Gas lift valve utilizing a diaphragm pilot

A pilot operated gas lift valve utilizing a diaphragm formed of polymeric or elastomeric material and exposed to lift gas pressure on one side and atmospheric pressure on the other side, the diaphragm being able to withstand very high differential pressures and endure an extremely great number of operating cycles. The gas lift valve may be provided with an extension on the pilot valve member and this extension is exposed at all times to production fluid pressure, in which case, production fluid pressure will affect the operation of the gas lift valve. Thus, the gas lift valve may be 100 percent sensitive to production fluid pressure and totally insensitive to lift gas pressure, or its sensitivity to production fluid pressure may be as little as about four percent, depending upon the cross sectional area of the extension. Use of the diaphragm in the pilot valve mechanism provides essentially friction free operaton. Use of atmospheric pressure and a spring on the side of the diaphragm opposite the lift gas pressure avoids the effects of downhole temperatures on the pilot valve. Diaphragms formed of Teflon, especially virgin Teflon are disclosed should last for the life of most gas lift wells, and for operation in excess of 100,000 cycles. Also, diaphragms formed of elastomeric materials are also disclosed.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to wells which are produced by means of gas lift 
operations, and more particularly to a gas lift valve for use in such gas 
lift operations. 
2. Related Art and Information 
Gas lift valves have been used for many years to aid in the production of 
oil wells lacking sufficient natural pressure to flow naturally without 
assistance. Such valves commonly control the admission of lift gas into 
the well tubing from the well casing to aid in lifting formation liquids 
to the surface. Lift gas is generally injected into the well casing at the 
surface. Several types of gas lift valves have been known. Some gas lift 
valves open in response to casing pressure, some in response to tubing 
pressure, some admit gas into the tubing continuously, others 
intermittently. Some gas lift valves, for instance, are provided with main 
valves which are pilot actuated, that is, when their pilot valves open, 
their main valves are caused to open, and when their pilot valves close, 
their main valves close in response thereto. The pilot valve may respond 
to casing pressure or to tubing pressure or to the difference between 
those two pressures. 
Listed here are certain U.S. patents which disclose prior gas lift valves 
which may be pertinent to the invention disclosed and claimed in this 
present application. 
______________________________________ 
Re. 25,292 
2,994,335 3,086,593 
3,125,113 
3,183,922 3,311,126 3,311,127 
______________________________________ 
U.S. Pat. No. 2,994,335 issued to W. A. Dudley on Aug. 1, 1961 and its 
reissue Patent Re. 25,292 issued on Dec. 4, 1962, disclose a gas lift 
valve which has a pilot valve with a bellows and spring, the spring for 
biasing the pilot valve toward closed position and the bellows, exposed to 
casing pressure for moving the pilot valve toward open position. When 
casing pressure rises to a predetermined value the bellows lifts the pilot 
valve to open position in opposition to the spring. When the pilot valve 
opens casing pressure enters through the pilot valve to act upon the main 
valve and move it to open position against the force of its spring to 
allow transfer of lift gas into the tubing. When the casing pressure falls 
below a predetermined value the pilot valve will close and this will 
result in the main valve closing, it being moved by its spring. 
U.S. Pat. No. 3,086,593 which issued on Apr. 29, 1963 to C.B. Chitwood 
discloses a gas lift valve having a pilot valve including a bellows 
attached to the pilot valve member and charged with a compressed gas. The 
bellows hold the pilot valve on its seat (closed) when the casing pressure 
to which it is exposed is below a predetermined level. When the casing 
pressure rises above such predetermined level, the bellows will be 
compressed and will unseat (open) the pilot valve. Opening the pilot valve 
allows casing pressure to move the main valve to open position against the 
compression of its spring. When casing pressure falls below the 
predetermined level, the pilot valve closes, whereupon the main valve is 
returned to closed position by the spring. 
U.S. Pat. No. 3,125,113 issued to C.P. Lamb, et al., on Mar. 17, 1964. This 
patent discloses a gas lift valve which is controlled by a pilot employing 
a bellows 37 (FIG. 1A) and 76 (FIG. 3). When pressure exterior of the 
bellows compresses the same, the pilot valve 75 is lifted off its seat 74 
and casing pressure passing through the open pilot valve and through 
passage 77 into chamber 67 to act upon piston 66 to open main valve 65. 
U.S. Pat. No. 3,183,922 which issued May 18, 1965 to C.P. Lamb, et al., 
discloses a pilot operated gas lift valve. The pilot valve (ball 72) is 
held on seat 71 by pilot spring 74 and bellows 63. The bellows is exposed 
to tubing pressure conducted thereto through outlet 21, main valve stem 
bore 34, and passage 62. Casing pressure is communicated to the ball and 
seat via passage 59. When casing pressure increases to a predetermined 
value, ball 72 will be unseated and casing pressure flowing through the 
seat will pass through passage 62 and will be applied to piston 35 to thus 
move it down in opposition to main valve spring 44. Main valve 48 attached 
to the piston will thus be unseated and moved to its open position. When 
the casing pressure falls to a predetermined value, the pilot spring and 
the bellows will return the ball 72 to its seat to bar further entry of 
casing pressure. This will allow tubing pressure to equalize on upper and 
lower sides of the piston and permit spring 44 to close the main valve. 
