Technical requirements and scope of the ASME A/SA 194 standard
The ASME A/SA 194 standard regulates the production of nuts intended for use in assemblies exposed to high temperatures and critical pressures. The nomenclature includes products made of carbon, alloy, and martensitic corrosion-resistant steel grades. The nominal size range covers imperial parameters from 1/4 to 4 inches and metric sizes from M6 to M100. For austenitic stainless steels, the minimum allowable size is 1/4 inch or M6. EV Group China strictly adheres to these specifications: any substitution of steel grade without prior written approval from the customer is prohibited.
Hot-rolled steel bars serve as the raw material for production. Additional mechanical processing by centerless grinding or cold drawing is permitted. Austenitic grades undergo solution annealing or combined processing (annealing followed by strain hardening). If delivery of strain-hardened products is required (according to supplementary requirement S1), EV Group China specialists recommend that customers familiarize themselves with section 7.2.2 and Appendix X1 of the standard.
In addition to the basic provisions, the standard provides for supplementary requirements S1–S6. These conditions are optional and are implemented only if the corresponding specifications are included in the contract or order.
The documentation uses two systems of measurement: inch-pound and SI. In the absence of a specific notation regarding the use of the metric version (“M”) in the order, EV Group China will supply products in accordance with the imperial system. It is important to note that values in these systems are not interchangeable equivalents; combining metric and imperial parameters is not permitted to ensure compliance with technical requirements.
Note: Grade 2M has been officially replaced by 2HM. During the transition period, the use of both markings on products is permitted.