Inspection materials for pipeline installation – the product quality certificate for the fittings lacks information regarding hardness.

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Currently, there are two main categories of manufacturing standards for pipe fittings: one is for general industries, which makes use of GB/T12459 (dimensions) and GB/T13401 (performance) together. One category is used in the petrochemical industry, referring to SH/T3408 (dimensions, performance). The standards for both of the above industries require testing of the hardness of pipe fittings. Alloy steel must be tested individually, while 3% of each other batch is sampled. That is, the product quality certificate should include hardness test data. Especially for stainless steel fittings with large diameters, some manufacturers may not carry out solution treatment due to limitations in the size of their heating furnaces; this is indicated by hardness values that are above the specified limits. In the product quality certificates currently under review, it was found that no mention was made of hardness testing.