Gas Safe Register’s Technical Team are warning of the dangers of over-tightening test points on gas meters.
Gas metering refurbishment specialists have noted that significant numbers of predominantly domestic gas meters are being returned damaged, because the nut on the test point has been over-tightened.
The test point has a machined face seal that ensures a gas-tight seal, with two smooth metallic surfaces being drawn together by means of a mechanical thread. This gas-tight seal usually requires little more than a light turning force with a suitable tool, such as a suitably sized screwdriver or spanner, to ensure a gas-tight seal. It should always be tested with an approved leak detection fluid [LDF] after completing any work.
Over-tightening the screw in the test point is relatively difficult to achieve, but it can be done by using too much force and/or inappropriate tools. Over-tightening will commonly result in failure, either:
• The test point nut will shear off, or
• The test point shank will develop a longitudinal split.
Both these failures may result in an escape of gas. Where a gas escape has occurred, it should be repaired or, where it is not possible to repair the damage, the current Gas Industry Unsafe Situations Procedure (GIUSP) should be implemented and the appropriate actions and warning notices/labels completed and issued.
Photos 1 and 2 show the damage that can be caused by over-tightening the screw on the test point.