Gas pressure reduction device with conduit from low pressure chamber

Abstract

A pressure reduction device e.g. for gas mains, and having a slam shut valve, has a valve with a valve disc 336, actuator assembly 330, 332, 334 and a valve seat 312, high pressure chamber (100a, fig

Description

Field of disclosure The present application relates generally to pressure reduction devices, and more specifically to a pressure reduction device for gas mains having a slam shut valve. Background Mains gas is typically transferred to homes and businesses using a high pressure supply network. Pressure reduction devices are used to reduce the pressure of a supplied mains gas to make it suitable for use in homes and businesses. In the event of an overpressure or under pressure condition at the low pressure side of the system, a safety mechanism may be put in place to shut off the pressure reduction device. Figure 1 shows a pressure reduction device in accordance with the prior art. It comprises a chamber 10 having a high pressure inlet pipe 11 and a low pressure outlet pipe 12. A separator 13 separates the high pressure side from the low pressure side. The chamber 10 has a base 14 and a lid 15. The base 14 is integrally formed with the chamber. The lid 15 is removable. Bolts for attaching the lid to the chamber are not shown. Within the high pressure side of the chamber 10 there is an axial flow valve 20 of a type known in the art and described, for example in US Patent 3838704. Above the valve 20 is a slam-shut valve seat 21 and a slam-shut valve 22. The slam-shut valve has a shaft 23, a power spring 24 and a diaphragm 25. A sense line 26 passes from the outlet pipe 12 to the undersigned of the diaphragm 25. In operation, high pressure mains gas enters through inlet pipe 11 passes down through the axial valve 20 into the low pressure side of the chamber 10 and out of the outlet pipe 12. The sense line 26 senses pressure in the outlet pipe 12 by connecting the outlet pipe to the underside of the diaphragm 25. When pressure rises in the outlet pipe 12 this causes the diaphragm 25 to flex upwards. This is turn causes the shaft 23 to be released (by movement of ball bearings that are not shown) causing the power spring 24 to urge the slam-shut valve 22 downwards onto the valve seat 21, thereby closing the slam-shut valve and preventing high pressure gas from entering the axial flow valve 20. This is a safety mechanism governed by strict regulations. When the slam-shut valve closes, it must be manually reopened by pulling a toggle 30 on the top of the shaft 23. If access to the slam-shut valve 22 or the valve seat 21 is required, the lid 15 is removed from the chamber 10 and the entire assembly of slamshut valve and axial flow valve is withdrawn upwards for access and maintenance. On the right hand side, at the exit to the low pressure outlet pipe 12, a non-return valve is added (not shown). This takes the form of a flap that prevents gas from passing from right to left in the event that there is a build-up of pressure downstream. The assembly can be used above or below ground. When used below ground it is necessary to dig a trench to accommodate the entire chamber, the inlet pipe, the outlet pipe and the non-return valve. There is a need to minimise the overall size of the trench to be dug to accommodate the system. There is also a need for easy access and maintenance when the system is below ground. Summary of the Invention A pressure reducing device is provided comprising: a valve comprising a valve disc, an actuator assembly and a valve seat; a high pressure chamber; a low pressure chamber; a pressure reducing means (e.g. an axial flow valve); and a non-return valve at an exit from the low pressure chamber. The high pressure chamber and the low pressure chamber are in fluid communication via the pressure reducing means. The valve seat is disposed between the high pressure chamber and the low pressure chamber, upstream from the pressure reducing means, to isolate the high pressure chamber from the low pressure chamber in response to a pressure condition in the low pressure chamber. The nonreturn valve is inside the low pressure chamber. Preferably, an outlet pipe passes from inside to outside of the low pressure chamber, wherein the non-return valve is positioned at an upstream end of the outlet pipe. The non-return valve may comprises a flap mounted at the upstream end of the outlet pipe, hinged to pass into the pipe in normal flow but to close against a valve seat when pressure at the outlet end of the pipe exceeds that in the low pressure chamber. The pressure reducing device preferably has a first lid for sealing the high pressure chamber, a second lid for sealing the low pressure chamber, instrumentation and / or control equipment mounted on the second lid, and a tube passing from the outlet pipe to the second lid, to convey gas at low pressure between the outlet pipe and the instrumentation and / or control equipment. A novel method of manufacture of a pressure reducing device is provided. The method comprises forming a chamber with a high pressure chamber, a low pressure chamber and a hole in the low pressure chamber to receive an outlet pipe; forming an outlet pipe assembly comprising the outlet pipe, a non-return valve located at an upstream end of the outlet pipe and a rigid tube connected perpendicular to the outlet pipe; inserting the outlet pipe through the hole in