U.S. Pat. No. 3,311,126 which issued to William A. Dudley on Mar. 28, 1967 
and discloses a pilot operated gas lift valve. This device has a pilot 
valve 60 which engages seat 70. Pilot spring 75 biases the pilot valve 
towards its seat. A bellows 72 is also connected to the pilot valve. Port 
69 communicates casing pressure into the pilot valve chamber. When casing 
pressure reaches a selected level, the bellows 72 compresses, overcomes 
spring 75, and lifts pilot valve 68 off its seat. Casing pressure then 
flows through seat 70 and its passage 71 into the chamber (47) therebelow 
where it acts upon piston (18). The piston is thus depressed, compressing 
spring 55 and opening the main valve 17 to permit flow of lift gas from 
the casing into the tubing through inlet screen 38, inlet ports 37 and 
through bores 42 and 43, to exit through outlet ports 39. When the casing 
pressure falls below the selected level, pilot valve 68 closes, chamber 
(47) is shut off from the casing pressure and becomes equalized with 
tubing pressure, the excess pressure bleeding to the tubing through bore 
64 of the piston (18) and its stem 17. With pressures equalized above and 
below the piston, main valve spring 55 moves the main valve to closed 
position. 
U.S. Pat. No. 3,311,127 issued to William A. Dudley on Mar. 28, 1967 and 
discloses a pilot operated gas lift valve in which two pressure responsive 
members 35 and 53 are used as bellow-phragms to contain an incompressible 
liquid therebetween. This liquid is metered through adjustable needle 
valves to control the length of time that the gas lift valve remains open 
before it closes. This patent is not believed to be pertinent to the 
instant application. 
No pilot operated gas lift valve was found in the prior art having a 
diaphragm subject to lift gas pressure and functioning to unseat the pilot 
valve to cause opening of gas lift valve. 
SUMMARY OF THE INVENTION 
The present invention is directed toward a pilot operated gas lift valve 
having body means with a flow course therethrough connecting an inlet 
opening with an outlet opening, and means for connecting the same in a 
well flow conductor, a main valve in the body for controlling flow 
therethrough, a spring for biasing the main valve toward closed position 
and a pilot valve for controlling opening and closing of the main valve, 
the pilot valve having a seat, a stem for closing the seat, a spring 
biasing the stem toward seat-closing position, and a diaphragm engaged 
with the stem and responsive to lift gas pressure for unseating the stem 
and allowing lift gas to then act upon a piston which will subsequently 
move the main valve to open position. 
It is therefore one object of this invention to provide a pilot operated 
gas lift valve in which a diaphragm sensitive to lift gas pressure 
functions to move the pilot valve to open position. 
Another object is to provide a gas lift valve having a pilot having no 
sliding seals and its pilot valve member therefore operates virtually 
without friction. 
Another object is to provide such a pilot operated gas lift valve in which 
such diaphragm will withstand very high pressure. 
Another object is to provide such gas lift valve in which the diaphragm is 
especially long lasting. 
Another object of this invention is to provide such improved pilot operated 
gas lift valve which the affects of temperatures are negligible. 
Another object is to provide a pilot operated gas lift valve of the 
character described whose main valve and body are provided with 
metal-to-metal seals which co-engage to close the flow course 
therethrough. 
Another object is to provide such a gas lift valve in which when the main 
valve is closed a positive pressure acts thereon to help maintain it in 
closed position. 
Another object of this invention is to provide a pilot operated gas lift 
valve of the character described which is adapted for use in the offset 
receptacle of a side pocket mandrel. 
Another object of this invention is to provide a pilot operated gas lift 
valve adapted for mounting on the exterior of a well tubing. 
Other objects and advantages may become apparent from reading the 
description which follows and from studying the accompanying drawings, 
wherein:

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIG. 1, it will be seen that a pilot valve 10 for 
controlling an associated valve (not shown) is schematically illustrated. 
Valve 10 includes a housing 11 having a passage therethrough providing an 
inlet 12 and an outlet 14. Inlet 12 intersects a bore 16 which is reduced 
as at smaller bore 18. A valve seat is provided as at 20 where small bore 
18 opens into bore 16. A valve member 24 having a tip 26 is shown engaged 
with and closing the seat 20 but is movable away from seat 20 to permit 
fluid communication therethrough between the inlet 12 and the outlet 14. 
In normal use, flow takes place through the pilot from the inlet 12 to the 
outlet 14 when the valve member 24 is not engaged with seat 20. 
Valve member 24 extends upwardly through bore 16 and into chamber 30. The 
valve member terminates at its upper end with a large flat head 32. A 
pilot spring 34 having its upper end engaged with the upper end 36 of 
chamber 30 has its lower end resting upon the upper end of the flat head 
32. The compression in main spring 34 biases the valve member 24 
downwardly, forcing the valve tip 26 into intimate contact with seat 20 so 
that the pilot valve is normally closed. 
