| Pressure Rating | Maximum working pressure | Specify the continuous working pressure and the required relief-setting range. The valve block should have a rated pressure equal to or higher than the system design requirement. | Hydraulic schematic, pressure test report, nameplate data, material certificate, and technical datasheet showing rated pressure and setting range. | Use consistent pressure units such as bar or MPa. Confirm that the supplier’s test equipment is calibrated and that pressure ratings are valid for the selected port configuration. | Request documented adjustment procedures, replacement springs or cartridges, and a pressure re-test method. |
| Flow Capacity | Rated and peak flow | Match the block to the system’s normal flow and short-duration peak flow. Excessive flow can increase pressure drop, heat generation, and response instability. | Flow-versus-pressure-drop curve, internal passage dimensions, or test data at the specified hydraulic fluid viscosity. | Compare data using the same fluid conditions, especially viscosity and temperature. Confirm whether the stated flow is continuous or intermittent. | Provide troubleshooting guidance for pressure drop, overheating, noise, and unstable relief operation. |
| Valve Function | Direct-acting or pilot-operated design | Choose direct-acting designs for compact, fast-response circuits and pilot-operated designs where higher flow capacity and lower operating losses are required. | Functional schematic, response characteristics, minimum pilot flow, and operating limits. | Confirm the intended application, fluid cleanliness requirement, mounting orientation, and compatibility with the complete circuit—not only the valve block. | Keep service parts available and provide cleaning, inspection, and adjustment instructions. |
| Fluid Compatibility | Fluid type, temperature, and seals | Define the hydraulic fluid, operating temperature range, seal material, and compatibility with additives. Common seal choices include elastomers selected for the specified fluid and temperature. | Fluid compatibility statement, seal material identification, temperature limits, and contamination-control requirements. | Do not assume compatibility from appearance alone. Confirm the exact fluid specification and whether the product will be exposed to water, moisture, or aggressive additives. | Supply seal kits with material identification, storage guidance, and recommended replacement intervals based on service conditions. |
| Materials | Body, cartridge, and spring materials | Select materials according to pressure, corrosion exposure, temperature, and required service life. Steel, stainless steel, and treated aluminum are used in different application conditions. | Material certificates, surface-treatment details, hardness data where applicable, and corrosion-resistance information. | Check whether material grades and treatment specifications are traceable to the purchase order and inspection records. | Document allowable repair methods and clarify which components may be replaced rather than reworked. |
| Port Standard | Thread, flange, and connection interface | Specify the connection standard, nominal size, port orientation, and sealing method. Thread form and sealing method must be compatible with the mating components. | Dimensioned drawing, port identification, thread specification, tolerance data, and interface inspection report. | Clearly distinguish metric, ISO, BSP, and other thread requirements. A visually similar thread may still be incompatible or unsafe. | Provide port plugs, seal specifications, conversion guidance, and replacement interface components where applicable. |
| Leakage Control | External and internal leakage | Define the acceptable leakage limit and the test method. Leakage criteria should be linked to the application, pressure, fluid, temperature, and test duration. | Hydrostatic or hydraulic test record, test pressure, hold time, fluid temperature, and acceptance criteria. | Use a written inspection plan. Avoid accepting generic statements such as “100% tested” without a measurable test condition. | Set a warranty evaluation process that separates installation errors, contamination damage, seal wear, and manufacturing defects. |
| Cleanliness | Particle contamination level | Define a cleanliness target suitable for the hydraulic system and identify flushing, plugging, and packaging requirements before shipment. | Cleanliness test method, particle-count report, flushing record, and evidence that all ports were capped after cleaning. | Contamination introduced during machining, assembly, or ocean transport can damage precision valve components. Include cleanliness requirements in the purchase order. | Provide installation flushing instructions, contamination diagnostics, and guidance for filter inspection. |
