US3863672A

US3863672A - Dual action pilot

Info

Publication number: US3863672A
Authority: US
Inventors: Gerold F Theriot; Frank M Hoofnagle
Original assignee: BWB Controls Inc
Current assignee: BWB Controls Inc
Priority date: 1973-09-06
Filing date: 1973-09-06
Publication date: 1975-02-04
Anticipated expiration: 1992-02-04

Abstract

A dual action high-low pressure sensing pilot valve comprising an elongated valve body incorporating a single pressure receiving piston and a pair of independently adjustable compression spring biased valve actuating pistons selectively operable by the single pressure piston.

Description

United States Patent [1 1 [111 3,863,672

Theriot et al. Feb. 4, 1975 [5 DUAL ACTION PILOT 3.7mm 2/1973 Peters .1 |37/596.18 ux 751 Inventors: Gerald F. Theriot, Bourg; Frank M. 46947 M973 Pete Hool'nagle, Houma, both of La. Primary Examiner-Alan Cohan [73] Assignee. B.W.B. Controls, Inc., Houma, La. Assismm Examiner Grald A. Michalsky [22] Filed: Sept. 6, 1973 [2]] App]. No.: 394,850

[ ABSTRACT [52] U.S. Cl. l37/596.l8, 137/458 A dual action higmow pressure sensing pilot valve [51] Ill". Cl. FlSb 13/042 p i g an elongated valve y incorporating a [58] F'eld Search 137/458 59614159618 single pressure receiving piston and a pair of indepen- 137/625'66 dently adjustable compression spring biased valve ac- 1 References Cited gulzrlirggispstons selectively operable by the single pres- UNITED STATES PATENTS 3,621,881 11/1971 Vicari 137/625.66 7 Claims, 4 Drawing Figures Adi/afar Remy Actuator g I ,82 Supp y 22 "72 Control 1 Flu/d Sensing Pressure PIJENYEU 41975 SHEET 1 [1F 2 Fig.

Pneumatic e/ay Acfuaror Acfuafor Out ng Pressure pp y SEEEI P m PATENIEB FEB 41975 I M 8 6 M II Fig.3 56

DUAL ACTION PILOT The present invention relates to new and useful improvements in dual action pilot valves of the type utilized within the safety system of a petroleum producing platform and the like specifically for the purpose of assuring that pressure is maintained within a predetermined range.

The valve herein is generally of the type disclosed in US. Pat. No. 3,621,881 and operates in a similar environment controlling the supply of control fluid to a remotely located actuator.

To those familiar with dual action pilot valves, it is well appreciated that such pressure sensing valves are judged largely on their sensitivity. Sensitivity here describes not only the accuracy with which the pilot consistently senses and controls pressure, but also the amount of pressure which the pilot requires to put it into its operating range (in service) as opposed to that which takes it out of its operating range (out of service). As an example, if it takes 1,200 psi in order to put a pilot set at 800 psi low in service, and it is desired that the high range barrier be set at l,200 psi high, then the pilot would be useless. It would be out of service on high before it could come in service on low. The failure to, thus far, achieve a successful dual action pilot has been due primarily to the insensitivity of the pilots heretofore devised. The sensitivity enjoyed by single acting pilots seemed, prior to the instant invention, out of reach by one which controls both high and low pressures.

The instant invention, contrary to the prior art dual action pilots, as for example exemplified in US. Pat. No. 3,621,881, has a sensitivity equivalent to that of a single pilot, basically because it in operation actually works as two independent single pilots, each of which is adjustable completely independently of the other, contrary to the above noted patent wherein adjustment of the high range setting is specifically dependent upon the adjustment of the low range setting. In addition, the valve of the present invention utilizes only a single pressure piston which controls movement of both the low pressure piston and the high pressure piston in a smooth and positive manner.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.

FIG. I is an enlarged cross-sectional view through the dual action pilot valve in its low pressure shut-in position;

FIG. 2 is a cross-sectional detail taken substantially on a plane passing along line 2-2 in HO. 1;

FIG. 3 is a cross-sectional view through the valve with the components therein orientated in the position assumed when the line pressure is within the desired range; and

FIG, 4 is a similar cross-sectional view wherein the components are within the position assumed when the pressure exceeds the upper range limit causing a high pressure shut-in of the well or the like.

