Hydraulic Cylinder Specification and RFQ Checklist

A useful hydraulic cylinder RFQ defines the application, operating conditions, physical interfaces, and acceptance requirements clearly enough for suppliers to quote the same scope. Bore, rod diameter, and stroke are important, but they do not describe every requirement. Load direction, available pressure, mounting, fluid compatibility, cycle conditions, and documentation can change the proposed cylinder and its price.

Use the checklist below to separate confirmed requirements from information that still needs engineering work. Enter units, drawing revisions, and responsible owners instead of filling unknown fields with guessed values. The result should be a traceable request and a basis for comparing technical deviations. It is not a substitute for cylinder sizing, machine risk assessment, or approval of the final production drawing.

Contents

1. Define the RFQ stage and responsibility
2. Complete the cylinder specification sheet
3. Describe load, pressure, and motion as operating conditions
4. Make dimensions and interfaces unambiguous
5. Specify fluid, environment, and optional functions
6. Agree acceptance tests and document deliverables
7. Compare quotations using a deviation register
8. Separate quotation approval from production release
9. Frequently asked questions

Define the RFQ stage and responsibility

State whether the request is for a budget estimate, a firm technical quotation, a replacement assessment, or manufacture to an approved drawing. Each stage supports a different level of commitment.

For a concept-stage cylinder, the supplier may be expected to propose bore, rod, mounting, and seals from application requirements. For a build-to-print order, the buyer may control those details. Make that distinction explicit, and still require the supplier to identify inconsistencies or unsupported requirements.

Assign each field one of four requirement states: confirmed, provisional, supplier proposal requested, or not applicable. An empty cell means information is missing; it must not silently mean zero pressure, no testing, or no documentation.

Identify the technical owner, purchasing contact, machine or project reference, document revision, and response date. Ask all bidders to answer against that same revision. If sizing is unfinished, use the hydraulic cylinder sizing guide before treating preliminary dimensions as released requirements.

Complete the cylinder specification sheet

The following is an original worksheet. Replace every blank with a value, an explicit status, or “not applicable.” Use a separate operating-condition attachment when one value cannot represent the full cycle.

Field	Value or attachment to complete	Unit / condition to identify
Project and RFQ revision	______	Machine ID, revision, date
Order scope	______	Design proposal, replacement, or build to print
Cylinder arrangement	______	Single/double acting, rod arrangement
Required push and pull	______	N or kN; direction and load case
Supply and chamber pressures	______	bar or MPa; measurement location and condition
Peak pressure events	______	Magnitude, duration, frequency, evidence
Bore and rod diameter	______	mm; fixed or proposed
Stroke and end positions	______	mm; required and permitted travel
Closed length and envelope	______	Datum references and drawing revision
Mounts and rod end	______	Type, dimensions, tolerances, attachment
Ports and orientation	______	Thread, sealing form, position, viewing direction
Speed and cycle profile	______	mm/s, travel time, starts/cycles, dwell
Load guidance and orientation	______	Alignment, side loads, mechanism drawing
Fluid and temperature	______	Fluid designation; oil and ambient ranges
Environment and finish	______	Corrosion, dust, washdown, coating requirement
Cushions, valves, and sensing	______	Functions, interfaces, and supply responsibility
Acceptance and documents	______	Agreed procedure, criteria, records, drawings
Quantity and delivery scope	______	Prototype/lot sizes, accessories, packaging

Add a status, evidence reference, and owner for each row. For example, “rod diameter: supplier proposal requested; load case LC-03; mechanical engineer” communicates a real task. Writing a guessed rod diameter without that qualification does not.

Use the hydraulic cylinder terminology glossary to align terms between engineering and purchasing.

Describe load, pressure, and motion as operating conditions

Report whether the load is pushing, pulling, suspended, driven by a linkage, or changing direction. Distinguish required cylinder force from the mass of the object being moved. Kilograms describe mass; newtons or kilonewtons describe force. “A ten-ton cylinder” is ambiguous unless the force convention and conditions are defined.

Supply pressure is also not necessarily the pressure at the working chamber. Include relevant line losses and opposing-chamber pressure in the engineering attachment. Separate normal operation, maximum expected operation, transient events, and the specified cylinder rating. Do not use a relief-valve setting as the only description of the pressure history.

Parker's HMI selection guide distinguishes full-bore pushing area from annular pulling area and highlights rod-strength and attachment checks. A larger rod therefore changes more than appearance or robustness. Parker selection guide

For motion, give extension and retraction speeds, relevant travel lengths, acceleration or stopping requirements, dwell periods, and expected cycles. Identify moving mass and end-of-stroke conditions if cushioning is requested. “Fast operation” and “heavy duty” are descriptions that need measurable supporting conditions.

Where several load cases exist, label them and identify the required combinations. Maximum speed at a light load and maximum force at a low speed should not automatically be treated as simultaneous requirements.

Make dimensions and interfaces unambiguous

Attach a drawing with a stated revision, units, and reference datums. Define how closed length is measured: for example, between the specified mounting centers in the retracted condition. Identify the required working stroke separately from the available machine travel and any prohibited overtravel.

Dimension the mounting interfaces, pin or thread connections, relevant fits, overall envelope, and service clearances. State who supplies pins, bearings, rod-end accessories, and fasteners. A cylinder body can fit while its attachments or hoses interfere with the machine.

Port descriptions need both the connection standard and sealing arrangement. Similar-looking thread dimensions do not establish interchangeability. Define port orientation from an identified viewing direction, especially where different cylinder rotations could fit the same mounting.

