| Bellows seal design | Design and manufacture bellows-sealed gate valves in accordance with MSS SP-117. | The bellows assembly must provide a secondary stem seal and be suitable for the specified pressure, temperature, fluid, and cycle requirements. | Approved drawings, bill of materials, bellows design calculations, and MSS SP-117 compliance statement. | Critical |
| Pressure-temperature rating | Valve pressure-temperature ratings must be established in accordance with ASME B16.34. | The selected pressure class and material group must cover the design pressure and design temperature without exceeding the applicable rating table. | ASME B16.34 rating calculations, pressure class documentation, and material-temperature limits. | Critical |
| End connections and dimensions | Provide end connections and face-to-face dimensions compatible with the purchase specification and applicable piping standards. | Flanged, butt-welding, or threaded ends must be clearly specified; flange dimensions and pressure class must match the approved piping interface. | Certified dimensional drawings, end-connection details, and interface inspection records. | High |
| Fugitive-emission performance | Demonstrate qualification under ISO 15848-1 when low-emission service is specified. | The supplier must state the ISO 15848-1 tightness class, temperature class, mechanical-cycle class, and test medium used for the qualification. | Independent or witnessed type-test report identifying the valve design, test configuration, packing arrangement, and measured leakage. | Critical |
| Production leakage testing | Offer production acceptance testing to ISO 15848-2 where the purchase order requires it. | Routine testing must use documented procedures, calibrated instruments, defined stabilization time, and recorded leakage results. | Production test procedure, calibration certificates, individual valve test reports, and nonconformance records. | Critical |
| Bellows material | Use a corrosion- and temperature-resistant bellows alloy selected for the process conditions. | Material selection must consider corrosion, pressure, temperature, fatigue, weldability, and the required operating cycles. | Material test certificates, heat identification, chemical composition, mechanical properties, and weld procedure records. | Critical |
| Welding and non-destructive examination | Maintain qualified welding controls for pressure-retaining parts and bellows connections. | Welding must be performed to an approved procedure by qualified personnel; required examination methods and acceptance criteria must be defined in the inspection plan. | WPS/PQR documentation, welder qualifications, weld maps, NDE reports, and repair records. | High |
| Pressure shell and seat testing | Provide pressure and closure testing in accordance with the purchaser’s specified valve-testing standard. | Test pressures, duration, leakage limits, test medium, and acceptance criteria must be stated before manufacturing release. | Inspection and test plan, hydrostatic or pneumatic test reports, calibrated gauge records, and final inspection release. | Critical |
| Operating cycles and maintainability | Document the expected operating cycle capability and maintenance requirements for the bellows and valve assembly. | Cycle capability must be supported by design calculations or representative qualification testing; the supplier must identify replacement intervals and field limitations. | Cycle-test data, maintenance manual, recommended spare-parts list, and installation instructions. | High |
| Quality management and traceability | Maintain a documented quality system with full material and manufacturing traceability. | Heat numbers, component identification, inspection status, deviations, and final documentation must remain traceable from receiving through shipment. | Quality-system certificate, manufacturing quality plan, material certificates, inspection records, and final data book index. | High |
| Documentation and delivery readiness | Submit complete technical and quality documentation before shipment. | Documentation should include drawings, certificates, test reports, preservation instructions, nameplate data, and conformity declarations applicable to the order. | Approved vendor document register, final data book, packing list, and shipment release certificate. | High |