the low pressure chamber from inside the low pressure chamber; accurately locating the tube in position to receive a lid; sealing the outlet pipe around the hole in the low pressure chamber; and closing the low pressure chamber. The step of sealing preferably comprises sealing a base on the chamber, placing a first lid on the high pressure chamber and a second lid on the low pressure chamber, wherein the tube passes through a hole in the second lid. The first lid preferably extends partly over the low pressure chamber and has a conduit passing through the first lid, extending from the low pressure chamber to a slam-shut valve in the high pressure chamber. According to another aspect of the invention, a pressure reducing device is provided comprising: a valve comprising a valve disc, an actuator assembly and a valve seat; a high pressure chamber closed by a first lid; a low pressure chamber; and a pressure reducing means. The high pressure chamber and the low pressure chamber are in fluid communication via the pressure reducing means. The valve seat is disposed between the high pressure chamber and the low pressure chamber and upstream from the pressure reducing means, wherein the actuator assembly causes the valve disc to engage with the valve seat to isolate the high pressure chamber from the low pressure chamber in response to a pressure condition in the low pressure chamber. The device is characterized by a conduit disposed in the first lid and fluidly connecting the low pressure chamber to the actuator assembly. The first lid preferably comprises an extension portion that extends partially across the low pressure chamber. According to another aspect of the invention, a pressure reducing device is provided comprising: a valve comprising a valve disc, an actuator assembly and a valve seat; a high pressure chamber closed by a first lid; a low pressure chamber; and a pressure reducing means. The high pressure chamber and the low pressure chamber are in fluid communication via the pressure reducing means. The valve seat is disposed between the high pressure chamber and the low pressure chamber and upstream from the pressure reducing means. The actuator assembly causes the valve disc to engage with the valve seat to isolate the high pressure chamber from the low pressure chamber in response to a pressure condition in the low pressure chamber. The valve disk is configured to pass through an opening in the first lid. A method of operating the pressure reduction device comprise transferring a gas from the high pressure chamber to the low pressure chamber via the pressure reducing means, and communicating a pressure condition in the low pressure chamber to the actuator assembly via the conduit in the first lid. A method of manufacturing a lid for a pressure reducing device is provided comprising: forming a lid for a high pressure chamber of the device, the lid having a width dimension and a depth dimension extending perpendicular to the width dimension and an extension portion for extending partially beyond the high pressure chamber and across a low pressure chamber of the device; forming a first conduit into and through the lid following the width dimension, the first conduit extending from an outer surface of the extension potion. A second conduit may be formed into a lower surface of the extension portion and following the depth dimension joining the first conduit. A third conduit may be formed extending from an upper surface of the lid at the end of the first conduit opposite to the extension portion through the depth dimension and joining the first conduit. Other ways may be devised for forming the conduit in the first lid to fluidly connect the low pressure chamber to the actuator assembly. Preferred embodiments of the various aspects of the invention are now described, by way of example only, with reference to the drawings. Brief Description of the Drawings Fig. 1 depicts a known pressure reduction device. Fig. 2 is a perspective view of a chamber for a pressure reduction device according to the present disclosure. Fig. 3 is a cross-sectional view of the chamber of Fig. 2 Fig. 4 shows, in cross section, details of the low-pressure side of a pressure reduction device according to the present disclosure. Fig. 5 show, in cross section, details of the high-pressure side of a pressure reduction device according to the present disclosure. Figs. 6 and 7 show enlarged details of Fig. 5. Fig. 8 shows the slam-shut valve of Fig. 5 in greater detail. Detailed Description Referring now to Figs. 2 and 3, a chamber 100 for a pressure reduction system is shown in perspective view and in vertical cross section. The chamber 100 has a high pressure chamber 100a and a low pressure chamber 100b, a high pressure inlet pipe 101 a low pressure outlet pipe 102, a high pressure side opening 103 and low pressure side opening 104. A separator wall 110 separates the high pressure chamber 100a from the low pressure chamber 100b. Below it is described that a first lid will be mounted over the opening 103 and a second lid will be mounted over the opening 104. It will also be described that an extension portion of the first lid will extend across a hole 105 communicating with the low pressure chamber 100b. The chamber 100 has a base 112. There is a non-return valve 114 connected to the inlet side of the low pressure outlet pipe 102, inside the chamber 100. The non-return valve takes the form of a