Valve Body RFQ Guide: Features, Interfaces, and Inspection

What Makes a Valve Body RFQ Complete?

A complete RFQ defines the finished body, its mating interfaces, and the evidence required for acceptance. Start with the controlled drawing and flow model. Then assign responsibility for machining, closures, cleaning, and testing. A similar product photograph helps identify the component family, but it cannot establish a pressure rating or an internal passage design.

Use the aluminum valve body manufacturing page to review supplier scope. Use this guide to resolve the feature-level questions before sending the package.

Which Passages and Walls Need Individual Control?

Map each passage zone to its function and final manufacturing state. The same outer shape can contain different flow paths, wall boundaries, and machining access. The valve designer controls the hydraulic geometry, flow direction, trim selection, and complete-valve flow coefficient, Cv.

• Identify inlet, outlet, branches, turns, seat regions, and isolated cavities on one approved flow model.
• Separate core-formed surfaces, surfaces left as cast, drilled passages, blended transitions, and final machined surfaces.
• For each zone, state its local datum, surface requirement, allowed transition, machining stock, inspection access, and acceptance stage.
• Review core location, thick-to-thin transitions, feeding, tool access, and datum transfer against the final passage model.

A dimensional report, X-ray image, or body tightness result does not establish complete-valve Cv. Keep hydraulic design changes under the designer's approval. A manufacturing proposal that changes a passage transition should identify the affected zone and its approval owner.

Review gravity casting and permanent mold capability and the casting process selection guide when the route remains open.

What Must Be Specified for Ports and Threads?

Define each port by function, sealing method, and inspection requirement. A thread designation does not describe the entire sealing interface. Separate pressure-sealing features from fastener threads and temporary test connections.

Use the same port identifiers on the drawing, hydraulic schematic, gauge record, and test setup. Mark unused connections explicitly. Thread acceptance and body pressure-tightness are separate checks; define both when the project requires them.

How Should Spool Bores and Cartridge Cavities Be Defined?

Define bore function before choosing its machining and measurement requirements. Spool, sleeve, locating, and auxiliary bores can require different geometry and surface controls. A surface roughness result alone does not establish roundness, straightness, or fit.

ISO 7368:2025 addresses geometry for two-port slip-in cartridge cavities. It does not specify rated pressures. Apply it only when the designer selects that interface. Screw-in and slip-in cavities must not share an assumed geometry or compatibility claim.

Source: ISO 7368:2025, official scope.

• Cross-reference cavity ports to the circuit and the selected cartridge's port convention.
• Define the final acceptance state after heat treatment, machining, and any permitted finish.
• If honing or another finishing operation is required, agree the process owner, tooling, wear controls, and measurement plan during review.
• Specify where bore size, geometry, and surface texture are measured; select methods suitable for access and the controlled tolerance.

Request special finishing and gaging as project requirements. The casting and CNC machining page describes the confirmed manufacturing scope.

How Are Cross-Drilled Access Holes Closed?

Treat a permanent closure and its prepared seat as one controlled interface. An instruction to plug a hole after machining leaves hardware, installation, cleaning, and acceptance responsibilities unresolved.

For every permanent closure, specify the installation side, local wall, material compatibility, prepared bore or thread, surface condition, and required tooling. Assign hardware supply, identity checks, installation, and final inspection. Changes to the closure system need the designated approval owner's authorization.

1. Machine and deburr the intersecting passages.
2. Prepare the seat and verify the accessible internal edges.
3. Clean, dry, and inspect the passage before access is lost.
4. Install the approved closure and record the required retention and tightness evidence.

If cleaning follows installation, confirm that the closed geometry still allows the specified cleaning and verification. Record the sequence in the agreed manufacturing plan.

What Defines an ISO 4401 Mounting Face?

Release the exact interface code and port map, together with the project drawing. ISO 4401:2005 covers mounting surfaces for four-port hydraulic directional control valves. A trade label such as CETOP or NG alone does not identify the complete interface.

• State whether the supplied component is a valve body, subplate, or manifold pad.
• Map pressure, tank, and work ports, plus any optional pilot or drain connection.
• Locate fixing holes and orientation features, including locating-pin holes where specified.
• Define mounting-pad boundaries, datum relationships, flatness, surface texture, thread depths, and the final acceptance state.
• Assign seal recesses, sealing rings, fasteners, and assembly testing to named project roles.

