of the loading element when the loading element has moved a predetermined distance relative to the valve linkage. According to another aspect of the invention, an over-pressure protection apparatus is adapted for use with a fluid regulator to prevent damage to the fluid regulator during an over-pressure condition. The over- pressure protection apparatus includes a first member, such as a pusher post, rigidly connected to valve linkage of the fluid regulator, a second member, such as a diaphragm post, rigidly connected to a loading element of the fluid regulator and a further member, such as a spring, coupled between the first and second members. The further member allows relevant movement between the first and second members when a force on the first side of the loading element results from an over-pressure condition within the fluid regulator.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages of the present invention will be apparent upon reading the following description in conjunction with the drawings, in which:

Fig. 1 is a side elevational view of a pilot operated gas pressure regulator including an over¬ pressure protection device according to the present invention;

Fig. 2 is a cross-sectional view of a pilot operated gas pressure regulator including an over- pressure protection device according to the present invention;

Fig. 3 illustrates the over-pressure protection device of the present invention during normal operation of the gas pressure regulator of Fig. 2; Fig. 4 illustrates the over-pressure protection device of Fig. 3 during an over-pressure condition;

Fig. 5 illustrates a further view of the over¬ pressure protection device of Fig. 3; Fig. 6 illustrates a further over-pressure protection mechanism of the pilot operated gas pressure regulator of Fig. 2 during normal operation thereof; and

Fig. 7 illustrates the over-pressure protection mechanism of Fig. 6 during an over-pressure condition.

DETAILED DESCRIPTION

Referring now to Fig. 1, a pilot operated pressure regulator 10 includes an actuator spring casing 12 attached to one side of a regulator body 14 by a series of flange screws 16. An actuator diaphragm 18 is disposed between the spring casing 12 and the regulator body 14. A pilot spring casing 20 is attached to the other side of the regulator body 14 by a set of flange screws 24 with a pilot diaphragm 22 disposed between the pilot spring casing 20 and the regulator body 14. Closing caps 26 and 28, which are removable to allow calibration of the pressure regulator 10, are disposed on the actuator spring casing 12 and the pilot spring casing 20, respectively. A lower regulator casing 30 is integrally formed with or connected to the regulator body 14 and couples the regulator body 14 to a fluid pipeline fitting 32. The fitting 32 is adapted to transmit a varying amount of fluid, such as gas, from a gas inlet 34 to a gas outlet 36. A pilot supply tube 38 provides fluid communication between the gas inlet 34 and a gas inlet 40 on a pilot control assembly 41. The pilot control assembly 41 includes a gas outlet 42 which is in fluid communication with a gas inlet 44 on the actuator spring casing 12 through a loading tube 46.

Referring now to Fig. 2, the internal components of the pilot operated pressure regulator 10 are shown in detail wherein, for the sake of illustration, the components of the pilot control assembly 41 have been rotated 90 degrees with respect to Fig. 1. As illustrated in Fig. 2, a main actuator assembly 50 of the regulator 10 includes a loading element in the form of the main actuator diaphragm 18, mounted at its perimeter between the regulator body 14 and the actuator spring casing 12, and a diaphragm plate 54 mounted to a central portion of the diaphragm 18.

A pusher post 56 is disposed on one side of the diaphragm plate 54 and threadably engages a diaphragm post 58 inserted through a suitable aperture in the diaphragm plate 54 and the diaphragm 18. The diaphragm post 58 slidably engages the diaphragm plate 54 so that the pusher post 56 and the diaphragm post 58 are moveable with respect to the diaphragm 18 and the diaphragm plate 54. The diaphragm post 58 includes a threaded end 60 upon which a spring seat 62 and a set of locking nuts 64 are mounted. A closing spring 66 is disposed between the spring seat 62 and a section of the actuator spring casing 12 to bias the regulator 10 in a closed position, as described hereinafter. A pressure equalization spring 68 is disposed between the diaphragm plate 54 and a spring seat 70 on the diaphragm post 58. The pressure equalization spring 68 biases the diaphragm plate 54 against a sealing surface 69 of the pusher post 56.

