valve orientations 1

[Kaplin]

I have an 8" globe valve mounted horizontally on a 300psi hydraulic line. Even after overhauling the valve, it still passes. Could the horizontal orientation of the valve be part of the problem? Are some valves better than others in certain orientations?

Thanks!

 

[quark]

Kaplin!

The characteristic of globe valve (particularly metal to metal seat and closure) is to leak. It's no pun. See for any scratches on the closure or thin grooves. Horizontal position is not a problem.

Regards,

Truth: Even the hardest of the problems will have atleast one simple solution. Mine may not be one.

 

[owlscreech]

When you say horizontal, do you mean that the stem is horizontal? (as opposed to the flow stream)

Also how is the disc (plug) guided? If it is the body, is there full (or nearly full contact) or are there guide ribs? If not body, then how?

 

[Parthaa1]

Position of the valve is not so important in the case of globe valve.In this perticular case the seat(metal to metal contact)may be worn-out or the stem centre line is not exactly perpendicular to the seat plane and hence a small gap exits around the circumference when the valve stem is tightened .I pressume this may be one of the reasons for the leak.

 

[fhasan]

What exactly do you mean when you say you have overhauled the valve. Did you repair the seat or plug or just cleaned up the valve trim and body. Knowing what you already have done may help in diagnosing the valve problem more accurately.

 

[Lakeshore]

Agreeing with most... orientation does not matter. Fhasan is correct in requesting an explanation of "overhaul." The biggest culprit I have found is poor actuator performance. What type of actuator are you using? Best regards,

Lakeshore Tech

 

[chuchcatlanta]

The orientation will effect the valve IF it is not a "caged" style valve-the weight of the valve stem will cause wear faster on one side due to the gravitationally assisted friction.

 

[valvetech]

Everyone makes a valid point here, If the valve is stem guided, the plug "can" be influenced by the orientation and pressure. This will depend on the valve and the pressures.
since the valve has been "overhauled" (presuming that means either new seats installed or the old one cleaned inspected and reinstalled in good condition) that the valve has metal seats and they are either ANSI CLass III or Class VI which allows for leak by.
Check the valves specifications and if the seats are metal, then if you want a positive shuttoff (bubble tight) then you will need to change to a soft seated material.
Keeping in mind that the ANSI Standard for Class VI or bubble tight only applies to the test conditions (Air or Nitrogen @ 50 - 125 F 50 psig or Maximum operating differential pressure whichever is less). So if you hydrallic fluid at 300 psi there can be leak by and the valve will stilll meet the standard.
Check with the manufaturer and see what they can do for you to achieve the desired results you need.

 

[BillBirch]

We should remember that globe valves are not meant for shut-off, In process industries, (oil & gas / petrochemical), globe valves are normally isolated by more positive isolation valves such as gate or ball valves - globes throttle and are not expected to isolate.

 

[eanlex71]

When you mentioned 8" globe valve, is it a manually or pneumatically/electrically actuated?

If it is the former, what is the design rating of the valve? Almost all big sized globe valves(DN125 & above)can only withstand a certain limit of differential pressure across the valve.Once the limit is crossed, most manufacturers would recommend the use of a balancing disc which is designed to reduce this d.p. so that the valve can be easily open/close.

If the valve is of the former(pneumatic/electric actuated), then, would recommend that you check the closing force of the actuator and as they were mentioned, to which class is the leakage rate of the valve is being designed for.

Hope this is helpful.

Best regards,
Alex

 

[NAYAN]

Is it possible to define the ageing of soft components(Ex.:gaskets,Oring..etc) in control valve/ on-off valve & positioner?.Do we have any tool for that.
please guide us.

 

[Kaplin]

Thank-you for all your tips. We have decided to replace the russian globe valve with a trunnion mounted ball valve as this will provide a better seal as an isolation point. I'm not sure why a globe valve was installed as an isolation point in the first place...

Thanks again.

Christine.