SLIDING PLATE VALVE

Abstract: A plate valve (10) includes two sliding plates (12a, 12b) and carries seal portions (31a, 31b) with an elongate slot (30). The valve body (11) includes a second elongate slot (32) with seal portions (33a, 33d) extending from the valve aperture (18). A cable of different diameters can be accommodated and sealed by the cooperating resilient seal portions.

Description: SLIDING PLATE VALVE The invention relates to a sliding plate valve of the type used in the gas industry, for example. Sliding plate valves are extensively used to provide a low profile mechanism to isolate main pipes for gas and water. In addition they can be used as an entry point for mains inspection for the passage of a camera, for example, through the pipe. Where a tow line or camera signal cable is to move through a pipeline, it is necessary, where fluid under pressure is still present in the pipeline, to provide such access for such cables under sealed conditions. A sliding plate valve suitable for such situations is disclosed in UK patent number GB 2 261 277 which employs a notch and seal arrangement to trap such a cable whilst sealing the pipe by means of the plate valve. The present invention is concerned with providing improvements over such a configuration. According to the invention there is provided a plate valve having a bore for passage of a fluid; a sliding plate for closing the bore, a first recessed seal portion on the valve body extending from the bore and a second recessed 2 seal portion on the sliding plate adapted to cooperate with a cable or the like to effect a seal with the cable and the first seal portion on closure of the plate. In a preferred embodiment two slide plates are provided each with an associated first and second recessed seal portion. The plate valve may include an incorporated equalisation valve. The invention will now be described by way of example according to the accompanying drawings in which: Figure 1 shows the known valve plate arrangement in the open position; Figure 2 shows the known plate arrangement in a position sufficiently closed so as to seal around the cable; Figure 3 shows a sectional view through the plate valve showing the cable sealed against the valve body; Figure 4 shows an alternative embodiment the subject of the present invention, which has a resilient recessed portion for the cable which cooperates with a resilient recessed portion on the plate valve; 3 Figure 5 shows the sealing mechamsm of Figure 4 around a small cable; Figure 6 shows the sealing mechanism of Figure 4 around a larger diameter cable; Figure 7 shows a dual slide plate version of the plate valve; Figure 8 shows a detail of the plate valve with a pressure equalisation valve for use in the Figure 4 embodiment; and Figure 9 shows a detail of the plate valve of the Figure 9 with an added equalisation valve for use with the dual plate configuration. The arrangement of Figures 1 to 3 corresponds to the device shown in Patent No. GB 2 261 277 B. The plate valve 10 includes a body portion 11 with a circular aperture 18 therethrough and a sliding plate 12 operable by means of a linkage 13 and handle 14. The plate 12 incorporates, on its front face, a 'V shaped portion 15 terminating in a semi-circular notch 16 which will hold the cable 20 in use. As shown in Figure 1 , operation of the plate will cause the cable 20 to move into the notch 16 and become trapped against the dual seals 21, 22 on the 4 valve body 11 (see Figure 3). If the cable had not been present the plate would have moved further inside chamber 19 so that the notch 16 would be fully within the chamber to seal the plate even without a cable present. It is seen that the seals 21 and 22 seal both the plate and the cable. The seal " parts 23 and 24 of the circular seals will seal the plate towards the linkage mechanism. A vent/purge aperture 25 allows release of fluid, for example, which would otherwise become trapped in the chamber 19. In the improved arrangement shown in Figure 4 the plate carries its own cable seal and the main body sealed portion is recessed to take the seal outside of the main bore portion to prevent damage to the seal when equipment is passed through the plate valve. It also allows different cable thickness to be more readily handled. As shown in Figure 4, the plate 12 has been modified by providing an elongate slot 30 in the centre of the 'V shaped portion 15. The slot 30 carries a generally semi - elliptical resilient seal portion 31 (e.g. thermo¬ plastic rubber) which will deform when in contact with the cable. At the body portion 11 of the valve at the periphery of the bore aperture 18, a second elongate slot 32 is provided extending into the body portion 11 away from the bore to provide a recess outside the bore. This also carries a resilient seal portion 33. In operation, when a relatively small diameter cable 20a is utilised, the valve plate will close around the cable in the manner shown in Figure 5. In the event that a larger diameter cable 20b is passed through the valve, see Figure 6, on closure, the cable can still be accommodated without intruding into the bore. The resilient seal portions 31 and 33 will deform to effect the seal. In a further modification, incorporating the above, a dual gate version with two plates is employed as shown in Figure 7. Here, two sliding plates 12a, 12b move over a central body (plate) portion 40. Seals 41 and 42 cooperate with sliding plate 12a and seals 43 and 44 cooperate with sliding plate 12b. The slot 32 extending into the body portion away from the fluid bore has seal portions 33a-d provided which cooperate with the cable if present or the slide plates 12a, 12b above if no cable is present to effect the seal. The dual plates 12a, 12b slide forward and back under the control of drive mechamsm 46 which terminates in handle 47. A latch 48 can be moved into contact with handle 47 to hold the valve in the desired position. The dual plates provide extra safety when dealing with high pressure fluids because 6 even if one seal partially fails, sufficient sealing in the valve is still provided. When a cable is present, even if there is some slight passage of fluid around the first seal into the chamber area, the second seal is very effective as the pressure difference around the second seal is much lower. In a modified version of Figure 4, illustrated in Figure 8, an equalisation valve is incorporated to equalise pressure between the valve inlet and outlet prior to opening the slide valve. As shown in Figure 8, the body 11 has an equalisation valve portion 50 mounted thereon and includes bores 51 and 52 extending into the body to facilitate a passage to the main bore 18. The equalisation valve includes a generally cylindrical valve portion 53 which terminates at plug 54 at the lower end and a cap 55 at the upper end. A pad 56 and an O - ring seal 57 assist in sealing. The valve portion 53 includes an inset channel portion 59 which, when the portion 53 is rotated, can complete the path through the bores 51 and 52 for equalisation purposes. An indicator extension 60 in the cap 55 shows the rotational position of the valve spindle 53. When closed the face of spindle 53 blocks the passage between bores 51 and 52. In a further modification shown in Figure 9, the equalisation valve can operate with the dual plate version of the plate valve of Figure 7. The equalisation valve 60 of Figure 9 mounted on the plate valve, extends in to plate valve body 11 and includes bores 61 , 62, 63 passing into the body to couple with the main bore 18. Triple valve spindle segments 65, 66 and 67 with associated seats 70, 71 and 72 respectively, are moveable to open a passage between the inlet and outlet of the plate valve via bore 73. Each valve segment includes a seal 74,75 and 76 respectively to prevent fluid leakage.

