×
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

High Points Vents and Low Point Drains

High Points Vents and Low Point Drains

High Points Vents and Low Point Drains

(OP)
All,
Let me start my quest with this subject.
My question is does the location of high point vent depends on flow direction? And does the number of H P vents depends on the length of piping?
To be more precise, attached file is part of routing for Amine Oxide. Which is suitable location for a high point vent in the piping point A or Point B to place a H P vent after the first riser starting from right side.

And Is one H P vent sufficient in horizontal run of 40' near point B or in point C segment?
Does it require more H P vents or L P drains?

Thanks
Disciple

RE: High Points Vents and Low Point Drains

Consider that vents are almost always used under startup and after shutdown conditions of very low flow => rarely - though not "never" - at high flow conditions when flow direction matters.   

Drains frequently require flow backwards down pipes after the pump/pressure vessel/pressure is "off" => again, which sometimes causes problems when check valves actually really work and prevent the fluid from actually draining out.

RE: High Points Vents and Low Point Drains

the vents and drains are correct on your routing. we don't need more.

RE: High Points Vents and Low Point Drains

(OP)
thanks for the contribution

My context of refering to flow direction is like when the flow is from left side of pipe in attached iso, the air inside the pipe will be pushed and displaced by the fluid. If the vent is just after the top elbow of riser there will be less possibility that the air will be released from the vent completely most of the air will go further. If we keep the elbow at the end of horizontal run after the riser it may allow more air to escape. This is my thought process only.

Again I have doubt whether keeping the vent at the end of horizontal run will make any difference because the air can travel after that point in the pipe as it travels from the top of riser position.

I would appreciate if somebody can elaborate the concept of positioning the high point vent.

Thanks

RE: High Points Vents and Low Point Drains

indimech

Most of the cases I've seen have the vent right at the top where the pipe changes from vertical to horizontal.   

Patricia Lougheed

******

Please see FAQ731-376: Eng-Tips.com Forum Policies: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

RE: High Points Vents and Low Point Drains

air will be released completely as long as the vent is on the highest point.
fluid level raises evenly on horizontal part, air will be pushed to the highest point.

RE: High Points Vents and Low Point Drains

indimech,

The location of the vent (or Drain) is important and should be given careful consideration BUT not for the reason that you stated.  It has nothing to do with flow direction.

The criteria for the location of High Point (Hydro-test) vents and low point (Hydro-test) drains is access.  

The Installation contractor is normally responsible for doing the Hydro-test and need to get to the vent or drain.  They do not think very kindly of piping designers that put vents (or drains) in locations that are not accessible.  

RE: High Points Vents and Low Point Drains

(OP)
@ vpl
I have also seen most of the vents just after the riser. But I don't know it is just a practice followed in piping or is there any logical technical reason.

@ 0123
Your reply leads me to think whether the fluid fills a pipe level by level like a tank or it fills like displacing the air, like a pig pushing the product, and filling the pipe completely in a cylindrical manner.
If flow velocity is less it would fill level by level but at high velocity also will it fill level by level?

@ pennpiper
Do you mean that as long as the vent is on highest point, assuming that highest point is on a horizontal section of pipe, position of vent doesn't matter whether it is start of horizontal run or end or in between if it is accessible to the personnel?

Doesn't a high point vent have any other use apart from pressure testing ? Say during start of another batch ?

RE: High Points Vents and Low Point Drains

indimech,

High point vent is used for hydro-test and start-up.

In hydro-test, fluid level would fill level by level.

In start-up, I only know for steam line, steam will mix some air acting as a piston. Air would not be vented completely even putting a vent at the end of horizontal run after the riser. Normally a vent is placed at the remote end of each line.

So, pennpiper is right, we only consider accesibility for the location of high point vent.
 

RE: High Points Vents and Low Point Drains

(OP)
If we consider a process which goes through 4 batches per day and CIP cycle after each batch then during start of every batch doesn't the conditions are same as startup or hydrotest.
If we don't use vents during start of each batch why do we need to use vent in hydro test?

Sorry for asking too much but whenever I start thinking lot of questions come to my mind..Please bear with me.

And thanks for replying.

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