×
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

The safest way to blow down natgas lines
3

The safest way to blow down natgas lines

The safest way to blow down natgas lines

(OP)
I would like to know...I know you have to gas free it and all....is it possible for one of you engineers to design a type of "mini-flare" system, equipped with a reducer, a propane tank to pre-light it before the gas hits it so it can be burning already, like at methane plants, of which have large flares with the same thing...sort of..I just thought after that mess up there in Middleton, Conn. that it was possible to flare it off instead of just letting it blow all over the place, causing a dangerous situation

RE: The safest way to blow down natgas lines

No that doesn't work,  because if the gas/air mixture is just right, when it hits the flare stack it will not burn it will instead detonate.

Better, is to just make sure the gas reaches somewhere safe, open, and is diluted beyond flammability without an ignition source available.

Keith Cress
kcress - http://www.flaminsystems.com

RE: The safest way to blow down natgas lines

No really sure on the question but if is not uncommon to provide either permanent or temporary flare stacks at remote locations to allow safe blowdown of pipelines for maintenance.

In western Canada, you have to have an available flarestack to blowdown a pipeline as regulations would not permit blowing down sour gas to atmosphere.

If the gas in the pipeline is too rich to burn (the normal situation) then there is little risk of blow back / detonation in a properly design flare stack.  If the gas may contain a combustible mixture then you could add additional gas to make it too rich to burn or  install a detonation arrestor in piping immediately upstream of the flare stack.

RE: The safest way to blow down natgas lines

(OP)
rneill, you ought to expand on that idea for the United States, you got the right idea of what I'm talking about, and Canada already does it...and make $$$ on it here in the states!

RE: The safest way to blow down natgas lines

Here is some information from the CSB website concerning purging natural gas lines.  This information incorporates some of the proposed changes prior to the Middletown incident.   i would reword some of the information by changing recommended to mandatory.

I would monitor the CSB site for future updates.

No amount of rules and regulation can overcome a lapse in common sense.

http://www.csb.gov/UserFiles/file/CSB%20Gas%20Purging%20Urgent%20Recommendations%20(2).pdf

  

RE: The safest way to blow down natgas lines

(OP)
No kidding unclesyd...that there was ultimate failure of common sense there...and I worked another type of powerplant that has these same issues, lack of common sense.

RE: The safest way to blow down natgas lines

Blowing down any large pipeline segment through a flare burn would either take too long, or cost too much in lost gas, thus the use of diffuser/muffler stacks for high velocity blowdowns to atmosphere, or stopple fittings on each side of the damaged part of a pipeline can usually be justified where H2S and other contaminates are not present.  For small volumes only common sense, or a van full of procedures for those with none, should be necessary.  ConAgra needs more common sense in general AND an 18-wheeler full of procedures.  I think actually breathing some oxygen once in awhile would be a useful procedure for them too.
 

**********************
"The problem isn't working out the equation,
its finding the answer to the real question." BigInch
http://virtualpipeline.spaces.live.com/

RE: The safest way to blow down natgas lines

On natural gas: Many dosnt realise this - but NG is not that easy to light. NG has a fairly narrow band for LEL/HEL

5%/15%. So you can e.g. mix 50% air into your NG - and it still cant ignite it.

This is actually done here in Denmark to make "city gas". City gas has a lower heating value and therefore consumers would have to replace all their equipment if the utility company switched to NG in those cities where "city gas" was installed before NG came around.

But - small mobile flares do exist. Heres a link (just found it by google search. Do not know the quality or limits of their services):

http://www.bjservices.com/website/pps.nsf/AllDocs/JWIE-7QUKZU/$File/FlaringServices.pdf

Best regards

Morten

RE: The safest way to blow down natgas lines

we owned a potable flare trailer NAO I beleive.  We had pre built turbo tips with 3 foot tall stacks.  Each tip was good for 5,000 pouinds/hr or so.  We could assemble up to 10 or 12.  we had a 1 1/2 needle valve that we would mannually control flow.  A 20 pound bottle of C3 with coiled tubing was used as the pilot.  

We would mow down the grass and set up the flare all 2" with ansi 150 4 bolt flanges.

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