Who claims that valve maintenance doesn´t pay off?
Most of you readers who have read my articles knows that I´m a great fan of valve maintenance, cleaning, lubricating and moving the valves on a regular basis. This will prolong their performance and lifetime. However, there are some arguing that it´s too expensive; as one needs personnel and time to be able to perform the aforementioned tasks.
These companies, say the ‘non-believers’ in maintenance, tend to operate according to the moto run to failure and then replace. As a result, they tend to purchase valves that are not equipped for maintenance. Remember that lubrication fittings and auxiliary valves are possible leak points; and HSE don’t like that.
A short while ago in connection with a shutdown, I was on an oil and gas to maintain some of the valves. The valves in question were barrier valves for a replacement job that were to be performed during the shutdown.
When stopping the production, two 18” inlet valves were leaking. Both valves were trunnion mounted double piston valves and both seats on both valves had an unacceptable leak rate. Having detected the leaks, there were two alternatives: close the sub-sea valve some kilometer from the installation and reduce the pressure towards the installation, set the barriers and replace the leaky valves. This job would take several days extra, with a production loss of 9 mill US $ per day. The other option was to maintain and try to seal the valves; which would be done with fully pressurized system, while the preparation for the shutdown was ongoing and one would not lose any time.
The valves in question were installed with two lubrication fittings to each seat and an auxiliary valve in the cavity. The valve was in fact prepared for maintenance, the paper work was done, and we were ready to rock. We tested the valve into the cavity to registrar the leak rate. We injected valve cleaner in accordance with my procedure and left the valve in six hours to let the cleaner do its job. After 6 hours we did some more work on the valves tested them and it appeared that they were 100% sealed on all four seats.
I must add that before accepting the job I was given all information about the valves: the operating condition, all GA drawings, P&ID and how the valves were operated. Therefore, I was confident that I would be able to fix the valves. By the way, the picture in this column is not from the valve in question but illustrates what was causing the leak, namely; deposit build up on the seats or/ and the ball preventing a good contact between the seal areas of the ball and seats.
To conclude, if a valve is without lubrication fittings and an auxiliary valve, you don’t have any chance in maintaining a leaky valve. If the valve is equipped with two lubrication fittings to each seat, but without an auxiliary valve into the cavity, you will a have a 50 / 50 chance of fixing the valve. Only when the valve is equipped with lubrication fittings and an auxiliary valve into the cavity you will have a 90% chance of fixing that valve, only when performed correctly.
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