GB2484338A

GB2484338A - Valve seal

Info

Publication number: GB2484338A
Application number: GB1016971.2A
Authority: GB
Inventors: Alun Hobbs
Original assignee: HOBBS VALVE Ltd
Current assignee: HOBBS VALVE Ltd
Priority date: 2010-10-08
Filing date: 2010-10-08
Publication date: 2012-04-11
Anticipated expiration: 2030-10-08
Also published as: GB2484338B; GB201016971D0

Abstract

A valve used to control the flow of fluid in the oil and gas industry comprises a valve body 10 having an internal flow passage 12 extending between an inlet and an outlet of the valve. A valve member 11 is disposed in the valve body 10 for controlling the flow of fluid along the passage 12 between the inlet and outlet, and is moveable between open and closed positions by rotational shaft 13 coupled to the valve member 11. The shaft 13 extends externally of the valve body 10 through a bore formed therein, and an annular seal 15 is disposed around the shaft 13 for providing a seal between the shaft 13 and the valve body 10. The seal 15 is formed of a material comprising a filler and/or reinforcing material and a binder of hydrogenated nitrile-butadiene rubber (HNBR). The hydrogenated nitrile-butadiene rubber material is able to withstand extremely high temperatures to maintain an operational seal around the shaft 13 without any leakage.

Description

VALVE

This invention relates to a valve for controlling the flow of fluid and more particularly to a valve which is able to withstand high temperatures.

Valves such as ball valves and butterfly valves are well known for controlling the flow of fluids along ducts. A typical such valve comprises a valve body having an inlet, and outlet and a valve member disposed inside the valve body for controlling the flow of fluid along a passage extending between the inlet and outlet.

Generally the valve member is connected to an actuator shaft, which extends through the body to a point externally thereof. The external portion of the shaft is connected to a hand wheel, lever, motor or other actuator for moving the valve member inside the valve body between open and closed positions.

In order to prevent the egress of fluid from the valve body along the shaft, it is well known to provide an annular seal between the shaft and the valve body. One such arrangement is disclosed in EP0063452 and comprises an annular seal disposed inside a cavity or so-called stuffing box in the valve body, through which the shaft extends. The seal is held in-situ by a clamping ring, which axially compresses the seal inside the stuffing box and causes it to expand radially to form an effective seal between the shaft and the valve body.

Typically valve shaft seals are formed of PTFE, which is hardwearing. However, a disadvantage of FTFE is that it can melt under high temperatures, thereby making it unsuitable for use in some applications, such as in valves used to control the flow of water for fire fighting installations in the oil and gas industry.

In order to overcome this problem, it is also well know to use a graphite material as a valve shaft seal. However, a disadvantage of using a graphite seal in a stainless steel valve body is that galvanic corrosion can potentially occur between the graphite and the stainless steel if the valve is exposed to sea water.

Whilst asbestos is fireproof and able to act as a valve shaft seal, the use of asbestos is generally avoided for obvious health reasons.

We have now devised a valve which alleviates the above-mentioned problems.

In accordance with the present invention, there is provided a valve comprising a valve body having an internal flow passage extending between an inlet and an outlet of the valve, a valve member disposed in the valve body for controlling the flow of fluid along the passage between the inlet and outlet, a rotational shaft coupled to the valve member, the shaft extending externally off the valve body through a bore formed therein, and an annular seal disposed around the shaft for providing a seal between the shaft and the valve body, wherein the seal is formed of a material comprising a filler and/or reinforcing material and a binder of hydrogenated nitrile-butadiene rubber (HNBR).

The material used for the seal is known for use as a thin static gasket between pipe flanges, which gaskets are able to withstand high fluid temperatures in the pipe. We have surprisingly found that such material is also suitable for use as a dynamic seal between moving parts and can provide an extremely effective fire resistant valve shaft seal.

Preferably the filler material is a particulate and preferably comprises china-clay and/or silicon dioxide (silica).

Preferably the reinforcing material comprises fibres of aromatic polyamide or so-called aramid fibres and/or glass fibres.

