×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

When do you use a Ball Valve followed by a Globe valve?
3

When do you use a Ball Valve followed by a Globe valve?

When do you use a Ball Valve followed by a Globe valve?

(OP)
Hello,
I'm looking at a P&ID with an inlet ESD Valve with a bypass around it that contains a ball valve followed by a globe valve.

This may be a very basic question but, can someone please tell me what the basis is for having a ball valve in series with a globe valve?  

thank you.   

RE: When do you use a Ball Valve followed by a Globe valve?

Hi Juujee12,

Is the globe valve perhaps for modulating control, with the ball valve simply to isolate it for maintenance?

Can't tell for sure without looking at the P&ID...

Good on ya,

Goober Dave

RE: When do you use a Ball Valve followed by a Globe valve?

(OP)
Hi DRWeig,
Thanks for the response.

Sorry I can't upload the P&ID, but just picture a normally fully open ESD valve on a line with a bypass around it for maintenance.  The bypass line has a ball valve and globe valve in series. that's it. no other blinds or hardware.

The ESD is normally full port open and is not modulated. There is no control required at this point, it's not like a bypass around a control valve.  

thanks again,
Juujee12

RE: When do you use a Ball Valve followed by a Globe valve?

I would say that a ball + globe in series is not typical practice.
There must be some system specific reason.
One guess is to manually throttle flow around the ESD when it is closed.
Of course this defeats the purpose of the ESD.

RE: When do you use a Ball Valve followed by a Globe valve?

3
without observing the P&ID and since you mention ESD inlet valve, the bypass piping with ball & globe valve are most likely used to purge and pressurize the plant piping after an ESD event.  simply opening a large diameter ESD valve without purging & pressurizing the plant in a controlled fashion may very well be catastrophic.  the globe valve will be used to control the amount of gas for purge and to control the pressurization rate.  the ball valve is either full-open or fully closed - definitely no throttle control.  so, likely open the ball valve and then control purge and pressurization via the globe valve.

hope this helps.
-pmover

RE: When do you use a Ball Valve followed by a Globe valve?

(OP)
pmover you've given me a very logical reason for the arrangement. much appreciated. I'm sure that's why a globe valve was installed for re-pressurization after a shutdown event, or for start-up.

thanks again to everyone for your help!

RE: When do you use a Ball Valve followed by a Globe valve?

Also at a fairly low dP a large size ball valve will be impossible to open - even with a powerfull actualtor (the most common reason for installing a bypas). Besides - i would say its a very common thing - at least for system with valve larger than say 6-8" and any signifiant pressure.

The reason why you cant move the valve is in he way the seal work that prevents the valve from leaking.

The globe valve is of course for a controlled release - sometime a RO is used instead.

Best regards

Morten

RE: When do you use a Ball Valve followed by a Globe valve?

Ball valve shutoff > Globe valve shutoff

RE: When do you use a Ball Valve followed by a Globe valve?

As above

Assuming the arrangement to be on a high pressure gas facility. The pressurisation is manally controlled to prevent (minimise) the seat erosion on the ESD valve. Also J-T cooling can result in temperatures below the MDMT. On some arrangements, eg compressors with auto start, the pipework downstream of the globe valve is stainless steel. The globe valve will be on the low pressure side (or the maintainable side).

The larger ESD valve can be a rotating seat so that the same bit of seat is not subjected to the wear in the same point.

RE: When do you use a Ball Valve followed by a Globe valve?

I agree with pmover.  Its a black start-up arrangement for after an ESD event.  If its a natural gas line, its probably providing fuel to start the generator.

Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources