FR2879721A1 - Gas such as liquefied petroleum gas, pressure regulator valve for gas inlet conduit, has piston with minimum and maximum contact surfaces respectively in contact with pressurized and relaxed gas - Google Patents

Abstract

The valve has a case comprising an intermediate portion (2b) that is divided by an inner wall (5) in which an opening (8) is disposed for permitting the sliding of a piston (10). The piston has a minimum contact surface (S) in contact with pressurized gas, and a maximum contact surface (S`) in contact with relaxed gas. A vent hole (21) is disposed in the portion to permit communication between atmosphere and volume under the piston.

Description

2879721 1

  The present invention relates to a gas expander for mounting on a gas supply conduit connecting a source of gas to a user device.

  The regulators usually used have the characteristic of being upstream piston type, that is to say they are based on an expansion system in which a piston is positioned upstream of a seat forming a through orifice gas, a spring allowing, through a piston rod passing through the seat, to maintain the piston spaced from said seat, and therefore its closed position.

  The operation of such a pressure reducer is based on its equilibrium point between the upstream and downstream gas pressure forces tending to close the piston, and the restoring force of a prestressed element tending to open the piston. piston, in general a spring, chosen according to the equilibrium point, and therefore the desired expansion pressure. This prestressed element can be adjustable.

  Ideally, the upstream pressure is constant and it is therefore the downstream pressure that controls the opening or closing more or less important of the piston in case of overpressure or underpressure at the user device. However, since the piston is positioned upstream of the seat, it is particularly sensitive to variations in the feed pressure of the expander and all the more so since its surface in contact with the gas is important.

  Thus, in case of increase of the gas supply pressure, the balance of forces will be reached for a lower expansion pressure, and therefore the pressure reducer will deliver a lower pressure. Conversely, in the event of a decrease in the pressure of the feed gas, the expansion pressure necessary to achieve the balance of forces will be higher.

  This is particularly troublesome in the case of LPG for example.

  Indeed, high pressure LPG has the characteristic of being in pressure equilibrium between the liquid and vapor phases, the value of the equilibrium pressure being highly dependent on the temperature of the medium. Thus, in summer, the upstream pressure will be higher than in winter, the balance of forces exerted on the piston is then modified as explained above, and the downstream pressure delivered to the user device is not more constant. For example, it has been noted that for a pressure regulator whose pressure is at 1.5 bar relative to nominal conditions, the equilibrium point may vary by +2879721 or -0.5 bar. This can cause disturbances in the user device which is downstream of the regulator which it receives the pressure directly.

  The object of the present invention is to overcome this disadvantage, and for this purpose consists of a gas expander having at least one inlet orifice intended to be connected to a source of pressurized gas and at least one outlet orifice intended to deliver the expanded gas to a user device, said regulator comprising a pressure regulation mechanism controlled by the displacement of at least one movable element, each mounted on a prestressed member, and adapted to seal the passage of the gas, characterized in that each movable element is shaped so as to have, on the one hand, a minimum contact area for the pressurized gas penetrating through the inlet orifice, and, on the other hand, a maximum contact area with gas expanded in the vicinity of the outlet orifice, to allow the delivery of a gas expanded at a determined pressure regardless of the pressure of the gas at the inlet.

  Thus, the forces exerted on the mobile element by the gas under pressure are, because of the reduced contact surface of said movable element with the pressurized gas, much lower than that exerted by the expanded gas on the same mobile element. As a result, a variation of the supply pressure will have only a small effect on the equilibrium point of the movable element. The movable element may be of the piston or membrane type, for example.

  Preferably, the prestressed member exerts forces on the movable element tending to its displacement in the direction of the opening of the passage of the gas. Advantageously, the prestressed member is a spring.

  According to a preferred embodiment of the invention, an expansion valve comprises an upstream compartment into which the inlet of pressurized gas and a downstream compartment into which the expanded gas outlet opens, the two compartments being separated by an inner wall to through which slides the movable element.

  Advantageously, the movable element is in the form of a piston comprising, on the one hand, a head located in the vicinity of the outlet orifice, and on the other hand, a rod having an end adapted to cooperate with a seat to close the gas passage.

  Advantageously, the rod comprises an inner channel opening on the one hand, at the level of the piston head near the outlet orifice, and on the other hand, at the end of the stem. located near the inlet.

