A valve to API 6A and NACE MR0175-2003. This check valve has an internal part that is a nonpressure-containing (but pressure-controlling) component. The part is loaded only with a compressive load; therefore, there is no tensile stress in the part, only a compressive stress.
Section 1.4 states that NACE is applicable to "total tensile stress (applied plus residual)". Since our part only has a compressive stress, it doesn't have to meet NACE MR0175.
Depending on the shape of the part, it's entirely possible for a compressive load to produce a tensile stress.

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