3 replies to this topic

[justinbasha]

Hi There:

I am currently working on a "Management of Change" request on one of our oil production facility sites. I am currently tasks with looking at retiring a pressure vessel and its associated piping in place.   It has been requested that the piping and the pressure vessel be decommissioned from the rest of the system but not removed as there is additional costs with removing the equipment from site that the company does not want to incur at this time.

 

I have looked at the walked down the system and have come to the following conclusion. 

1.  all nozzle connections on the vessel that could allow process fluid into or out of the vessel should be blinded off.  This should satisfy ABSA (Alberta Boiler Safety Authority) the regulatory body for managing pressure vessels here in Alberta, Canada. 

2.  Blind off all piping connections from the tee off the main piping stream to the vessel.  This will prevent dead legs of fluid that could potentially rupture in cold weather climate.

3. Drain and purge vessel and associated piping.

 

My question/concern is if the piping from the vessel to the main process line is drained and purged, how do I determine that there is no associated danger of this piping rupturing as it is blocked in on either site as part of taking it out of service.   Is there a calculation that I can preform to ensure that the pressure on a hot summer day will not rupture?

 

Thank you in advance for your help

 

J  

 

 

 

[fallah]

justinbasha,

 

In such existing blocked in piping with no liquid inside and positive isolation from main piping streams, appears there would be no risk of fracture even in a hot summer day...

[Zauberberg]

How can it rupture if it is drained and depressurized? The Sun radiation itself cannot cause such a scenario.

 

If you are concerned for the portion of piping upstream of the spades where liquid may sit stagnant and get blocked on both ends (so there is a trapped volume of liquid), you can provide a thermal relief valve.

Edited by Zauberberg, 01 June 2015 - 10:17 AM.

[AymanAyadi]

There is no risk for an increasing pressure in a partially liquid filled piece of pipe.

 

For no proved isolation technique, it is well recommended to positively pressurize the pipe @ 1 barg with nitrogen and install pressure gauge in a visible part of the pipe to monitor pressure.

 

Nitrogen preserve the piping from corrosion by eliminating O2 (sweeping or pressurization/depressurization). (well drained and maybe drayed piping sys is the key step for a good preservation).