A lever assembly includes a pivoting actuator lever 72 connected to a bracket 74 at a pivot point 76. The actuator lever 72 is drivingly engaged with an end of the pusher post 56 and moves a valve stem 78 and a main valve disk 80 towards or away from a valve seat 82. The valve seat 82 is formed on the end of a passageway connecting a gas inlet chamber 84 to a gas outlet chamber 86. As a result, movement of the diaphragm 18 and the diaphragm plate 54 causes movement of the valve linkage comprising the pusher post 56, the actuator lever 72 and the valve stem 78 which, in turn, moves the valve disk 80 towards or away from the valve seat 82. Movement of the valve disk 80 away from the valve seat 82, i.e., to the regulator open position, enables fluid flow between the gas inlet 34 and the gas outlet 36 in an amount dependent upon the position of the diaphragm 18 and the diaphragm plate 54.

The closing spring 66 biases the diaphragm post 58, the pusher post 56, the diaphragm 18 and the diaphragm plate 54 to the position illustrated in Fig. 2 in which the valve disk 80 contacts the valve seat 82, i.e., the closed position of the regulator 10. The amount of pressure applied by the closing spring 66 can be calibrated using the threaded end 60 of the diaphragm post 58. The gas outlet chamber 86 is in fluid communication with a chamber 90 via passageways 92. As a result, a force acts on the diaphragm 18 and the diaphragm plate 54 in an amount dependent upon the pressure of the gas in the gas outlet chamber 86, i.e., the downstream gas pressure. Furthermore, the gas within a fluid loading chamber 94 creates a force on the opposite side of the diaphragm 18 and the diaphragm plate 54. The pressure of the gas within the loading chamber 94 is controlled by the pilot control assembly 41 via the loading tube 46.

The pilot control assembly 41 includes a loading element in the form of the pilot diaphragm 22, mounted at its perimeter between the regulator body 14 and the pilot spring casing 20, and a diaphragm plate 96 disposed on one side of the pilot diaphragm 22. A set spring 98 is disposed between the diaphragm plate 96 and a spring seat 100 and supplies a control pressure to one side of the pilot diaphragm 22 and the diaphragm plate 96. The amount of pressure applied by the set spring 98 against the diaphragm 22 can be adjusted using an adjusting screw 102 disposed beneath the closing cap 28.

A diaphragm post 104 is rigidly mounted to the diaphragm 22 and the diaphragm plate 96 and is sealingly engaged therewith. The diaphragm post 104 is movably coupled to a pilot valve disk 105 through valve linkage including a pusher post 106, a pilot actuator lever 108 which pivots on a pivot pin 109, and a pilot actuator stem 110. Movement of the diaphragm 22 and the diaphragm plate 96 causes movement of the pusher post 106, the actuator lever 108 and the valve stem 110 which, in turn, moves the valve disk 105 towards or away from a valve seat 112. The valve seat 112 forms an aperture between the gas inlet 40 and the gas outlet 42 of the pilot control assembly 41.

As indicated in Fig. 2, one side of the pilot diaphragm 22 is exposed through an aperture 114 to the downstream gas pressure in the chamber 90 while the other side of the diaphragm 22 is biased towards the main actuator assembly 50 by the set spring 98. When the control force exerted on the diaphragm 22 by the set spring 98 exceeds the force exerted on the diaphragm 22 by the downstream gas in the chamber 90 (indicating that the downstream gas pressure is less than the control pressure) , the set spring 98 forces the diaphragm 22 to move the pilot valve disk 105 away from the valve seat 112. Thereafter, gas flows from the gas inlet chamber 84 of the fitting 32, through the pilot supply tube 38 and the gas inlet 40 to the gas outlet 42 of the pilot control assembly 41. Thereafter, gas flows through the loading tube 46 and into the loading chamber 94. In this manner, the pressure in the loading chamber 94 is determined by the control pressure exerted on the diaphragm 22 by the set spring 98 and the pressure of the gas in the gas inlet chamber 84 of the regulator 10.

When the force exerted on the diaphragm 18 by the gas in the loading chamber 94 overcomes the force exerted on the diaphragm 18 by the closing spring 66 and the gas in the chamber 90, the diaphragm 18 moves towards the pilot control assembly 41 and thereby, moves the main valve disk 80 away from the valve seat 82. This action, in turn, allows gas to flow from the gas inlet 34 to the gas outlet 36 which increases the pressure of the gas within the chamber 86 and, therefore, the pressure of the gas within the chamber 90.

When the gas in the chamber 90 reaches the control pressure, it overcomes the force exerted on the pilot diaphragm 22 by the set spring 98 and forces the diaphragm 22 to move the pilot valve disk 105 against the valve seat 112 which, in turn, prevents further gas from entering the loading chamber 94. Thereafter, the pressure in the loading chamber 94 bleeds off into the chamber 90 through a bleed hole 115. When the pressure of the gas in the loading chamber 94 equalizes with the pressure of the downstream gas in the chamber 90, the closing spring 66 moves the diaphragm 18 away from the pilot control assembly 41 and, thereby, closes the main valve disk 80 against the valve seat 82 which, in turn, prevents further gas flow between the gas inlet 34 and gas outlet 36.