flap with a hinge at its upper edge, so that it hangs down from the hinge under gravity. The flap closes against a valve seat when pressure at the outlet end of the pipe exceeds that in the low pressure chamber. At the outlet end of the low pressure pipe 102 there is a simple flange 115. A pipe 116 is connected to the outlet pipe 102 and passes upward through the lid of the chamber 100. This pipe 116 is welded to the low pressure pipe 102. It has a diameter of about 25mm (1 inch). There is a hole 120 in the chamber 100, where the outlet pipe 102 exits from the chamber 100. The hole 120 is sized to accommodate the outlet pipe 102 with a loose fit. The hole has a bevelled edge (bevelled from the outside). There is an inlet flange 117 at the inlet end of the high pressure inlet 101. The arrangement of the chamber is very compact. To achieve this compact arrangement a particular sequence of manufacturing steps is described. First, the outlet pipe 102 is assembled. The non-return valve 114 is attached and the pipe 116 is welded in place, perpendicular to the outlet pipe 102. The flange 115 is not yet added. Before adding the base 112, the chamber is inverted. The outlet pipe 102, with its non-return valve 114 and its pipe 116, is inserted into the chamber 100 from the base side. It is passed through the hole 120 at the right hand side, ready for welding in position. The loose fit and bevelled edge of the hole facilitates pushing the outlet pipe 102 through the hole 120 from an off-axis position. Before welding in position, the chamber is inverted top side up and a jig (not shown) is mounted on top of the chamber at the low pressure side opening 104. The jig is bolted temporarily in place to exactly position the upper end of the pipe 116. Using the jig to exactly position the pipe, the outlet pipe 102 is then welded at a weld line around the hole 120. The bevelled edge to the hole 120 is advantageous to receive weld metal and form an even sealed weld line. Finally (in any order), the flange 115 is added and the base 112 is added. The base may have a groove to receive and accommodate the walls of the chamber, and a weld line may be formed around the base where the chamber walls meet the base. Referring now to Fig. 4, details of the low pressure side of the system are shown, including the outlet pipe 102, the non-return valve 114, the flange 115 and the pipe 116. After completing fabrication of the chamber 100, the chamber can be painted. All surfaces are painted except the areas surrounding the openings 103 and 104 and the end faces of the outlet flange 115 and the inlet flange 117. After painting, assembly of the system can commence. Assembly includes adding a lid 200 with various measurement and control components 202 that need not be described in detail. The jig that was used to locate the pipe 116 is removed and an O-ring 203 is added to the pipe 116. The lid 200 is inserted in place. The pipe is now accurately positioned, and the O-ring 203 provides a seal to the lid 200. The lid 200 can be bolted down to the housing 100 and all necessary control and measurement components 202 can be added. On the right hand side, a simple shut off valve 210 is bolted to the flange 115. Referring now to Fig. 5, a novel slam-shut valve arrangement is shown. The arrangement has a lid (a "first lid") 300 for mounting on the opening 103 of the high pressure side of the container 100. The first lid 300 has a wide internal aperture 301 into which a body 305 is mounted with a diaphragm lid 308. A diaphragm 309 is located between the body 305 and the lid 308. Mounted below the opening 301 is a flange adaptor 310 having holes 311 for gas to enter. Below these is a valve seat 312 with a knife edge 314. Mounted below the valve seat 312 is an axial flow valve 320. A diffuser may be disposed downstream of the axial flow valve in the low pressure chamber. The slam-shut valve has an actuator assembly comprising a shaft 330 a weak spring 332 and ball bearings 334. The actuator assembly is connected to a valve disc 336. It may be noted that the aperture 301 in the lid 300 is wider than the diameter of the valve disc 336. Formed in the first lid 300, extending from the centre to the right hand side is a conduit 340. This conduit extends horizontally to the low pressure side of the vessel 100 and has an inlet tube 342 extending downward towards the low pressure side of the vessel and an outlet 344 that will be explained in more detail. Inlet tube 342 connects into hole 105 in the extension portion of the first lid, shown in Fig. 2. Fig. 6 shows the inlet end of the conduit 340 in greater detail. It shows the tube 342 extending downwards with an O-ring 350 around the tube 342 for sealing purposes. There is a plug 352 at the right hand end to close the conduit 340. Referring to Fig. 7, the outlet end of the conduit 340 is shown in greater detail. It has a vertical shaft 360 extending from the lid 300 into the body 305 of the slam-shut valve and an upward extending conduit 370 extending to the underside of the diaphragm 309. There is a tube 374 (e.g. a plastic or elastomeric tube) in the shaft 360, in the lower part of the shaft 360 where the shaft extends through the lid 300. The tube 374 extends into an upper part of the shaft 360 in the body 305. An O-ring seal 372 seals the outlet of the conduit. It may be noted that the first lid 300 extends further to the right hand side than to the left hand side. In