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Installation of exhaust stack to foundation/footer
2

Installation of exhaust stack to foundation/footer

Installation of exhaust stack to foundation/footer

(OP)
What is the proper proceedure to install an exhaust stack to the support pad (foundation).  What is standard grout height on a 56" diameter x 40 foot stack.

RE: Installation of exhaust stack to foundation/footer

This rather depends on the design of the base of your stack.  Does the exhaust pass up through the foundation or is the exhaust connected to the stack at some distance above the base?

I suspect it may be the latter so the procedure will be as follows:-

Calculate the weight of the stack and also any wind forced on the 40' of pipe sticking out of the ground.  Once you have these figures you can then design your footing.

You can bolt the stack to the base slab if you have a bolted flange on the bottom of the stack.  The load calculation for the bolt stresses will be in most standard text books under bolted moment connections.  If you are bedding the footing on grout then the grout must have sufficient compressive strength to carry the sum of

a)  The weight of the stack and
b)the compressive stress generated on the base from the moment generated by the wind load.

The installation procedure will generally be to have the fixing holding down bolts cast into the base ready to accept the stack.  The stack is craned over the bolts and held up just above the concrete on steel shims.  Then tighten the nuts.  Finally pour the grout into the void between the foundation and the base of the stack.

Regards

Andy Machon
Andy@machona.freeserve.co.uk
 
 

RE: Installation of exhaust stack to foundation/footer

A typical grout height for a 56" diameter stack would be 1 inch.  The  grout is intended to allow more exact trueing/ plumbing of the stack and more accurate placement at the design base elevation.  As you get larger in diameter, and the potential variability of the top of concrete increases, a greater height of grout can be considered.  In line with Ginger's advice the plumbing and elevation setting is done with the shims.  After that is completed, grouting to fully support the stack base plate is performed.

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