RF Pad for Anchor Chair - API 650 Storage Tank

[MOHAMMED89]

Dear All,

I have one one doubt regarding the requirement of RF pad for Anchor chair.

The tank is designed as per API 650. i saw in many tank farms RF is not provided for the Anchor bolts of the API 650 tanks, And some tanks RF pad is provided.

So my question is wheather RF pad is required?? or Not??

Anchor chair is deigned as per AISI Steel Plate Engineering Data, Volume 2, Part 5, “Anchor Bolt Chairs.”

Tank Height is 21 m and dia 15m.

Thanks in advance

 

[JStephen]

Normally, a reinforcing pad would only be used if it is not possible to satisfy the shell stress requirements with a reasonably sized chair.

 

[Duwe6]

Try calc'ing the tank using chairs 300mm tall [bars on both sides of each anchor], my 'guesstimate' is that this will be about right for use w/o repads.

 

[JStephen]

Where you run into problems is using thin shell (3/16, say) and satisfying the "1.5 x failure" load requirements which can lead to high bolt loads on a moderately loaded tank. Typical bolt chairs will be around 12" high x 6" wide, ie, 300mm x 150mm, but can be made taller and wider if required. If it's a problem, it may be advantageous to use more bolts of smaller size. It may be advantageous to increase the first ring of shell plate to avoid adding repads if anchors are numerous.