GB2231174A

GB2231174A - Gas pressure regulator arrangement

Info

Publication number: GB2231174A
Application number: GB8907240A
Authority: GB
Inventors: Kenneth M Cooper; Robert Anthony Johnson
Original assignee: Bryan Donkin Co Ltd
Current assignee: Bryan Donkin Co Ltd
Priority date: 1989-03-30
Filing date: 1989-03-30
Publication date: 1990-11-07
Also published as: GB8907240D0

Abstract

In a pilot-operated gas regulator arrangement, the risk of an increase in downstream pressure occurring after operation of an overpressure cut off device 14 is obviated or mitigated by tapping the high pressure gas supply for the pilot regulator from the control orifice 16 of the main regulator 12 at a location 21 downstream of the valve seat with which the valve head 24 of the overpressure cut off device cooperates automatically to cut off flow of gas through the gas distribution system. <IMAGE>

Description

GAS PRESSURE REGULATOR ARRANGEMENTS This invention relates to gas pressure regulator arrangements, and relates particularly to pilotoperated gas pressure regulator arrangements.

Gas pressure regulators are frequently pilot operated in order to improve their control characteristic and allow them to operate, for instance, with higher inlet pressures. The function of the pilot regulator is to provide the appropriate controlling pressure to the main regulator causing the latter to modulate as necessary in order to maintain the requisite downstream system pressure.

It is necessary in such configurations to provide the pilot regulator with a high pressure source of gas to enable it to supply the main regulator it the necessary range of control pressure. It is conventional for such a high pressure supply to be taken from the upstream side of the main gas pressure regulator. The pilot regulator will frequently incorporate a bleed and since it is not normally permissible to allow gas to bleed to atmosphere, it is necessary to pipe the bleed into an appropriate low pressure gas system. Conventionally this would be the system in which the pressure is being controlled by the main gas pressure regulator, i.e.

it will be piped into the gas distribution system downstream of the main regulator.

It can be seen, therefore, that there is a bleed of gas from upstream to downstream of the main regulator and, while in large gas distribution systems this is generally of no consequence, there are instances, such as gas burner installations for example, where such a bleed will ultimately result in an unacceptably high system pressure downstream of the main regulator. While many such regulators would be fitted with an automatic overpressure cut off device to protect the downstream system from an unacceptably high pressure, many of such overpressure cut off devices operate by closing off gas supply on the opposite end of the control orifice of the main gas regulator.Since the feed to the pilot regulator is conventionally upstream of this control orifice, the operation of the automatic over pressure cut off device does not prevent a further increase in the downstream system pressure, due to the effect of the pilot regulator bleed.

It is an object of the present invention to provide a pilot-operated gas regulator arrangement which obviates or mitigates the risk of the aforesaid increase in downstream system pressure occuring after the overpressure cut off device has operated.

According to the present invention this is achieved by tapping the high pressure gas supply for the pilot regulator from the control orifice of the main regulator at a location downstream of the valve seat with which the valve head of the overpressure cut off device cooperates automatically to cut off flow of gas through the gas distribution system.

More specifically, there is provided a pilotoperated gas regulator arrangement for a gas distribution system and comprising a main gas regulator having a control orifice between high pressure and low pressure sides of the gas distribution system, a pilot regulator supplying control gas from the high pressure side of the main regulator to a modulating control element of the main regulator, there being a gas bleed from the pilot regulator to the low pressure side of the gas distribution system, and an overpressure cut off device incorporated in the main regulator and adapted to shut off the supply of gas from the high pressure side to the low pressure side of the main regulator if the main regulator gas outlet pressure exceeds a predetermined level, the pilot-operated gas regulator arrangement being characterised in that the control gas supply to the pilot regulator from the control orifice is tapped from the latter at a location downstream of the overpressure cut-off device.

As a result of the present invention gas supply to the pilot regulator is shut-off as is the gas bleed therefrom into the low pressure side of the gas distribution system.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a plan view of a pilot operated gas pressure regulator arrangement incorporating the present invention; Fig. 2 is a part-sectional view of th regulator arrangement of Fig. 1 is, to an enlarged scale; Fig. 3 is a sectional view of the control orifice region of the main gas regulator; and Fig. 4 is a fragmentary detail sectional view of the control orifice.

