×
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

Temp loss gas pipe to ground for buried pipe

Temp loss gas pipe to ground for buried pipe

Temp loss gas pipe to ground for buried pipe

(OP)
My company is in the process of building a new natural gas supply station. This station  will serve a large volume customer located 2000' away. This customer will be served via 200' of 6" SCED-40 buried piping from station. We are taking pipeline gas at 750 PSIG - preheating - then reducing to 200 PSIG. This customer will be using at 275 PSIG - 300,000 Cubic Feet per hour. Their contract mandates a minimum gas temperature of 60 Degrees F. I have been asked to determine the temperature drop across the buried piping so as we can determine the required preheat temp. This pipeline will be in an area where frost depths are up to 3 feet. The pipe depth will be 3 feet.

There was a paper written in 1981 that was submitted to PSIG (Pipeline Simulation Interest Group) www.psig.org named "8101 - A Closer Look at Transient Heat Transfer from Pipeline Gas to Nearby Ground".  I believe this paper focuses on the Jacobs Two-Phase Soil method. I have found the equation for this method, but am not comfortable with all the variables- particularly the soil conductivity which is in units of BTU/HR*Ft*F.  I've been trying to get this paper - no luck yet.

Anyway, I was hoping someone could give me some advice on this.

RE: Temp loss gas pipe to ground for buried pipe

BTU/(Hr*ft*degF)  is not very useful for most equations; however, BTU/(Hr*ft*degF)*(12*in/1*ft) will give you BTU*in/(Hr*ft^2*degF).  The second form will make your calculations dimensionally correct for many applications.

RE: Temp loss gas pipe to ground for buried pipe

I'm a little confused about the details of your problem.  If the customer is 2,000' away then 200' of pipe won't reach them.  If the customer is expecting 275 psig gas your 750 to 200 reduction won't work for him.

Assuming that you keep the gas close to 300 psig, then 7.2 MMCF/d in 6-inch pipe is 22 ft/s with 3.5 psi dP over 2,000 ft.  That gives you a residence time of 91 seconds.  

You have to calculate your thermal entry length to determine how much pipe would be required to cool the gas to reach 20% of original dT.  With the thermal entry length you can determine how much you need to preheat the gas.

David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The harder I work, the luckier I seem

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