The valve housing 11 is provided with a first annular seal 40 and a second 
annular seal 42 which normally seal above and below the inlet port 12 to 
direct upstream pressure thereinto. 
Between the inlet 12 and the chamber 30, the valve housing 11 is provided 
with an internal annular recess 50 which surrounds bore 16, as shown. 
Also, the valve member 24 is provided with an external annular recess 52. 
Recesses 50 and 52, ideally, have their upper ends at the same level when 
valve tip 26 is seated on seat 20. As shown, recesses 50, 52 are of equal 
width, which results in their lower ends being aligned also, but such is 
not necessary. 
A diaphragm 60 is disposed in recess 50 and is provided with a short lower 
lip 62 and with a long upper lip 64. Both of these lips extend radially 
inwardly, as shown from the web 65 of the diaphragm. It is noticed that 
the upper lip 64 extends deep into recess 52 of the valve member 24 but 
lower lip 62 stops short of reaching stem 24. Diaphragm 60 may be made of 
a sturdy but flexible polymeric material such as Nylon, Teflon, Delrin, 
Polyamide, or the like. This upper lip 64 bridges the gap between the 
inner wall 16a of bore 16 and the outer surface 24a of the valve member 
24. 
A spring indicated by the reference numeral 68 biases the upper lip 64 of 
the diaphragm 60 against the upper wall of recess 52 to establish an 
initial seal and prevent leaking of gas or liquids into chamber 30. 
Pressure, which enters housing 11 inlet 12 is communicated by bore 16 to 
recess 50 where it acts upon diaphragm 60 to press it into intimate 
sealing contact with the walls of recess 50. This pressure also presses 
the upper lip 64 into intimate contact with the upper wall of recess 52 
Thus, the upper lip of diaphragm 60 seals between the valve member 24 and 
the housing 11 and prevents pressurization of chamber 30, which remains at 
atmospheric pressure. 
In conventional use of pilot valve 10 in a gas lift well, casing pressure 
would be communicated to the inlet 12 and the tubing pressure would be 
communicated to the outlet 14. Thus, when valve tip 26 is spaced from seat 
20, lift gas from the casing would enter the pilot valve through inlet 
port 12 and would find its way to the closed valve seat 20 and also to the 
diaphragm 60. Thus, tubing pressure would act upon that area of the valve 
tip 26 which is exposed, as shown, below the surface of seat 20. Tubing 
pressure acting upon this area of the valve member sealed by the seat 16 
constitutes a force which tends to lift and thus unseat the valve member. 
Casing pressure acts against upper lip 64, tending to flex it upwardly and 
lift the valve member, thus tending to unseat the valve also. 
Casing pressure acts upwardly against that portion of the lower end of the 
valve which is above the seat 20. This, too, constitutes a force tending 
to lift the valve member and unseat the valve. 
Casing pressure acts equally in both upward and downward directions in 
external recess 52 of the valve member and the resulting upward and 
downward forces obviously balance or cancel one another. 
The casing pressure can, if it is sufficiently great, lift the valve member 
off seat against the downward force of pilot spring 34. This, of course, 
causes the upper lip 64 of the seal member to flex. The point of flexure 
may be taken as located along a circular path which lies approximately 
midway between the outer cylindrical surface of the valve member and the 
inner cylindrical surface of the housing at the upper lip of the 
diaphragm. This circle defines the pressure sensitive area of the pilot 
valve 10. 
At the time that the valve member is unseated, the force of the tubing 
pressure acting upwardly against the exposed area of the valve tip plus 
the force of the casing pressure acting upwardly against the pressure 
sensitive area minus the exposed area of the valve tip must equal the 
force of pilot spring 34. Thus: 
F.sub.ps =P.sub.t (A.sub.vt)+P.sub.c (A.sub.s -A.sub.vt) 
where: 
F.sub.ps =Force of pilot spring 
P.sub.t =Pressure in tubing 
A.sub.vt =Area of valve tip 
P.sub.c =Pressure in casing 
A.sub.s =Sensitive area of pilot valve 
The pilot spring 34 may be adjusted by suitable means (not shown) so that 
it will open when the conditions of pressure at inlet 12 and outlet 14 
reach levels predetermined. 
A pilot operated gas lift valve constructed in accordance with the present 
invention is illustrated in FIGS. 2A, 2B, and 2C where it is indicated 
generally by the reference numeral 100. Gas lift valve 100 utilizes a 
pilot valve which operates upon the same principles as does the pilot 
valve schematically shown in FIG. 1 as just described. 
