| API 6A conformity | The check valve design, materials, pressure ratings, end connections, testing, marking, and documentation should conform to the edition of API Specification 6A stated in the purchase order. | Review the controlled technical specification, product drawings, pressure-rating tables, and a valid certification or licensing record when API Monogram use is claimed. | The exact API 6A edition and product scope must match the ordered valve; a general quality certificate is not proof of API 6A conformity. | Critical |
| Applicable design standard | Use API Specification 6A, which is harmonized with ISO 10423 for many wellhead and Christmas-tree equipment requirements. The purchase specification should define the governing edition. | Check the design-basis statement, revision-controlled drawings, calculation package, and deviation list. | No undocumented substitution between standards or editions should be accepted. | Critical |
| Pressure rating and bore | Confirm nominal size, nominal working pressure, temperature rating, bore configuration, and connection type, such as flanged, studded, or other specified API 6A connection. | Verify nameplate, dimensional drawing, pressure-rating chart, connection dimensions, and material temperature limits. | Every ordered parameter should be traceable to the approved purchase order and data sheet. | Critical |
| Product specification level | Select the API 6A Product Specification Level, or PSL, required by the well-control risk assessment and procurement specification. Higher PSL selection should be justified by service conditions. | Review the purchase order, quality plan, inspection and test plan, traceability records, and test reports against the specified PSL. | PSL selection is not interchangeable with pressure rating or performance requirement. | Critical |
| Performance requirement | Define the required pressure-containing and pressure-boundary performance, including closure behavior, allowable leakage, test pressure, holding time, and test medium in the approved specification. | Witness or review hydrostatic and low-pressure tests, pressure charts, calibrated-gauge records, test-medium details, and signed test certificates. | Acceptance limits must be stated before testing; visual confirmation alone is insufficient. | Critical |
| PR1 or PR2 capability | Where required, specify API 6A performance requirement PR1 or PR2. PR2 involves additional performance testing beyond the basic PR1 qualification route. | Request the applicable qualification report, test procedure, test records, and clear identification of the tested valve design and size range. | A PR2 claim should be supported by relevant qualification evidence, not only by a product brochure. | High |
| Material selection | Select body, bonnet, trim, hinge or piston components, seals, and fasteners for the specified pressure, temperature, fluid composition, erosion risk, and corrosion environment. | Review material certificates, heat numbers, chemical analysis, mechanical properties, heat-treatment records, and approved material specifications. | Material certificates should be traceable from raw material through final valve documentation. | Critical |
| Sour-service suitability | For hydrogen-sulfide-containing service, specify compatibility with NACE MR0175/ISO 15156 where applicable, including material hardness, environment limits, and manufacturing controls. | Check sour-service material declarations, hardness results, heat-treatment records, coating details, and any purchaser-approved exceptions. | Sour-service compliance depends on the actual material and service environment; it should not be assumed from API 6A compliance alone. | Critical |
| Non-destructive examination | Apply the NDE methods and extent required by the selected PSL, purchase specification, and approved inspection and test plan. Typical methods may include visual, dimensional, magnetic-particle, liquid-penetrant, ultrasonic, or radiographic examination. | Review personnel qualifications, written procedures, equipment calibration, examination reports, indications, and disposition of nonconformities. | The method, coverage, acceptance criteria, and reporting format must be defined before inspection. | High |
| Dimensional and visual inspection | Verify face-to-face or end-to-end dimensions, connection geometry, bore, marking, surface condition, coating, flow direction, and accessibility for installation and maintenance. | Use approved drawings, calibrated measuring equipment, inspection checklists, photographs, and final visual inspection records. | Dimensional deviations require documented engineering approval before shipment. | High |
| Quality management system | Prefer a documented quality management system certified to ISO 9001 or an equivalent system appropriate for pressure-containing equipment. | Verify certificate scope, validity dates, issuing body, manufacturing location, corrective-action process, and audit status. | An ISO 9001 certificate supports quality-system evaluation but does not replace API 6A product conformity evidence. | Medium |
| Traceability and data book | Provide a complete manufacturing data book containing the valve identification, drawings, bill of materials, material certificates, heat-treatment records, NDE reports, pressure tests, calibration records, and release certificate. | Conduct a document review before shipment and confirm serial-number, heat-number, component, and test-record consistency. | Missing or inconsistent traceability records should be treated as a documentation nonconformity. | Critical |
| Third-party inspection | For critical drilling-rig applications, include an independent inspection body when required by the operator, rig contractor, classification society, insurer, or purchase order. | Define hold points, witness points, inspection notification periods, approved inspector qualifications, and final inspection release requirements. | Third-party inspection should supplement, not replace, the manufacturer’s quality controls and test records. | High |
| Factory acceptance testing | Complete the agreed factory acceptance test before dispatch, covering pressure integrity, closure performance, dimensions, marking, documentation, and any specified functional checks. | Approve the test procedure in advance and retain signed test sheets, calibrated instrument records, photographs, and punch-list closure evidence. | Shipment should occur only after all critical test and documentation findings are closed. | Critical |
| Installation and commissioning support | Provide installation instructions, flow-direction guidance, bolting and gasket requirements, cleaning precautions, torque information where applicable, and commissioning checklists. | Confirm availability of controlled manuals, technical drawings, recommended spare-parts lists, and remote or on-site technical assistance. | Instructions should match the supplied configuration and service conditions. | High |
| Maintenance and repair capability | Maintain documented procedures for inspection, disassembly, seal replacement, repair limits, reassembly, pressure testing, and return-to-service approval. | Review maintenance manuals, repair qualification records, technician training, tooling lists, and post-repair test procedures. | Repairs affecting pressure-containing or pressure-controlling parts require controlled engineering and quality approval. | High |
| Spare-parts availability | Provide a recommended spare-parts package covering seals, gaskets, fasteners, wear components, and other replaceable items appropriate to the valve design and operating environment. | Check part numbers, material compatibility, storage life, packaging, preservation requirements, and quoted lead times. | Critical spares should be available within the operator’s required response period. | High |
| Warranty and claims handling | Require clearly defined warranty duration, coverage exclusions, notification procedures, evidence requirements, corrective-action responsibilities, and turnaround commitments. | Review the contractual warranty, sample claim workflow, nonconformance-reporting process, and escalation contacts. | Warranty terms should cover manufacturing defects and should not conflict with required operating conditions. | Medium |
| Response time and field service | Establish service-level targets for technical inquiries, failure analysis, emergency troubleshooting, spare-parts quotations, and on-site support. | Request documented support contacts, regional coverage, escalation procedures, service hours, and representative response-time commitments. | Support capability should be evaluated against the drilling-rig location, operating hours, and well-control criticality. | High |
| Preservation, packing, and transport | Protect internal surfaces, sealing elements, machined ends, and connection faces against corrosion, contamination, impact, and moisture during storage and transport. | Inspect preservation certificates, end protectors, lifting points, packaging labels, storage instructions, and shock or moisture indicators where specified. | Packaging must be suitable for the agreed transport route, storage period, climate, and offshore or onshore conditions. | Medium |
| Supplier assessment and scoring | Use a documented evaluation covering technical compliance, certification validity, inspection results, traceability, delivery performance, service capability, total cost, and verified operating references. | Maintain an audit checklist, weighted scorecard, risk register, corrective-action log, and approval status for each evaluated supplier. | Technical and well-control requirements should be pass/fail gates before commercial ranking. | Critical |