other words it has an extension on the low pressure side that means the first lid 300 extends partly beyond separator 110 and over chamber 100b. The conduit 340 is formed within the thickness of the first lid 300. The first lid thus extends across a surface of the high pressure chamber in a width dimension, and extends perpendicular thereto in a depth dimension and the conduit 340 extends vertically through the extension portion and horizontally through the depth dimension to fluidly connect the low pressure chamber to the actuator assembly. It is formed by drilling from the right hand side from the outside of the lid horizontally through the lid to the distance of the upwardly extending shaft 360. Separately, the shaft 360 is drilled from above to connect with the conduit 340. Separately the upwardly extending shaft 370 is drilled into the body 305 of the slam-shut valve. The right hand end of the conduit 340 is sealed with plug 352. The body and mechanism of the slam-shut valve are shown in greater detail in Fig. 8. In Fig. 8, it can be seen that a spring chamber extension 400 with a cap 402 is provided on top of the lid 308 of the slam-shut valve. This encases the shaft 330. A coloured ball 404 is mounted on the top of the shaft as an indicator. Further down the shaft are the ball bearings 334. These sit within a recess of cylinder 410. The recess is an annulus at the lower end of the cylinder 410 surrounding the shaft 330. The shaft has a shoulder 412 at which the diameter of the shaft increases from a narrow diameter to a wider diameter. There is a strong compression spring 420 below the body 305 extending to a shaft connector 425 that is rigidly connected to the shaft. In normal operation, referring to Fig. 5, gas flows through the holes 311 into the axial valve 320 and through to the low pressure side of the system. In the event of an over-pressure situation on the low pressure side of the system, gas passes through the inlet 342 of the conduit 340 to the underside of the diaphragm 309. The conduit 340 acts as a sense line for sensing an over-pressure event in the low pressure side of the system. When pressure increases below the diaphragm 309, this causes the diaphragm to flex upwards against a weak force in the weak spring 332. This causes the ball bearings 334 to be released from the constraint of the annular recess in the cylinder 412. The ball bearings move outwards beyond the shoulder 412 of the shaft 330 and the shaft is free to move downwards. The shaft quickly moves downwards under the strong force of compression spring 420, causing the valve disc 336 to slam shut against the knife edge 314 of the valve seat 312. The valve disc 336 has a rubber or silicone annulus 470 to provide a good seal against the knife edge 314 and also to protect the knife edge 314 from damage. The overall construction is that of an actuator assembly that causes the valve disc to engage with the valve seat to isolate the high pressure chamber 100a from the low pressure chamber 100b in response to a pressure condition in the low pressure chamber 100b. The ball bearings and shaft can be described as a captive ball and cage mechanism. The diaphragm is configured to actuate the ball and cage mechanism in response to the pressure condition in the low pressure chamber. Other resettable release mechanisms are possible, such as a spring and pawl mechanism. To reset the valve, the ball 404 is visibly moved downwards within the extension 400. The operator removes the extension 400 and pulls the ball upwards, thereby pulling the shaft upwards on the valve against compression force in the spring 420 until the shoulder 412 passes above the setting position and the ball bearings 334 can return to their reset position (move readily inwards under force of the cylinder 410 being pushed downwards by the weak spring 332). The operator replaces the extension 400. The extension 400 protects the shaft 330 from the environment and from damage, as does the cap 402. The indicator ball 404 is a handy visual indicator for an operator to determine whether the valve has closed. The first lid, the valve, and the pressure reduction means are all removably attached to the opening 103 of the high pressure chamber 100a as a combined unit. In the event that the slam-shut valve requires maintenance, for example if the rubber / silicone seal 470 is compromised or other damage is caused, it is not necessary to remove the entire lid 300 and all the elements above and below. For maintenance purposes it is sufficient to remove the body 305 from the lid 300 to provide access to the opening 301. The opening 301 is wide enough for the slam-shut valve disc 336 to be lifted upwards and clear of the valve seat 312 and other elements for inspection and and / or maintenance. fig7 shows there is an o-ring 390 sealing the body 305 to the lid 300. The body 305 is bolted to the lid 300 by means of two or more bolts. Body 305 is accurately aligned with the lid 300, and its rotational position is accurately positioned by the tube 374 This means that the shaft 370 is in flow communication with the shaft 360 and with the conduit 340. The conduit 340 is integral to the valve actuator assembly to fluidly connect the conduit 340 to the actuator assembly. The lid 300 has six bolts four around the circumference of the opening 103 and two in the lid 300 extension portion. These bolts accurately align the lid 300 to the body 100. Ensuring