GB2305489A

GB2305489A - Valve

Info

Publication number: GB2305489A
Application number: GB9519292A
Authority: GB
Inventors: Leon Phipson
Original assignee: Delta Fluid Products Ltd
Current assignee: Delta Fluid Products Ltd
Priority date: 1995-09-21
Filing date: 1995-09-21
Publication date: 1997-04-09
Anticipated expiration: 2015-09-21
Also published as: GB2305489B; GB9519292D0

Abstract

A shut-off ball valve has a valve housing (1) with inlet and outlet passages (1a, 1b). A pivotal ball valve member (3) is mounted in the housing (1) for pivotal movement relative thereto to control the flow of fluid. Relatively soft seals (4) providing primary sealing means engage against the valve member (3). Fire-resistant seals (5) provide secondary sealing means, and a spring (7) urges the seals (4 and 5) and the member (3) into mutual contact. The fire-resistant seals 5 are held off the valve member 3 by the soft seals 4. If the soft seals are deformed or destroyed by high temperatures the fire-resistant seals can then be urged against the valve member 3 to maintain the integrity of the seal.

Description

VALVE This invention relates to a valve and is more particularly concerned with a valve in which a rotatable valve member is used for controlling the flow of fluid through the valve. The invention is particularly, but not exclusively, concerned with shut-off ball valves.

A fire-proof ball valve has been disclosed in GB-A-2186347 where a metallic shut-off ball is rotatable within a metallic housing and has elastomer gaskets which surround entries of inlet and outlet flow passages into a ball chamber in the housing and which engage sealingly with the ball valve. Such elastomer gaskets provide a primary sealing function but are not fire-proof. In addition to such gaskets, copper sealing sleeves are provided which are fitted into the inlet and outlet flow passages of the housing where they open into the ball chamber.

The copper sleeves are in constant abutment with the shut-off ball. Such copper sleeves provide a secondary sealing function during normal use but are mainly intended to perform the primary sealing function when the elastomer seals become distorted or destroyed during a fiie and lustt their sealing function. With this type of sealing arrangement, there is still a risk that leakage can occur at the time when the gasket starts to distort under the action of heat.

It is an objection of the present invention to obviate or mitigate this disadvantage.

In accordance with the present invention, there is provided a valve comprising a valve housing having an inlet passage and an outlet passage, a pivotable valve member mounted in the housing for pivotal movement relative thereto to control the flow of fluid through the housing between the inlet and the outlet passages, and sealing means for sealing the valve member relative to the housing, said sealing means including (a) primary sealing means engaging against the rotary valve member and (b) secondary, fire-resistant sealing means, wherein urging means is provided for effecting relative movement between the valve member and the primary sealing means in a direction to urge them into mutual contact.

The provision of such urging means enables a more effective seal on the valve member to be obtained at the critical time when the primary sealing means starts to distort under the action of heat and before the secondary sealing means has reached a temperature at which it is designed to operate with maximum efficiency.

It is preferred to arrange the secondary sealing means so that they are normally spaced from the valve member but are acted upon by the urging means so as urge the secondary sealing means and valve member into mutual engagement as the primary sealing means distorts under the action of heat. This has the advantage that the secondary sealing means does not contact the valve member during normal use of the valve and there is no risk of the relatively hard secondary sealing means scoring the surface of the valve member during repeated operation of the valve member. Scoring of the surface of the valve member can lead to loss of sealing.

Preferably, the urging means comprises a spring which acts on both the primary and the secondary sealing means.

The present invention is of particular use in known types of valve in which the inlet and outlet passages are arranged on opposite sides of a chamber in the housing in which the valve member is located, the valve member having a passage therethrough via which communication takes place between the inlet and the outlet passages in a first pivoted position of the valve member and where communication between the inlet and outlet passages is prevented when the valve member is in a second pivoted position.

In a particularly convenient embodiment, the primary sealing means comprises a pair of primary sealing rings disposed in respective recesses in the housing surrounding the inlet and outlet passages, and the secondary sealing means comprises a pair of secondary sealing rings, each of which surrounds, or is surrounded by, a respective one of the primary sealing rings and is held away from the valve member by virtue of engagement of the respective primary sealing ring with the valve member.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawing which is an axial section through a valve according to the present invention.

