×
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

Static Pressure Increase Due to Thermal Expansion
2

Static Pressure Increase Due to Thermal Expansion

Static Pressure Increase Due to Thermal Expansion

(OP)
I had a rupture disk fail due to thermal expansion in a 6" dia CS aboveground pipeline.  How can I determine the pressure increase?
Thanks.

RE: Static Pressure Increase Due to Thermal Expansion

Inside the pipe was what?

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: Static Pressure Increase Due to Thermal Expansion

At a rough guess, the pressure increase was greater than the burst disk pressure rating...

 

RE: Static Pressure Increase Due to Thermal Expansion

For a more complete answer,

find the CTE (cubic) for the fluid, multiply by the appropriate temperature differential to find change in fluid volume with no pressure change.  Call this DVF.

Find the CTE for the pipe material, multiply by temp. difference, cube the result - this is the change in volume of the pipe with no pressure diff., call it DVP.

Calculate the dVol/dpressure for the pipe - requires knowledge of pipe stress equations.  Call this factor DVDPP.

Calculate the dVol/dpressure for the fluid - this is also known as the fluid's bulk modulus.  Call it DVDPF

The pressure is the common factor here, i.e. Ppipe = Pfluid.

So, calculate the pressure rise, plug it into the pipe equations to find the volume expansion of the pipe, subtract that number from the volume expansion of the fluid, and recompute the pressure rise in the fluid, use the new pressure to recalculate the pipe expansion....etc.

There is probably an algebraic solution too, but I don't have time to work it out for you.

 

RE: Static Pressure Increase Due to Thermal Expansion

(OP)
Natural gasoline is in the line with 10 psi blocked-in.  Ambient temperatures were a low of 28 degrees F and a high of 54 degrees F.  Length of line is 1800 ft.  The rupture disk is designed to fail at 270 psi.  What I'm really looking for is if under these conditions, would thermal pressure increase enough to rupture the disk?

Thanks for your help.

RE: Static Pressure Increase Due to Thermal Expansion

Oh.  And don't forget to include the compliance (expansion) of other parts in the system...like expansion tanks, fittings, air bubbles, rubber parts...

RE: Static Pressure Increase Due to Thermal Expansion

willymarv,

There is a note in an old Crane Valve catalog no. 60 page 14 about tests with 33 API fuel oil in a closed filled vessel.  Two tests run from 76 deg F and then 82 deg F start to a 95 deg F final /  113 deg F final, showed a linear rise in pressures.  The 113 deg F final temperature resulted in a final pressure over 2500 psi (250 psi initial = 2250 psi rise), while the second test to 95 deg F resulted in final pressure 1575 psi (150 psi initial = 1425 psi rise).  So the pressure increased by 73 to 75 psi / deg F.
Crane Valve Co was trying to make point about pressures in a bonnet cavity of a shut-in gate valve.  The same could be said for pipeline without any expansion bottles or vapor pockets.  Crane Valve chart of tests has the title of 'Thermo-Piezo Effects of Oil at Constant Volume'.

Your Nps-6 pipe system could have had an increase over 1800 psi if the rupture disk did not open.  The Nps-6 pipe Sch40 rating might be 1300 psig except for flanges or valves.     

RE: Static Pressure Increase Due to Thermal Expansion

I believe that it would rupture the disk without too much trouble.

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: Static Pressure Increase Due to Thermal Expansion

I was thinking about 4000 psi would be possible for 30 F diff, but that number depends on if the pipe was filled at 28 F.  That's pretty big temp differential.  If it was filled anywhere around 45 or lower, I thought there was a pretty good possibility.  Normally these things have thermal relief valves back to a tank or into an oily water drain, rather than rupture disks because a relatively small temp difference will set them off.

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: Static Pressure Increase Due to Thermal Expansion

If this pipe really contained gasoline, then I question the wisdom of having a bursting disc. Why not a 1" thermal revlief valve that discharges on the other side of the block valves.

Regards,

athomas236

RE: Static Pressure Increase Due to Thermal Expansion

I would never use a disk or relief valve for risk of spills.  Use a 1/2" check valve loop around the valve that blocked the line in so that it was allowed to experience thermal expansion.  

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