×
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

Captured Vent line

Captured Vent line

Captured Vent line

(OP)
I have a question, I am trying to figure out how to calculate exactly how far a pressure wave will travel up a captured vent line located after a pressure relief valve, or rupture disk.

Right now I am thinking to just figure out at what point the pressure will equal to zero as the volume increases as a function of the piping length.

Any tips or thoughts?

RE: Captured Vent line

it will depleat in the same manner as the flow that the pressure wave produces would lose pressure with friction as that flow travels up or down the pipe.  There is no difference between a flow caused by a rupture plate, a leak, an opening valve or any other pressure difference, except in a wave form, the pressure behind it is not sustained by a continuous feed of the fluid needed to maintain it at the  wave's peak value, so it falls off behind the peak as the wave advances and the deterioration from friction becomes cumulative as the distance traveled increases.

RE: Captured Vent line

(OP)
So could I just treat it as total pressure (head) loss?
 

RE: Captured Vent line

It is a head loss calculated by an appropriate friction factor equation.  The problem is that it is not likely to be possible to consider it a steady state for the whole length of the pipe, so the flowrate varies all along the pipe as the pressure wave travels down it.  You'd have to break the pipe up into a lot of short segments and calculate the inflow, the outflow  and the resulting pressure in each segment for a short enough period of time that allows you to assume a steady state condition exists for a few 1/10ths of a second in each segment of pipe, then do it again, etc. etc.

You may find that there is no zero psig pressure at any one point, but that a wave front with a high peak pressure and a low pressure trough trailing behind it moves down the pipeline, or something else.  It all depends on the magnitude of the flow developed by the transient pressure blow in relation to the pipe maximum capacity transient pressure and flow and whatever normal flow state is being sustained there before and after the transient passes.
 
Its a whole lot easier to get hold of a hydraulic analysis program with transient analysis capability, or just find some competent engineer that you can pay to do it for you.

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