The pilot-operated gas pressure regulator arrangement is generally indicated at 10 and has coupling flanges 11 to permit it to be connected into pipework (not shown) of a gas distribution system (also not shown) having a high pressure side HP and a low pressure side LP.

The regulator arrangement 10 comprises a main regulator 12, a pilot regulator 13 operatively associated therewith, and an overpressure cut off device 14 incorporated therein.

The main regulator body 15 incorporates a control orifice in the form of a sleeve 16 suitably secured by convenient means (not shown) between the high and low pressure sides HP, LP of the main gas regulator 12.

0-rings 17, 18 are interposed between the control orifice sleeve 16 and the body 15 to ensure there is no gas leakage therebetween from the high pressure side Tip to the low pressure side LP.

Orifices 19 are formed in the control orifice sleeve 16 at angularly spaced intervals and con.municate with an annular gas flow passage 20 which is tapped as indicated at 21 to permit passage of a high pressure gas flow via a pipe 22 to the pilot regulator 13 which provides the controlling pressure for a modulating control element, e.g. a diaphragm assembly (not shown) of the main regulator 12. A gas bleed (not shown) from the pilot regulator 13 is directed into the low pressure side LP of the gas distribution system.

It is to be noted that the tapping 21 is located at a location intermediate the high pressure and low pressures side HP, LP of the main regulator 12.

The ends 16A and 16B of the sleeve 16 provide respectively seats for the valve head 23 of the main regulator 12 and the valve head 24 of the overpressure cut off device 14.

The position of the valve head 23 relative to its seat 16A is modulated to control outlet gas pressure downstream of the end 16A of the sleeve 16 of the main regulator 12.

The valve head 24 is normally disposed at its maximum open position relative to its valve seat 16B, i.e. upstream of the tapping 21, and engages its valve seat 163 automatically in an emergency to shut off the supply of gas if the outlet gas pressure from the main regulator exceeds a predetermined safe level. When this shut off occurs the gas supply via the taping 21 is also shut off as is the gas bleed from the pilot regulator 13 to the low pressure side LP of the gas distribution system.

Claims

1. A pilot-operated gas regulator arrangement for a gas distribution system comprising, in operative association, a main gas regulator, a pilot regulator and an overpressure cut off device and in which a high pressure gas supply for the pilot regulator is tapped from a control orifice of the main regulator at a location downstream of a valve seat with which a valve head of the overpressure cut off device cooperates automatically to cut off flow of gas through the gas distribution system.

2. A pilot-operated gas regulator arrangement for a gas distribution system and comprising a main gas regulator having a control orifice between high pressure and low pressure sides of the gas distribution system, a pilot regulator supplying control gas from the high pressure side of the main regulator to a modulating control element of the main regulator, there being a gas bleed from the pilot regulator to the low pressure side of the gas distribution system, and an overpressure cut off device incorporated in the main regulator and adapted to shut off the supply of gas from the high pressure side to the low pressure side of the main regulator if the main regulator gas outlet pressure exceeds a predetermined level, the pilot-operated gas regulator arrangement being characterised in that the control gas supply to the pilot regulator from the control orifice is tapped from the latter at a location downstream of the overpressure cut-off device.

3. An arrangement as claimed in claim 2, in which the control orifice is in the form of a sleeve arranged between high and low pressure sides of the main gas regulator.

4. An arrangement as claimed in claim 3 comprising an orifice traversing the sleeve and communicating with an annular gas flow passage in communication with the pilot regulator to permit passage thereto of high pressure gas from the control orifice.

5. An arrangement as claimed in claim 4 in which the sleeve is formed with angularly-spaced orifices in communication with the annular gas flow passage into which is tapped a gas flow pipe connected to the pilot regulator.

6. An arrangement as claimed in any one of claims 3 to 5 comprising O-ring seal means between the control orifice sleeve and the main gas regulator body to prevent gas leakage between the high and low pressure sides thereof.

7. An arrangement as claimed in claim 6, comprising two 0ring seals, one upstream of the annular gas flow passage and one downstream of the latter in terms of the direction of gas flow through the main gas regulator.

8. An arrangement as claimed in any one of claims 3 to 7 in which the ends of the control orifice sleeve respectively provide valve seats for the valve head of the main gas regulator and the valve head of the overpressure cut off device.

9. A pilot-operated gas regulator arrangement for a gas distribution system, substantially as hereinbefore described with reference to the accompanying drawings.