Device 100, as shown, is adapted for installation in a side pocket mandrel 
(not shown). Side pocket mandrels are well known. They typically are 
formed with a belly or side pocket in which an offset receptacle is 
located. The offset receptacle is substantially parallel to the bore of 
the well tubing of which it forms a part. The receptacle will receive a 
gas lift valve installed therein through use of a kickover tool and 
wireline apparatus by which such gas lift valve may also be retrieved. The 
offset receptacle has a lateral port in its wall, and when the gas lift 
valve is installed in the side pocket mandrel, it is locked and sealed 
therein with its inlet port in communication with the lateral port of the 
receptacle. Such is the case for gas lift wells which produce well fluids 
through the tubing in response to lift gas being injected into the casing 
at the surface. If gas is to be injected into the tubing and well products 
are to be produced through the casing, side pocket mandrels for such 
installations are available. Side pocket mandrels and gas lift valves of 
various types are available from Otis Engineering Corporation, Post Office 
Box 819052, Dallas, TX 75381-9052. 
Gas lift valve 100 includes body means 102 which is shown attached as by 
thread 104 to a latch 106 having a fishing neck 108 by which a handling 
tool such as a kickover tool releasably engages the device for installing 
the same in or removing it from a well. The latch 106 includes a 
downwardly facing stop shoulder 109 for limiting downward movement of the 
latch in the receptacle of the side pocket mandrel, and a latch lug 110 
which engages below a lock shoulder in the receptacle for releasably 
locking the device in the receptacle. The device is releasable by upward 
jarring impacts which cause shearing of a pin (not shown) to permit the 
lug 110 to retract. The device can then be withdrawn from the receptacle 
and the well. 
Body means 102 comprises a spring housing 112 whose upper end is connected 
directly to the lower end of the latch 106 as at thread 104, an 
intermediate pilot housing 114 attached as by thread 116 to the lower end 
of spring housing 112, an upper pilot housing 120 which is attached as by 
thread 122 to the upper end of intermediate pilot housing 114 and extends 
upwardly inside the spring housing 112. The connection at thread 116 is 
sealed by suitable seal means, such as resilient o-ring seal 124, to help 
maintain atmospheric pressure inside the spring housing. 
Lower pilot housing 128 is connected to the lower end of intermediate pilot 
housing as by thread 130 and this connection is sealed by o-ring 132. Main 
valve housing 136 is connected to the lower end of lower pilot housing 128 
as by thread 138, and this thread need not be sealed. A nose 140 is 
connected to the lower end of main valve housing 136 as by thread 142 as 
shown. 
The device 100 carries the usual packing means including an upper packing 
set 150, at the connection of the intermediate pilot housing to the lower 
pilot housing for sealingly engaging the inner wall of the side pocket 
receptacle above its lateral port, and a lower packing set 152 for 
sealingly similarly engaging the side pocket receptacle below its lateral 
port. 
The main valve housing 136 is provided with inlet means comprising one or 
more inlet ports such as inlet 154. The inlet means have a flow capacity 
sufficiently small to choke the flow of lift gas as desired so that when 
the main valve is open, casing pressure will exist exterior thereof and 
tubing pressure will exist interior thereof. It is preferable to provide 
plural inlets in order to balance the entry of lift gas therethrough. Four 
such inlet ports are recommended, and four one-eighth inch (3.175 
millimeters) ports, for instance, might perform well in some 
installations. The flow capacity of the inlet means is in any case 
determined by the quantity of lift gas required for the desired production 
rate in the installation, considerations being given to the well 
productivity, depth of the gas lift valve, tubing size, pressure and 
density of the lift gas, et cetera. The nose 140 on the lower end of main 
valve housing is formed with suitable outlet means such as windows 156. A 
flow passage indicated by the arrow 158 connects inlet 154 with outlet 
156. Windows 156 communicate With the outlet of the receptacle. Thus, when 
the gas lift valve is open, as will be explained, lift gas may transfer 
from the casing to the tubing through the receptacle and the device 100 
disposed therein. When the valve is closed, such transfer of lift gas is 
prohibited. 
Main valve member 160 having a bore 161 is slidably mounted in bore 162 of 
main valve housing 136 and is at all times sealingly engaged by annular 
seal ring 164 and is biased by main spring 165 toward its closed position, 
seen in FIG. 2C, wherein its tapered seal surface 166 sealingly engages 
corresponding main seat surface 167 of seat member 170. Thus, when main 
valve 160 is seated as shown in FIG. 2C, lift gas entering main valve 
housing 136 through inlet 154 cannot move past the engaged seats 166, 167, 
or past the seal 164 (See FIG. 3). When, however, the main valve member 
160 is moved away from its seat, lift gas may flow from inlet 154, pass 
between the seat surfaces 166, 167, then move downwardly through passage 
158 (arrow), depress check valve 172 against the compression of spring 174 
and exit the device through windows 156 of nose 140 and into the well 
tubing. 
The area sealed by engagement of seat surface 166 at the upper end of main 
valve 160 is slightly larger than the area sealed by annular seal 164, 
thus providing added force to aid spring 165 in holding main valve 160 
firmly engaged in its closed position. It is readily seen, then, that when 
the main valve is unseated and flow takes place through inlet ports 154, 
these ports restrict such flow and casing pressure no longer biases the 
main valve upwardly. Casing pressure above piston 180 then moves the main 
valve to its full open position without delay. 
