Forklift Lifting Hydraulic Cylinder — Single-Acting Mast Lift Cylinder

The forklift lifting hydraulic cylinder is the single component that determines how high a forklift can stack and how much weight it can carry to that height. This single-acting cylinder extends under hydraulic pressure to raise the mast carriage and retracts under load weight when the control valve opens the return path to tank. Korea Ever-Power offers 5 models with Φ56 and Φ60 bore diameters, a uniform 1,500 mm stroke, and 18.1 MPa rated working pressure — covering counterbalance forklifts from 1.5 to 3.5 tonnes. Hardened and chrome-plated Φ45 piston rods, precision-honed cylinder bores, and integrated check valve provisions deliver the controlled, drift-free fork descent that warehouse operations demand.

分类： Forklift Hydraulic Cylinders

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Single-Acting · 1,500 mm Stroke · 5 Models

Forklift Lifting Hydraulic Cylinder

The cylinder that carries the load. Every kilogram lifted by a forklift passes through this single-acting hydraulic cylinder — from ground level to maximum stack height. Rated at 18.1 MPa with a 1,500 mm full stroke, it provides the controlled vertical force that raises the mast carriage, forks, and payload in a single smooth motion. When the operator lowers the forks, the control valve meters the return oil flow to provide a controlled descent speed regardless of load weight.

Forklift-Steering-Hydraulic-Cylinder-Application-2

Φ56–60

Bore (mm)

1,500

Stroke (mm)

18.1

MPa Max

32–50

Weight (kg)

Why Forklift Lift Cylinders Are Single-Acting — Not Double-Acting

A question that mechanical engineers outside the forklift industry frequently ask: why is the lift cylinder single-acting when the tilt cylinder on the same machine is double-acting? The answer involves both physics and safety.

The lift cylinder only needs hydraulic force in one direction — upward. Gravity provides the return force for free. The combined weight of the carriage, forks, and payload creates a constant downward force that retracts the piston rod when the control valve opens the return path. A double-acting lift cylinder would add weight, cost, and a second hydraulic hose run up the mast for no functional benefit — the load always wants to come down.

The safety benefit is equally important. In a single-acting system, the only way the forks can descend is through a metered flow path back to the hydraulic tank. If a hose bursts on the pressure side, the forks stay at their current height — the load weight pushes against the check valve in the circuit, which blocks flow in the return direction. This fail-safe characteristic is why every forklift hydraulic cylinder used for vertical lifting is single-acting: a hose failure causes a stop, not a drop.

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Extend (Lift)

Hydraulic pressure pushes piston upward. Oil flows from pump → directional valve → cylinder bore port. Full bore area generates lift force.

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Retract (Lower)

Load weight pushes piston down. Oil returns through metered flow control valve → tank. Descent speed is independent of load weight.

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Hold (Stationary)

Check valve blocks return flow. Load weight cannot force oil out of cylinder. Forks hold position indefinitely without pump pressure.

Complete Dimensional Specifications — All 5 Models

Five lifting cylinder models serve the 1.5–3.5 tonne counterbalance forklift range. The two bore diameters (Φ56 and Φ60) correspond to two load capacity classes, while the different installation distances (1,658 to 1,808 mm) accommodate different mast frame geometries. Two hydraulic port thread standards are available — G1/2 BSP for forklifts originally equipped with BSP hydraulic fittings, and M22×1.5 metric for metric-standard systems.

Forklift lifting hydraulic cylinder dimensional drawing showing stroke, bore, rod and installation distance

Drawing Number	Bore (D)	Rod (d)	Stroke (S)	Install Dist (L)	Pressure	Ports (M)	Weight
N30M300-5/400000-000	Φ56	Φ45	1500	1658	18.1 MPa	G1/2	32.6 kg
A2A30M300-400000-000	Φ56	Φ45	1500	1658	18.1 MPa	M22×1.5	36 kg
3.5N4.5H-400000-003	Φ60	Φ45	1505	1780	17.5 MPa	M22×1.5	41 kg
N35M300-5/400000-001A	Φ60	Φ45	1500	1808	18.1 MPa	G1/2	46 kg
A2A35M300-400000-000	Φ60	Φ45	1500	1808	18.1 MPa	M22×1.5	50 kg

All dimensions in mm. Installation distance (L) measured at full retraction, pin centre to mounting face. Stroke tolerance ±2 mm. Weights are dry. The Φ56 bore models (N30M, A2A30M) share a common mast channel width; the Φ60 bore models (3.5N, N35M, A2A35M) require the wider channel found on 3.0–3.5 tonne mast frames.

