Does anybode have a good reference on requirements for the allowable amount of dirt in gas with regards to the valves - block, ESDV and control valves?
MortenA, Check with the various Manu'f. on their recommendations. In my experience, any reduction to a minimum, of scale, dirt and debris will always make the equipment last longer and be more reliable.
There will always be some dirt in the gas, whether it comes from millscale or from the gas itself. Good practice is to put a strainer ahead of every control valve, even if it means that you put multiple strainers in one line.
For cage guided control valves it could cause bad performance as the dirt gets caught between cage and plug. Pending on the partical size it could also clog the cage.
For on off duty, if the seals are in the flow path it could cause premature sela failure.
I doubt if any supplier will give guidance on this as its very hard to quantify.
You'll have to look at the inherent flow paths of each design to see what is best.
I know that BP did an erosive study on control valves in the past and graded valve brands or else talk to the valve manufacturers that ar esupplying to the upstream (untreated) hydrocarbon market.
In Holland a lot of these upstream valves are from Mokveld