For a replacement, provide the original model and serial identification, available drawings, photographs with scale and orientation, and measured interface dimensions. Mark measured values as measured rather than original design values.

A sample cylinder cannot reliably reveal every material, heat treatment, seal compound, fatigue requirement, or original acceptance condition. Separate what inspection establishes from what must be confirmed. Preserve any useful service history, including the reason for replacement, without assuming the old cylinder's design remains suitable for a changed machine.

Specify fluid, environment, and optional functions

Name the hydraulic fluid or controlled specification, not just “hydraulic oil.” Include expected fluid temperature, ambient exposure, contamination-control requirements where defined, and any special media. Require confirmation of compatibility for the proposed sealing and material system.

Parker's cylinder-specification guidance treats mounting, rod dimensions, sealing, and operating conditions as interacting choices. It supports reviewing the combination rather than selecting each option independently. Parker specification guidance

Describe corrosion exposure, dust, washing, external heat, or other environmental conditions. If a coating or corrosion-performance requirement is needed, identify its specification and acceptance evidence. A generic request for “stainless” or “heavy chrome” leaves material and performance questions unresolved.

Optional function	Requirement to clarify
Cushioning	End or ends, moving conditions, adjustment and verification responsibility
Position sensing	Measurement range, output, supply, connector, and installation
Integrated valves	Function, location, hydraulic interface, and system responsibility
Protective covers	Travel envelope, environment, inspection and maintenance access

Explain what the option must accomplish. Avoid adding components only because they appear on another cylinder. Review system functions with the basic hydraulic system design guide.

Agree acceptance tests and document deliverables

Specify the acceptance basis before comparing prices. ISO 10100:2020 covers hydraulic cylinder acceptance tests, while ISO 4413:2010 addresses general rules and safety requirements for hydraulic systems and components. Their public descriptions identify their scope; they do not supply all the clauses needed to write a compliant test procedure. ISO 10100, ISO 4413

Where a standard is invoked, state the agreed edition, applicable requirements, and who verifies the complete text. Do not insert a universal proof-pressure multiplier, hold time, or leakage limit into every RFQ.

For each agreed test, record the specimen configuration, fluid, temperature, pressure or load condition, duration or cycle definition, measurement method, acceptance criterion, and report content. Include uncertainty and decision rules where they matter to quantitative acceptance.

Distinguish routine checks on every cylinder from qualification or endurance testing of representative samples. State sampling, witness requirements, responsibility, and how nonconforming results are handled.

Request the necessary dimensional report, functional or leakage-test record, traceability identification, approved drawing, operating information, and spare-parts information. Material or coating certificates should be requested when required by the project, with their scope defined.

The hydraulic test bench buyer’s checklist helps frame test capability and reporting. A cylinder supplier's statement that a part was tested is useful only when the relevant method and acceptance basis are clear.

Compare quotations using a deviation register

Compare responses row by row before comparing totals. Require each supplier to classify its response as complies, deviation, option, excluded, or to confirm.

Requirement / revision	Supplier response	Evidence / deviation	Buyer decision and owner
Load case and pressure	______	Calculation or rating reference: ______	______
Mounting and envelope	______	Drawing / dimensional difference: ______	______
Fluid and seal system	______	Compatibility basis: ______	______
Cycle and cushioning	______	Conditions or limitations: ______	______
Tests and documents	______	Included method and report: ______	______
Delivery scope	______	Accessories, packaging, exclusions: ______	______

These are blank comparison fields, not claims about actual suppliers. Ask for deviations in writing, even when a proposal is described as “equivalent.” An alternative can be acceptable, but the responsible engineer must decide against the application requirements.

Separate unit price, tooling or engineering charges, qualification work, recurring documentation, accessories, packaging, and delivery assumptions. Compare delivery dates against the same approval milestone. A lead time measured from approved drawings differs from one measured from purchase-order receipt.

Maintain open technical items in the register until they have evidence and a recorded decision. A lower price with unresolved testing or interface exclusions is not yet a like-for-like offer.

Separate quotation approval from production release

A quotation can be commercially acceptable while its design remains provisional. State which event authorizes manufacture: an approved drawing, a closed clarification register, a purchase release, or the project's defined combination.

Freeze the relevant drawing and specification revisions at release. Resolve discrepancies between the quotation, model code, drawing, and order before production starts. Avoid leaving the supplier to decide which conflicting requirement takes precedence.

Record later changes with their effect on fit, force, testing, price, and delivery. Obtain the appropriate approval rather than silently substituting a different seal, mount, or rod size.

If the supplier revises its model code after clarification, check that the final code and approved drawing still describe the same assembly.

Keep the signed decision and evidence in the project record. The blank checklist in this article provides structure; it does not represent an engineer's approval or a completed supplier assessment.

Frequently asked questions

Can I request a quotation without a complete drawing?
Yes, if you clearly request a design proposal and provide the application requirements. Identify missing information and who will resolve it before manufacture.

Is bore, rod diameter, and stroke enough for a replacement?
No. Confirm mounting, closed length, ports, fluid, ratings, functions, and the original or revised application. Matching three dimensions does not establish interchangeability.

Should I specify only the required tonnage?
Use a defined force unit and operating conditions. Load mass, linkage geometry, pressure, and push/pull direction must be translated into the cylinder requirement.

Can all suppliers use their standard test procedure?
They may propose one, but the buyer must review it against the agreed acceptance basis. “Standard test” alone does not demonstrate that quotations include equivalent verification.

Complete the worksheet, attach the drawings and operating cases, and assign unknowns before technical and purchasing review.