GB2153436A - Pressure accumulators - Google Patents

Abstract

A hydropneumatic pressure accumulator is to be coupled to a flanged end of a pipe 88. To avoid the need for a special flanged forged container, a flanged neck-member 82 is secured to the liquid part of a conventional pressure accumulator container 81 by means of the valve assembly 90, the external screw- threads of which are engaged in internal threads in neck member 82. A metal seal 80 is interposed between the container 81 and the neck member 82 to present a continuous, preferably homogeneous external surface especially for underwater applications. Other forms of the seal are described. <IMAGE>

Description

SPECIFICATION Pressure accumulators The present invention relates to pressure accumulators. A principal object of the invention is to provide, in an economic manner, a pressure accumulator which is suitable for.use in adverse conditions which preclude reliance on normal elastomeric seals.

The invention is concerned with pressure accumulators of the kind comprising a container in the form of a spherical shell or cylindrical shell with approximately hemispherical ends, the shell having a liquid port at one end, norma!ly its lower end, and a gas port at its other, normally upper, end, a bladder mounted within the shell and dividing the interior of the shell into a gas chamber communicating with a gas charging valve in the gas port, and a liquid chamber in communication with the oil port, and a liquid valve assembly mounted in the oil port and forming a connection for connecting the oil chamber to an external circuit, the valve assembly being closable by the bladder as the latter moves towards the liquid port when substantially all of the liquid is expelled through the liquid port.

Such accumulators are in wide use and are normally mounted by means of the liquid valve assembly which extends outwardly from the shell through the oil port of the shell, an 0 ring type seal being located between the liquid port of the shell and the adjacent outer surface of the liquid valve assembly.

An alternative arrangement has been known for a long time in which the container is extended at the oil port by a neck portion which is integral with the remainder of the container and is in use directly coupled to the adjacent pipework or other installation to provide both a liquid connection and support for the accumulator. In the case, however, of large, high pressure hydro-pneumatic accumulators, the production of such containers is much more difficult and expensive as compared with the containers for otherwise identical accumulators of the more conventional designs which are supported by the liquid valve assembly and sealed with O-rings.

According to the present invention there is provided a hydro-pneumatic pressure accumulator comprising a container having substantially hemispherical ends, one of which is formed with a liquid port, a bladder mounted within the container to divide the interior of the container into a gas chamber and a liquid chamber, a liquid outlet member retains in the liquid port and extending outwardly therefrom, the liquid outlet member being provided with means for preventing extrusion of the bladder through the outlet member, a neck member surrounding the outwardly extending portion of the outlet member, the neck member being secured to the container by the outlet member with sealing means between the neck member and the container.Preferably the sealing means are either wholly metallic or include an outer metallic ring so that the container, outer periphery of the sealing means and the neck all present a metallic surface to the exterior. A continuous protective paint film can then be applied overthe whole of the exterior of the assembly.

With such an arrangement, the container may be a completely standard container. Some minimal machining may be necessary around the liquid port to accept the chosen sealing arrangement but no changes are required in the metal forming procedures by which the container is made.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which Fig. 1 is an axial sectional view of a hydro pneumatic pressure accumulator in accordance with the invention, Figs. 2 to 5 are views similar to the lower part of Fig. 1 but showing alternative sealing arrangements, and Figs. 6 and 7 show a further alternative sealing arrangement respectively before and after compression.

The hydro pneumatic pressure accumulator shown in Fig. 1 comprises a steel shell 1 which has been formed from a tubular blank to provide hemispherical upper and lower ends 2 and 3 formed respectively with a gas port 4 and a liquid port 5. The interior of the container 1 is divided by an elastomeric bladder 6 into a gas chamber 7 within the bladder and a liquid chamber 8 outside the bladder. A gas charging fitting 9 has a head portion 10 engaged in the bladder 6 and extends upwardly and outwards through the gas port 4 to carry a gas charging valve 11 through which gas can be introduced under pressure to charge the gas chamber 7 through a central pasasage 12 in the fitting 9.

A liquid outlet member 13 has a top flange 14 of external diameter slightly less than the internal diameter of the oil port 5. The outlet member 13 can thus be introduced into the interior of the container through the liquid port 5 and can then be retained by means of a divided ring 15 the two parts of which are bonded to an elastomeric ring 16 which can be folded to enable it, together with the two segments of the ring 15, to be introduced into the container through oil port 5 and then engaged on the outlet member 13 under the flange 14.