  Advantageously, the inner channel has, at the inlet orifice, a frustoconical end. This feature facilitates the flow of gas and thus further reduce the contact surface in direct contact with the gas under pressure.

  According to an alternative embodiment, the expander comprises a flexible membrane attached to the piston head and attached to the expander at its periphery. Advantageously, the membrane is fixedly attached to the piston head by its central portion.

  The invention will be better understood with the aid of the detailed description which is described below with reference to the appended drawing in which: FIG. 1 is a cross-sectional view of a pressure reducer according to a first embodiment of the invention .

  Figure 2 is a cross section of a pressure regulator according to a second embodiment of the invention.

  An expansion valve 1 according to a first embodiment, as shown in Figure 1, comprises an outer housing 2 comprising a lid 2a, an intermediate portion 2b and a lower portion 2c. An inlet 3 for the arrival of pressurized gas is arranged in the lower part 2c and an outlet 4 for the evacuation of the expanded gas is formed in the lid 2a. The intermediate portion 2b is divided by an inner wall 5 into an upstream compartment 6, closed by the lower part 2c and into which the inlet 3 opens, and a downstream compartment 7, closed by the cover 2a and into which the outlet 4 .

  An opening 8 is made in the inner wall 5 so as to allow the sliding of a piston 10, a seal 9 sealing the sliding.

  More precisely, the piston 10 comprises a hollow cylindrical rod 11 capable of sliding through the inner wall 5 through the opening 8. The rod 11 has an inner channel 18 passing through, on the one hand, in the upstream compartment 6 by a first frustoconical end 12 converging downstream, and secondly, in the downstream compartment 7 by a second end 13 also frustoconical diverging downstream. The end 2879721 4 also has a head 14 adapted to slide integrally with the rod 11 inside the downstream compartment 6. A seal 15, located at the edge of the head 14, seals the sliding. The rod 11 also has a length sufficient for the end 12 of the inner channel 18 to come into contact with a wall 20 of the housing 2, which then closes the inner channel 18. A seat 19 intended to provide the sealing of the closure is provided in the wall 20 facing the end 12.

  Furthermore, a vent hole 21 is made in the intermediate part 2b so as to allow communication between the atmosphere and the volume under the piston 10 and thus avoid any rise in pressure during the displacement of the piston 10.

  It follows from this configuration that the movable element constituted by the piston 10 will have, on the one hand, a minimal contact surface S to the pressurized gas, the latter being substantially reduced to the section of the hollow rod 11, and on the other hand, a maximum contact surface S 'to the expanded gas, the latter being substantially equal to the surface of the head 14 of the piston 10. Moreover, the contact surface S being frustoconical, it offers a direct connection to the flow gas pressure even less important.

  At rest, that is to say when no gas flows through the expander, the head 14 of the piston 10 is kept away from the inner wall 5 by a spring 16 bearing on the one hand, on the internal wall 5, and secondly, on the head 14 of the piston.

  In operation, the gas under pressure is introduced into the pressure reducer 1 through the inlet 3. The gas then flows from the upstream compartment 6 under pressure to the downstream compartment 7 via the internal channel 18 of the rod 11 of the piston 10 before to exit the regulator through the output 4 to supply the user device.

  The forces tending to move the piston 10 away from the casing 2 are those coming from the gas under pressure and that exerted by the spring 16. The balance of the forces exerted on the mobile element at equilibrium is thus written: XS Patience + Fressort = Pdétente XS 'When the outlet pressure is too high, the force exerted by the gas expanded on the head 14 of the piston 10 is then sufficient to overcome the repulsion force of the spring 16 and the end 12 is pressed against the wall 20 in the seat 19, thus closing the inner channel 18 sealingly.

  When the outlet pressure decreases, the downstream compartment 6 is no longer supplied with gas, the return forces of the spring become greater than the pressure forces exerted by the gas expanded on the piston 10 and consequently cause the separation of the end 12 of the housing 2 and thus the opening of the inner channel 18. The pressurized gas flows again from the upstream compartment 6 to the downstream compartment 7.

  In case of variation of the supply pressure, the variation of the resulting opening force is equal to the product of the variation of the supply pressure by the surface on which this pressure is exerted, namely the contact surface. S. This being very much less than the contact area S ', the resulting variation is negligible. The equilibrium point of the piston 10 does not undergo any significant variation.

