API-661 evaluates loads on air-cooled heat exchangers.
The API-661 graphic below shows the type of open exchanger body analyzed by this standard. Calculations cover the allowed loads on the vertical, co-linear nozzles (item 9 in the graphic) found on most single or multi-bundled air-cooled heat exchangers.
API 661 contains the following compliance requirements:
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7.1.10.1 - Each nozzle, in its design corroded condition, must be capable of withstanding the simultaneous application of the moments and forces defined in the Typical Construction of a Tube Bundle with Plug Headers figure in the API 661 code.
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7.1.10.2 - The design of each fixed or floating header, the design of the connections of fixed headers to side frames, and the design of other support members should ensure that the simultaneous application (sum) of all nozzle loadings on a single header does not cause any damage. The components of the nozzle loadings on a single header should not exceed the following values:
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Mx : 6100 N•m (4500 ft•lbf)
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My : 8130 N•m (6000 ft•lbf)
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Mz : 4070 N•m (3000 ft•lbf)
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Fx : 10,010 N (2250 lbf)
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Fy : 20,020 (4500 lbf)
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Fz : 16,680 (3750 lbf)
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