Posted by David Sear
Here’s a quick question: where would you find some of the the most critical valves in Oman?
Obviously any answer will be subjective, but Koso’s Lyn Thomas is adamant that the most important ones are the three relief valves to be found at the end of PDO’s main oil pipeline.
Effectively carrying all the oil produced in Oman to a treatment plant, this pipeline has to cross a mountain range.
And therein lies the heart of Mr Thomas’ argument.
Lyn Thomas is Regional Sales Manager, Severe Service, Middle East, for Nihon Koso Co., Ltd.
Says Mr Thomas: “For obvious safety reasons the plant is fitted out with an emergency shutdown valve. If that valve closes, then in effect you still have a train of oil coming down the mountainside. This has a large momentum and high energy content. These relief valves must then automatically open to divert that oil along branch lines and into storage tanks.”
So far so good. And indeed, during a recent incident, the originally fitted valves did open at exactly the right time.
However, the pressure drop (and energy dissipation) across the valves was so great that the single stage units were destroyed in the process due to high vibrations! An oil spill was also caused.
Tortuous path
Looking to find a solution, engineers turned to the surge relief valves offered by Japanese company, Koso.
These energy absorbing valves each have twelve stages (so-called tortuous paths) and Koso engineers were convinced they would do a proper job.
According to Mr Thomas, the valves had to meet a rather unusual specification.
“The client’s lead engineer insisted that, during operation, he should be able to put his hand on the valve and feel no appreciable vibration. Fortunately, our valves have all passed that test.”
Set to open at pressures above 48 bar, each of the three Japanese-made valves is rated at fifty per cent of flow.
Interestingly, they are operated by a rather unusual source.
Mr Thomas: “There is no compressed air or electricity on site. Therefore, we are using the pressure of the oil in the pipeline itself to operate the valves.”
Mr Thomas concludes with a rather interesting anecdote.
“There is an extra reason why these valves need to work perfectly. In the event of a spill, any oil would flow downhill and the area to be affected is a local hospital!”