A check valve includes a check valve spring 116 which biases a check valve plug 117 against a stop.

The check valve is disposed between the chamber 90 and the gas outlet 42 of the pilot control assembly 41 and operates to dissipate gas from the loading chamber 94 into the chamber 90 when the differential between pressure in the loading chamber 94 and the chamber 90 becomes too great.

The configuration of the pilot operated pressure regulator 10 as described herein enables precise control of the gas flow in a pipeline and provides gas from the regulator inlet 34 to the regulator outlet 36 more quickly in response to a load demand. In effect, the pilot control assembly 41 operates as an amplifier which increases the response time of the pressure regulator 10 in the presence of a load demand and, thereby, provides downstream gas at a desired pressure in a more consistent manner.

An over-pressure condition occurs in the regulator 10 when, for example, the pressure of the gas within the gas outlet chamber 86 is a predetermined amount greater than the pressure of the gas within the gas inlet chamber 84 or is otherwise greater than expected such that the force exerted by the gas in the chamber 90 on the pilot diaphragm 22 is a predetermined amount greater than the force exerted on the pilot diaphragm 22 by the set spring 98. During an over-pressure condition, pressure within the chamber 90 forces the pilot diaphragm 22 to compress the set spring 98 until the valve disk 105 comes into contact with the valve seat 112.

Without protection, the force exerted on the diaphragm 22 during an over-pressure condition would, thereafter, be absorbed by that diaphragm, the diaphragm plate and the valve linkage comprising the pusher post, the actuator lever, the valve stem and the valve disk associated the pilot control assembly 41. Such action may cause any or all of these components to bend, break or otherwise become damaged in a way which would prevent or degrade the future operation of the regulator 10. However, as explained hereinafter, the pressure regulator 10 of Fig. 2 is protected from damage during an over-pressure condition because the diaphragms thereof are capable of moving with respect to the valve linkage associated with these diaphragms during an over-pressure condition.

As illustrated in Fig. 3, the pilot control assembly 41 includes an overtravel spring 118 disposed between a spring seat 120 formed on an end of the pusher post 106 and a spring seat 122 formed on an end of the diaphragm post 104. During normal operation of the regulator 10, i.e., in the absence of an over¬ pressure condition, the overtravel spring 118 forces the spring seat 120 into contact with a seating surface 123 of the diaphragm post 104 so that the diaphragm 22 and diaphragm plate 96 move in one-to-one correspondence with the pusher post 106.

During an over-pressure condition, the diaphragm 22 and the diaphragm plate 96 compress the set spring 98 until the valve disk 105 contacts the valve seat 112. Thereafter, as illustrated in Fig. 4, the diaphragm 22 and the diaphragm plate 96 begin to compress the overtravel spring 118, causing movement between the spring seat 120 of the pusher post 106 and the spring seat 122 of the diaphragm post 104, until the diaphragm plate 96 comes into contact with one or more travel stops 124 which may, for example, be integrally formed with the pilot spring casing 20. Thereafter, the force imparted to the diaphragm 22 and the diaphragm plate 96 is absorbed by the travel stop 124 instead of the valve linkage associated with the diaphragm 22. As illustrated in Fig. 4, the diaphragm plate 96 reaches the stop 124 before the overtravel spring 118 reaches its compression limit.

When the over-pressure condition is removed, the overtravel spring 118 forces the spring seat 120 of the pusher post 106 away from the spring seat 122 of the diaphragm post 104 until the spring seat 120 contacts the seating surface 123 of the diaphragm post 104. Thereafter, normal operation of the pressure regulator occurs.

As illustrated in Fig. 5, which depicts the components of the pilot control assembly 41 of Fig. 4 rotated by 90 degrees, the pusher post 106 includes two generally L-shaped leg portions 126 and 127 connected so as to form a channel or aperture therebetween through which the diaphragm post 104 is disposed.

Referring now to Figs. 6 and 7, the operation of the pressure equalization spring 68 associated with the actuator diaphragm 18 will be described. As illustrated in Fig. 6, during normal operation of the regulator 10, the diaphragm 18 and the diaphragm plate 54 are biased against the sealing surface 69 of the pusher post 56 by the pressure equalization spring 68. Because the diaphragm plate 54 is sealingly engaged with the sealing surface 69, gas cannot travel from one side of the diaphragm 18 to the other side of the diaphragm 18, i.e., between the chambers 90 and 94.