The valve illustrated in the drawing is a shut-off ball valve for controlling the flow of gas through a conduit in which the valve is fitted and which is required to retain its sealing characteristics in the event of a fire. The valve comprises a metal (e.g. brass) housing (1) having aligned inlet and outlet flow passages (la) and (it), respectively. Defined within the housing (1) between the passages (lea) and (ib) is a chamber (inc) in which a pivotable valve member 3 in the form of a brass ball is provided. The ball (3) has a bore (3a) therethrough providing communication between the inlet and outlet passages (lea) and (ib) when the ball (3) is in the orientation illustrated in the drawing.The ball (3) is sealed with respect to the housing (1) by a pair of primary annular seals (4) formed of PTFE. Each seal (4) are disposed within the housing so as to surround the junction between a respective one of the passages (lea), (ib) and the chamber (inc). Each seal (4) engages against the surface of the ball (3) around the adjacent end of the bore (3a) therethrough. The seals (4) are relatively soft and, because of their material of construction, do not damage the surface of the ball (3) in use.

The valve further comprises a further pair of secondary seals (5) which, in this embodiment, are formed of stainless steel and which are therefore relatively hard and fire-resistant. Each seal (5) comprises an annular region which is disposed inwardly of a respective one of the seals (4) and a rear flange region which projects outwardly so as to engage against the rear face of that seal (4) so as to be disposed between the latter and a respective abutment shoulder (id) in the housing (1).

The valve is also provided with urging means in the form of a disk spring (7) which is formed of a fire resistant material, in this embodiment, a metal such as stainless steel. The spring (7) engages against that abutment surface (led) which is associated with the outlet passage (ib) and serves to urge the seals (4) and ball (3) into mutual abutment. In this respect, it is to be appreciated that the ball (3) is free to float to a limited extent within the ball chamber (inc). The axial extent of each seal (5) is such that it is shorter than the axial extent of each respective seal (4) whereby it is spaced a short distance from the adjacent surface of the ball (3) when the respective seal (4) is in engagement with the ball.

The ball (3) can be pivoted by an external handle (10) via a spindle (6) between the pivoted position illustrated in the drawing in which the valve is completely open and a position 900 displaced from this in which the valve is completely closed. During such pivotal movement, the seals (5) lie just clear of the surface of the ball (3) and so there is no risk of the relatively hard seals (5) scoring the surface of the ball (3). An effective primary seal is maintained by the primary seals (4) which are urged into engagement with the ball (3) by the spring (7).

In the event of a fire, the PTFE seals (4) start to soften and distort as the temperature rises but are maintained against the ball (3) by the spring (7).

By the time the seals (4) have become so distorted that sealing is no longer effective, the harder, temperature-resistant secondary seals (5) have reached a temperature at which they are malleable and have been urged into effective sealing engagement with the ball (3) under the action of the spring (7). The ball-engaging end of each secondary seal (5) is preferably shaped to conform to the adjacent surface of the ball (3).

Claims

1. A valve comprising a valve housing having an inlet passage and an outlet passage, a pivotable valve member mounted in the housing for pivotal movement relative thereto to control the flow of fluid through the housing between the inlet and the outlet passages, and sealing means for sealing the valve member relative to the housing, said sealing means including (a) primary sealing means engaging against the rotary valve member and (b) secondary, fire-resistant sealing means, wherein urging means is provided for effecting relative movement between the valve member and the primary sealing means in a direction to urge them into mutual contact.

2. A valve as claimed in claim 1, wherein the secondary sealing means are arranged so that they are normally spaced from the valve member but are acted upon by the urging means so as to urge the secondary sealing means and valve member into mutual engagement as the primary sealing means distorts under the action of heat.

3. A valve a claimed in claim 1 or 2, wherein the urging means comprises a spring which acts on both the primary and the secondary sealing means.

4. A valve as claimed in any preceding claim, of the type in which the inlet and outlet passages are arranged on opposite sides of a chamber in the housing in which the valve member is located, the valve member having a passage therethrough via which communication takes place between the inlet and the outlet passages in a first pivoted position of the valve member and where communication between the inlet and outlet passages is prevented when the valve member is in a second pivoted position.

5. A valve as claimed in any preceding claim, wherein the primary sealing means comprises a pair of primary sealing rings disposed in respective recesses in the housing surrounding the inlet and outlet passages, and the secondary sealing means comprises a pair of secondary sealing rings, each of which surrounds, or is surrounded by, a respective one of the primary sealing rings and is held away from the valve member by virtue of engagement of the respective primary sealing ring with the valve member.

6. A valve as claimed in claim 1, substantially as hereinbefore described with reference to the accompanying drawing.