ESDV assembly Factory Acceptance pressure testing

[PatWHendersen]

Hello

Can anyone tell me if there is a standard for the minimum pressure testing required fo Emergency Shut Down Valves, Blowdown Valves, HIPPS & risers as a final assembly?

I'm finding that some manufacturers state that pressure testing is required for the full assemblies and once tested should not be disassembled eg for painting of the valve.

Other manufacturers at the other end of the scale are happy to present a procedure showing full pressure testing of the bare stem valve with a full Dp stroke test performed on the aseembly and then disassembly for painting with only a dry stroke test required on re-assembly.

The first scenario seems a much more stringeent test and more reliable test of the assembly's integrity.

Those offeriong the seperate testing state that valves can't be painted once assembled with actuator and controls due to possible damage of these units. Thesy can size andd these intricate peices of pressure, torque and mechanical function... just not paint them???

Both can't be right though.

Is there an international or industry standard to guide this?

Any help on the suject would be greatly appreciated.

Thanks and best Regards
Pat.

 

[gerhardl]

Sadly, as a general rule, the world tends to differ more than unite.

The products itself differ even more: the largest emergency shutdown valve I have sold weighs about 5 tons, equipped with oil-hydraulic cylinder and counterweigt shutdown. This is of course an illustration that practical issues must always be taken into consideration, and that 'general rueles' cannot apply and cover all cases, for all sizes and valve-types and pressure classes.

You state : "I'm finding that some manufacturers state that pressure testing is required for the full assemblies and once tested should not be disassembled eg for painting of the valve, ...-and that this seems more reliable." This would probably be true for some smaller constructions, and often when relief pressures is high.

But: The actual practical relief pressure for the mounted valve may deviate from the one adjusted to under ideal test conditions in a test bench. Pipe layout and components before and after the valve might give large differences from the ideal test-bench conditions.

Ideally all valves should be tested mounted in place/pipeline. This is however not possible as a lot of the valves under your general group is releiving at pressures so high that this is not allowed or obtainable when mounted in the operational pipeline.

On the other hand a lot of valves can be tested mounted in the pipeline.

A lot of valves is also tested ready painted and mounted, but in testbench. Some valves and devices are not suited for retesting without service ( possibly scratched seats/parts etc).

Different applications and branches will require special conditions and rules.

.....and so on!

And: No, I do not know a standard able to cover all this!