Claims: CLAIMS 1. A plate valve having a bore for passage of a fluid; a sliding plate for closing the bore, a first recessed seal portion on the valve body extending away from the bore and a second recessed seal portion on the sliding plate adapted to cooperate with a cable or the like to effect a seal with the cable and the first seal portion on closure of the plate. 2. A valve as claimed in claim 1, wherein the first and second seal portions include a resilient insert. 3. A valve as claimed in claim 1 or 2, including a pair of sliding plates each with an associated first and second recessed seal portion. 4. A valve as claimed in claim 3, including a centre plate portion with an aperture forming part of the bore between the sliding plates and seal means mounted on a recessed portion of the centre plate to cooperate with cable to assist in sealing. 5. A valve as claimed in claim 3 or 4, wherein a tandem operating 9 mechanism is provided to control the slide plates. 6. A valve as claimed in claim 5, wherein locking means are provided to hold the valve operating mechamsm in a set position. 7. A valve as claimed in any one of claims 3 to 6, wherein the valve body and the centre plate each includes a pair of resilient seals for effecting a seal on the major surfaces of each sliding plate. 8. A valve as claimed in any preceding claim, wherein an equalising valve mechanism is incorporated. 9. A valve as claimed in claim 8, wherein the equalisation valve includes at least two passages fro connection to the plate valve bore and valve means operable to selectively connect the at least two passages when equalisation is required. 10. A plate valve substantially as described herein with reference to any of the embodiments in Figures 4 to 9 of the accompanying drawings.

Inventors: CARRUTHERS ALEC, CARRUTHERS, ALEC
Applicants: BRITISH GAS PLC, CARRUTHERS ALEC, BG PLC, CARRUTHERS, ALEC
Application year: 1999
Main classification: F16K3
IPC codes: F16K3