When the main valve 160 is allowed to be returned to its seat by the 
compression of main spring 165, as when the force holding the main valve 
open subsides, flow through the gas lift valve will be stopped and the 
check valve 172 will be closed by its spring 174. 
Main valve 160 is moved to open position by piston 180 (see FIG. 4) 
slidably mounted in cylinder bore 182 of seal member 170. Piston 180 has 
at least one finger 181 extending downwardly therefrom. This finger (or 
fingers) provides ample passage for allowing lift gas to enter the upper 
end of bore 161 of main valve 160, as seen in FIG. 5 where four fingers 
181 are shown. 
Opening and closing of main valve 160 is controlled by pilot valve means 
which is to be described. 
Seat member 170 not only is provided with the cylinder bore 182 in which 
piston 180 is slidable and seat surface 167 engageable by main valve 160, 
but also is provided with a reduced bore at its upper end which provides a 
pilot seat surface 195 engageable by mating seat surface 196 formed on 
pilot valve 200, as shown. 
Seat member 170 is formed with an external annular flange 202 which is 
confined between downwardly facing shoulder 204 of lower pilot housing 128 
and the upper end face of main valve housing 136. Tightening of thread 138 
secures the seat member 70 rigidly in place. 
Lower pilot housing 128 is provided with a second inlet means comprising at 
least one lateral opening such as inlet 208 located above the first 
mentioned inlet means 154 and below upper packing set 150, thus 
communicating casing pressure into the lower pilot housing and also to the 
pilot seat 195. It may be desirable to provide two such inlet ports 208 as 
seen in FIG. 6. 
Pilot valve 200, when seated upon seat surface 195 as shown in FIG. 2C 
prevents flow of lift gas therepast, but when the pilot valve is lifted 
from its seat, lift gas communicated thereto through second inlet 208 is 
allowed to flow therethrough and to bear upon the upper end of piston 180 
causing it to be displaced downward. Such displacement of the piston 
causes its dependent fingers 181 to engage main valve 160 and move it 
downward against the compression of main spring 165, thus opening the main 
valve to permit the flow of lift gas through inlet 154, passage 158, past 
check valve 172 and out through windows 156 of nose 140 on its way to the 
well tubing. The lift gas thus transferred into the tubing helps to lift 
the well products to the surface. 
Pilot valve 200 includes stem means 210 comprising lower pilot stem 211 and 
upper pilot stem 212 attached thereto as by thread 213 which is not at 
first tightened but is secured after adjustment as by screw 214. Screw 214 
is installed but not tightened until proper adjustment has been made as 
will be described later, then screw 214 is tightened by access through 
lateral opening 208. Two such screws 214 may be desirable. If so, two 
ports 208 will be needed. Pilot valve stem 210 extends upwardly through 
bore 220 of intermediate pilot housing 114 and into bore 222 of upper 
pilot housing 120. Just above the level of the upper end of intermediate 
pilot housing 114, the upper pilot housing is reduced in diameter as at 
224 and a pair of opposed openings such as holes or slots 226, are formed 
through its wall. A cross pin 230 extends through the pair of slots 226 
and its opposite ends are received in holes 232 formed in a ring 234 which 
surrounds the upper pilot housing and has a free sliding fit thereon. 
Cross pin 230 rests across the upper end of upper valve stem 210. 
A pilot spring such as coil spring 240 surrounds the upper pilot housing 
120 and its lower end rests upon the upper face 242 of ring 234. The bore 
222 of upper pilot housing 120 is reduced at its upper end and is 
internally threaded as 246. A suitable washer such as washer 250 having a 
central hole 252 therethrough and a downwardly facing shoulder 254 on its 
lower side is placed on the upper end of pilot spring 240. A bolt 256 
having a thread 257 extends through the hole 252 of washer 250 and is 
threaded into thread 246 of upper pilot housing 120, as shown. The head 
260 of the bolt 256 engages the upper side of the washer 250 and is 
tightened to compress spring 240 as desired. The spring load is 
transferred through ring 234 and cross pin 230 to the upper end of the 
pilot stem 210. The force of spring 240 thus biases the pilot valve toward 
seat 195 of seat member 170 as before explained. 
The lower pilot stem 211 is formed with an external flange 274 at its upper 
end and with a central threaded upwardly opening blind bore as at 276, 
while the lower end is threaded as at 213 as mentioned before. Thread 276 
is well tightened. The lower pilot stem 211 is disposed in bore 220 of 
intermediate housing 114 and its external flange 274 is engageable with a 
corresponding upwardly facing shoulder 280 to limit downward movement of 
the lower pilot stem during assembly and adjustment only. The flange 274 
is never shouldered after adjustment has been completed. After adjustment, 
downward movement of the pilot stem is limited by engagement of the pilot 
valve seating surface 196 with the pilot seat surface 195. 
