×
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

Leak at LPG storage inner tank

Leak at LPG storage inner tank

Leak at LPG storage inner tank

(OP)
Hi everybody,
In annular space of full containment LPG storage tank, the temperature is more or less equal to inner tank thats why we suppose that there is a leak.

my question is: What are the techniques to find leak on full containment inner tank full of LPG?

do we have to empty the inner tank for inspection?

Thank you for your help.

RE: Leak at LPG storage inner tank

Annulus pressure?

I always thought the annulus was kept at atmospheric pressure and any rise in pressure indicated a leak.

Can you safely vent the space to see if it pressrises back?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Leak at LPG storage inner tank

(OP)
Thank you for your suggetions.
it's a new LPG tank and it's the first filling with LPG liquid.

The annular space temp of the tank is equal to inner tank temp.

The contractor proposed to perform one of the two techniques to confirm that there is or no leak on inner tank explained below:

1. to check the variation of liquid level inside inner tank during a period.
2. to empty the tank, for internal inspection.

which technique is better?
For time being I have no other infromation.

Thank's

RE: Leak at LPG storage inner tank

Doing troubleshooting with such limited information is very poor practice, and it will almost certainly bring no results. I sympathize with you, but there must be a way to collect key information/documents, and do some field measurements.

You need to find out where the temperature sensor is physically located (perhaps installed too close to the inner wall) and verify readings of other transmitters in the annular space.
Next, look at the drawings and see if there is any purge (usually N2) through the insulation between the two walls, and where this purge is routed (flare or vent), and get some samples for gas composition.

Dejan IVANOVIC
Process Engineer, MSChE

RE: Leak at LPG storage inner tank

Until you find out or give us more information about the tank, specifically what is in the annulus and what sort of process measurements you have available there is not much more I can advise.

The whole point of a double skin vessel is that an leak in the inner tank is contained, but also that you are aware of it by means of pressurisation or other sensors within the annulus.

Both "techniques" you mention seem quite poor. There should be no guesswork about whether you have a leak or not.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Leak at LPG storage inner tank

Keep in mind that the tank contractor is motivated to not find a leak.

1 seems insufficiently accurate to rule out a leak, and offers no information about the location if it does suggest that there is a leak.

RE: Leak at LPG storage inner tank

Tommy,

Your sketch shows "LNG". Is it LNG or LPG in question? It makes a whole lot difference with regards to evaporation temperatures.

Secondly, what is the storage temperature? What is the temperature of the liquid phase inside the tank?
Moreover, is there any Nitrogen purge through the insulation between the walls?

Your Excel file shows that all 8 temperature sensors are showing the same value, and according to the sketch they are distributed inside the perimeter of the outer (concrete) tank wall, and closer to the outer wall. I don't think this indicates a leak.

Please reply with the requested information.

Dejan IVANOVIC
Process Engineer, MSChE

RE: Leak at LPG storage inner tank

Refrigerated LPG would be at approx -35degC, while LNG would be at approx -160degC for what looks like an atmospheric storage tank. In either case, if the annulus temp is -3 to -4degC, that is still miles away from -35degC, so is there a problem?

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