GB2265675A

GB2265675A - Sealing arrangement for radioactive material

Info

Publication number: GB2265675A
Application number: GB9207158A
Authority: GB
Inventors: Iain Lyle Sinclair Gray; Ronald William Thom Sievwright; Jennifer Caroline Elliott
Original assignee: Nirex UK Ltd
Current assignee: Nirex UK Ltd
Priority date: 1992-04-01
Filing date: 1992-04-01
Publication date: 1993-10-06
Anticipated expiration: 2012-04-01
Also published as: GB2265675B; GB9207158D0

Abstract

A sealing arrangement for hermetically sealing two mating surfaces comprises two seals (1, 2) arranged to lie between the surfaces. Each seal (1, 2) provides hermetic sealing over a respective different temperature range and lie serially along the surfaces between the regions to be isolated. A main seal integrity test arrangement is provided in the form of a port 3 and passage 8. This allows for the introduction of a fluid into or the evacuation of a region between the two seals (1, 2) to detect a leak. The port (3) is also provided with at least two test port seals (6) which seal with a plug (5). The plug (5) is also provided with a test port (7) to allow the integrity of the test port seal to be tested. <IMAGE>

Description

SEALING ARRANGEMENT The present invention relates to a sealing arrangement for hermetically sealing two mating surfaces.

The provision of seals having a high integrity is important for containing dangerous materials such as radioactive materials. Specifically, for the transport of radioactive material, requirements are laid down by the International Atomic Energy Authority in their Safety Series No. 6 "Regulations for the Safe Transport of Radioactive Material". These regulations stipulate a fire accident scenario, as one of the conditions which a package for the transport of radioactive material must withstand to be classed as 'Type B' packages.

A sealing arrangement is described in GB 2175885 wherein a pair of laterally spaced sealing members are provided between a lid and a container body. To test the integrity of the sealing arrangement, a passage between the two sealing members is pressurised using a gas, and any pressure changes in the gas in the passage is monitored.

Such conventional sealing arrangements generally perform well either in normal and high temperatures or in normal and low temperatures, or for moderately high temperatures. However, no sealing arrangement involving the use of elastomeric seals is available to provide high integrity sealing over a wide temperature range.

The present invention provides a sealing arrangement for hermetically sealing two mating surfaces, comprising at least two seal members arranged to lie between said surfaces; each said seal member providing hermetic sealing over a different respective temperature range.

Preferably, the seal members are arranged to Iie serially along the surfaces between regions to be isolated.

The integrity of the sealing arrangement can be tested using a test arrangement comprising means to introduce a fluid into or evacuate a region between two of the seal members to enable detection of a change in pressure in the region.

Conveniently, the test arrangement comprises a passage through one of the mating surfaces to a test port.

Since only one of the seal members operates to provide sealing for a particular temperature range, it is necessary to provide the test port with a test port seal arrangement to enable a hermetic seal connection to be made to the passage. The test port seal arrangement preferably comprises a plug to engage at least two test port seal members where the test port seal members are arranged to lie between mating surfaces of the plug and the test port.

Since a leakage is possible via the test port, preferably, the sealing arrangement includes test port seal integrity test means which comprises means to introduce a fluid into or evacuate a test port region between two of the test port seal members to enable detection of a change in pressure in the test port region.

Conveniently, the seal members are formed of a resilient deformable material which is compressed by the mating surfaces to provide hermetic sealing therebetween.

Examples of the present invention will now be described with reference to the accompanying drawings, in which:- Figure 1 is a schematic drawing of a container incorporating the sealing arrangement according to one embodiment of the present invention; and Figure 2 is a schematic drawing of a second container incorporating the sealing arrangement according to a second embodiment of the present invention.

Referring now to Figure 1, a container 12 comprises a container body 11 and a lid 10. The material which is to be isolated from the external environment is contained within the container 12 and a sealing arrangement is provided between the body 11 and lid 10.

The sealing arrangement comprises first and second seal members 1 and 2 arranged to lie serially along the mating surfaces of the body 11 and lid 10. The seal members 1 and 2 are provided in respective recesses in the mating surface of the lid 10 or body 11. The seal members 1 and 2 are formed of resilient deformable material which is compressed by the mating surfaces of the body 11 and lid 10 to provide hermetic sealing therebetween. The two seal members 1 and 2 have different temperature capabilities such that each of the seal members 1 and 2 provides hermetic sealing over a different temperature range. In order to provide an effective sealing arrangement over a wide temperature range is therefore essential that the temperature ranges at which the seal members 1 and 2 provide satisfactory performance must overlap.

In the arrangement shown in Figure 1 the seal members 1 and 2 are placed such that the first seal member 1 is closest to the interior of the container 12 and provides a satisfactory sealing performance at the higher temperature end of the temperature range. The second seal member 2 is arranged furthermost from the interior of the container 12 and provides satisfactory sealing performance at the low temperature end of the temperature range of the sealing arrangement.

