| Connection Compatibility | Confirm that thread type, sealing method, tube size, and mating geometry are compatible with the hydraulic system. | 100% dimensional compatibility with the approved drawing and mating component. | Controlled product drawings, thread gauges, inspection reports, and first-article samples. | ISO 8434 series; SAE J514; ISO 1179 series; ISO 6149 series. |
| Pressure Capability | Evaluate working pressure, proof pressure, and burst pressure for the complete fitting and connection system. | The fitting working pressure must meet or exceed the system design pressure after considering temperature, tube size, material, and connection type. | Pressure-rating tables, design calculations, proof-test records, and independent laboratory reports. | ISO 19879; SAE J514; applicable hydraulic hose and tube assembly specifications. |
| Proof and Burst Testing | Check whether production samples are tested under controlled pressure conditions without leakage, permanent deformation, or rupture. | Proof and burst test levels must follow the applicable product standard or the buyer-approved technical specification. | Test procedures, calibrated pressure-gauge records, sample identification, and signed test reports. | ISO 19879 and the applicable fitting-product standard. |
| Leak Tightness | Review static and, where applicable, dynamic leakage performance at the intended pressure and temperature range. | No visible leakage during the specified test period; acceptance limits should be defined in the purchase specification. | Leak-test records, test-medium details, test duration, pressure profile, and inspection criteria. | ISO 19879; project-specific hydraulic-system requirements. |
| Material Selection | Verify that the fitting material is suitable for fluid compatibility, operating temperature, pressure, and environmental exposure. | Material grade and heat treatment must match the approved drawing and declared mechanical-property requirements. | Material certificates, heat numbers, chemical-composition reports, and mechanical-test results. | Applicable material specification, ISO 683 series, ASTM material standards, or buyer-approved equivalent. |
| Corrosion Protection | Assess the surface treatment and corrosion resistance required for indoor, outdoor, marine, or chemically exposed applications. | Coating type, coating thickness, appearance, adhesion, and corrosion-test duration must be specified before quotation. | Coating certificates, thickness measurements, adhesion results, and salt-spray or cyclic-corrosion test reports. | ISO 9227 for neutral salt-spray testing; ISO 4042 for electroplated fastener coatings where applicable. |
| Dimensional Accuracy | Verify critical dimensions such as thread profile, cone angle, tube-seat geometry, port depth, and sealing surfaces. | All critical characteristics must remain within the approved engineering tolerances. | Coordinate-measuring-machine reports, thread-plug or thread-ring gauge records, and inspection plans. | Approved product drawing and the dimensional requirements of the applicable ISO or SAE standard. |
| Surface and Sealing Quality | Inspect sealing surfaces for scratches, dents, burrs, cracks, contamination, and machining defects. | No defect that can impair sealing, pressure resistance, assembly, or service life. | Visual inspection criteria, surface-roughness measurements, sample photographs, and nonconformance records. | Approved drawing, internal workmanship standard, and applicable sealing-interface specification. |
| Cleanliness | Determine whether residual chips, abrasive particles, oil, and packaging debris could contaminate valves, pumps, or actuators. | Cleanliness level must be defined by particle size, particle count or mass, extraction method, and inspection frequency. | Cleanliness-test reports, flushing records, filtered-fluid inspection, and sealed-packaging procedures. | ISO 16232 principles may be used for particulate cleanliness evaluation; hydraulic-system requirements should control acceptance. |
| Traceability | Confirm that each production lot can be traced to raw material, heat treatment, machining process, inspection results, and shipment. | Lot number and manufacturing date should be traceable from the shipped product back to the material certificate. | Lot-control procedure, batch labels, material heat numbers, inspection records, and retention policy. | ISO 9001 quality-management and documented-information requirements. |
| Quality Management | Evaluate process control, calibration, corrective action, change management, and internal audit practices. | A documented quality-management system with current certification or equivalent objective evidence. | Quality certificate, process-control plan, calibration list, audit results, and corrective-action records. | ISO 9001; IATF 16949 may be relevant for automotive applications. |
| Production Consistency | Determine whether the supplier controls variation between machines, shifts, production lots, and manufacturing locations. | Critical dimensions and functional characteristics should be monitored using statistical process control where risk justifies it. | Control charts, capability studies, first-piece approval, and periodic requalification records. | ISO 22514 series for process capability concepts; buyer-approved control plan. |
| Sample Validation | Use representative samples to verify fit, function, pressure performance, corrosion resistance, and packaging before volume purchasing. | Samples must be manufactured using the intended production process, materials, coatings, and inspection methods. | First-article inspection report, sample approval record, functional test results, and signed deviation list. | ISO 2859-1 may support lot-sampling plans; product-specific validation requirements take priority. |
| Change Control | Check whether the supplier must notify the buyer before changing material, tooling, coating, process route, sub-supplier, or production location. | No significant change should be implemented without documented review, risk assessment, and buyer approval where contractually required. | Engineering-change procedure, change-notification form, requalification plan, and revision-controlled drawings. | ISO 9001 change-control principles and the buyer's quality agreement. |
| Packaging and Identification | Verify protection against impact, moisture, corrosion, contamination, mixed lots, and incorrect identification during international transport. | Each package should identify part number, quantity, lot number, material or coating designation, and manufacturing origin as required by the purchase order. | Packaging specification, label samples, corrosion-inhibiting method, carton-strength requirements, and shipping inspection records. | ISO 780 for handling marks; contractual packaging and labeling requirements. |
| Supply Continuity | Assess capacity, critical-process dependencies, raw-material availability, backup equipment, and recovery planning. | The supplier should provide documented capacity, normal lead time, maximum feasible output, and a business-continuity plan. | Capacity statement, production schedule, contingency plan, approved-subcontractor list, and on-time-delivery history. | ISO 9001 operational-planning principles and buyer-defined supply-continuity requirements. |
| Commercial Comparison | Compare total landed cost rather than unit price alone, including testing, tooling, packaging, freight, duties, inspection, and failure risk. | Use a standardized total-cost model and compare suppliers against identical technical and delivery conditions. | Itemized quotation, tooling ownership terms, inspection charges, freight assumptions, warranty terms, and payment conditions. | Buyer-developed total-cost-of-ownership model. |
| Supplier Approval Decision | Combine technical compliance, production capability, quality evidence, logistics performance, and commercial risk into one approval decision. | Approve only suppliers that pass mandatory safety and compatibility criteria; use weighted scoring for non-critical criteria. | Supplier audit report, risk matrix, scorecard, corrective-action closure, and signed technical agreement. | ISO 9001 supplier-evaluation principles and the buyer's supplier-approval procedure. |