GB2310478A - Full nozzle relief valves - Google Patents

Abstract

A full nozzle relief valve comprises a body (1) having a basal bore (4) through which an annular nozzle (5) extends into the interior of the body (1). The nozzle (5) is insertable fully into position in the bore (4) as an axially sliding fit and is secured in position by a threaded locking ring (19). An O-ring (22) located in an external annular recess in the nozzle (5) provides a fluid-tight seal between the nozzle (5) and the body (1).

Description

Relief Valves This invention relates to safety and other types of relief valves and more particularly to means for securing the nozzle in the body of a so-called "full nozzle" relief valve. The invention is especially applicable to relief valves of the pilot-operated type, but is nonetheless applicable also to, for example, spring-operated relief valves.

Conventionally, the annular nozzle of a full nozzle relief valve is threadedly secured in a bore formed in the base of the valve body. The nozzle has at its lower end an integral flange, the periphery of which is formed with a number of flats whereby the nozzle can be screwed up to tightness with the nozzle flange abutting the underside of the valve's mounting flange. Usually, there is an annular gasket sandwiched between the two flanges that provides a fluid-tight seal between the body and the nozzle. This type of arrangement has been used for decades, notwithstanding the disadvantage of having to form a screw thread internally of the bore in the body. Also, there is a further disadvantage of this arrangement insofar as pilot-operated relief valves are concerned. Thus, in such relief valves, the pilot signal is fed from the inlet side of the valve via a so-called Pitot tube that is sealingly secured in a radial bore formed in the nozzle flange and, when tightening up the nozzle, it is difficult to ensure that, when fully tightened, the radial bore will be in the correct orientation for enabling the Pitot tube to be connected to the rest of the rigid pilot signal tubing.

The above disadvantages may be overcome by using a so-called 'half-nozzle' design, but other disadvantages then arise, such as the need to use a cage to retain the half nozzle in place and the need, for certain applications, to make the entire valve body of an expensive, corrosionresistant metal such as a stainless steel, whereas full nozzle designs may usually have cheaper cast iron or carbon steel bodies.

It is an object of the present invention to provide a full nozzle relief valve which overcomes one or both of the above-mentioned disadvantages associated with conventional designs.

According to the present invention, therefore, there is provided a full nozzle relief valve, for example a full nozzle safety relief valve, including a body having a basal bore through which an annular nozzle sealingly extends into the interior of the body, characterised that the nozzle is insertable fully into position in said bore as an axially sliding fit and in that releasable locking means are provided to lock the nozzle, once fully inserted, in position in the bore.

Preferably, and as in conventional designs, the full nozzle is provided at its basal end with a flange, which usually will be integrally formed with the rest of the nozzle and which, when the nozzle is in position, abuts the underside of the valve's mounting flange.

Alternatively, or in addition, however, axial insertion of the nozzle may be limited by mutually engaging annular shoulders formed, respectively, internally of the basal bore and externally on the nozzle.

The releasable locking means is preferably an internally threaded nut or ring that engages an externally threaded upper portion of the nozzle and which, when tightened, abuts an annular shoulder formed internally of the valve body adjacent to the inner end of the basal bore and thus secures the nozzle in position. The nut or ring may be formed with peripheral flats in order to facilitate tightening thereof with a spanner or the like. Further, the nut or ring may be restrained against rotation, once it has been fully tightened, by means of, for example, a grub screw. Preferably, this extends axially through the nut or ring and engages the aforesaid annular shoulder abutted by the nut or ring.

It is, of course necessary or at least desirable for there to be a fluid-tight seal between the body and the nozzle. This may, in principle, be provided by tight metal-to-metal contact between the wall of the basal bore and the external surface of the nozzle. Preferably, however, the nozzle is a loose sliding fit in the basal bore. This is especially so where the valve is pilot-operated so that, before the locking means is tightened, the nozzle may readily be rotated relative to the body so as correctly to orientate the bore that receives the Pitot tube. In such a case, the fluid-tight seal may, for example, comprise a gasket sandwiched between the body mounting flange and, if present, the basal flange on the nozzle, as in conventional designs. Alternatively the seal may comprise one or more resilient O-rings held captive in, for example, one or more annular channels formed externally in the outer cylindrical surface of the nozzle.

It will be appreciated from the above that, because of the means by which the nozzle is retained in position relative to the valve body, it is unnecessary to form an internal thread in the basal bore of the body and that, in the case of a pilot-operated relief valve, the radial bore for receiving the Pitot tube may readily be correctly orientated. However, and as will be understood, the invention affords advantages also for spring-operated relief valves.

A pilot-operated safety relief valve constructed in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawing which is a sectional side elevation of the valve.

In the drawing, the main body 1 of the relief valve has a mounting flange 2 integrally formed with it at its lower end. The mounting flange 2 has a number of vertical bores 3 formed in it for receiving bolts (not shown) that, in use, secure the valve to a pressure vessel or pipeline (not shown). The flange 2 surrounds the lower portion of a cylindrical bore 4 formed in the base of the body 1 and, secured in the bore 4, is an annular inlet nozzle S as will be described in detail below.