During an over-pressure condition, the gas in the chamber 90 forces the diaphragm plate 54 in the closing direction until the pusher post 56 reaches its travel limit, i.e., the valve disk 80 of Fig. 2 contacts the valve seat 82. Thereafter, as illustrated in Fig. 7, the force on the diaphragm plate 54 generated by the over-pressure condition causes the diaphragm plate 54 to compress the pressure equalization spring 68 and move away from the sealing surface 69 until the diaphragm plate 54 comes into contact with one or more travel stops 130 which may, for example, be integrally formed with the actuator spring casing 12. Simultaneously, pressure between the chamber 90 and the loading chamber 94 equalizes due to the flow of gas past the sealing surface 69 and through the aperture in the diaphragm 18 and the diaphragm plate 54 through which the diaphragm post 58 is inserted. Although the over-pressure protection mechanism having a spring disposed between a diaphragm and valve linkage has been illustrated in Figs. 2-5 for use in the pilot control assembly of a pilot operated gas pressure regulator, this over-pressure protection configuration can be used in any other desired type of fluid pressure regulator such as a pressure regulator having only a single diaphragm assembly. The over¬ pressure protection mechanism illustrated in Figs. 3-5 could, for example, also be used between the diaphragm 18 and the pusher post 56 of the main actuator assembly 50.

Furthermore, although the over-pressure protection mechanism of the present invention has been described as including a spring disposed between a diaphragm and valve linkage to allow movement therebetween during an over-pressure condition, any other desired components which act to bias valve linkage and a diaphragm (or other loading element) against one another during normal operation of a regulator but which allow movement therebetween during an over-pressure condition can be used instead. Still further, although the loading element used with the present invention has been described as a diaphragm and a diaphragm plate assembly, the inventive over-pressure protection mechanism can also be used with a loading element comprising a diaphragm only, or any other desired loading element such as a piston, bellows, etc.

The foregoing detailed description has been given for clearness of understanding only and no unnecessary limitations should be understood therefrom, as modifications will be obvious to those skilled in the art.

Claims

1. A fluid regulator comprising: a fluid inlet; a fluid outlet; a valve disposed between the fluid inlet and the fluid outlet which allows fluid to flow therebetween at a rate related to the position of the valve; a loading element having one of a first side and a second side facing a chamber; valve linkage disposed in the chamber which couples the valve to the loading element so that movement of the loading element causes movement of the valve; means for applying a first force to the first side of the loading element; means for applying a second force to the second side of the loading element; and means disposed in the chamber and coupled between the loading element and the valve linkage for allowing the loading element to move relative to the valve linkage when the difference between the first force and the second force reaches a predetermined amount.

2. The fluid regulator of claim 1, wherein the allowing means comprises a spring.

3. The fluid regulator of claim 1, wherein the valve linkage includes a pusher post, wherein the loading element includes a diaphragm having a diaphragm post, and wherein the allowing means comprises a spring disposed between the pusher post and the diaphragm post.

4. The fluid regulator of claim 3, wherein the diaphragm post extends through an aperture in the pusher post and the spring compresses when the difference between the first and second forces reaches the predetermined amount to enable movement of the diaphragm post with respect to the pusher post.

5. The fluid regulator of claim 4, wherein the diaphragm post includes a seating surface and the spring biases the pusher post against the seating surface when the difference between the first and second forces has not reached the predetermined amount.

6. The fluid regulator of claim 1, further comprising stop means for stopping movement of the loading element when the allowing means has allowed the loading element to move a predetermined distance relative to the valve linkage.

7. The fluid regulator of claim 1, wherein one of the first and second force applying means comprises a spring.

8. The fluid regulator of claim 1, wherein one of the first and second force applying means comprises a fluid chamber adapted to receive a pressurized fluid.

9. An over-pressure protection apparatus adapted for use with a fluid regulator having a loading element coupled to a valve through valve linkage adjacent one side of the loading element, wherein the loading element is adapted to move the valve linkage and the valve in response to a force caused by pressure on the loading element, the over-pressure protection apparatus comprising: a first member rigidly connected to the valve linkage on the one side of the loading element; a second member rigidly connected to the loading element and disposed on the one side of the loading elemen ; and means coupled between the first and second members for allowing relevant movement between the first and second members when the force on the loading element results from an over-pressure condition within the fluid regulator.

