external floating roof API650
external floating roof API650
(OP)
hi,
I have an external floating roof 60m dia tank experiencing problems with deformations possibly because of vapour bubbles underneath. Water accumulation on top exacerbates the deformation but as soon as the vents are open, the water comes back towards the central area which to me suggests that the internal vapour pressures are responsible for this deformation. This is a 5mm pontoon roof, oil tank to API 650 (designed to 0.7 specific gravity).no product on the tank, seals working perfectly.
Q: what other factors can be responsible for slightly tilting the roof (pontoon corrosion?, flooded pontoon?)
some brainstorming would help.
thanks
I have an external floating roof 60m dia tank experiencing problems with deformations possibly because of vapour bubbles underneath. Water accumulation on top exacerbates the deformation but as soon as the vents are open, the water comes back towards the central area which to me suggests that the internal vapour pressures are responsible for this deformation. This is a 5mm pontoon roof, oil tank to API 650 (designed to 0.7 specific gravity).no product on the tank, seals working perfectly.
Q: what other factors can be responsible for slightly tilting the roof (pontoon corrosion?, flooded pontoon?)
some brainstorming would help.
thanks





RE: external floating roof API650
RE: external floating roof API650
shell bulge and differential settlement are now being investigated. no frozen swivel as the tanks are in a tropical zone.
how much is out of level is difficul to say: we see this when the rain accumulates on one side (I have to ask the maint. people if it is all the time on the same side?)but we know that when the bleeders are open the roof assumes initial position.
we assume it is a ballooning effect of the central area where gas bubbles are buit up. I could not find anything in the Codes that tells me how much deflection of the floating roof I can have. that is another matter but still of interest. thanks
RE: external floating roof API650
Steve Braune
Tank Industry Consultants
www.tankindustry.com
RE: external floating roof API650
The sequence in my mind is:
- large gas bubble (5-6 dia)due to unstable components forms in the centre
- roof is slightly balooning in the centre
- rain (+ the poss effect of wind ) accumulates on the roof and is pushed sideway as the centre deck is already slightly ballooned
- tilt (bear in mind: this is a sl;ight tilt) occurs
we opened the bleeder vents 1 first-> water tends to come to the centre then the second bleeder vent no 2 opened which gave gas release (+ some crude) following which water runs towards the centre which suggests a) the central deck was ballooned and b) the cause was the formation of gas