| Calibration | Relief pressure setting | Specify the nominal setting, tolerance, test temperature, flow condition, and whether the setting is factory-fixed or field-adjustable. | Calibration certificate, serialized test record, adjustment-lock details, and final inspection data. | Require traceability between the product serial number, calibration record, and purchase-order line item. | Define field recalibration limits, adjustment tools, seal replacement rules, and the required test equipment accuracy. |
| Documentation | Technical and compliance file | Prepare a document package covering the drawing, bill of materials, datasheet, installation instructions, test report, maintenance instructions, and packing list. | Controlled revision number, approval status, language requirements, certificate list, and document-delivery schedule. | Use one approved revision for quotation, production, inspection, and shipping. Record all engineering changes before mass production. | Ensure manuals, spare-part lists, and troubleshooting documents remain available for the expected service period. |
| Quality Inspection | Inspection and acceptance plan | Define dimensional inspection, material verification, pressure testing, leakage testing, calibration checks, surface finish, marking, and packaging inspection. | Inspection and Test Plan, sampling level, nonconformance procedure, calibration records, and final inspection report. | For new suppliers, consider pre-shipment inspection or an approved third-party inspection process before releasing the balance payment. | Establish a corrective-action process with response deadlines, evidence requirements, and return-material authorization procedures. |
| Packaging | Protection against contamination and corrosion | Use clean internal port plugs, sealed protective bags, cushioning, moisture control, and durable labels. Prevent movement and impact during handling. | Packaging specification, photographs before dispatch, gross and net weight, carton dimensions, and package-count list. | Packaging should suit the transport mode and expected storage time. Confirm whether wood packaging requires treatment and marking under destination-country rules. | Include unpacking instructions, storage limits, inspection steps after long-term storage, and replacement packaging for returns. |
| Shipping | Trade terms, lead time, and shipment size | Confirm production lead time, inspection time, transport mode, shipment quantity, delivery point, and agreed trade term before order confirmation. | Commercial invoice, packing list, transport document, country-of-origin information, harmonized tariff classification, and delivery schedule. | Compare total landed cost: product price, tooling, inspection, freight, insurance, duties, taxes, brokerage, and local delivery. | Maintain a documented process for transit damage claims, missing items, customs holds, and expedited replacement shipments. |
| Traceability | Serial, lot, and batch identification | Use durable identification linked to the production lot, material batch, calibration record, inspection result, and shipment quantity. | Serial-number register, lot certificate, barcode or data-matrix record, and packaging-to-product reconciliation. | Traceability supports controlled recalls, warranty decisions, and multi-country inventory management. | Set a retention period for quality records and define how historical production data can be retrieved. |
| Supplier Capability | Capacity, process control, and continuity | Evaluate machining capability, heat treatment or surface treatment control, assembly capacity, testing equipment, staffing, and backup processes. | Process flow chart, equipment list, capacity statement, quality certificates, audit findings, and business-continuity plan. | Assess single-source risk, tooling ownership, raw-material availability, geographic concentration, and realistic monthly capacity. | Agree on spare-parts availability, engineering support contacts, escalation levels, and maximum response times. |
| Commercial Terms | MOQ, tooling, payment, and warranty | Separate one-time tooling charges from unit pricing. Define minimum order quantity, sample approval, payment milestones, warranty scope, and exclusions. | Quotation with validity period, tooling ownership clause, approved sample record, warranty terms, and change-notification requirements. | Protect the approved design through written change control. Do not accept substitutions in materials, seals, or processes without approval. | Specify replacement, repair, credit, and technical-support obligations, including target response time and evidence needed for claims. |
| Total Cost of Ownership | Purchase cost plus operating risk | Evaluate unit cost together with pressure stability, leakage risk, service life, spare parts, downtime, inspection, freight, and field-service cost. | Costed bill of materials, expected service intervals, failure-rate data where available, spare-parts pricing, and logistics assumptions. | A lower purchase price may be offset by higher testing, warranty, customs, replacement, or downtime costs. Compare suppliers using landed and lifecycle cost. | Track field failures, return rates, mean time to resolution, spare-parts consumption, and corrective-action effectiveness. |
