Check the availability of floating roof tank

[elowami]

How can we check the availability (ready for start-up) of floating roof tanks which suspended (out of service) for long periods of time.

is there any test or procedure for this?

thanks

 

[jari001]

I'd probably start by looking at API 650 to know what the design criteria are and then check that the tank in the field still meets the needed criteria. Is the reason for suspension of use still in effect?

There's the more general questions like structural integrity, seal integrity, did anyone steal parts from this tank, spill containment still in working condition, automation up to date/install new automated equipment, all documentation still available...

 

[elowami]

The reason for the suspension of the floating roof tanks from the service because the plant is completely suspended for long time 6 years. Before the shutdown there were no problems with the storage tanks.

 

[LittleInch]

So the issue will be how were they left for 6 years? Drained completely with the roof sorting on its support legs and inert atmosphere?

Even if so after 6 years you need to enter the tank and inspect for corrosion, water egress and what the roof drain system looks like. Any flexible fabric or similar will need to be reviewed and probably replaced. In short get a tank cleaning company to inspect it and advise.

If the roof is sitting on its legs remember that until it is fully floating your inlet flow needs to be carefully managed as the vapours will be venting out of the roof vents.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[jari001]

I second the inspection advice from LittleInch. I'd also try to do some dummy runs with personnel of normal operations and some emergency responses (using water if possible); even if you can't flow anything through the system, your dummy runs should be in the field and visit any manual valves, pumps, etc. so that operators get the best picture of what it all takes. That initial inspection is going to be critical, it will set the mindset of everyone involved going forward.

 

[elowami]

- The storage tanks have been suspended for 6 years due to the deteriorating security situation in the area.
- The tanks are completely empty and left under nitrogen pressure.

in case of using water for test, how can I get rid of the water residue after discharged (drained) from the tank?

Thank you Mr. LittleInch and Mr. jari001 for your cooperation

 

[LittleInch]

I find it difficult to believe that the nitrogen is still there. Floating roof tanks are not gas tight and their design pressure is virtually atmospheric so unless someone has been pouring nitrogen in for 6 years under very low pressure, it will have reverted mainly to air (79% nitrogen). A pressure vessel yes Ok, but a FR storage tank - no way.

Check for bullet holes...

Seriously, you need to vent the nitrogen and go in and inspect it.

If you think it's all Ok then there should be no need for a water fill, but how you dispose of that amount of water I can't help you with - this is a very local issue.

Otherwise your tank should have water drain lines / sumps / slopes to drain water or open it up again and go in with squeezes and mops / vacuum line to suck out all the water.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[elowami]

Thank you Mr. LittleInch

 

[jari001]

If you can't practically complete a water run/fill, then you can't do it. I don't think it is a MUST, but a nice to have as a shakedown activity. Like LittleInch has emphasized, you and some qualified personnel have to prepare the tank for entry and then inspect it to great detail.