ASPHALT IMPREGNATED BOARD BELOW TANK PLATE AS PER API 650 1

[rencygisac]

Dear Gents,

As per our tank foundation drawings we are supposed to install an asphalt impregnated board at the bottom of tank bottom plate.Since this asphalt board is in touch with the tank bottom plate Is there any chance to catch fire on it while doing the POST WELD HEAT TREATMENT of the weld joints of tank? Moreover this while doing welding of the plates is there any chance to get fire because of the spatters of welding? If it catches fire is there any other alternative for this? Is there any other practices to avoid catching of fire during construction of tank. Kindly advice. Thanks in advance

Rency isac

 

[JStephen]

Pad products have been used under floors that were then welded in place. Pad around the perimeter of a tank can be slipped in after welding of that area is completed. I can't imagine how the pad would survive efforts to stress-relieve the plate resting on it, though.

 

[MJCronin]

I do not understand why this is a problem....

Why do the thin floor plates in an API-650 tank require post-weld heat treatment ?

Please do not answer "that is what the client requires in his specification".....

What is the specific tank floor material, thickness, and weld type for your particular tank ?

Who is supplying this board ? Have you contacted them ??

Is this the first tank for you, where asphalt impregnated board is used ?

MJCronin
Sr. Process Engineer
Venture Engineering & Construction

http://www.VentureEngr.com

 

[fegenbush]

MJCronin,

PWHT of the complete tank is often specified for caustic storage. Whether or not it actually prevents stress corrosion cracking in the floor seams may be subject to debate.

 

[JStephen]

I assumed either the vertical shell welds or the entire tank was to be stress-relieved, and either would heat the attached bottom also.

The board in question is usually a cane-fiber asphalt-impregnated expansion joint material. It is intended for use in concrete, not under tanks, and it is unlikely the manufacturers would have data on high-temperature applications of it. Maybe a maximum temperature, which is likely less than 1200 degrees.

 

[JStephen]

I assumed either the vertical shell welds or the entire tank was to be stress-relieved, and either would heat the attached bottom also.

The board in question is usually a cane-fiber asphalt-impregnated expansion joint material. It is intended for use in concrete, not under tanks, and it is unlikely the manufacturers would have data on high-temperature applications of it. Maybe a maximum temperature, which is likely less than 1200 degrees.

 

[rencygisac]

Dear Gents,

We are supposed to do the PWHT where the flush type clean out man hole is coming. This is as per API 650. For details of the location of asphalt impregnated board please find the attached drawing. Datasheet of the asphalt impregnated board is also attached along with this thread for your reference. Kindly help me to resolve this problem.

 

[rencygisac]

Please find attached drawing where the location of asphalt impregnated board is marksd

 

[IFRs]

Unless you are PWHT the entire tank, the flush cleanout must be shop PWHT. Per 650 5.7.4.1 All flush-type cleanout fittings and flush-type shell connections shall be thermally stress-relieved as an
assembly prior to installation in the tank shell or after installation into the tank shell if the entire tank is stress-relieved. This is a pretty big tank to PWHT the enter tank. However, if you are PWHT the entire tank in the field then you have a combustible issue and the best idea I have seen is to lift the tank after PWHT to install the fiberboard. You may also have an issue with heating the foundation and especially the HDPE Liner, the telltale pipe, the polysulfide sealant, etc.