Butterfly valves

Details Butterfly valves Butterfly valves

2000-01-20

2000-11-21

Shaver, Kevin

Valves and valve actuation

With means to increase head and seat contact pressure

Seat pressed to valve

251306, 251314, 137557, F16K 2500, F16K 500, E03B 707

Patent

active

061491306

DESCRIPTION:

BRIEF SUMMARY
This invention relates to butterfly valves such as those disclosed in our Patent Specification GB 2031198. The closure member in a butterfly valve is a disc rotatable through substantially 90.degree. from the closed to a fully open position. The disc may be adapted to seal against a frustoconical valve seat. To prevent the disc from binding in or scuffing excessively against the seat, the seat axis may be set at an angle to the valve bore axis, with the axis of rotation of the disc offset from the central plane of the disc towards the broader rim of the seat, and off centre from the valve bore axis, towards that side of the bore to which the projected apex of the valve seat points.
More particularly, the invention concerns the provision in such valves of a safety feature known as a double block and bleed facility. In many safety critical systems, adjacent parts are connected together by a series of two seals forming a double barrier. The space between the seals is connected to a port which may be used to monitor leakage past one of the seals, to bleed off or neutralise pressure changes caused by leakage into or from the space, or to inject fluid, for example to temporarily seal the leak or purge the system. Two separate valves may be connected together in series by a conduit which is ported to provide a double block and bleed facility. Some valves, for example gate valves, may include separate seals against upstream and downstream faces of their closure members. These seals define an isolated chamber which may be ported to provide a double block and bleed facility within a single valve. As disclosed for example in GB 2277977, GB 1604095, GB 1512482 and GB 1428066 butterfly valves having twin discs or discs with twin sealing rims are known in which when the valve is closed, the space enclosed between the discs or rims communicates with a port in the valve body thereby providing a double block and bleed facility. In GB 901607, such a space is defined between a pair of rubber sealing rings mounted in a metal ring received in a rebate in a cylindrical valve casing.
The present invention aims to provide improved sealing arrangements for such passages in butterfly valves in which the valve seat is a separate element.
In accordance with the present invention we provide a butterfly valve comprising a closure disc sealable at its rim to a valve seat, the rim and seat when so sealed defining between them an annular space which is connected to a port to provide a double block and bleed facility, wherein the valve seat is a separate element having a mating face lying transversely of the valve bore and sealed to a shoulder in the body of the valve, the port comprising a passage connected at one end to the space and extending through the mating face to the exterior of the valve, characterised in that the space is formed by a groove provided around the periphery of a resilient seal element for co-operation with a substantially flat face of the valve seat or closure disc edge; the seal element comprising two rings between which a recessed rigid ring is sandwiched to form the groove. There will generally be a clearance between the valve body and the valve seat to permit its ready installation. Routing the port through the mating face avoids the necessity of sealing the port with respect to the seat/body clearance. Preferably the passage extends substantially normal to the mating face, for example substantially parallel to the valve bore axis.
The two rings between which the recessed rigid ring is sandwiched may be laminated from metal foil/carbon fibre. The seal element is preferably carried by the closure disc.
Illustrative embodiments of the invention are described below with reference to the drawings in which:
FIG. 1 is a cross-sectional view of a preferred embodiment of the present invention;
FIG. 2 is a section on line 2--2 of FIG. 1;
FIG. 3 is a section on line 3--3 of FIG. 1; and
FIGS. 4 and 5 are views corresponding to FIGS. 1 and 2 but showing a second embodiment of the invention.
Referring to FIGS. 1 to 3, a pref

REFERENCES:
patent: 3076631 (1963-02-01), Grove
patent: 4249568 (1981-02-01), Duggan
patent: 4265426 (1981-05-01), Thurston et al.
patent: 4598734 (1986-07-01), Moyes
patent: 4785844 (1988-11-01), Pankov
patent: 5520209 (1996-05-01), Goins et al.

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