Lift Force Output — What the Numbers Mean for Your Load Capacity

The lift force produced by the cylinder is not the same as the forklift's rated load capacity — it is substantially higher. The cylinder must lift not only the payload but also the weight of the carriage, forks, mast inner channel, chains, and hoses. On a typical 3-tonne counterbalance forklift, the dead weight of the mast assembly above the cylinder is approximately 300–500 kg. The cylinder force must exceed the sum of the payload and the dead weight to produce upward acceleration.

Bore	Piston Area (cm²)	Force at 18.1 MPa (kN)	Equivalent Lift Mass (kg)	Typical Forklift Class
Φ56	24.63	44.6	4,546	1.5–2.5 t
Φ60	28.27	51.2	5,219	3.0–3.5 t

Force = pressure × area. Equivalent lift mass = force ÷ 9.81 m/s². These values represent maximum static force at the cylinder rod. The actual rated load capacity of the forklift is lower because it accounts for mast dead weight, chain pulley losses (typically 3–5%), and the required acceleration margin for a responsive lift response. The 3.5N4.5H model at 17.5 MPa produces 49.5 kN (5,042 kg equivalent).

Understanding Free Lift, Primary Lift, and Secondary Lift

The lifting cylinder with its 1,500 mm stroke is part of a chain-and-pulley system that multiplies the cylinder stroke into total fork travel. How this multiplication works depends on the mast type — and understanding the mast type is essential for selecting the correct cylinder replacement.

Two-Stage (Simplex) Mast

The lift cylinder extends and simultaneously raises the inner mast channel through a chain-and-sheave system. The fork travel is approximately equal to the cylinder stroke (1:1 ratio). With the 1,500 mm stroke cylinder, maximum lift height is approximately 1,500 mm above the mast collapsed height. No free lift — the mast begins extending as soon as the forks leave the ground.

Triple-Stage (Triplex) Mast

The cylinder first extends through a free-lift phase — the forks rise inside the collapsed mast channels without increasing the overall mast height. After the free lift is exhausted, the cylinder continues extending and raises the intermediate and outer mast channels through a 2:1 chain multiplication. With the 1,500 mm stroke, total fork travel can reach 3,000–4,500 mm depending on chain routing.

Full Free Lift (FFL) Mast

Uses a separate short free-lift cylinder (in addition to the main lift cylinder) that raises the forks to the full height of the collapsed mast before the main lifting cylinder begins extending. This configuration is standard for container-entry forklifts that must enter standard shipping containers (2,591 mm internal height) with the mast collapsed. The main lifting cylinder specification remains the same.

Replacement note:
When replacing the lifting cylinder, always verify whether your mast uses a separate free-lift cylinder. If it does, the main lift cylinder installation distance will be different from a non-FFL mast of the same forklift model. Measure the installation distance (L) on the existing cylinder before ordering — do not rely on the forklift model number alone.

Built for 10,000+ Hours — Construction and Material Specification

Cylinder Tube Material	Seamless cold-drawn steel tube, DIN 2391 / EN 10305-1
Bore Finish	Precision honed, Ra 0.2–0.4 μm
Piston Rod Material	SAE 1045 / C45 medium carbon steel, induction hardened
Rod Surface Treatment	Hard chrome plated, 20–30 μm thickness, Ra ≤ 0.2 μm
Piston Seal	NBR compound, single-lip design for single-acting operation
Rod Seal	Polyurethane U-ring + PTFE wear ring
Dust Wiper	Double-lip design, metal-reinforced
Proof Test Pressure	27 MPa (1.5× working pressure)
External Finish	E-coat primer + polyurethane topcoat, salt spray 500+ hours

Load Drift Test — The Critical Quality Check for Lift Cylinders

The single most important performance parameter for a forklift lifting hydraulic cylinder is not its lift force or its speed — it is its drift rate. Drift is the slow, unintended descent of the forks when the control valve is in the neutral (hold) position. A small amount of drift is normal due to thermal contraction of the hydraulic oil as it cools, but excessive drift indicates internal seal bypass or a leaking check valve.

Forklift lifting hydraulic cylinder internal components and precision machining

Korea Ever-Power Lift Cylinder Drift Specification

≤ 25 mm

Maximum drift in 10 minutes
under rated load at full extension

0 mm

Permitted external leakage
at rod seal under rated pressure

Industry standard per ISO 10827 allows up to 50 mm drift in 10 minutes for forklift mast cylinders. Korea Ever-Power specifies ≤ 25 mm — half the permissible limit — as the factory acceptance criterion. Every cylinder is tested at rated load on a vertical test stand before shipment.