Referring now more specifically to the drawings, reference numeral is used to generally designate the pilot valve comprising the invention. This valve 10 includes an elongated valve body 12 having a centrally located elongated bore 14 terminating at its upper end in a substantially enlarged spring chamber 16, and at its lower end into an enlarged pressure chamber 18.

A control fluid inlet port 20 is provided inward or downward from the spring chamber 16 with a first bleed port 22 located below the inlet port 20 and a control fluid outlet port 24 located below the bleed port 22. A second bleed port 26 communicates with the top of the pressure chamber 18 at the adjoining end of the bore 14. All of these ports will normally extend laterally through the valve body 12. A pressure inlet port 28 is provided in the lower end of the body 12 and communicates directly with the pressure chamber l8 through a bore 30 having a diameter substantially reduced relative to that of the pressure chamber 18. This lower end of the body is specifically adapted to be screwed into a pressure line whenever it is desired that the pressure be sensed.

An elongated sleeve-like outer piston 32 is slidably positioned within the bore 14 and of a sufficiently smaller outer diameter than the inner diameter of the bore [4 so as to provide for positive fluid passages therebetween. The piston 32 is of a greater length than the bore and terminates, at its upper end, in an outwardly enlarged spring seating head 34 which receives the lower end of an expanded coil compression spring 36, the upper end of which bears against a spring retaining ring 38 adjustably threaded within the upper internal portion of the spring chamber 16 whereby a variation or adjustment of the compressive force of the spring 36 can be easily effected. An adjustable stop, in the nature of an elongated sleeve 40, is threadedly received within the spring chamber 16 in surrounding relation to the compression spring 36 and presents a lower edge in spaced relation above the spring retaining head portion 34 so as to constitute a stop therefor upon an upward shifting of the outer piston 32.

An elongated inner piston 42, of a greater length than the outer piston 32, is slidably received therein and of a size so as to define fluid passage means therebetween. The upper end of the piston 42 is, immediately above the spring chamber received enlarged head 34 of the outer piston 32, provided with an enlarged spring seating head portion 44 which receives and seats the lower end of an expanded coil compression spring 46. The upper end of the spring 46 is retained by a vertically adjustable spring retaining member 48 threadedly received within and vertically adjustable relative to a plug 50 closing the upper end of an elongated sleeve 52 rising from the piston member head 34 between the

springs

46 and 36. The upper end of the spring chamber 16 is closed by a threaded plug 54 including a central cavity 56 therein which receives the upper manipulating end of the upper spring retainer 48. Appropriate pressure bleed

ports

58 and 60 are provided within the sleeve member 52 and the wall of the spring chamber 16 so as to preclude the buildup of any pressure therein such as could affect the adjustment or sensitivity of the valve. It will be noted that the downward movement of the inner piston 42 under the pressure of the associated spring 46 is limited by engagement of the retaining head 44 against the retaining head 34 of the outer piston. The spring-biased downward movement of the outer piston 32 is in turnlimited by the engagement of the head portion 34 thereof against the lower end wall of the spring chamber 16. It should also be appreciated that the inner spring 46 is of a substantially greater rigidity than the outer spring 36 whereby a compression of the outer spring 36 will be effected prior to that of the inner spring 46.

Positioned within the pressure chamber 18 is a pressure piston 62 from which depends an integral shank or stem 64 into the bore 30 leading from the inlet port 28 to the pressure chamber 18. The piston 62 and stem 64 form an integral pressure receiving member having two pressure receiving faces, one of which is designated by reference numeral 66 and constitutes the lower face of the piston 62, and the other of which, designated by reference numeral 68, constitutes the lower face of the stem 64.

With reference to FIG. 1 in particular, the valve unit has been illustrated therein in the low pressure shut-in position resulting from a line pressure, sensed through inlet port 28, which has dropped below the low range limit allowing the

springs

36 and 46 to fully expand so as to position the

pistons

32 and 42 at their lower extremities. In this position, it will be noted that the outer position 32 projects into the pressure chamber l8 with the inner piston 42 projecting even further into the pressure chamber 18 beyond the outer piston. The lower pressure receiving member is also seated at its lower extremity.

