GB2140127A

GB2140127A - A plug valve

Info

Publication number: GB2140127A
Application number: GB08305388A
Authority: GB
Inventors: Rowley John Bircham
Original assignee: Hattersley Newman Hender Ltd
Current assignee: Olympus Ormskirk Ltd
Priority date: 1983-02-26
Filing date: 1983-02-26
Publication date: 1984-11-21
Also published as: GB8305388D0

Abstract

In a plug valve comprising a housing 1 defining a chamber 2 which houses a plug 5 with grooves 35a, 35b for sealing compound, a plug actuator 7 is operatively connected to the plug 5, and spaced seal means 13, 14 are provided to inhibit leakage past the actuator 7. As shown the actuator is stepped at 12 to support a sealing ring 13 which may be of PTFE and the seal 14 is in the form of an adjustable gland disposed around the actuator. The two seals provide a double barrier improving the valve fireproof qualities. An intermediate member 8 having mutually perpendicular projections or recesses 9, 10 may connect the plug 5 and actuator 7. <IMAGE>

Description

SPECIFICATION A plug valve The present invention relates to a Plug valve having a parallel sided plug.

Plug valves of this broad general type are well known and generally comprise a cast and machined metal housing which defines a substantially cylindrical chamber in which a complementary substantially cylindrical metal plug is disposed. The plug has an extension at one (usually its upper) end through which it may be rotated. The degree of rotation between the fully open and the fully closed position is one quarter turn (45o). In the fully open position a flow passage in the plug is aligned with inlet and outlet ports leading into and out of the housing. In the fully closed position, this flow passage is approximately at right angles to the line between these ports and forms a barrier to flow of fluid between them.

The plug is externally grooved and a sealing compound is disposed in these grooves to form a substantially fluid type seal between the external wall of the plug and the interior wall of the chamber in the housing. A feed channel leads from externally of the housing to the groove to permit the sealing compound to be replenished or topped up without having to strip down the valve.

The above described plug valve has been in use for many years and works extremely well in practice. In certain circumstances of a hazardous nature, the valve may not be considered to be sufflicient fire proof.

According to the present invention, a plug valve comprises a housing defining a chamber, an inlet port leading to the chamber, and an outlet port leading from the chamber, a plug disposed within the chamber for movement in the chamber between one position in which an aperture in the plug is aligned with the ports to permit flow between the ports and another position in which that aperture is disaligned with those ports and the plug provides a barrier to flow between the ports, grooves in the plug for accommodating sealing compound, a plug actuator operatively associated with the plug so as to enable the plug to be moved thereby between the two positions whilst permitting relative movement therebetween in the direction of the ports, and first and second seal means disposed between the actuator and the housing, the second seal means being disposed externally of the first seal means with respect to the chamber and both seal means being operative to inhibit or prevent leakage of fluid from the chamber past the actuator.

In a preferred embodiment of the invention, the operative association of the plug and actuator is via an intermediate member. This member has mutually perpendicular projections on its upper and lower faces which cooperate with respective slots in the base of the actuator and the top of the plug. The first seal means may comprise a sealing ring of PTFE or other suitable material and the second seal means may comprise a conventional adjustable gland. The sealing ring may be supported on a shoulder or step formed on the actuator thereby obviating any precision machining of that shoulder or step.

In order that the invention may be more clearly understood, one embodiment thereof will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic cutaway view of a plug valve in accordance with the invention, Figure 2 is a sectional view of a plug valve of the type shown in Figure 1 but differently orientated,and Figure 3 is a plan view of part of the valve.

of Figure 1 but to an eniarged scale.

Referring to Figure 1, the valve comprises a cast and subsequently machined housing 1 defining a chamber 2, an inlet port 3 leading to the chamber 2 and an outlet port 4 leading from the chamber 2. A plug 5 is disposed in the chamber 2 and may be rotated one quarter turn (45 ) between the fully open position shown and the fully closed position. In the fully open position a bore through the plug 5 (shown in dashed line at 6) is aligned with the inlet and outlet ports 3 and 4 to permit fluid flow therethrough between these ports. To close the valve the plug 5 is turned through one quarter turn (45 ) in the anticlockwise direction so that the plug 5 forms a barrier to continued fluid flow.

To turn the valve between the open and closed positions an actuator 7 is provided disposed above the plug 5. This actuator 7 is drivably connected to, but physically separated from the plug 5 by means of an intermediate member 8. Referring to Figure 3, this member 8 is a flat cylinder and has a projection 9 in its upper face and a similar projection 10 on its lower face. The projection 9 slots into a complementary slot in the undersurface of the actuator 7 and the projection 10 into a complementary slot in the upper surface of the plug 5.

