#NGCFE #Plumber Medium pressure soundness testing is relatively easy to understand if you work on medium pressure supplies regularly. It can however be confusing if like most engineers, you only ever see a medium pressure meter every five years when resitting your ACS.
Every medium pressure meter also has an UPSO (under pressure shut off device) that typically operates at 15mb or less. We need to carry out an additional let-by test of this valve.
The test starts in the same way that any soundness test would by the carrying out of a let-by test of the ECV. This test is carried out by manually holding open the UPSO and gradually introducing 7-10mb pressure to the system. The test should last for 1 minute while manually holding open the UPSO lever.
Upon completion of the first stage let-by test, we then let go of the UPSO lever (allowing it to close as there is less than 15mb in the system) and open the ECV fully This will allow roughly 2bar pressure to the point of the UPSO but no further. The gauge should still be reading between 7-10mb. We should allow 1 minute for this stage of the let-by test ensuring that the UPSO doesn’t pass any gas.
Once we are satisfied that the ECV and UPSO are not letting by, we can close the ECV and release the pressure in the system and open the UPSO manually to relieve the pressure. We now hold open the UPSO while introducing 18-19mb into the system and allow 1 minute for temperature stabilisation. After the stabilisation period, we should, if necessary, readjust the pressure to 18-19mb, it’s important to remember that during the stabilisation test, the UPSO will be open as there is more than 15mb in the system so no need to manually hold open the UPSO lever.
On completion of the stabilisation test, we then allow a further 2 minute test as we would for a low pressure supply test.
As always, should you want to learn more about anything gas or industry related, please contact us at the
National Gas Centre for Excellence on 01924973260 or visit www.ngcfe.co.uk .