The outer piston 32 mounts four O-ring seals which slidably engage the wall of the bore 14 while retaining an effective seal therewith. Assuming the position of FIG. l, the upper seal 70 is orientated above the inlet port 20, the second seal 72 is located below the inlet port 20, the third seal 74 is provided below the outlet port 24, and the fourth seal 76 is provided toward the lower end of the bore 14.

The inner piston 42 is provided with two O-ring seals. The upper seal, designated by reference numeral 78, is provided between the first and

second seals

70 and 72 of the outer piston. The second O-ring seal mounted on the inner piston 42, designated by reference numeral 80, is provided between the third and fourth

outer piston seals

74 and 76.

An upper fluid port 82 is provided through the outer piston 32 so as to communicate the bore 14 with the passage between the pistons. This fluid port 82 is provided, again in the position of FIG. 1, between the upper seal 78 of the inner piston 42 and the second seal 72 of the outer piston 32. A second fluid port 84 is provided through the outer piston 32 between the seal 74 of the outer piston and the seal 80 of the inner piston.

With the arrangement of the pistons as in FIG. 1, such being the low pressure sensed position, it will be noted that the outlet 24 is directly communicated with the bleed port 22 allowing a bleed off of pressure of everything down line of the pilot. By the same token, the control fluid inlet 20, while communicating with the

fluid ports

82 and 84, is sealed off from the outlet port 24.

With reference to FIG. 3, when the line pressure is within the desired range, the piston member 62 is forced upwardly. The substantially greater rigidity of the inner spring 46 retains the spring retaining enlarged head 44 of the inner piston 42 against the enlarged spring retaining or seating head 34 of the outer piston 32 while the relatively weaker outer spring 36 compresses under the introduced force resulting in movement of the inner and outer pistons as a unit. Upon an upward shifting of the outer and

inner pistons

32 and 42 as a unit, the upper fluid port 82 remains in communication with the inlet port while the outer piston sealing ring 74 is shifted upwardly between the outlet port 24 and the bleed port 22, bringing the fluid port 84 into communication with the outlet port 24 while still retaining communication between the

fluid ports

82 and 84. This, as will be readily appreciated, provides for a through communication between the inlet port 20 and the outlet port 24 while precluding communication between the outlet port 24 and the bleed port 22. With this arrangement, the control fluid passes freely through the pilot allowing the system to operate within the desired range. lt will be appreciated that in the position of FIG. 3, the force acts solely against the compression spring 36 with an adjustment of the force required thereon being easily effected through an adjustment of the thread mounted ring 38. The inner spring 46 remains uncompressed and acts somewhat in the manner, at this stage, of a rigid member interconnecting the inner and outer pistons.

FIG. 4 illustrates the high pressure shut-in position which occurs when the sensing pressure exceeds the upper range limit. When this occurs, the plug 50 or a spacer 86 thereon being seated against the upper cap 54, the spring 46 compresses through an upward movement of the inner piston 42 relative to the outer piston 32 resulting from the substantially increased pressure on the pressure piston 62. Upon such an increase in pressure occurring. the lower seal of the inner piston 42 shifts upwardly to lie between the

fluid ports

82 and 84, thereby terminating communication therebetween and sealing off the control fluid from the inlet port 20 to the outlet port 24. At the same time, the outlet port 24 is communicated, through the fluid port 84, with the lower bleed port 26 for a bleeding of the down line pressure. It should be appreciated that in moving from the desired range to beyond the high pressure limit, the sensing pressure, through the

pistons

62 and 42, acts only against the inner spring 46 with an adjustment of the high pressure range being easily effected through an adjustment of the compressive force of the inner spring 46 through the upper adjustable retainer 48. This adjustment, as well as the effect thereof, is completely independent of the low range compression spring 36 and the adjustment thereof.