10. The over-pressure protection apparatus of claim 9, wherein the allowing means comprises a spring.

11. The over-pressure protection apparatus of claim 9, wherein the first member comprises a pusher post including a spring seat thereon, the second member comprises a diaphragm post having a further spring seat thereon and wherein the allowing means comprises a spring disposed between the spring seat of the pusher post and the further spring seat of the diaphragm post.

12. The over-pressure protection apparatus of claim 11, wherein pusher post includes a surface having an aperture therein, the diaphragm post extends through the aperture and the spring is adapted to compress when the force on the loading element results from an over¬ pressure condition to enable movement of the diaphragm post with respect to the pusher post.

13. The over-pressure protection apparatus of claim 12, wherein the diaphragm post includes a seating surface and the spring biases the pusher post against the seating surface when the force on the loading element does not result from an over-pressure condition.

14. The over-pressure protection apparatus of claim 9, further including a stop adapted to stop movement of the loading element when the first and second members have moved a predetermined distance with respect to one another.

15. An over-pressure protection apparatus adapted for use with a fluid regulator having a fluid inlet, a fluid outlet and a valve operable to communicate a varying amount of a fluid between the fluid inlet and the fluid outlet, comprising: a moveable loading element having a surface in fluid communication with one of the fluid inlet and the fluid outlet; valve linkage disposed on one side of the loading element and coupled between the loading element and the valve which is adapted to move the valve in response to movement of the loading element; a first member rigidly connected to the valve linkage and disposed on the one side of the loading element; a second member rigidly connected to the loading element and disposed on the one side of the loading element; and means coupled between the first and second members for allowing relevant movement between the first and second members during an over-pressure condition

16. The over-pressure protection apparatus of claim 15, wherein the surface of the loading element is in fluid communication with the fluid outlet.

17. The over-pressure protection apparatus of claim 15, wherein the allowing means comprises a spring.

18. The over-pressure protection apparatus of claim 15, wherein the first member comprises a pusher post including a spring seat thereon, the second member comprises a diaphragm post having a further spring seat thereon and wherein the allowing means comprises a spring disposed between the spring seat of the pusher post and the further spring seat of the diaphragm post.

19. The over-pressure protection apparatus of claim 18, wherein pusher post includes a surface having an aperture therein, the diaphragm post extends through the aperture and the spring compresses during an over¬ pressure condition to enable movement of the diaphragm post with respect to the pusher post.

20. The over-pressure protection apparatus of claim 15, further including a stop adapted to stop movement of the loading element when the first member has moved a predetermined distance with respect to the second member.

21. A pilot operated fluid regulator which is protected from damage during an over-pressure condition, comprising; a fluid inlet; a fluid outlet; a valve adapted to control the flow of a first fluid between the fluid inlet and the fluid outlet; a first chamber in fluid communication with the fluid outlet; a second chamber; a diaphragm which separates the first chamber and second chamber and which is coupled to the valve such that movement of the diaphragm operates the valve; and means for controlling the pressure of a further fluid in the second chamber, including; a control valve which controls the flow of the further fluid into the second chamber, control valve linkage coupled to the control valve, a control diaphragm having a side exposed to the fluid at the fluid outlet and coupled to the control valve linkage such that movement of the control diaphragm operates the control valve, and means coupled between the control diaphragm and the control valve linkage for allowing the control diaphragm to move relative to the control valve linkage during an over-pressure condition.

22. The pilot operated fluid regulator of claim 21, wherein the allowing means comprises a spring.

23. The pilot operated fluid regulator of claim 21, wherein the control valve linkage includes a pusher post, the control diaphragm includes a diaphragm post and the allowing means comprises a spring disposed between the pusher post and the diaphragm post.

24. The pilot operated fluid regulator of claim 23, further comprising stop means for stopping movement of the control diaphragm when the allowing means has allowed the control diaphragm to move a predetermined distance relative to the control valve linkage.

25. The pilot operated fluid regulator of claim 21, wherein the diaphragm includes an aperture therein and the valve includes valve linkage having a sealing surface, and further including a spring which biases the diaphragm against the sealing surface to seal the aperture in the absence of an over-pressure condition and which allows movement of the diaphragm away from the sealing surface to allow fluid to travel through the aperture from the first chamber to the second chamber during an over-pressure condition.

26. The pilot operated fluid regulator of claim 25, further including a stop which stops movement of the diaphragm during an over-pressure condition after the diaphragm has moved away from the sealing surface.