The main body 1 also has formed in it an outlet 6 through which relieved fluid issues in the event that the fluid pressure in the pipeline or vessel becomes excessive. The outlet 6 is surrounded by an integral flange 7 which may have a number of bores (not shown) formed in it whereby a flanged pipeline may be connected thereto by bolts for conveying relieved fluid to a remote location.

The upper end of the main body 1 is formed with an aperture 8 in which is secured the valve mechanism designated generally 9. The mechanism 9 may take any one of a number of alternative designs, the construction and operation of which will be familiar to those skilled in the art and so need not be described in detail herein. Briefly, however, the mechanism illustrated comprises a disc-like closure 10, for example made of filled PTFE, secured to the base of a holder 11, to the upper end of which is secured a piston 12 housed in a cylindrical chamber 13. In use, pressurised fluid is transmitted from the vessel or pipeline, via a Pitot tube 14, pipework 15 and a pilot valve (not shown), into the chamber 13. Normally, when the pressure in the vessel or pipeline is at or below a pre-determined ("set") pressure, as set on, and sensed by, the pilot valve, the fluid pressure in the chamber 13 is maintained at a sufficiently high level that the closure 10 will firmly engage the annular seat 16 ofthe nozzle 5. The relief valve therefore remains in a closed position (the position shown in the drawing). However, in the event that the fluid pressure in the vessel or pipeline builds up and exceeds the set pressure, the pilot valve causes the fluid in the chamber 13 almost instantaneously to exhaust to atmosphere whereupon, under the action of fluid pressure in the vessel or pipeline, the piston 12, holder 11 and closure 10 flilly lift. Thus, fluid is relieved through the outlet 6 via the nozzle 5 until the pressure in the vessel or pipeline reduces to about the set value, again as sensed by the pilot valve, whereupon the valve recloses.

The features and operation described above are all conventional, but in accordance with the present invention the nozzle 5 is secured in the body 1 in a novel and advantageous way.

More particularly, the bore 4 in the body 1 is substantially plainwalled along the whole of its length and receives, as a sliding fit, an externally plain-walled portion of the nozzle 5. The base of the nozzle S is provided with a flange 17 which abuts the underside of the mounting flange 2.

A portion of the nozzle S adjacent to its upper end is formed externally with a screw thread 18 engaged by a locking ring 19 which, when tightened, abuts an annular shoulder 20 formed internally of the body 1. The nozzle 5 is thereby firmly secured in position.

The ring 19 is formed with a threaded bore 21 for receiving a grub screw (not shown) which, when tightened up against the shoulder 20, prevents the ring 19 from loosening during service.

A fluid-tight seal between the bore 4 and the external cylindrical surface of the nozzle 5 is ensured by providing a resilient O-ring 22, for example of a fluorocarbon such as VITON (trade mark), that is retained in an annular channel formed in the external surface of the nozzle 5.

The flange 17 is provided with a radial bore 23 in which the Pitot tube 14 is secured by a weld, as is conventional. The Pitot tube 14 is coupled, say at 24, to the rigid pipework 15 and, so needs to be correctly aligned with the lower end of the pipework 15. The correct alignment may readily be realised simply by appropriately rotating the nozzle S before the ring 19 is tightened.

Needless to say, the body 1 and nozzle 5, in particular, may be made of a variety of materials. By way of example, the body 1 would typically be of carbon steel and the nozzle 5 of stainless steel such as 316 SS.

Claims (7)

1. A full nozzle relief valve including a body having a basal bore through which an annular nozzle sealingly extends into the interior of the body, charactensed in that the nozzle is insertable fully into position in said bore as an axially sliding fit and in that releasable locking means are provided to secure the nozzle, once fully inserted, in position in the bore.

2. A relief valve according to claim 1 wherein the nozzle is provided at its basal end with an abuttment surface which, when the nozzle is in position, abuts the valve body and wherein the releasable locking means comprises an internally threaded nut or ring which engages an externally threaded upper portion of the nozzle and which, when tightened, abuts an annular shoulder formed internally of the valve body adjacent to the inner end of the basal bore therein, thereby to secure the nozzle in position.

3. A relief valve according to claim 2 wherein means are provided to restrain rotation of the nut or ring once it has been fully tightened.

4. A relief valve according to claim 2 or claim 3 wherein the abuttment surface comprises a radially outwardly extending flange which, when the nozzle is in position, abuts the underside of the valve body.

5. A relief valve according to any one of claims 1 to 4 wherein sealing means are provided to form a fluid-tight-seal between the valve body and the nozzle.

6. A relief valve according to claim 5 wherein the sealing means comprise one or more annular sealing rings located in one or more annular channels formed in an outer cylindrical surface of the nozzle.

7. A full nozzle relief valve substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawing.