Specifies that the minimum nozzle thickness (trn) will be the maximum of:
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trn = (.134, trn for internal pressure) less than or equal NPS 18
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trn = (OD/150, trn for internal pressure) greater than NPS 18
This option is useful when nozzle loadings are unknown, such as when a pressure vessel is designed and built long before the attached piping system. By using this option in addition to UG-45, you have some additional metal available to satisfy thermal bending stresses. This option is not selected by default.
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These formulae are not in the ASME Code, but are commonly used in industry.
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You can also specify the minimum wall thickness of the nozzle, Trn, using Nozzles
. The minimum wall thickness value then overrides the value calculated by this option.