The use of float pans in bulk fuel storage tanks

[DLV53]

Have a DoD requirement to use float pans in three bulk fuel storage tanks. Is there any way to meet the intent of the float pans without using them. The reason I am asking is the sub contract has built the tanks without installing the float pans. I am trying to avoid having them tear them open and install them. Thanks in advance! V/r Dan

 

[LittleInch]

Can you define"float pans"

Do you mean floating suction?

Needs more data but to be honest I doubt it. If the client wants them the client gets theM.

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

 

[DLV53]

Thank you for responding! The float pan is a honeycomb design that floats on the surface of the fuel (oil)it is meant to reduce the amount of vapor build up. Thanks again!

D

 

[georgeverghese]

As far as I know, there is no need for an internal floating roof ( which I believe is what you call an internal floating pan) on regular diesel storage tanks, unless these are located in some hot climes where external air temps can be >55degC for several hours in the day. See page 20 and fig 9 in the attachment which discusses DoD requirements.

https://www.cedengineering.com/user...el Facilities - Atmospheric Storage Tanks.pdf

 

[LittleInch]

But how on earth had the sub contractor not built something as fundamental as a floating roof!!

Forgetting a nozzle or a flange the wrong size maybe, but an internal roof??

I know what I would say if I was the client. I wouldn't even think about getting to wriggle out of this.

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

 

[DLV53]

Thank you both for the input. The tanks are located in the middle east. and are considered mission critical. Based on your input I will hold them to the fire to put them in. Their reasoning was that the local country fuel provider does not require them so they did not put them in

 

[LittleInch]

I'm not absolutely sure what these are (but it sounds like an internal floating roof), but that sounds like a pretty lame excuse to me.



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

 

[georgeverghese]

Think it has to do with difference of opinion between the DoD and the subcontractor on the number of hours a day at greater than 55degC to make the tank contents rise in temp to 55degC. Some ways of reflecting away solar radiation would be to use reflective aluminum paint / adding on external insulation. Internal floating roofs arent all 100% reliable either.

 

[DLV53]

Agree. But due to the tactical nature of the asset it needs to remain the color scheme of the current design. The sub basically relied on the fact that the host nation did not require the pans. But like safety regs, mission critical requirements are written due to a failure during a critical event. I was trying to find another path for them to take without having to rip the tanks apart but there does not seem to be any other way to meet the intent of the pans. I am all about requirements but not blind to the fact that the intent or function of the requirement can be met by alternate means. If we go for a relief on the use of the pans without an alternate plan I would have to get concurrence from the end user and I do not see that happening.

D

 

[georgeverghese]

It seems unusual that this no one in your organisation noticed non compliance to this basic requirement up till now. Having to rip up the roofs to install these IFRs' now is going to be painful not only for the sub, but for people in your company too, since both CAPEX and schedule delays will be unavoidable. Another suggestion to mitigate the risk of operating this tank at >55degC, with lower impact on cost and time than internal floating roofs (and IF the client is willing to accept this deviation to design standards), would be to acknowledge the increased volatility of diesel at these temperatures, redo the hazardous area classification around the tank vents and respecify any electrical / instrumentation around these vents to suit. A redesign of the free vents on this tank may also be required.

 

[IFRs]

The DoD has a thing for honeycomb internal floating roofs even though they represent outdated technology and are less strong, less safe, have higher emissions and have more maintenance issues than other versions of full-contact IFRs. IFRs are typically not needed for VOC containment and fire protection in typical jet or diesel tanks unless the storage conditions or facility emissions profile requires them. They do help for product contamination - water and dust. You only have to make a relatively small hole in the tank shell or roof to put the parts inside. Not really a big deal or very large cost, possibly expected anyway if the IFR was going to be installed after the hydrotest.

 

[Metermatic]

If this has been resolved, great, but most IFR's can be retrofitted via the manway. We have done quite a few, full contact IFR's and pontoon style.

Pontoon style a minnumen of 800mm manway, for full contact an entrance of 400 x 1400 is needed.