Roof drain for Aluminium IFR 2

[Vicky07]

Hi all.
Can a swivel roof drain be fixed with an Aluminum IFR? Is a Swivel roof drain required in a IFR tank?

Thanks
Vicky

 

[JStephen]

A swivel roof drain is to drain rainwater off of an external floating roof, and wouldn't normally be used with an internal floating roof.
Some of the aluminum floaters do have roof drains scattered around, but they are small stub drains that drain back into the product.

 

[IFRs]

Short answers: -1- you could probably engineer a solution to putting a swivel type drain on an aluminum internal floating roof and -2- they are not required by API standard for any type internal floating roof.

Roof drains for internal floating roofs are not intended to drain large volumes of rain, melting snow, etc. Swivel type drains like those used on external floating roof tanks are not appropriate and are not needed for internal floating roofs because the fixed roof does not let the weather in. Drains for internal floating roofs are optional and are intended to drain small amounts of product that somehow get on top of the floating roof or small amounts of water that leak through the fixed roof.

Until recently all aluminum internal floating roofs came with small siphon type drain tubes. These may be of limited usefulness - they are unlikely to be where some random leak or product burps on top. They make weak points on the deck while increasing emissions. To be effective, drains need to be in every isolated section of the deck and need to be in all the low areas whose locations may be difficult to predict with any real accuracy. Typically this means a lot of drains which reduces strength, safety and effectiveness of the floating roof. The intent of the API standard is not met by putting just a few drains around the deck. Sometimes drains are sold with plugs to reduce losses but of course this makes the device a drain in name only and skirts the intent of the API standard. Sometimes drains are sold with balls or plugs on top but testing has shown them to be ineffective at best and their ability to reduce emissions is unproven.

Getting product on the deck can and should be avoided with engineering controls and why would you want water in your product or sitting at the tank bottom anyway?

According to API 650 if drains are included the floating roof supports and connections can be designed for a live load of only 5 PSF, if drains are not included then the same supports and connections need to be designed for 12.5 PSF. Only one vendor that I am aware of has designed a deck for 12.5 PSF and therefore can eliminate drains.

Remember - you read this on the internet (and on the AST Forum), it is only one person's opinion and these items may not answer your questions or fit your specific needs or situation.

 

[Vicky07]

Thanks IFRs & stephen