shaft 370 is fluidly connected to hole 105 communicating with the low pressure chamber 100b. The arrangement as described has a number of advantages. First it may be noted that with reference to Fig. 4, placing the non-return valve 114 inside the low pressure side of the chamber 100 obviates the need for extending the low pressure outlet pipe 102 further to the right to provide for both a non-return valve and a flange 115. Only the flange 115 is positioned outside the vessel. This is made possible by the complex sequence of manufacturing steps whereby the pipe 116 is accurately aligned to the lid 200. This in turn is made possible by separate provision of the base 112. The pipe 116 has two purposes. It acts as a pressure sense line from the outlet pipe 102 downstream of the non-return valve 114 for purposes of instrumentation and control 202. Its second purpose is as a dump for release of gas in the opposite direction. There may be a number of reasons for causing gas to be released in small quantities from the instrumentation and control 202. When a small amount of gas is to be released, it must be dumped into the low pressure side. The pipe 116 is of sufficient diameter that when a small volume of gas is released into it, it does not provide for a pressure drop along its length and therefore does not interfere with measurements or control in the instrumentation and control equipment 202. A second advantage of the arrangement has already been described viz. the ease of maintenance of the lower portions of the slam-shut valve through easy access from above, particularly when the vessel is situated belowground. Additionally, the need for an external sense line is eliminated. By virtue of the conduit 340 extending through the thickness of the lid 300 and extending to the low pressure side of the container 100, a conduit is provided from the low pressure side to the slam-shut valve diaphragm 309 without any external sense line. This has two advantages. First it reduces the footprint of the vessel, because there is no need for any sense line connector at the outlet pipe 102, thus shortening the length of the outlet pipe 102. Furthermore it avoids external lines that might be subject to damage or environmental degradation. It also reduces the part count, thereby reducing the overall cost. It may be noted that the features that give rise to each of these advantages can be implemented separate from other features that give rise to each of the other advantages. Thus, for example, features of Fig. 3 and / or 4 can be implemented separate from features of Fig. 5 or Fig. 8. Equally, features of Fig 8 are not dependent on features of Fig. 3. 4 or 5 and the conduit described with reference to Figs. 5, 6 and 7 (and partially shown in Fig. 4) can be implemented independently of other features of Figs 3, 4, 5 and 8. The above description is given by way of example only and modifications of detail would be apparent to those skilled in the art within the scope of the appended claims. Examples Example 1 is a pressure reducing device comprising: a valve comprising a valve disc, an actuator assembly and a valve seat; a high pressure chamber; a low pressure chamber; a pressure reducing means; and a non-return valve at an exit from the low pressure chamber; wherein: the high pressure chamber and the low pressure chamber are in fluid communication via the pressure reducing means; the valve seat is disposed between the high pressure chamber and the low pressure chamber, upstream from the pressure reducing means, to isolate the high pressure chamber from the low pressure chamber in response to a pressure condition in the low pressure chamber; and the non-return valve is inside the low pressure chamber. Example 2 is a pressure reducing device according to example 1, further comprising an outlet pipe passing from inside to outside of the low pressure chamber, wherein the non-return valve is positioned at an upstream end of the outlet pipe. Example 3 is a pressure reducing device according to example 2, wherein the non-return valve comprises a flap mounted at the upstream end of the outlet pipe, hinged to pass into the pipe in normal flow but to close against a valve seat when pressure at the outlet end of the pipe exceeds that in the low pressure chamber. Example 4 is a pressure reducing device according to example 2 or 3, further comprising a first lid for sealing the high pressure chamber, a second lid for sealing the low pressure chamber, instrumentation and / or control equipment mounted on the second lid, and a tube passing from the outlet pipe to the second lid, to convey gas at low pressure between the outlet pipe and the instrumentation and / or control equipment. Example 5 is a method of manufacture of a pressure reducing device comprising: forming a chamber with a high pressure chamber, a low pressure chamber and a hole in the low pressure chamber to receive an outlet pipe; forming an outlet pipe assembly comprising the outlet pipe, a non-return valve located at an upstream end of the outlet pipe and a rigid tube connected perpendicular to the outlet pipe; inserting the outlet pipe through the hole in the low pressure chamber from inside the low pressure chamber; accurately locating the tube in position to receive a lid; sealing the outlet pipe around the hole in the low pressure chamber; and closing the low pressure chamber. Example 6 is the method of example 5, wherein the step of