Lift Cylinder Working Environments

High-Throughput Warehousing

Multi-shift distribution centres running 16–24 hours per day accumulate 2,500–4,000 full lift cycles per week. At this rate, the lifting cylinder completes over 200,000 full-stroke cycles in a single year. The combination of precision bore honing and chrome rod plating used in these hydraulic cylinders is specifically designed for this sustained cycle count, maintaining the ≤ 25 mm drift specification through the full 3–5 year seal replacement interval.

Lumber Yards and Outdoor Storage

Outdoor forklifts handling lumber, steel stock, and building materials operate in rain, dust, and temperature extremes. The double-lip metal-reinforced dust wiper prevents abrasive contaminant ingress that would score the rod surface and destroy the rod seal within months. The E-coat plus polyurethane external finish provides corrosion protection that withstands 500+ hours of salt spray testing — far exceeding the requirements of inland operations.

Food and Beverage — Clean Environments

Food-grade warehouses subject forklifts to regular washdown procedures using alkaline cleaning agents. The seal materials used in the lifting cylinder — polyurethane rod seal and NBR piston seal — are resistant to the pH 9–11 cleaning solutions commonly used in food processing environments. The zero external leakage specification ensures that no hydraulic oil contaminates the product handling area, supporting HACCP and food safety compliance.

Inspection and Maintenance Schedule for Lift Cylinders

Interval	Inspection Item	Action Threshold
Daily (pre-shift)	Visual check for oil weep at rod seal area	Any visible oil film on rod → schedule seal replacement
Weekly	Fork drift test: raise forks to max height with rated load, hold 10 min, measure descent	Drift > 50 mm in 10 min → remove cylinder for seal inspection
500 hours	Inspect rod surface for scoring, pitting, chrome damage	Scratches visible/tangible with fingernail → schedule re-chrome or rod replacement
2,000 hours	Check cylinder mounting hardware, pivot pins, chain anchor bolts	Any radial play in pivot > 0.5 mm → replace pin/bush
5,000–8,000 hours	Full cylinder reseal (planned preventive replacement)	Replace complete seal kit regardless of condition

Forklift Lifting Hydraulic Cylinder — Technical Questions

Why are there two models with the same bore and stroke but different weights?

The weight difference between paired models (e.g., N30M at 32.6 kg vs A2A30M at 36 kg) reflects different mounting configurations and wall thicknesses designed for different forklift OEM platforms. The heavier variant typically has a thicker cylinder tube wall and a more robust bottom mounting bracket to accommodate the higher dynamic shock loads present on certain chassis designs. Both variants produce the same lift force and share the same seal kit.

My forks lower too fast — is this a cylinder problem?

Usually not. Fork descent speed is controlled by the flow control valve in the hydraulic circuit, not by the cylinder itself. If the descent speed has increased over time, check the flow control valve adjustment first (it may have vibrated out of its set position). If the flow control valve is correctly set but the forks still descend too quickly, check the directional control valve spool for wear — a worn spool allows oil to bypass the metering path. The cylinder only causes fast descent if the piston seal has failed completely, which is rare and would also produce excessive drift when the forks are holding a load.

Can I use a G1/2 port model in place of an M22×1.5 port model?

No — the thread forms are incompatible and cannot be cross-threaded even with adapters without risking a high-pressure leak. G1/2 BSP is a 55° Whitworth pipe thread; M22×1.5 is a 60° metric thread. Forcing a metric fitting into a BSP port (or vice versa) will strip the threads and create a hazardous pressurised oil leak at the cylinder. Always match the port thread to the forklift's existing hydraulic fitting standard.

What causes a "jerky" or "stick-slip" lift motion?

Stick-slip during the lift stroke is almost always caused by air trapped in the cylinder. Air compresses under hydraulic pressure and then suddenly releases as the piston moves past the air pocket, creating the characteristic jerky motion. Bleed the cylinder by cycling it through full extension and retraction 10–15 times with no load, with the bleed screw open. If stick-slip persists after bleeding, check the piston wear ring — a worn wear ring allows metal-to-metal contact between the piston and bore, creating friction spikes.

How do I select the correct model for my forklift?

Measure three parameters on the existing cylinder: (1) bore diameter — measure internal diameter at the cylinder mouth with the rod retracted, Φ56 or Φ60; (2) installation distance — measure from the bottom mounting face to the top mounting point with the cylinder fully retracted; (3) port thread — identify G1/2 BSP or M22×1.5 metric. These three values uniquely identify one of the five models. Contact Korea Ever-Power forklift hydraulic cylinders technical support with your forklift make, model, and serial number for cross-reference verification.