The actuator 7 is stepped at 1 2 and a polytetrafluorethylene (PTFE) ring 1 3 is disposed on the step and provides a first seal between the actuator and surrounding wall of the housing 1. The head end of the actuator 7 is provided with a square section 1 6 to receive an appropriate tool for turning. A gland 14 surrounds the stem of the actuator 7 and provides a second seal between actuator 7 and housing 1. This gland 14 may be adjusted by means of a ring 1 5 which is connected by bolts 1 8 to the housing 1.

The plug 5 is supported on a base 1 7 which is of circular cross section, externally screwthreaded and screwed into a complementary screwthreaded aperture in the housing 1. The plug therefore is capable of movement transversely of a vertical axis through the valve independently of the actuator 7 under the action of line pressure on the upstream side of the closed valve. If the plug were not capable of such movement independently of the actuator 7, the plug would tend to cant over under such pressure and the risk of favouring of the plug 5 in the housing 1 would be increased. The ring 1 3 and gland 14 provide a double barrier improving the fireproof qualities of the valve and increasing its suitability for use in hazardous situations such as might be met in oil refineries and the like.

Figure 2 is a cross-section through a plug valve similar to that of Fiure 1 but where the section taken is at right angles to the through flow direction of the valve. In this figure parts equivalent to those of the valve of Figure 1 have been given the same reference numerals as those Figure 1 parts preceded by the reference numeral 2 Both the valve of Figure 1 and that of Figure 3 are provided with the usual grooves in the external cylindrical face of the plug 5 to receive sealing compound.

Referring to Figure 1, there are upper and lower horizontal grooves 35a, between which vertical grooves 35b extend. Some of these vertical grooves 35b communicate with the horizontal grooves directly whilst others can communicate with those grooves indirectly by way of a cavity in the wall of the chamber 5.

A directly communicating groove 35b is visible to the left and an indirectly communicating vertical groove 35b to the right of the centre line of Figure 1. No vertical grooves are visible on Figure 3 but the wall cavity is shown in this figure at 236. The grooves may be fed with sealing compound via a passage 19, 219 which incorporates a check or non return valve 30, 230 and which extends through the stem 7, 27 and member 8, 28. A bolt 31, 231 may be screwed into the upper end of this passage to push sealing compound disposed in it into the grooves.

When the plug is moved to the closed position only blind vertical grooves are exposed to the fluid in the line. This exposure tends to scoop sealing compound from the blind grooves but this displacement of sealing compound is limited to that from the exposed groove only (rather than from the remainder of the groove network) since at that point connection beteen that blind groove and the remainder of the network via a cavity 236 is broken as the cavity and blind groove are not in line. Compound displaced may be replenished when the groove and cavity are next in line.

It will be appreciated that the above embodiment has been described by way of example only and that many variations are possible without departing from the scope of the invention.

Claims

1. A plug valve comprises a housing defining a chamber, an inlet port leading to the chamber, and an outlet port leading from the chamber, a plug disposed within the chamber for movement in the chamber between one position in which an aperture in the plug is aligned with the ports to permit flow between the ports and another position in which that aperture is disaligned with those ports and the plug provides a barrier to flow between the ports, grooves in the plug for accommodating sealing compound, a plug actuator operatively associated with the plug so as to enable the plug to be moved thereby between the two positions whilst permitting relative movement therebetween in the direction of the ports, and first and second seal means disposed between the actuator and the housing, the second seal means being disposed externally of the first seal means with respect to the chamber and both seal means being operative to inhibit or prevent leakage of fluid from the chamber past the actuator.

2. A plug valve as claimed in claim 1, in which an intermediate member is disposed between the plug and the actuator and provides the operative association between the plug and actuator.

3. A plug valve as claimed in claim 2, in which means are provided on the intermediate member to enable it to operatively engage the plug and actuator.

4. A plug valve as claimed in claim 2, in which the means provided on the intermediate member comprises a projection or recess which engages in a corresponding recess or projection respectively on the plug and actuator.

5. A plug valve as claimed in claim 4, in which the means provided on the intermediate member comprises two mutually perpendicular projections on opposite faces thereof which engage in respective recesses formed in the adjacent faces of the plug and actuator.

6. A plug valve as claimed in any preceding claim, in which the first seal means comprises a sealing ring.

7. A plug valve as claimed in claim 6, in which the sealing ring is made of polytetrafluoroethylene.

8. A plug valve as claimed in claim 6 or 7, in which the sealing ring is disposed on a shoulder formed on the actuator.

9. A plug valve as claimed in any preceding claim, in which the second seal means comprises an adjustable gland.

10. A plug valve as claimed in any preceding claim in which the plug is provided with grooves for the accommodation of sealing compound.

11. A plug valve substantially as hereinbe fore described with reference to Figure 1 or Figure 2 of the accompanying drawing.