sealing comprises sealing a base on the chamber, placing a first lid on the high pressure chamber and a second lid on the low pressure chamber, wherein the tube passes through a hole in the second lid. Example 7 the method of example 6, wherein the first lid extends partly over the low pressure chamber and has a conduit passing through the first lid, extending from the low pressure chamber to a slam-shut valve in the high pressure chamber. Example 8 is a pressure reducing device comprising: a valve comprising a valve disc, an actuator assembly and a valve seat; a high pressure chamber closed by a first lid; a low pressure chamber, and; a pressure reducing means; wherein: the high pressure chamber and the low pressure chamber are in fluid communication via the pressure reducing means; the valve seat is disposed between the high pressure chamber and the low pressure chamber and upstream from the pressure reducing means, wherein the actuator assembly causes the valve disc to engage with the valve seat to isolate the high pressure chamber from the low pressure chamber in response to a pressure condition in the low pressure chamber, characterized by a conduit disposed in the first lid and fluidly connecting the low pressure chamber to the actuator assembly. Example 9 is the device of example 8, further comprising a sense line integral to the actuator assembly to fluidly connect the conduit of the first lid to the actuator assembly. Example 10 is the device of example 8 or 9, wherein the first lid comprises an extension portion that extends partially across the low pressure chamber. Example 11 is the device of any previous example, wherein the first lid extends across a surface of the high pressure chamber in a width dimension, and extends perpendicular thereto in a depth dimension, wherein the conduit extends vertically through the extension portion and horizontally through the depth dimension of the first lid to fluidly connect the low pressure chamber to the actuator assembly. Example 12 is the device of any previous example, wherein the valve disc is configured to pass through an opening in the first lid. Example 13 is a pressure reducing device comprising: a valve comprising a valve disc, an actuator assembly and a valve seat; a high pressure chamber closed by a first lid; a low pressure chamber, and; a pressure reducing means; wherein: the high pressure chamber and the low pressure chamber are in fluid communication via the pressure reducing means; the valve seat is disposed between the high pressure chamber and the low pressure chamber and upstream from the pressure reducing means; and the actuator assembly causes the valve disc to engage with the valve seat to isolate the high pressure chamber from the low pressure chamber in response to a pressure condition in the low pressure chamber, characterized in that the valve disc is configured to pass through an opening in the first lid. Example 14 is the device of any preceding example, wherein the low pressure chamber is closed by a second lid, wherein the second lid comprises a conduit in fluid communication with the low pressure chamber to provide a pilot line. Example 15 is the device of example 14, wherein the pilot line is in fluid communication with the pressure reducing means via the first lid. Example 16 is the device of any preceding example further comprising a non-return valve disposed inside the low pressure chamber. Example 17 is the device of any preceding example further comprising a diffuser disposed downstream of the pressure reducing means in the low pressure chamber. Example 18 is the device of any preceding example, wherein the pressure condition is an overpressure condition. Example 19 is the device of any previous example, wherein the first lid supports the valve seat and the pressure reducing means. Example 20 is the device of any previous example, wherein the first lid, the valve, and the pressure reduction means are removably attached to the chamber as a combined unit. Example 21 is the device of any previous example, wherein the pressure reducing means is an axial flow valve. Example 22 is a method of operating the pressure reduction device of any of example 8 to 12, comprising: transferring a gas from the high pressure chamber to the low pressure chamber via the pressure reducing means; and communicating a pressure condition in the low pressure chamber to the actuator assembly via the conduit in the first lid. 5 Example 23 is a method of manufacturing a lid for a pressure reducing device comprising: forming a lid for a high pressure chamber of the device, the lid having a width dimension and a depth dimension extending perpendicular to the width dimension and an extension portion for extending partially beyond the high pressure chamber and across a low pressure chamber of the device; forming a first conduit into and through the lid following the width dimension, the first conduit 10 extending from an outer surface of the extension potion. Example 24 is a method of example 22, further comprising forming a second conduit into a lower surface of the extension portion and following the depth dimension joining the first conduit. Example 25 is the method of either of examples 23 and 24, further comprising forming a third conduit extending from an upper surface of the lid at the end of the first conduit opposite to the 15 extension portion through the depth dimension and joining the first conduit.