Adjusting nut 284 is screwed onto thread 212 of lower pilot stem 211 and 
adjusted to limit upward movement thereof relative to the intermediate 
pilot housing 114, as needed. With flange 274 against shoulder 280 nut 284 
is adjusted so that it is spaced say 0.020 inch (0.5 millimeter) from the 
lower end of intermediate pilot housing 114. This adjustment is preserved 
by tightening jam nut 285 against adjusting nut 284. After jam nut 285 has 
been tightened, the pilot stem is again moved down until its flange 274 is 
shouldered up, after which the clearance between nut 284 and the lower end 
of intermediate pilot housing 114 is checked. After jam nut 285 has been 
finally tightened, the stroke of the pilot valve 200 is adjusted. 
The stroke of the pilot valve is adjusted while it is assembled, thusly: a 
wrench is inserted through each of the threaded openings 208 of lower 
pilot housing 128 and is engaged in each of the set screws 214. These 
wrenches will prevent the pilot valve member 200 from rotating while 
thread 213 is carefully unscrewed until the seat surface 196 of the pilot 
valve member 200 just touches the corresponding seat surface 195 of the 
seat member 170 and adjusting nut 284 just engages the intermediate pilot 
housing 114. Thread 213 is then further made up 1/4 to 1/3 of a turn only, 
after which this adjustment is preserved by tightening the set screws 214, 
thread 213 being a 20-pitch thread. Thus, the stroke of the pilot valve 
stem is adjusted to 0.0125 to 0.0167 inch (about 0.3175 to 0.4233 
millimeter). 
Threaded openings 208 are left open for installation of the device 100 in a 
well since these openings provide passages for communicating casing 
pressure into the pilot mechanism. 
The upper pilot stem 212 has its lower end portion reduced in diameter as 
at 286 and is threadedly connected into the threaded bore 276 at the upper 
end of the lower pilot stem 211. An external annular recess about the 
pilot stem is defined about the reduced diameter portion 286 and between 
the upper end face 288 of the lower pilot stem 211 and the downwardly 
facing shoulder 290 on the upper pilot stem 212. 
A spacer ring 292 is interposed between the lower end face of upper pilot 
housing 120 and an upwardly facing shoulder formed in the intermediate 
pilot housing 114 by the enlarged bore which is threaded as at 122. This 
spacer controls the width of recess 293 and assures proper space for 
diaphragm 300, seen in FIG. 7. 
Diaphragm 300 is shown schematically in FIG. 7. It is preferably formed as 
shown of a body of virgin Teflon (Tetraethylfluorocarbon) material. While 
other polymeric or elastomeric material might be usable for this 
application, Teflon was chosen because of its impermeability to well 
fluids. It is essentially formed with a first disklike wall 302 and a 
second similar wall 304 connected together at their outer edges by a web 
306. The first wall is formed with a small central hole 310 therethrough 
and the second wall is formed with a large hole 312 therethrough. The 
first wall is the flexible portion and acts as a diaphragm. The small hole 
receives the lower reduced end of upper pilot stem 212 and is a fairly 
close, but not necessarily tight, fit therewith. The outer edge of the 
diaphragm is received in recess 293 and within the spacer 292 as shown in 
FIG. 2B. The inner portion of first wall 302 of the diaphragm engages and 
seals with downwardly facing shoulder 290 of upper pilot stem 212 and the 
outer portion thereof seals against the lower end of upper pilot housing 
120. The second wall 304 engages and seals with the lower wall of internal 
recess 293. 
Diaphragm 300 is formed with fairly thick walls and functions to seal the 
area thereabove inside and around the upper pilot housing and, of course 
within the spring housing 112, so that well fluids and the like cannot 
flow therepast and increase the pressure therein beyond atmospheric 
pressure. 
To enhance the sealing of the diaphragm 300 with the downwardly facing 
shoulder 290 of upper pilot stem 212, a coil spring 320 is engaged between 
the upper end 288 of lower pilot stem 211 and the lower side of 
washer-like ring 322 having its upper side in contact with the lower side 
of the diaphragm as shown. The spring 320 thus applies an upward bias to 
the diaphragm at all times to assure its sealing contact with the upper 
pilot stem so that atmospheric pressure will be preserved in the region 
above the diaphragm. The inward portion of the upper face of ring 322 is 
raised as shown in order to concentrate the spring load at the lip of the 
diaphragm and further assure that the diaphragm will seal more dependably, 
even during low pressure conditions, both while the diaphragm is flexing 
and while it is flexed. Since the diaphragm must exclude fluids from the 
atmospheric chamber thereabove, it is highly recommended also that spring 
means be provided for pressing the short or lower lip of the diaphragm 
into firm sealing contact with upwardly facing shoulder 293 of the 
intermediate pilot housing 114. (Suitable springs for such applications 
are used on flange face seals for holding internal pressures. These are 
one-way seals. Such seals are available from FURON, Mechanical Seal 
Division, P.O. Box 520, Los Alamitos, CA 90720.) 
Casing pressure entering the device through threaded inlet 208 acts upon 
the under side of diaphragm 300 tending to flex it upwardly and lift the 
pilot stem to unseat it from the pilot seat. The diaphragm thus provides a 
sensitive area which is sensitive to casing pressure. Atmospheric pressure 
in spring housing 112 acts upon the upper side of the diaphragm. The 
sensitive area of the diaphragm may be defined as the area within that 
circle which lies between the outside diameter of the upper pilot stem, at 
the shoulder 290, and the inside diameter of the upper pilot housing, at 
the lower end thereof. It is readily seen that, since the upper pilot stem 
is a fairly close sliding fit in the lower portion of bore 222, the 
sensitive area of the diaphragm is approximately equal to the 
cross-sectional area of the upper pilot stem where it contacts the upper 
side of the diaphragm. 
It is readily seen that since the diaphragm seals about the pilot valve 
stem which only moves a very short distance, flexing the diaphragm, this 
movement is virtually friction free because no sliding seal means is used. 
The pilot valve arrangement of the gas lift valve 100 differs from the 
pilot valve 10, illustrated in FIG. 1, in one important particular. While 
the pilot valve seating surfaces could be formed much like those of the 
pilot valve 10, and piston 180 could be formed solid, the piston 180, as 
seen in FIG. 2C is formed with a central bore 330 with an internal recess 
therein carrying a seal ring 331, and a probe 332 extends downward from 
the pilot valve sealing surface 196. This probe 332 may be formed integral 
with the pilot valve 200 or it may be formed separately therefrom and 
attached thereto by suitable means, such as a thread, for instance. 
The probe 332 is not necessary and the pilot valve member 200 can be formed 
without it, if the pilot valve mechanism is to be insensitive to tubing 
pressure and respond to casing pressure alone. 
The piston 180 (FIG. 4) is formed with an external annular recess near its 
upper end in which is carried a suitable non-sealing ring 180a. A Teflon 
ring 180b scarf-cut as at 180c has been found suitable. Also, two thinner 
scarf-cut Teflon rings (not shown) in the same recess have been 
substituted for ring 180a and found suitable. The piston must leak a 
little so that it can vacate the volume of gas above it when the pilot 
valve closes, since this is necessary if the main valve 160 is to be 
returned to its closed position by the main valve spring 165. 
In order for the gas lift valve 100 to function properly the pilot valve 
must be adjusted to the required opening pressure based upon well 
conditions. 
To adjust the pilot valve, a source of pressure is connected into the upper 
inlet 208. If two inlets 208 are provided, one must be plugged as by 
installing a pipe plug 209 therein, as shown in FIG. 6. The spring housing 
112 is removed. The adjusting bolt 256 is screwed in, if necessary, to 
provide more than enough compression in pilot spring 240. 
It should be understood that during assembly of the gas lift valve, a Nylon 
pellet 349 is placed in the threaded opening of the upper pilot housing, 
after which the set screw 350 is installed and tightened. The Nylon pellet 
349 is thus compressed into firm engagement with thread 257 to maintain 
further adjustments of the bolt 256. This procedure is necessary since 
compression of the spring 240 results in its coils being too close 
together to permit access to screw 350 with a wrench. 
Pressure is then applied to the pilot through the upper inlet 208. There 
should be no leaks. The pressure connected into the pilot is adjusted to 
equal the desired opening pressure for the pilot valve. Maintaining this 
desired opening pressure on the pilot, the adjusting bolt 256 is unscrewed 
slowly to reduce the compression in the pilot spring 240. When the 
compression in pilot spring becomes reduced sufficiently, the pressure in 
the pilot will flex the diaphragm and lift the pilot stem to unseat the 
pilot valve. This adjustment is preserved by tightening screw 350 to lock 
the adjusting bolt to the upper pilot housing. 
Since the pilot valve 200 of gas lift valve 100 is provided with the 
dependent probe 332 whose cross-sectional area is exposed at all times to 
tubing pressure, the force of such tubing pressure acting upon the pilot 
mechanism must be taken into account. Of course, since the probe is 
smaller in area than the opening through the pilot valve seat surface 195, 
the probe has no affect upon the opening of the pilot valve. It does have 
its affect upon holding the main valve open. 
The force-balance equation for opening of the pilot valve, therefore will 
be the same as that given hereinabove with respect to the pilot valve 10 
of FIG. 1. 
While the device 100 of FIGS. 2A, 2B, and 2C has been shown to utilize a 
diaphragm having upper and lower sealing lips, other forms of diaphragms 
may be used. And, while the diaphragm utilized in the device 100 was 
described as being formed of Teflon, preferably virgin Teflon, other 
materials (polymeric or elastomeric) might be used, especially in the 
diaphragms shown in FIGS. 8-12. 
Referring now to FIG. 8, it is seen that a modified form of gas lift valve 
100a is shown which may be like that of device 100 with the exception of 
the diaphragm and the manner in which it sealingly engages with the 
housing. 
The device 100a is provided with a diaphragm which is indicated by the 
reference numeral 300a and is illustrated in FIGS. 9 and 10. 
