Oliver Valves has successfully undertaken a series of requalification tests on historically established valve products for a major international oil and gas operator.

A 10mm flange to screw double block and bleed standard valves manufactured of carbon steel, with a ½in class 2,500lb RTJ flange at one end and a ½in NPT connection at the other, was charged with pure helium before each of the valves within the double block and bleed assembly was subject to 200 operating cycles at ambient and temperatures ranging between -20°C and +120°C.

“We used helium because it is the most searching of all the inert gas media available,” explained Paul Shillito, director of engineering. “Leakage through the gland seals and the seats was then continuously monitored using a mass spectrometer so we could be certain of total accuracy regarding leakage rates.”

The test was then repeated on a 14mm ball valve monoflange with a ¾in class 2,500lb RTJ flange. Leakage on both valve types was proved to be considerably lower than the allowable leakage rate. In terms of fugitive emission gland leakage, the maximum recorded figures were well below the stringent 1×10-5cc/min limit.

All of the tests were witnessed and endorsed by representatives of the customer. Following the test, the valves were stripped for inspection and found to have remained in a good and serviceable condition.

“The client has been a customer for a number of years but in this instance, as a part of a programme of continuous improvement on the behalf of the oil and gas operator, we had been asked to requalify the products,” said Mr Shillito.

“In the early 1990s, when these products were first assessed, it wasn’t standard practise to consider fugitive emissions. We are glad that we have had the opportunity to revisit the qualification process for a valve that has changed little over the course of the last 20 years and we are delighted with the positive results of this far more vigorous means of testing.”