Sticky FRP Tank

[darthsoilsguy2]

An old client has asked about a tank they have. Existing 8'Diamx25'H FRP tank has a resin bottom that is sticky. On one vertical side, the middle third of shell wall bulges in and out. Portions of the interior shell wall have a thin delaminating skin layer. The tank has been out of service and clean/empty for a longer time than anyone employed at the plant and it is well-cladded from the outside.

I figure there are 3 possible scenarios.

1. Incompatible product had been stored. Organic solvents and fuels are stored in this facility.
2. Tank was allowed to get to hot. (maybe accidental prolonged activation of the heating line since the other frps on-site don't seem to have been affected.
3. Fabrication problem.

Although I could see item #3 being in combination with #1 or #2, i couldn't see it as a stand alone root cause. Under the assumption that the manufacturer's QC would have mixed/cured the resin adequately if they're in the business of fabricating such large tanks. I suspect hoop stress creep deformed the sidewall once the resin problem developed.

throwing it out to there to see if anyone has crossed this condition or heard any case studies/theory on it.

 

[lganga]

darthsoilsguy2
1) Chemical attack: if the tanks have solvent, normally the resins are not able to stand with it.
But an internal inspection will detect that problem, cracks appear in the laminate.
For this service the tanks has their chemical barrier (5 to 7) out of thermoplastic and linked in GRP laminate.
The Bulges can be a consequence of the chemical attack to the GRP (chemical barrier corroded)
Then to get a good tank the type of procedure for the tank fabrication and the kind of construction standard is very important.
2) Mechanical resistance: the laminate and the reinforcement also the type of joint between bottom and shell tank should be checked.
3) Quality control: is very important as it defines the quality of the laminate (type of laminates for every stage and catalyze and chemical promoter applied)
British Standards have very good designs rules and good details in order to get a tank in which to trust.
About the very thin layer with no adherence, it happens in the 1mm of laminate which is a veil (usually synthetic able to get a very concentrate resin anticorrosion layer) and it is the first to be attacked by the fluid, but you should have another 5 o 4 mm of layer to support corrosion.
These are general ideas that can help you.
regards
Luis