3 replies to this topic

[Awais Ahmad]

Dear All,

 

As I have to attend the repair/maintenance activities of storage tanks, so one of the problem which I am facing right now is presented before you all for your expert advise;

 

Steam Plant has experience problem in few months back in relation to leaking of blow off hatch (BOH) that lead to shutdown the whole station as the gases/vapor containing H2S gas. The Engineers and operators have tried all their best to clear this problem, even the BOH Vendor has been called to check and he did not see any problem of BOH. With several test and scenarios the site team has come up to the conclusion that the possible cause of the problem and relocate one of the BOH as shown in the drawing and placed on the Nozzle by design as blind flange/man-hole and the leaking of vapor/gases stopped.

 

1. Current BOH location:

a. West side BOH remain same at Nozzle A1

b. East Side BOH has moved to Nozzle A2 (i.e. man-hole)

c. Manhole is moved to Nozzle A5 (east nozzle)

 

2. Both BOH are holding good with current installation.

 

Note : Credible scenario identified at site is: The tank roofs are vulnerable for pulsating vibrations from process/tank structure itself (might be considered normal for tanks integrity perspective). But for the devices those are dead weight type could be an issue to achieve the design intent/performance standard.

 

• Tank top roof is supported beneath West BOH and Manhole nozzles with braces from inside which confirm us that these 2 nozzles has rigid base.

• Since East BOH nozzle has no rigid base, pulsating vibrations could possibly be sufficient enough to oscillate BOH cover continuously might be resulting in leaking/passing.

 

With this brief note kindly advise that, if there will be no effects in terms of design against the changes then we can leave with it.

 

Regards

Awais Ahmad

Attached Files

•  BOH location Changes.pdf   610.52KB   80 downloads

[fallah]

Awais Ahmad,

 

The whole safety concept and detail of the safety devices on the tank roof isn't clear and hasn't been specified. Then if there would be no safety issue based on tank safety philosophy, the leaking BOH can be equipped with gasketed cover and lock down capability to avoid leakage due to pulsating vibration...