The API 661 Standard for Air Cooled Heat Exchangers for General Refinery Service covers the allowable loads on the vertical, collinear nozzles found on most single- or multi-bundled air cooled heat exchangers. The types of nozzles which may be checked are those which are labeled "9" in Figure 3-63.
API 661 has the following two requirements:
1 - each nozzle in the corroded condition shall be capable of withstanding the following moments and forces (referenced as Figure 8 values)
2 - the sum of the forces and moments on each fixed header (i.e. each individual bundle) will be less than 1500 pounds transverse to the bundle, 2500 pounds axial to the bundle, and 3000 pounds axial to the nozzle center line, while the allowed moments are 3000,2000, and 4000 foot-pounds respectively (referenced as Table allowables)
The input to the API 661 portion of the ROT program is relatively self-explanatory; typical input screens are shown in Figure 3-64 and the output report is shown in Figure 3-65.
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