The valve unit of the invention presents other distinctive and highly advantageous improvements. For example, the unit can be used for both low pressure (0 to 250 psi) and high pressure (l00 to 2,700 psi) systems. In connection therewith, it will be noted that the pressure piston 62 includes a sealing O-ring 88 about the enlarged pressure chamber receiving head thereof while a similar sealing O-ring 90 is provided about the lower end of the bore receiving stem 64. For a low pressure system, the O-ring 90 is removed which allows the incoming pressure to act upon the larger effective area of the pressure receiving surface 66. For a high pressure system, the O-ring 90 is retained and the O-ring 88 removed, thereby allowing the pressure to act upon a much smaller effective area as designated by the sur face 68. For ultra-high pressure systems (2,500 to 5,000 psi), a special base section with a smaller pressure piston can be used. In this connection, it will be noted that the entire base section, designated by reference numeral 92, is threaded on the lower end of the main body portion of the valve unit. Incidentally, the base portion also includes an easily accessible test port 94 and plug 96.

Also of significance in connection with the instant invention is the fact that a single pressure piston transmits the operating force to activate the valve portion of the device for both low and high range settings. This feature has two specific advantages which increase the sensitivity of the unit. First, there is a substantial reduction of wall friction since only a single O-ring is used, either the ring 88 or the ring 90. Secondly, the use of a single pressure piston insures that the force transmitted to the valve portion of the pilot increases uniformly and linearly with respect to an increase in the sensed pressure. This, in conjunction with the completely independent low and high range compression members, allows the pilot to be set so that the low and high range pressure settings are in relatively close tolerance of each other, even at high pressure ranges. This would be impossible, in for example, the unit shown in US. Pat. No. 3,621,881 in that the unit therein incorporates a radically reduced effective area on which the sensing pressure acts on the high range pressure piston. This means that it would require a considerably greater pressure acting against the high pressure piston to provide the same amount of force as that acting against the low pressure piston. Secondly, the high pressure piston of the patent mechanism must act against both the low and high range compression members, requiring a much greater force and a much higher pressure. This in turn would make close range settings for low and high sensing impossible.

Finally, the pilot of the present invention is a safe unit that can be worked on under pressure if necessary. In connection therewith, it will be noted that the pressure piston can travel no further upward than the top of the pressure chamber 18. Further, should any pressure he somehow trapped above the pressure piston, such pressure would bleed out of the bleed port at the top of the pressure chamber.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

What is claimed as new is as follows:

1. A pilot valve comprising a valve body, a bore within said body, first and second valve pistons movably disposed within said bore, said pistons being movable both as a unit and independently of each other, a control fluid inlet in communication with said bore, a control fluid outlet in communication with said bore, a control fluid bleed port, a pressure sensing inlet in said body, biasing means biasing said first and second valve pistons to a first position responsive to sensing of pressure below a predetermined minimum pressure where said control fluid inlet is blocked and said control fluid outlet is communicated with said bleed port, pressure means moving said first and second valve pistons as a unit to a second position responsive to the sensing of a predetermined pressure at said pressure sensing inlet, at which second position said control fluid inlet is communicated with said control fluid outlet and said bleed port is blocked, said biasing means comprises first and second compression springs respectively associated with said first and second valve pistons, the second spring being of greater rigidity than the first spring and maintaining said second piston in a fixed position relative to said first piston in said first and second positions, the first spring controlling movement of said first and second pistons as a unit from the first to the second po' sition, said pressure means moving said first and second valve pistons to a third position responsive to sensing an excess of pressure at said pressure sensing inlet thereby causing a blocking of said control fluid inlet, said pressure sensing means comprising a unitary pressure piston positioned inwardly of said pressure sensing inlet and operatively engaged with said valve pistons, and including means for independently adjusting the biasing force of the first spring without affecting the force required to move the second piston from the second piston to the third position.

2. The pilot valve of claim 1 including means for independently adjusting the biasing force of the second spring without affecting the force required to move the first and second pistons as a unit from the first position to the second position.

3. The pilot valve of claim 2 wherein said first piston comprises an elongated sleeve engaged at one end by the associated first spring and having a second end aligned with said pressure sensing inlet and said pressure piston, said second piston extending through said first piston and being engaged by the associated second spring at the end thereof corresponding to the spring engaged end of the first piston, abutment means limiting the spring induced movement of the second piston relative to the first piston, the second end of the second piston projecting beyond the second end of the first piston for engagement with the pressure piston.