The outlet fitting 13 has a plurality of outlet passages 16 arranged in a ring about a central ball 17 in which the stem of a poppet valve member 18 is slidable between a closed position in which a head 19 of the valve member 18 seats on a valve seat 20 on the other end of the outlet member 13 to prevent extrusion of the bladder 6 into the outlet. A spring 21 normally holds the valve member 18 in its upper, open position but will yield to allow the valve to be closed by the bladder 6.

The accumulator so far described is essentially conventional apart from the shape of the lower part of the outlet member 13.

In accordance with the invention, a neck member 30 is secured to the container 1 by means of the outlet member 13 with the interposition of sealing means 31. for this purpose, the outlet member 13 has a long screw threaded surface 32 on which corresponding screw threads on the interior of the neck member 30 are engaged. The upper end of the neck member 30 has a short spigot extension 34 which fits snugly in the liquid port 5.

The lowermost outer end of the outlet member 13 is shaped to engage a tool, for example, by being formed with an internal polygonal formation 35 or be formed with a set of external flats on an unthreaded end portion 36 of its outer surface. An upper portion 37 of the neck member 30 is also formed with a set of flats for engagement by an appropriate spanner. During tightening of the assembly shown in Fig. 1, the outlet member 13 may be turned relative to the container 1 and neck member 30 to provide appropriate preloading on the annular seal 31, without relative rotation of the neck member 37 and the container 1.

To prevent loosening off the screw threaded connection, as a result for example of vibration in operation, the threads may be coated with an appropriate anaerobic adhesive or an appropriate mechanical locking means may be employed. For example, as shown in the drawings, a locking ring 37 may be installed on the end portion of the screw threads on the outlet member 13 and/or other locking devices may be employed.

In its simplest form, the annular seal 31 may comprise a copper ring. Other possiblities are a steel ring and a composite arrangement consisting of an outer steel ring and an inner seal for example of P.T.F.E.

Similar sealing arrangements must be used at the upper end of the accumulator between a securing nut 41 on the gas fitting 9 at 42, and between the nut 41 and an end cap 43 which protects and seals the gas charging valve 11, this sealing arrangement being indicated at 44.

The completed accumulator is protected by an appropriate external paint system for the environment in which it is to be used. One example is a two-coat epoxy resin paint system.

In the modified accumulator in Fig. 2, the spigot portion 34 is slightly shortened to allow an O-ring 51 and its support ring 52 to be installed between the underside of the divided ring 15 and the upper edge of the shortened spigot portion 34-.

In the modified sealing arrangement shown in Fig.

3, the spigot portion 34 is altogether omitted and the entrance of the screw-threaded bore in the neck member is chamfered at 61 (here at an angle of 25 ) to receive a proprietary seal 60 and comprising a regularly extending annular flange 62 and a pair of opposed tapering axiallv extending flanges 63 and 64. A tubular distance ring 65 fits between the seal 60 and the outlet member 13. The mouth of the liquid port 5 of the container 1 is chamfered (here again at 25") to make sealings contact with the correspondingly chamfered surface of the upper axial flange 63 of the seal 60.

In all of the embodiments described above, the lower end of the neck member 30 has a radially extending flange 71,the upper surface of which forms an inclined shoulder 72 to be engaged by a divided clamping ring (not shown) for coupling the accumulator to a correspondingly flanged component with the interposition of a seal similar to but larger than the seal 60, the mouth of the neck member being appropriately chamfered at 73.

Figure 4 shows a modification of the arrangement shown in Figure 3 in which the seal 80 between the accumulator shell 81 and the neck member 82 is of the internally and externally tapered type available under the trade mark 'PAPER-LOK'. Here again, the mouth of the container is chamfered to correspond with the external taper of the seal 80 while the neck member 82 has a short thrusto-conical extension 83 which conforms to the internal tapered surface of the seal 80.