In FIG. 9, it is seen that the diaphragm 300a is essentially in the form of 
a disk 300b having a central opening 300c for receiving the reduced 
diameter portion of the upper pilot valve stem 212 and having its outer 
edge thickened as by a ridge 300d as shown. The ridge extends above the 
upper surface of the diaphragm, but does not extend below the lower 
surface thereof. 
In FIG. 8, it is seen that the outer edge portion of diaphragm 300a 
thickened by ridge 300d is engaged between upwardly facing shoulder 293a 
of intermediate pilot housing 114a and the lower chamfered end of upper 
pilot housing 102a. Upon tightening of the thread 122a, the ridge 300d of 
the diaphragm 300a is squeezed and deformed so as to be captured in the 
space provided at least in part by the chamfer and is effective to form a 
suitable seal between the diaphragm and the pilot housing 102a. 
The diaphragm 300a is caused to sealingly engage the upper pilot valve stem 
212 in exactly the same manner as before explained with respect to device 
100 previously described. The inner portion of diaphragm 300a is pressed 
upwardly against the downwardly facing shoulder of the upper stem by the 
spring 320 acting through washer 286. Thus, the diaphragm 300a seals 
between the pilot valve stem and the pilot valve housing to prevent 
leakage of fluids into the atmospheric chamber within spring cover 112 
while allowing the pilot valve stem 210 to move between its open and 
closed positions. 
In FIG. 11, the diaphragm 300e of device 100b is in the form of a plain 
flat disk having a central opening therethrough for receiving the reduced 
diameter portion 286b of upper pilot valve stem 212. The spring 320 causes 
the diaphragm to seal against the downwardly facing shoulder of the upper 
pilot valve stem while the outer portion of the diaphragm is sealed by a 
resilient seal ring such as o-ring 301 carried in a suitable recess formed 
in the intermediate pilot valve housing 114b as shown. While washer 286 is 
not shown in FIG. 11, its use is desirable. Tightening of the thread 122b 
causes the upper pilot valve housing 120b to press downwardly upon the 
diaphragm 300e, squeezing the seal ring 301 which seals both with the 
diaphragm and with the intermediate pilot valve housing 114b. 
Referring to FIG. 12, it is seen that the device 100c is provided with a 
diaphragm 300f which may be exactly like the diaphragm 300e shown in 
device 100b of FIG. 11, however, no o-ring or other resilient seal is 
used. Instead, the lower end face 120c of upper pilot housing 120d is 
formed with means such as one or more concentric ridges indicated at 120e 
projecting downwardly therefrom for increasing the stresses in the 
diaphragm material in order to enhance the effectiveness and dependability 
of the seal formed between the diaphragm and the intermediate pilot valve 
body 114c. The seal between the diaphragm and the pilot valve stem is 
effected in the same manner as before explained. 
The material for diaphragms 300a, 300b and/or 300c may be selected from the 
polymeric materials, Teflon being the most impervious, or from the 
elastomeric materials. The elastomeric materials are generally more 
flexible than Teflon and other similar polymeric materials and may be more 
desirable under certain conditions. But, for use in gas lift wells, Teflon 
is generally to be preferred. 
In FIG. 13, another form of the invention is illustrated. The pilot 
operated gas lift valve indicated by the reference numeral 400 is 
constructed exactly like the pilot operated gas lift valves previously 
described, but is adapted for attachment to the exterior of the well 
tubing T in a well known manner. Thus, the lower threaded end of the main 
valve housing 136a of device 400 is screwed into the upwardly facing 
threaded opening of lug 402 as at 404 or, alternatively, an adapter (not 
shown) may be used for this connection. Lug 402 is attached as by a weld 
406 to the exterior of a section 410 of the well tubing T. 
In use, when the main valve opens, lift gas in the casing (not shown) 
enters the inlet 154a of gas lift valve 400, flows therethrough, and 
depresses the check valve 172a, compressing its spring 174a, and then 
flows through the flow port 410 into the tubing T. A drain passage may be 
provided as at 412 for draining the bore 414 in which the check valve 
slides and which contains the lower portion of its spring. 
It may be desirable to install an adapter (not shown) onto the lower end of 
main valve housing 136a for containing the check valve and spring and then 
screwing the adapter into a conventional external lug provided on a gas 
lift mandrel available for use with such externally mounted gas lift 
valves. 
Thus, it has been shown that a novel pilot operated gas lift valve has been 
provided which fulfills all of the objects set forth early in this 
application. It should be understood, however, that while the gas lift 
valve has been illustrated and described with respect to installations 
wherein lift gas is injected down the casing and is transferred through 
the gas lift valve into the tubing to aid in lifting production fluids to 
the surface, the subject gas lift valve can, as well be used in 
installations which are the reverse of that just mentioned where 
production is had through the casing and lift gas is injected down the 
tubing. 
The foregoing description and drawing are explanatory and illustrative only 
and various changes in sizes, shapes, materials, and arrangements of 
parts, as well as certain details of construction, may be made within the 
scope of the appended claims without departing from the true spirit of the 
invention.