Preferably the hydrogenated nitrile-butadiene rubber (HNBR) is vulcanised.

Preferably the seal has an axial length or thickness of at least 10mm and may comprise a one-piece annular member of said seal materials or a plurality of thinner annular members of said materials stacked together in face-to-face registration.

Preferably the seal is mounted in an annular cavity or so-called stuffing box in the valve body, through which the shaft extends.

Preferably means are provided for axially compressing the seal in the stuffing box.

An embodiment of the present invention will now be described by way of an example only and with reference to the accompanying drawings, in which: Figure 1 is a sectional view through a butterfly valve in accordance with the present invention; and Figure 2 is a perspective view of a valve shaft seal of the valve of Figure 1.

Referring to the drawings, there is shown a butterfly valve comprising a valve body 10 having an internal passage 12 extending between an inlet and an outlet of the valve. A disc-shaped valve member 11 is mounted inside the valve body 10 for selectively opening and closing the passage 12. The valve member 11 is mounted to a rotatable shaft 13 which extends radially outwardly through the valve body 10 to the exterior of the valve.

The shaft 13 extends through a bore in the valve body 10, the outer end of the bore being enlarged to define a cavity or so-called stuffing box 14. An annular shaft seal is disposed inside the stuffing box 14 around the shaft 13. A flanged collar 16 is then clamped in-situ by bolts 17 to axially compress the seal 15 inside the stuffing box 14, such that an effective seal is formed between the shaft 13 and the valve body 10. In this manner, the egress of fluids from the passage 12 along the shaft 13 is prevented. The shaft 13 can be rotated about its longitudinal axis to move the valve member 11 between its open and closed positions or to a position therebetween.

The seal 15 is formed of a material which comprises china-clay, silicon dioxide, aramid fibres and glass fibres contained within a hydrogenated nitrile-butadiene rubber (HNBR) matrix binder. The seal 15 may comprise a one-piece member of these materials or it may comprise a plurality of thinner seal members stacked together as shown.

The seal 15 is able to withstand extremely high temperatures to maintain an operational seal around the shaft 13 without any leakage. The present invention thus provides a fire safe valve, which is free of asbestos or graphite based stem seals.

Claims

CLAIMS1. A valve comprising a valve body having an internal flow passage extending between an inlet and an outlet of the valve, a valve member disposed in the valve body for controlling the flow of fluid along the passage between the inlet and outlet, a rotational shaft coupled to the valve member, the shaft extending externally of the valve body through a bore formed therein, and an annular seal disposed around the shaft for providing a seal between the shaft and the valve body, wherein the seal is formed of a material comprising a filler and/or reinforcing material and a binder of hydrogenated nitrile-butadiene rubber (HNBR).
2. A valve as claimed in claim 1, in which the filler material is a particulate.
3. A valve as claimed in claim 2, in which the tiller material comprises china-clay andlor silicon dioxide (silica).
4. A valve as claimed in any preceding claim, in which the reinforcing material comprises fibres of aromatic polyamide. or so-called aramid fibres and/or glass fibres.S..... * S ***** *
5. A valve as claimed in any preceding claim, in which the reinforcing material comprises glass fibres. S...S

*5**SS * 25
6. A valve as claimed in any preceding claim, in which the hydrogenated nitrile-butadiene rubber (HNBR) is vulcanised.

S..... *
7. A valve as claimed in any preceding claim, in which the seal has an axial length or thickness of at least 10mm.
8. A valve as claimed in any preceding claim, in which the seal comprises a one-piece annular member of said materials.
9. A valve as claimed in any preceding claim, in which the seal comprises a plurality of annular members of said materials stacked together in face-to-face registration.
10. A valve as claimed in any preceding claim, in which the seal is mounted in an annular cavity or so-called stuffing box in the valve body, through which the shaft extends.
11. A valve as claimed in any claim 10, in which means are provided for axially compressing the seal in the stuffing box.
12. A valve substantially as herein described with reference to the accompanying drawings. * ** fli.. * * ** 3 * S S. tS *5s** * 5 a. * * * * * S.S....' * S