The neck member 82 has at its lower end a flange 84 formed with a ring of bolt holes 85 aligned with corresponding bolt holes 86 in a flange 87 of a coneended pipe 88 which is secured to the neck member 82 by bolts (not shown) passing through the holes 85 and 86, sealing being effected by a larger diameter 'PAPER-LOK' seal 89. In Figure 4, the arrangement is shown prior to full tightening of all the components. To assist in the tightening process, the lower end of the valve assmebly 90 is prefereably formed with a hexagonal socket 91 by means of which it may be turned relative to the treaded neck member.

The arrangement shown in Figure 5 differs from that shown in Figure 4 only in that the neck member 92 has its lower end formed in a similar manner to that of the neck member 37 in Figure 1 for use with a split external clamping ring (not shown) when making a connection to an adjacent pipe end 93 with the interposition of a metal seal 94.

Figures 6 and 7 show a further alternative sealing arrangement which can be used between the container 101 and the neck member 102. A similar (but smaller) arrangement may be used for the seals.

42 and 44 on either side of the nut 41 in respect of the gas valve in Figure 1 and also in the other versions of the accumulator.

In this arrangement, both the container 101 and neck member 102 have opposed flat surfaces 103 and 104 respectively. Between these surfaces is positioned a sealing assembly comprising an annular support member 105 and two washers 106 of deformable sealing material such as copper, fibre or polytetrafluoroethylene. The member 105 is formed of the same metal as the container 101 and neck member 102. In the uncompressed state shown in Figure 6, the member 105 has a relatively thin radial annular web portion 107 and thickedned bead portions 108 and 109 at its inner and outer peripheries. Each bead portion 108, 109 terminates ion a knife edge 110. The beads 108 and 109 and the web 107 form hollows or troughs on each side of the web 107. Located in the troughs are the two washers 106, the height of which is greater than the height of the knife edges 110 above the web. The volume of each washer 106 is equal to or slightly greater than the volume of the trough (considered up to the height of the knife edges 110).

When the assembly is tightened (by rotating the valve assembly 111 relative to the neck member 102) the washers 106 are deformed until they fill their respective troughs on either side of the web 107. Thereafter, the knife edges 110 engage the surfaces 103 and 104 thereby forming a continuous metal exterior surface from the container 101 to the neck member 102 (and also a continuous internal metal surface between these two members). If the volume of a washer 106 is greater than that of its trough, some of the material of th.e washer will be extruded through the gap between one of the knife edges and the adjacent sealing surface. During the final part of the tightening, however, the knife edge will cut through any such extruding material, thereby ensuring the continuous metal outer surface which can therefore be painted as required.

The accumulators described are particularly suitable for use in seawater, particularly where the container, neck member and at least the exterior surface of the sealing means between the two are all formed of the same metal, thereby preventing a electro-litic action.

Claims (7)

1. A hydro-pneumatic pressure accumulator comprising a continer having substantially hemispherical ends, one of which is formed with a liquid port, a bladder mounted within the container to divide the interior of the container into a gas chamber and a liquid chamber, a liquid outlet member retained in the liquid port and extending outwardly therefrom, the liquid outlet member being provided with means for preventing extrusion of the bladder through the outlet member, and a neck member surrounding the outwardly extending portion of the outlet member, the neck member being secured to the container by the outlet member with sealing means between the neck member and the container.

2. An accumulator according to claim 2, wherein the sealing means are either wholly metallic or include an outer metallic ring so that the container, outer periphery of the sealing means and the neck all present a metallic surface to the exterior.

3. a compression sealing assembly to form a seal under compressive pressure against a face of a member, the assembly comprising a relatively rigid element having inner and outer annular knife edges bounding an annular trough and which in use bear against an annular surface of the said member and an annular washer of deformable material in the trough, the height of the deformable washer prior to compression of the sealing assembly being greater than the height of the knife edges relative to the trough.

4. A sealing assembly according to claim 3, having knife edges and an annular washer of deformable material on both faces of a web portion of the element.

5. A sealing assembly according to claim 4 or 5, wherein the volume of the washer or each said washer prior to compression of the seal is not less than the volume of the trough.

6. An accumulator according to claim 1 or 2 wherein the said sealing means between the neck member and the container is formed by a sealing assembly according to any of claims 3 to 5.

7. A hydro-pneumatic pressure accumulator substantially as described with reference to any of the drawings.