Valve type 1

[vjr0512]

As per the client specification, Ball valve shall be used for on-off service. Actually one of the Valve in High pressure steam service has been used as Emergency Shutoff service ( 4" class 600).

Contractor is proposing to use Globe valve for this service..

Is the quick action of a quarter turn alone decides the on-off service or can a globe valve be used for such service when the leakage class is complied with the ball valve?

The steam pressure is approx 50 bar at 450 deg C.

Thanks to clarify

 

[LittleInch]

Use of a ball valve for ESD type usage is simple and relatively cheap and easy to operate / configure

Use of a globe valve where the closure action is linear rather than a turn is possible, even for ESD fast closure / spring return, but unusual and would not appear to offer any advantages and some disadvantages.

Even fully open I can't see how a globe valve can match the CV of a fully open full bore ball valve?? - Result permanent pressure drop. Doesn't bother the contractor but should bother the owner.

Sounds to me like they are trying to use up a spare valve instead of buying the proper valve.



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Also: If you get a response it's polite to respond to it.

 

[mk3223]

IMO, why to use a globe valve for an on-off purpose since a ball vale or gate valve can do the job and won't cause ant flow restriction issue.

 

[uaepiping]

Littleinch has put it nicely. The reasons for not using the globe valve are mainly two - unnecessary pressure drop and higher cost of globe valve!

 

[AzriHms]

Use Orbit valve that comes with actuator. Fast action shut-off and designed for your purpose. Never use globe valve for emergency (steam) shut off service.

Regards

 

[gerhardl]

An emergency shutdown valve should be selected for worst scenario: highest possible flow and fastest possibly needed closing time, both given by an exact given figure as possible.

In almost 100% of practical cases this will give valves (as already given by previous answers) with 90 deg closing action (ball, plug. and special designed butterfly valves with full opening), or also gate, knife-gate or needle type valves or others with one-stroke closing.

If you have been asked using a valve not according to normal safety or engineering dimensioning criteria, the answer is no.

 

[vjr0512]

Thanks to all for responding. We are proceeding to go with Ball valve now. Thanks once again

 

[vjr0512]

In continuation with the above, based on the delivery schedule, Contractor suggests to use Reduced bore ball valve. The main steam line is 6" and when it comes nearer to this ESD valve, the line size reduces to 4" and actual reduced bore of the ball valve is 2".
Contractor confirms that 2" size is sufficient and also the velocity criteria and the cv requirements.

Need your assistance the factors to be considered before giving green signal to the contrator

Thanks in advance.

 

[LittleInch]

glad you've finally got a decent valve there.

Just check the CV of the valve and look at the pressure drop and flowrate you need through this valve and compare it to a full bore valve and see if this extra pressure drop is acceptable to YOU or not.

Use of reduced bore valves are commonplace, but at the 4" size the reduction in area is at its worst compared (4:1) to say a 6" x 4" ( 2.25:1) or an 8" x 6" (1.7: 1).

What does either the P&ID or yur piping and valve specs say is acceptable?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.