Fluid handling – Systems – Flow path with serial valves and/or closures
Patent
1994-06-17
1996-12-17
Chambers, A. Michael
Fluid handling
Systems
Flow path with serial valves and/or closures
1374875, F16K 3136
Patent
active
055843212
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to control installations for gas transmission and distribution systems, and particularly to apparatus for reducing and controlling the pressure and/or flow of gas in a pipeline.
BACKGROUND ART
In a gas transmission and distribution system, gas (i.e. fuel gas) is normally transmitted at high pressure, but has to be distributed to end users through local networks at a pressure which is relatively low and is also controlled fairly accurately. A pressure reducing station is therefore required for coupling the high-pressure transmission line to the local distribution network.
Conventionally, a pressure reducing station comprises two streams in parallel, each stream containing an initial isolating valve, slam-shut valve, a suitable number of pressure regulating (reducing) valves depending on the amount of pressure reduction required, and a final isolating valve. A typical example of such a station is shown in our GB 2 217 877 A. Such a station is normally located above ground, and the fact that the various valves in each stream are arranged in a linear sequence means that it normally occupies a good deal of space.
There has recently been increasing interest in the possibility of pressure reducing stations which are largely buried. A buried station has various advantages: it is relatively unobtrusive, the liability of accidental or deliberate damage to it is reduced, and the noise emission from it is reduced.
A buried station naturally requires a hole or pit to be dug, and it is desirable to minimize the size of this pit. A somewhat different design has therefore been developed for buried pressure reducing stations. The basic feature of a buried pressure reducing station, in its current form, is a pair of pressure chambers, an inlet chamber and an outlet chamber. The inlet chamber usually includes a filter, end communicates with the outlet chamber through a valve stack (a valve assembly or cartridge) including a slam-shut valve and a suitable number of pressure regulating valves.
Various specific designs for such stations are known. The two chambers may be physically separate units located adjacent to each other, or they may be separate units but located in a common outer enclosure. More usually, however, they are separate regions of a single pressure body divided by internal walls. It is also common for such stations to be largely buried, as discussed above.
The valve stack has controls which have to be accessible from outside the chamber. In addition, the valve stack requires servicing at suitable intervals. The design of the station should therefore be such as to make the valve stack easily accessible. This is commonly achieved by locating the chamber containing the valve stack towards the top of the pressure vessel and providing it with a lid which can be removed to provide access to the valve stack. This chamber therefore typically has a port or opening in its base with which the valve stack fits. The chamber containing the valve stack may be either the inlet or the outlet chamber.
The valve stack obviously has to have a good seal to the port between the two chambers, to prevent the escape of high-pressure gas through that port directly to the outlet.
It would be possible to bolt the valve stack directly to the chamber wall surrounding the port. However, this would require access to the bottom of the chamber to release the valve stack, and this would generally be difficult. Some other sealing technique is therefore required.
A technique for achieving such a seal is to form the port and the mating end of the valve stack as accurately formed cylindrical surfaces, with one of them including a suitable seal (such as an O ring). The valve stack is attached to the lid of the chamber, and after servicing, the combined lid and valve stack is lowered into the chamber, with the bottom end of the valve stack being inserted into the port. The lid can then be locked in position, so locating the valve stack in position. An example of this technique, which can be described
REFERENCES:
patent: 2737197 (1956-03-01), Jaseph
patent: 4565212 (1986-01-01), Klein et al.
patent: 4791954 (1988-12-01), Hasegawa
patent: 5220940 (1993-06-01), Palmer
Hargreaves Alan G.
Swallow David
Woodford Peter J.
Chambers A. Michael
International Gas Apparatus Ltd.
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