GB2196706A

GB2196706A - Sealing devices

Info

Publication number: GB2196706A
Application number: GB08625908A
Authority: GB
Inventors: Christopher Charles Carter
Original assignee: English Electric Co Ltd
Current assignee: English Electric Co Ltd
Priority date: 1986-10-29
Filing date: 1986-10-29
Publication date: 1988-05-05
Also published as: GB8625908D0

Abstract

A sealing device for providing a seal between a concentric outer member (1) and inner member (3) which slides in a bore in the outer member e.g. a reactor standpipe in a nuclear fuelling maching, comprises an annular metallic seal (15) having a flat annular part (17) which is clamped to the outer member and a curved annular part (19) which forms an interference fit with the outer surface of the inner member and is held in engagement with that surface by tensile hoop stress in the seal. <IMAGE>

Description

SPECIFICATION Sealing devices This invention relates to sealing devices. In particular the invention relates to sealing devices capable of providing a gas tight seal between two concentric components.

Such a seal is required for example in a nuclear fuelling machine, a nose portion of which must slide onto and seal onto a reactor standpipe during refuelling operations. The sealing device used to provide this seal must be capable of operating at high ambient temperatures, high ionising radiation levels, and high reactor gas pressures, and furthermore must be capable of being coupled and uncoupled many thousand times without degradation of the sealing performance or degradation of the surfaces of the mating components. A sealing device which has been used for many years for this purpose comprises an elastomeric O-ring- seal backed by a circular section metal O-ring, this metal O-ring limiting the leak rate from the nose unit in the event of failure of the primary elastomeric O-ring seal.As the safety requirements of such nuclear fuelling machines have increased over the years, it has been found that the reactor gas leakage rates from such a known sealing device are too high.

It is an object of the present invention to provide a sealing device suitable for use in a nuclear fuelling machine, which has a lower leakage rate than previously used sealing devices.

According to the present invention a sealing device includes an annular metallic seal, a first circumferential portion of the seal being substantially planar, and the other circumferential portion of the seal being curved out of the plane of the first portion such that the other portion operates as an interference fit garter on a component to be sealed by the device.

One sealing device in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic diagram of the sealing device in use in a nuclear fuelling machine, only part of the machine being shown.

Figure 2 is a section through a component of the sealing device, the component being shown on a different scale to that of Fig. 1, and Figure 3 shows a detail of the component shown in Fig. 2 on a increased scale.

Referring firstly to Fig. 1, the sealing device is designed to seal a nose unit 1 carried on the lower end of a nuclear fuelling machine onto a nuclear reactor standpipe 3, this nose unit 1 sliding and sealing onto the standpipe 3 during refuelling operations. The sealing device comprises upper 5 and lower 7 annular housings, these being bolted onto the nose unit 1 of the fuelling machine by high temperature bolts 9, there typically being six or more such bolts positioned round the nose unit 1. A proprietory static metal C-ring 11 provides a static seal between the upper housing 5 and the nose unit 1.The upper housing 5 carries an elastomeric O-ring 13, which in use of the sealing device provides a primary seal between the nose unit 1 and the standpipe 3 for operation up to 300"C. Clamped between the upper 5 and lower 7 housings there is provided a metal garter seal 15 whose form is described in more detail hereafter, this seal 15 constituting a back-up seal between the nose unit 1 and standpipe 3 in the event of failure of the primary seal 13 due to for example fault conditions in which the ambient temperature of the sealing device may reach 600"C. A further metal C-ring 16 is provided between the seal 15 and upper housing 5 to close the secondary leak path between these components.

Turning now also to Figs. 2 and 3, the seal 15 comprises a ring of age hardened Inconel (RTM) 718. The outer portion 17 of the ring is substantially planar, such that in use of the seal 15, this portion may readily be clamped between the upper and lower housings 5, 7.

The inner portion 19 of the ring is smoothly curved out of the plane of the portion 17, such that in use of the seal the portion 19 of the ring operates as an interference fit garter on the standpipe 3. The seal 15 will typically be formed by cold spinning in several stages from an annealed sheet of Inconel (RTM) 718, the seal ring thus formed being subsequently heat treated so as to anneal the ring and finally age harden it.

Using a small amount of grease to lubricate standpipe 3 prior to each engagement by the nose unit 1 of the fuelling machine, it is found that repeated engagement and disengagement of the standpipe 3 and the nose unit 1 causes the surface finish of the standpipe to improve due to the burnishing/polishing action of the seal 15, the seal 15 is being found to operate satisfactorily with the slightest trace of lubricant.

During fault conditions such as reverse flow gas leading to construction of the O-ring 13 constituting the primary seal, the back-up seal 15 has been found to be able to withstand the thermal movements of the standpipe 3 and the nose unit 1. Under these conditions an adequate seal is maintained at ambient temperatures up to 600"C, reactor gas pressures of 600psig being held in intense ionising radiation fields.

It will be appreciated that whilst the sealing device described herebefore by way of example uses the seal 15 as a back up seal, in some applications a sealing device in accordance with the invention may use such an annular metallic seal as a primary seal at pressures up to 1500psig.

It will also be appreciated that the curved portion of such a seal which in use operates as an interference fit garter may be on the inner or the outer circumferential portion of the seal.

It will also be appreciated that a sealing device in accordance with the invention may be used to provide a seal to components of other than circular cross section, for example components of oval cross section the annular metallic seal deflecting to accomodate such a component, the seal being resilient enough to maintain its sealing properties.

Claims

1. A sealing device including an annular metallic seal, a first circumferential portion of the seal being substantially planar, and the other circumferential portion of the seal being curved out of the plane of the first portion such that the other portion operates as an interference fit garter on a component to be sealed by the device.

2. A sealing device according to Claim 1 in which the annular metallic seal forms a backup seal, the primary seal being constituted by an elastomeric O-ring.

3. A sealing device according to either of the preceding Claims in which said first circumferential portion is the outer circumferential portion.

4. A sealing device according to any one of the preceding Claims in which the annular metallic seal is formed by a cold spinning process from an annealled sheet of metal.

5. A sealing device substantially as hereinbefore described with reference to the accompanying drawings.

5. A sealing device according to Claim 4 in which said metal is Inconel (RTM).

6. A sealing device substantially as hereinbefore described with reference to the accompanying drawings.

CLAIMS Ammendments to the claims have been filed, and have the following effect: Claims 1 to 6 above have been deleted or textually amended.

New or textually amended claims have been filed as follows:

1. A sealing device to provide a seal between an outer member having a bore therein and an Inner member which can slide within the bore, the sealing device comprising an annular metallic seal having a first circumferential portion which is substantially planar and is arranged for attachment to the outer member; and a second circumferential portion which is curved out of the plane of the first portion towards the centre of the annulus such that the second portion operates as a garter which is an interference fit round the inner member.

2. A sealing device according to Claim 1, in which the annular metallic seal is formed from an annealed sheet of metal by a cold spinning process.

3. A sealing device according to Claim 2, in which the metal is Inconel (registered Trade Mark).

4. A sealing device according to any preceding claim, in which the annular metallic seal forms a back-up seal, and a primary seal is constituted by an elastomeric O-ring.