GB2303199A

GB2303199A - Valve assemblies

Info

Publication number: GB2303199A
Application number: GB9514183A
Authority: GB
Inventors: Bernard Mark Bentley; John Christopher Drew
Original assignee: L B BENTLEY Ltd
Current assignee: L B BENTLEY Ltd
Priority date: 1995-07-12
Filing date: 1995-07-12
Publication date: 1997-02-12
Anticipated expiration: 2015-07-12
Also published as: GB2303199B; GB9514183D0

Abstract

Opening of a valve is achieved by passing pilot air from an inlet 12 through a passageway 13 to act upon the enlarged under face 14 of a piston head 7. This is sufficient to overcome the bias of a spring stack 6 and pressure applied to a balanced stem head 11 so that a valve seal 4 is lifted off a valve seat 5. When the supply of pilot air is removed the pressurised air acting on the face 14 will bleed off again through the entry port 12 so that the valve will close again under the bias of the spring stack 6 and the pressure on the balanced stem area 11. A valve port 15 prevents high pressure air from entering into the low pressure actuation region behind the face 14, by leakage in the event of failure. The valve may be used as a drain valve in a pressurized vessel where the valve is actuated by means of a float valve in the vessel (figure 3).

Description

Improvements relating to Valve Assemblies It is an objective of this invention to provide a compact design of gas-operated valve assembly.

According to the present invention there is provided a valve assembly incorporating a valve piston carrying a valve seal at one end and having an enlarged head at the other end with biassing means acting on one face of the enlarged piston head to drive the valve seal towards a valve seat situated between inlet and outlet ports of the valve, and a pilot air inlet for directing pilot air to the other face of the enlarged piston head to overcome the closing bias on the valve seal through the piston This valve operates essentially by creating an uploading pressure on the enlarged piston head to cause the valve to open. It is highly desirable that the valve assembly should incorporate a passageway leading through the valve piston from the inlet port of the valve to a balanced stem area at the other end of the piston. This creates a balanced biassing closing force onto the valve seat.

Preferably the valve assembly will incorporate a vent outlet from the passageway within which the intermediate portion of the valve piston is slidably mounted, which will prevent direct communication from the high pressure inlet port through to the pilot air actuating region. Ideally the valve seal will be connected to one end of the valve piston by a roll pin providing a flexible mounting for the valve seal, so as to enhance the sealing effect. It is also preferable to provide an indicator pin which is attached to the valve piston and passes through the body of the valve assembly to indicate the state of the valve.

The invention further extends to a drain mechanism for a pressurised chamber comprising a float-operated valve for enabling pressurised gas within the chamber to enter into the pilot air inlet of a valve assembly of this invention as hereinbefore defined, when the float of the valve is lifted to a predetermined position, so as to connect a drain outlet of the chamber to the outlet port of the valve assembly via the inlet port thereof.

The invention may be performed in various ways and preferred embodiments will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a vertical section through an air operated stop valve of this invention in the open condition; Figure 2 is a similar cross-section showing the valve in the closed position; Figure 3 illustrates use of a valve of the form shown in Figures 1 and 2 controlling the drain outlet from a pressurised chamber; and Figure 4 is a partial section on line IV-IV of Figure 3.

The valve shown in Figures 1 and 2 has an inlet 1 leading to an outlet 2 via a valve chamber 3. A valve seal 4 sits on a valve seat 5 and is biassed into the closed position (as shown in Figure 2) by a spring stack 6 formed from disk springs acting on a piston head 7. The other end of the piston 8 has the valve seal 4 mounted thereon by a roll pin 9 allowing for a degree of flexibility so that the valve seal can float freely into the closed position so as to give a reliable low pressure seal. A balanced closing force is achieved by allowing the inlet air (or gas) to pass from the inlet 1 through a passageway 10 running through the piston 8 to a balanced stem area 11.

Opening of the valve is achieved by passing pilot air from an inlet 12 through a passageway 13 in the main outer body of the valve so that the pilot air will act upon the enlarged under face 14 of the piston head 7. The pressure exerted on the face 14 by the pilot air is sufficient to overcome the bias of the spring stack 6 and the pressure applied to the balanced stem head 11 so that the valve seal 4 is lifted off the valve seat 5. When the supply of pilot air is removed the pressurised air acting on the face 14 will bleed off again through the entry port 12 for the pilot air so that the valve will close again under the bias of the spring stack 6 and the pressure on the balanced stem area 11. A valve port 15 prevents high pressure air from entering into the low pressure actuation region behind the face 14, by leakage in the event of failure.

This unit is very small and compact. The simplified geometry allows for a one side assembly so that it is possible for all the components to be assembled from one direction as a cartridge into a larger existing component such as a filter base or a manifold block. The exact balanced stem area can be changed from one model to another to balance the valve forces for larger orifice valves and/or different operating pressures. The balanced stem area 11 gives an added load on the valve seal 4 in the closed position to give a fully pressure energised seal and reduces the spring force required to close the valve. Low friction O-rings act as seals through the assembly. A valve indicator pin 16 is provided which will show the operating status of the valve (since it projects when the valve is open). It also enables the user to monitor the closing action.The whole valve assembly can be constructed from non-magnetic materials should this prove necessary for particular applications.

As shown in Figures 3 and 4 the overall valve assembly 17 similar to that as shown in Figures 1 and 2 can be incorporated as part of an automatic drain mechanism for a high pressure chamber 18. If condensate accumulates in the chamber 18 this will ultimately act upon a float 19 which will lift a sleeve 20 so as to raise a valve seal 21 off a valve seat 22. The pressurised air in the chamber 18 will then be fed as pilot air to act on the face 14 of the piston head 7 so as to raise the valve seal 4 away from its valve seat 5 enabling the condensate within the chamber 18 to drain off to an outlet port 23. As the float 19 lowers again the valve seal 21 reengages with the valve seat 22 to close off the supply of pilot air to the valve assembly 17.

The pilot air within the valve assembly will then bleed off through the piston of the valve assembly to cause the stop valve to close. A manual override plunger 24 (Figure 4) can be operated from outside the assembly to lift the sleeve member 20 and thus check the operation of the autodrain system.

Claims

1. A valve assembly incorporating a valve piston carrying a valve seal at one end and having an enlarged head at the other end with biassing means acting on one face of the enlarged piston head to drive the valve seal towards a valve seat situated between inlet and outlet ports of the valve, and a pilot air inlet for directing pilot air to the other face of the enlarged piston head to overcome the closing bias on the valve seal through the piston.

2. A valve assembly according to Claim 1, wherein a passageway leads through the valve piston from the inlet port of the valve to a balanced stem area at the other end of the piston.

3. A valve assembly according to Claim 1 or Claim 2, wherein a vent outlet from the passageway within which the intermediate portion of the valve piston is slidably mounted.

4. A valve assembly according to any one of Claims 1 to 3, wherein the valve seal is connected to one end of the valve piston by a roll pin providing a flexible mounting for the valve seal.

5. A valve assembly according to any one of Claims 1 to 4, wherein an indicator pin is attached to the valve piston and passes through the body of the valve assembly to indicate the state of the valve.

6. A drain mechanism for a pressurised chamber comprising a valve assembly as defined in any one of Claims 1 to 6 and a float-operated valve for enabling pressurised gas within the chamber to enter into the pilot air inlet of said valve assembly, when the float of the valve is lifted to a predetermined position, so as to connect a drain outlet of the chamber to the outlet port of said valve assembly via the inlet port thereof.

7. A valve assembly or a drain mechanism for a pressurised chamber, and substantially as herein described with reference to the accompanying drawings.