Resolve conflicts between the selected interface, mating-component data, drawing, and model before machining. Keep the mounting face clean and protected after acceptance. A dimensionally correct pad still needs the correct passage connections and assembly conditions.

Source: ISO 4401:2005, official scope. Project dimensions and acceptance limits must come from the released interface documents.

How Do Installed Length and Flange Geometry Differ?

Control installation length separately from each end connection. Nominal size or pressure class alone does not establish either requirement. The designer must select the applicable drawing or standard edition for the actual body arrangement and material.

Give inlet and outlet separate entries if their axes, facing, or machining state differ. For a body clamped between mating flanges, the designer must define the gasket, alignment, and installed-length assumptions. Use interface requirements appropriate to the selected construction.

Which Wall Thickness Must Remain After Machining?

Specify the required remaining metal wall in the final accepted state. Keep the design minimum, service allowance, casting stock, and machining allowance as separate fields. Extra metal removed during machining cannot serve as an allowance for later service.

Map pressure walls near ports, threads, seat pockets, closures, and passage transitions. Identify adjacent holes and the final machined surfaces used for measurement. Assess core displacement and machining breakout against this map. State the verification method and access before tooling approval.

Do not count a coating, insert, or mating component toward a metal-wall requirement unless the released design permits it. Keep units and calculation rules consistent. Process capability and a nominal casting wall do not establish a service pressure rating.

What Controls Seat Pocket and Stem Alignment?

Follow the approved assembly's datum chain from the body-side seat pocket to the guiding and bonnet features. The actual seat, cage, retainer, or guide arrangement determines which relationships matter.

• Define the seat pocket profile, axial position, shoulder, retention feature, seal land, and local wall.
• Identify the controlling guide axis, bonnet pilot, joint face, fastener pattern, and any separate guide components.
• State the drawing-controlled position, runout, perpendicularity, or other alignment requirement and its inspection datum.
• Separate body dimensional evidence from seat design, trim fit, and assembled shutoff testing.

The valve designer owns the trim architecture and final functional acceptance. Specify which body features are inspected after final machining and cleaning. Do not infer a seat fit or leakage class from a photograph.

How Should Coating Masks and Cleanliness Be Specified?

Mark every protected interface and identify whether dimensions are accepted before or after finishing. Coating on a controlled bore, thread, seal land, or datum can change fit or inspection access.

• Provide a mask map for functional bores, threads, mounting faces, seal lands, and reference surfaces.
• Define permitted finish boundaries, edge conditions, and verification after mask removal.
• Specify internal burr acceptance and the cleanliness verification method, including sampling and record requirements.
• Define washing, drying, preservation, passage protection, and packaging needed to retain the accepted state.

Use the surface finishing guide for broader finish selection. Keep the valve drawing responsible for the exact mask boundaries and final interface requirements.

Which Checks Demonstrate the Required Condition?

Match each acceptance requirement to a method, manufacturing stage, sampling plan, and record. Different checks answer different questions. Define the applicable combination from the drawing and failure risk.

Project documents must define the pressure-tightness acceptance rule and test stage. Machining may expose a leak path that was not present at the casting surface. Define whether casting screening, final component testing, or both are required. A fixture seal must be distinguished from a permanent delivered closure.

Review quality-control equipment and records and pressure-tight casting and test scope when assigning these checks.

What Common Problems Should the Review Investigate?

Use the observed symptom to select checks before changing the process. The possibilities below guide investigation; they do not diagnose a specific returned body.

Record the finding, affected feature, corrective proposal, and approval owner. Avoid changing a passage, closure, or functional interface without reviewing its effect on the assembled valve.

When Is the Package Ready to Send?

Send the RFQ when suppliers can identify the same finished body and acceptance scope. Keep unresolved design decisions visible, with an owner and an explicit quotation assumption.

1. Release aligned geometry, feature maps, material condition, and applicable document editions.
2. Assign casting, machining, special finishing, closure installation, and test responsibilities.
3. List inspection records, first-article and production sampling, traceability, and change approval requirements.
4. Add annual volume, release pattern, sample needs, tooling status, destination, and packaging requirements.

Use the casting drawing requirements to resolve file-control gaps. Then send the valve body drawing package for quotation. The buyer resources library provides the supporting procurement guides.