BS EN ISO 10497_2010 Testing of valves - Fire type-testing requirements (ISO10497:2010)
What is it?:
This International Standard specifies fire type-testing requirements and a fire type-test method for confirming the pressure-containing capability of a valve under pressure during and after the fire test. It is not applicable to the testing requirements for valve actuators other than manually operated gear boxes or similar mechanisms when these form part of the normal valve assembly.
Why is it important?:
This standard is widely used for fire type testing.
We wish to make members aware that experience has shown that the practice of testing floating ball designs without independently measuring cavity pressure and providing cavity pressure relief is not recommended and potentially hazardous.
It appears to have become accepted practice to assume that the cavity pressure in a floating ball design will relieve back to the upstream pipe because the upstream seat is assumed to not be in contact with the ball. Therefore the cavity pressure can be assumed to be the same as the measured upstream pressure.
BVAA recommend pressure relief provision to protect against potential rupture of any valve type, even if it is designed such that liquid should not be trapped in the cavity. There is documented evidence that in the early part of a fire test that some small soft seat floating ball valves may not relieve cavity pressure. Only when the upstream soft seat is destroyed or sufficiently damaged by the fire will the cavity pressure be allowed to relieve back to the upstream pipe.
The BVAA recommends that all double seated gate valve designs, floating ball and trunnion mounted ball valve designs should be provided with cavity relief (12) and independent cavity pressure measurement (6) in accordance with Figure 1 of ISO 10497. If the test results for these designs are satisfactory and the cavity relief valve has not operated, the fire test has proved the ability of the test valve to relieve the cavity pressure.
When a cavity pressure relief valve is fitted the Fire Test report should include
a) details of the body cavity pressure relief valve setting as required by Clause 6.7 (x) and confirmation that the relief valve did not operate during the test b) a report of the cavity pressure Clause 6.7 (j)
Supersedes: No standard amended or superseded.
Published in Valve User Magazine Issue 47
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