4. The pilot valve of claim 3 wherein said pressure piston presents different size alternatively usable pressure receiving faces.

5. The pilot valve of claim 1 wherein said first piston comprises an elongated sleeve engaged at one end by the associated first spring and having a second end aligned with said pressure sensing inlet and said pressure piston, said second piston extending through said first piston and being engaged by the associated second spring at the end thereof corresponding to the spring engaged end of the first piston, abutment means limiting the spring induced movement of the second piston relative to the first piston, the second end of the second piston projecting beyond the second end of the first piston for engagement with the pressure piston.

6. A pilot valve comprising a valve body, a bore within said body, first and second valve pistons movably disposed within said bore, a control fluid inlet in communication with said bore, a control fluid outlet in communication with said bore, a control fluid bleed port, a pressure sensing inlet in said body, biasing means biasing said first and second valve pistons to a first position responsive to sensing of pressure below a predetermined minimum pressure where said control fluid inlet is blocked and said control fluid outlet is communicated with said bleed port, pressure means moving said first and second valve pistons as a unit to a second position responsive to the sensing of a predetermined pressure at said pressure sensing inlet where said control fluid inlet is communicated with said control fluid outlet and said bleed port is blocked, said pressure means moving said first and second valve pistons to a third position responsive to sensing of excess pressure at said pressure sensing inlet causing a blocking of said control fluid inlet, said biasing means comrequired to move the second piston from the second position to the'third position.

7. The pilot valve of claim 6 including means for independently adjusting the biasing force of the second spring without affecting the force required to move the first and second pistons as a unit from the first position to the second position.

l t 1 It fl

Claims

1. A pilot valve comprising a valve body, a bore within said body, first and second valve pistons movably disposed within said bore, said pistons being movable both as a unit and independently of each other, a control fluid inlet in communication with said bore, a control fluid outlet in communication with said bore, a control fluid bleed port, a pressure sensing inlet in said body, biasing means biasing said first and second valve pistons to a first position responsive to sensing of pressure below a predetermined minimum pressure where said control fluid inlet is blocked and said control fluid outlet is communicated with said bleed port, pressure means moving said first and second valve pistons as a unit to a second position responsive to the sensing of a predetermined pressure at said pressure sensing inlet, at which second position said control fluid inlet is communicated with said control fluid outlet and said bleed port is blocked, said biasing means comprises first and second compression springs respectively associated with said first and second valve pistons, the second spring being of greater rigidity than the first spring and maintaining said second piston in a fixed position relative to said first piston in said first and second positions, the first spring controlling movement of said first and second pistons as a unit from the first to the second position, said pressure means moving said first and second valve pistons to a third position responsive to sensing an excess of pressure at said pressure sensing inlet thereby causing a blocking of said control fluid inlet, said pressure sensing means comprising a unitary pressure piston positioned inwardly of said pressure sensing inlet and operatively engaged with said valve pistons, and including means for independently adjusting the biasing force of the first spring without affecting the force required to move the second piston from the second piston to the third position.

6. A pilot valve comprising a valve body, a bore within said body, first and second valve pistons movably disposed within said bore, a control fluid inlet in communication with said bore, a control fluid outlet in communication with said bore, a control fluid bleed port, a pressure sensing inlet in said body, biasing means biasing said first and second valve pistons to a first position responsive to sensing of pressure below a predetermined minimum pressure where said control fluid inlet is blocked and said control fluid outlet is communicated with said bleed port, pressure means moving said first and second valve pistons as a unit to a second position responsive to the sensing of a predetermined pressure at said pressure sensing inlet where said control fluid inlet is communicated with said control fluid outlet and said bleed port is blocked, said pressure means moving said first and second valve pistons to a third position responsive to sensing of excess pressure at said pressure sensing inlet causing a blocking of said control fluid inlet, said biasing means comprising first and second compression springs respectively associated with said first and second valve pistons, said first spring controlling movement of said first and second pistons as a unit from the first to the second position, said second spring controlling movement of the second piston from the second position to the third position independently of the biasing force of the first spring, and means for independently adjusting the biasing force of the first spring without affecting the force required to move the second piston from the second position to the third position.