Why Clear Specification Is Critical
When ordering a custom hydraulic cylinder, the quality and accuracy of your specification directly determines the accuracy of the quotation, the correctness of the manufactured part, and ultimately the performance of the equipment. A vague enquiry (“I need a 100mm cylinder, 500mm stroke”) will result in multiple back-and-forth clarifications and possible errors. A complete specification results in a fast, accurate quote and a correctly manufactured cylinder.
This guide covers the 8 parameters that Wuxi Hengshui Machinery engineers need to produce an accurate quotation and manufacturing drawing for a custom hydraulic cylinder.
Parameter 1: Bore Diameter (ID)
The bore is the inside diameter of the cylinder tube. This is the primary parameter because it determines the push force (extend force) at a given pressure.
Formula: Force (kN) = Pressure (bar) × π/4 × Bore² (mm²) × 0.001
Example: A 100mm bore cylinder at 200 bar produces approximately 157 kN of push force.
Common bore sizes at Wuxi Hengshui: 32, 40, 50, 63, 80, 100, 125, 160, 200, 250, 320, 400, 500mm and any non-standard dimension.
Parameter 2: Rod Diameter
The rod diameter affects the pull (retract) force and the rod’s buckling resistance under compressive load. As a rule of thumb:
- Light duty: rod = 0.5 × bore
- Standard duty: rod = 0.6–0.7 × bore
- Heavy duty / long stroke: rod = 0.8–1.0 × bore
For long-stroke cylinders or those with large side loads, a larger rod or a guided cylinder design may be required.
Parameter 3: Stroke Length
Stroke is the total travel distance from fully retracted to fully extended. Specify the required stroke clearly. Long strokes require special attention to rod buckling calculations and bearing length.
Also specify: retracted length (closed length / minimum overall length) if there is a space constraint.
Parameter 4: Working Pressure
Specify the maximum continuous working pressure in bar (or PSI). Also indicate the proof/test pressure if different from 1.5× working pressure (our default test level).
Pressure ranges at Wuxi Hengshui: up to 500 bar for standard designs; higher pressures by custom arrangement.
Parameter 5: Mounting Style
How the cylinder attaches to the machine structure. Common options include:
- Front flange (FF): bolted flange on the front head
- Rear flange (RF): bolted flange on the cap end
- Foot/side lug: bolts through the body to machine frame
- Clevis pin: pivoting pin mount at cap end
- Trunnion: pivoting pin at mid-body or cap end
- Rod eye/clevis: pivoting attachment at rod end
Providing a mounting drawing or reference to an existing cylinder is the most reliable way to specify this.
Parameter 6: Port Size and Position
Specify the thread type (BSP, NPT, metric), size, and port position (port A at cap end, port B at rod end is standard; alternative positions available). Cushion valves (deceleration at end-of-stroke) should be specified if required.
Parameter 7: Seal Material
Based on operating temperature and hydraulic fluid:
- NBR: General purpose, mineral oil, up to 100°C
- FKM (Viton): High temperature, phosphate ester fluid, up to 200°C
- Polyurethane: High pressure, high-wear dynamic sealing
Wuxi Hengshui Machinery uses Merkel (Germany) and Parker (USA) seal kits as standard.
Parameter 8: Surface Finish and Coating
Specify rod surface finish (hard chrome plating is standard, with minimum 25μm chrome thickness), cylinder tube bore honing specification (Ra 0.2–0.4μm is our standard), and any external coating requirements (paint colour/type, nickel plating, or special coatings for corrosive environments).
How to Submit Your Specification
The fastest way to get an accurate quotation is to:
- Send a dimensioned drawing (PDF, DWG, DXF, or STEP) to sales@wx-hxy.com
- Or complete the online inquiry form with the 8 parameters above
- Or send specifications via WhatsApp to +86 133 8224 8877
Wuxi Hengshui Machinery responds to all technical enquiries within 24 hours, with a preliminary quotation typically within 48 hours.