Exhaust pipe support 1

[bhuat34]

Can pipe support shoe, which is welded to the exhaust pipe, sit directly on the structural framing without thermal insulation between the two surface? The exhaust gas is approximately 600 deg.C. Can the heat transfer significant enough to heat up the structural support and post a safety issue to workers?

 

[rjstephens]

Hi bhuat34, The structural steel that we normally use is only good for 120 deg c, there will be heat transfer to the structure but it will dissapate approximately 500-800mm away, for instance a hanger rod in contact with a 560 deg c pipe is touchable ie 50-60deg c approximately 500mm above the pipe. For high temp. structure we would use a moly, crome alloy or high grade cs- boiler plate which can handle the higher temperatures.

 

[steve1]

You should obtain a copy of American National Standard MSS SP-58. I have an older version (1983 edition) and it provides a table of standard materials commonly used for pipe hangers and supports and the allowable stresses at various temperatures. For instance, for A36 steel, the allowable stress is 13.9 ksi at a temperature of 700 degress F. It also states that materials may not be used above the highest temperature for which a stress value appears (for A36 steel that would be 750 degrees F).

The standard does not discuss heat transfer between the pipe and the support. My opinion is that either one should assume (for the condition of direct pipe to steel contact) that all the heat is transfered to the support and comply with SP-58, or have an analysis that proves that only a specified amount of heat is transfered.

 

[butelja]

Many times the pipe shoe will be "scalloped" where it contacts the pipe to reduce heat transfer. Semicircular cuts are made in the plate so that only 1/4 to 1/3 of the plate actually contacts the pipe.

 

[metaltrade]

yes to both - structural integrity and safety hazard. the hazard analysis will reveal the corrective action necessary to reduce the risk associated with the temperature. im assuming that since your're in an operating facility, your company do practice PSM.