In order to test the integrity of the sealing arrangement provided by the seal members 1 and 2, there is provided a main seal integrity test arrangement comprising a port 3 having a passage 8 leading from the external environment to a region 4 at the two mating surfaces between the first and second seal members 1 and 2.

If it is required to test the sealing arrangement to determine its integrity, the test port 3 can be used to pressurise the region 4 between the first and second seal members 1 and 2. Thus this test is performed in a similar manner to that described in GB 2175885, but must be performed at a temperature at which the performance of the first and second seal members 1 and 2 overlaps.

The introduction of the test port 3 having the passage 8 between the external environment and the region 4 between the first and second seal members 1 and 2 introduces a possible path for leakage from the sealing arrangement since at a low temperature, the first seal member 1 will be less effective and sealing will be primarily provided by the second seal member 2. It is thus a requirement that the port 3 be provided with a sealing arrangement of high integrity in order to seal the port 3 when no test is being performed on the sealing arrangement provided by the first and second seal members 1 and 2.

The sealing of the test port 3 is provided by a plug 5 having at least two seal members 6 which are compressed by two mating surfaces of the plug 5 and the test port 3.

The temperature capabilities of the seal members 6 can be the same and they can operate at the same temperature region as the second seal member 2.

Since the seal members 6 in the test port 3 provide an important seal between the interior of the container 12 and the external environment, it is important that the integrity of this seal can be tested. Thus a test port 7 is provided for the introduction of a fluid into a region between the seal members 6. A pressure drop in this region can then be detected in order to detect a leak.

The seal members 6 are formed of resilient deformable material which is compressed by the mating surfaces of the plug 5 and the test port 3. Their arrangement is thus similar to that for the first and second seal members 1 and 2, although the seal members 6 are formed of the same material which has a satisfactory performance over a single temperature range.

Although in the description hereinabove the testing of the integrity of the seal members 1, 2 and 6 has been described as including the pressurisation of the regions between the seal members 1, 2 and 6, equally, the regions between the seal members 1, 2 and 6 could be evacuated to reduce the pressure therebetween. This test procedure inverses the pressure difference across the seal members 1, 2 and 6. This arrangement also enables the use of mass spectrometry for testing the integrity of the sealing arrangement.

Referring now to Figure 2, in principle, this illustrates the same sealing arrangement as shown in Figure 1. However, the mating surfaces of the body 11 and lid 10 of the container 12 are not planar (excluding the recesses provided for the seal members 1 and 2), but the lid 10 includes a recess 9 to accept an extension 13 of the body 11. The sealing arrangement is thus provided on an outer surface of the extension 13 of the body 11. In this arrangement the sealing arrangement operates in a like manner described with reference to Figure 1.

The sealing arrangement of the present invention thus provides for effective sealing over a wide temperature range. Although in the described embodiments only two seal members 1 and 2 have been described which seal the two mating surfaces of a container 12, any number of seal members can be used to increase the temperature range of operation of the sealing arrangement. Multiple seals can be used in series, with each seal having satisfactory sealing performance over a different temperature range. In this arrangement reliance for the integrity of the sealing provided by the sealing arrangement is based on a single seal, according to the prevailing temperature.

Claims

1. A sealing arrangement for hermetically sealing two mating surfaces, comprising at least two seal members arranged to lie between said surfaces; ' each said seal member providing hermetic sealing over a respective different temperature range.

2. A sealing arrangement as claimed in Claim 1, wherein said seal members are arranged to lie serially along said surfaces between regions to be isolated.

3. A sealing arrangement as claimed in Claim 2 including a main seal integrity test arrangement comprising means to introduce a fluid into or evacuate a region between two said seal members, to enable detection of a change in pressure in said region.

4. A sealing arrangement as claimed in Claim 3, wherein said main seal integrity test arrangement comprises a passage through one said mating surface to a test port.

5. A sealing arrangement as claimed in Claim 4, wherein said test port is provided with a test port seal arrangement to enable an hermetic connection to be made to said passage.

6. A sealing arrangement as claimed in Claim 5, wherein said test port seal arrangement comprises a plug and at least two test port seal members, arranged to lie between mating surfaces of said plug and said test port.

7. A sealing arrangement as claimed in Claim 6 including test port seal integrity test means comprising means to introduce a fluid into or evacuate a test port region between two said test port seal members, to enable detection of a change in pressure in said test port region.

8. A sealing arrangement as claimed in any preceding claim, wherein each said seal member is formed of a resilient deformable material which is compressed by said mating surfaces to provide hermetic sealing therebetween.

9. A sealing arrangement substantially as hereinbefore described with reference to any of the drawings.