What Does “Non-Standard” Mean in Hydraulic Cylinders?

A non-standard hydraulic cylinder (also called a custom or bespoke cylinder) is one manufactured to specific dimensions, pressure ratings, mounting configurations, or seal specifications that fall outside the dimensional standards of off-the-shelf catalogue products.

Standard hydraulic cylinders follow widely adopted bore/stroke series — such as ISO 6020 or ISO 6022 for mill-type cylinders, or NFPA T3.6.7 for tie-rod designs. Any cylinder that deviates from these standard series in bore diameter, stroke, port size, mounting style, seal material, or surface finish is classified as non-standard.

Why Choose a Non-Standard Hydraulic Cylinder?

Most industrial machinery — particularly metallurgical equipment, custom press lines, material handling systems, and OEM production machines — has space constraints, load profiles, and duty cycles that no off-the-shelf cylinder can optimally serve. Non-standard manufacturing allows engineers to:

• Match exact envelope dimensions (bore, stroke, retracted and extended length)
• Achieve the precise working pressure for the load without over-engineering
• Select seal materials appropriate for the operating temperature and fluid type
• Specify mounting flanges, clevis eyes, or trunnions to interface directly with existing structures
• Apply surface treatments (hard chrome, electroless nickel, PTFE coating) to resist corrosion or wear

Key Parameters That Define a Custom Hydraulic Cylinder

When ordering a non-standard hydraulic cylinder, you need to specify the following parameters:

1. Bore diameter (ID) — The inside diameter of the cylinder tube, which determines the thrust force at a given pressure.
2. Rod diameter — The diameter of the piston rod; larger rods handle higher column loads and buckling resistance.
3. Stroke length — The total travel distance of the piston from fully retracted to fully extended.
4. Working pressure — The maximum continuous operating pressure (bar or PSI).
5. Mounting style — Front flange, rear flange, side lugs, clevis, trunnion, or foot mounting.
6. Port size and position — The thread size and location of hydraulic inlet/outlet ports.
7. Seal material — NBR, FKM (Viton), polyurethane, or PTFE depending on temperature and fluid.
8. Surface finish — Hard chrome plating on rod, honing specification on bore (typically Ra 0.2–0.4μm).

How Wuxi Hengshui Manufactures Non-Standard Cylinders

Wuxi Hengshui Machinery Co., Ltd. specialises entirely in non-standard custom hydraulic cylinder manufacturing. Our production process begins with your drawings (DWG, DXF, PDF, STEP) or a physical sample, and proceeds through:

• Engineering review and drawing confirmation
• Raw material procurement (Huai Steel tube, Tianjin Seamless pipe)
• CNC rough and finish machining
• Precision honing to Ra 0.2μm
• Component cleaning and assembly with Merkel or Parker seals
• 100% hydrostatic pressure test at 1.5× rated working pressure
• Surface coating, packing, and export shipment

MOQ is 1 piece. Lead time is typically 15–25 working days. Contact our sales team at sales@wx-hxy.com with your drawings or specifications for a free quotation within 24 hours.

Why Seal Material Selection Matters

In a hydraulic cylinder, the seals are the most maintenance-sensitive component. Seal failure causes external leakage, internal bypass, and ultimately cylinder failure. The correct seal material must withstand the system’s operating pressure, temperature range, and the specific hydraulic fluid being used.

Wuxi Hengshui Machinery sources all seals from German Merkel and American Parker — two of the world’s leading manufacturers of hydraulic sealing systems. We offer three primary seal materials for custom hydraulic cylinders.

NBR (Nitrile Butadiene Rubber)

Best for: General-purpose industrial hydraulics with mineral oil

NBR is the most widely used hydraulic seal material. It offers excellent resistance to petroleum-based hydraulic oils, mineral oils, and many solvent vapours.

• Temperature range: −30°C to +100°C (−22°F to +212°F)
• Pressure resistance: up to 350 bar with appropriate backup rings
• Compatible fluids: Mineral oil (ISO VG 32–68), hydraulic oil (HM, HV type)
• Not recommended for: phosphate ester fluids, ketones, strong acids

NBR is the standard seal material in most Wuxi Hengshui cylinders for metallurgical, press, crane, and construction machinery applications where petroleum-based hydraulic oil is used.

FKM / Viton (Fluoroelastomer)

Best for: High-temperature environments, fire-resistant fluids

FKM (commercially known as Viton) provides superior heat resistance and chemical compatibility compared to NBR. It is the seal of choice for electric furnace cylinders, foundry equipment, and applications near high-temperature zones.

• Temperature range: −20°C to +200°C (−4°F to +392°F)
• Pressure resistance: up to 400 bar
• Compatible fluids: Phosphate ester (HFD), synthetic esters, high-temperature mineral oils
• Not recommended for: ketones, amines, steam at high temperatures

FKM seals are specified for Wuxi Hengshui electric furnace tilting cylinders, die casting machine cylinders, and any application where ambient temperatures exceed 100°C.

Polyurethane (PU)

Best for: High-pressure, high-speed, high-wear dynamic sealing

Polyurethane seals are harder than rubber-based seals and provide outstanding wear resistance and extrusion resistance under high pressures. They are used primarily for rod seals and piston seals in high-dynamic-load applications.

• Temperature range: −40°C to +90°C (−40°F to +194°F)
• Pressure resistance: up to 500 bar (ideal for high-pressure cylinders)
• Key advantages: Excellent abrasion resistance, low friction, good extrusion resistance
• Used for: Rod seals, wiper seals, piston seals in press and forging applications

Summary: Which Seal to Choose?

When ordering a custom cylinder from Wuxi Hengshui Machinery, specify your hydraulic fluid type, maximum operating temperature, and working pressure. Our engineers will recommend the appropriate seal package from our Merkel and Parker seal inventory. Contact our sales team at sales@wx-hxy.com.

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:

1. Send a dimensioned drawing (PDF, DWG, DXF, or STEP) to sales@wx-hxy.com
2. Or complete the online inquiry form with the 8 parameters above
3. 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.