  FIG. 2 represents an expander 30 according to a second embodiment. The expander 30 is made from a housing 35 comprising a cover 35a, an intermediate portion 35b and a lower portion 35c. As for the housing 2, the housing 35 comprises an inlet 3 of gas under pressure arranged in the lower part 35c and an outlet 4 of the expanded gas arranged in the cover 35a. An inner wall 5 of the intermediate portion 35b divides the housing 35 into an upstream compartment 6, closed by the lower part 35c, and a downstream compartment 7, closed by the cover 35a. Furthermore, the expander 30 comprises a piston 31 which differs from the piston 10 of the expander 1 in that a flexible membrane 32 is fixedly attached to the end 13 by means of a crimping ring 33. The membrane 32 is also fixed peripherally in the housing 35 by means of fixing screws 34. The flexibility of the membrane 32 allows the latter to be deformed to follow the movement of the rod 11.

  Furthermore, a vent hole 21 is made in the intermediate portion 35b so as to allow communication between the atmosphere and the volume under the piston 31 and thus prevent any rise in pressure during the displacement of said piston 31.

  In this configuration, the movable element constituted by the piston 10 has, on the one hand, a minimal contact surface S to the pressurized gas, the latter being substantially reduced to the section of the hollow rod 11, and other on the one hand, a maximum contact area S 'with expanded gas, the latter being substantially equal to the surface of the membrane 32.

  However, it should be noted that the contact surface of a membrane such as membrane 32 is more difficult to evaluate precisely, particularly because of variations in the intrinsic stiffness of the membrane as a function of temperature. As a result, an expansion valve 30 according to this embodiment is slightly less accurate than a regulator 1 according to the first embodiment.

  It is also interesting to note that such regulators 1, 30 have a reduced number of parts compared to a traditional regulator.

  Although the invention has been described in connection with particular embodiments, it is obvious that it is not limited thereto and that it comprises all the technical equivalents of the means described and their combinations if they are within the scope of the invention.

Claims (2)

7 CLAIMS   Gas expander (1, 30) having at least one inlet port (3) for connection to a source of pressurized gas and at least one outlet port (4) for supplying the expanded gas to a user device, said expander comprising a pressure regulating mechanism controlled by the displacement of at least one movable element (10, 31), mounted on a prestressed member (16), and capable of closing off the passage (18) of the gas , characterized in that each movable element is shaped so as to offer, on the one hand, a minimum contact surface (S) to the pressurized gas penetrating through the inlet orifice, and on the other hand, a surface of contact (S ') with the expanded gas in the vicinity of the outlet orifice, to allow the delivery of a gas expanded at a determined pressure regardless of the pressure of the gas at the inlet.   2. Regulator (1, 30) according to claim 1, characterized in that the prestressed member (16) exerts on the movable member (10, 31) efforts 20 tending to its displacement in the direction of the opening of the gas passage.   3. Expansion valve (1, 30) according to any one of claims 1 or 2, characterized in that the prestressed member is a spring (16).   4. Expansion valve (1, 30) according to any one of claims 1 to 3, characterized in that it comprises an upstream compartment (6) in which opens the inlet (3) of pressurized gas and a downstream compartment ( 7) in which opens the outlet (4) expanded gas, the two compartments being separated by an inner wall (5) through which slides the movable member (10, 31).   5. Expansion valve (1, 30) according to any one of claims 1 to 4, characterized in that the movable element is formed in the form of a piston (10, 31) comprising, on the one hand, a head (14) located in the vicinity of the outlet (4), and secondly, a rod (11) having an end (12) adapted to cooperate with a seat (19) for closing the passage (18) of the gas.   6. Regulator (1, 30) according to claim 5, characterized in that the rod (II) comprises an inner channel (18) opening, on the one hand, at the head (14) of the piston (10). , 31) near the outlet (4), and secondly, at the end (12) of the rod located near the inlet port (3).   7. Regulator (1, 30) according to claim 6, characterized in that the inner channel (18) has, at the inlet port (3), a frustoconical end (12).   8. Expansion valve (30) according to any one of claims 5 to 7, characterized in that it comprises a flexible membrane (32) attached to the head (14) of the piston (31) and attached to the expander by its periphery.   9. Expansion valve (30) according to claim 8, characterized in that the membrane (32) is fixedly attached to the head (14) of the piston (31) by its central portion.