Claims

1. A pressure reducing device comprising:a valve comprising a valve disc, an actuator assembly and a valve seat;a high pressure chamber closed by a first lid;a low pressure chamber, and;a pressure reducing means; wherein:the high pressure chamber and the low pressure chamber are in fluid communication via the pressure reducing means;the valve seat is disposed between the high pressure chamber and the low pressure chamber and upstream from the pressure reducing means,wherein the actuator assembly causes the valve disc to engage with the valve seat to isolate the high pressure chamber from the low pressure chamber in response to a pressure condition in the low pressure chamber, characterized bya conduit disposed in the first lid and fluidly connecting the low pressure chamber to the actuator assembly.

2. The device of claim 1, further comprising a sense line integral to the actuator assembly to fluidly connect the conduit of the first lid to the actuator assembly.

3. The device of claim 1 or 2, wherein the first lid comprises an extension portion that extends partially across the low pressure chamber.

4. The device of claim 3, wherein the first lid extends across a surface of the high pressure chamber in a width dimension, and extends perpendicular thereto in a depth dimension, wherein the conduit extends vertically through the extension portion and horizontally through the depth dimension of the first lid to fluidly connect the low pressure chamber to the actuator assembly.

5. The device of claim 4, wherein the conduit extends from an outer surface of the extension potion to the low pressure chamber.

6. The device of claim 5 comprising a second conduit formed into a lower surface of the extension portion and following the depth dimension joining the first conduit.

7. The device of claim 6 comprising a third conduit extending from an upper surface of the lid at the end of the first conduit opposite to the extension portion through the depth dimension and joining the first conduit.

8. The device of any previous claim, wherein the valve disc is configured to pass through an opening in the first lid.

9. The device of any preceding claim, wherein the low pressure chamber is closed by a second lid, wherein the second lid comprises a conduit in fluid communication with the low pressure chamber to provide a pilot line.

10. The device of claim 9, wherein the pilot line is in fluid communication with the pressure reducing means via the first lid.

11. The device of any preceding claim further comprising a non-return valve disposed inside the low pressure chamber.

12. The device of any preceding claim further comprising a diffuser disposed downstream of the pressure reducing means in the low pressure chamber.

13. The device of any preceding claim, wherein the pressure condition is an overpressure condition.

14. The device of any previous claim, wherein the first lid supports the valve seat and the pressure reducing means.

15. The device of any previous claim, wherein the first lid, the valve, and the pressure reduction means are removably attached to the chamber as a combined unit.

16. The device of any previous claim, wherein the pressure reducing means is an axial flow valve.

17. A method of operating the pressure reduction device of any of claims 1 to 16, comprising: transferring a gas from the high pressure chamber to the low pressure chamber via the pressure reducing means; andcommunicating a pressure condition in the low pressure chamber to the actuator assembly via the conduit in the first lid.

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