ALP2-S-30 ALP2-D-34-FG ALP2-D-16-FG Marzocchi Hydraulic Gear Pump

MARZOCCHI ALP2 Series Fixed Displacement External Gear Pump

Product Overview

The ALP2 series is an external gear, fixed displacement pump manufactured by Marzocchi Pompe S.r.l. in Italy. Founded in 1961, Marzocchi has grown through continuous investment and product development to become one of the world‘s largest manufacturers of gear pumps and motors.

The ALP2 series belongs to the Group 2 platform, featuring a high-strength aluminum alloy body with case-hardened alloy steel gears, offering displacements from 4.5 to 35.2 cc/rev. As a fixed displacement pump, the ALP2 series is renowned for high working pressure, high speed, high volumetric efficiency, and low noise. Manufactured to international standards, the series offers drop-in interchangeability with equivalent models from other major brands.

This page covers the following models: ALP2-S-30, ALP2-D-34-FG, ALP2-D-16-FG, ALP2-D-20-FG, ALP2-D-22-FG, and the full ALP2 series range.

Technical Specifications 

ALP2 Series General Specifications (Group 2)

• Series: ALP2 Series, Group 2

• Pump Type: External gear, fixed displacement

• Displacement Range: 4.5 – 35.2 cc/rev

• Max. Continuous Pressure (P1): 250 bar

• Max. Intermittent Pressure (P2): 270 bar

• Max. Peak Pressure (P3): 290 bar

• Max. Speed: 4,000 rpm

• Body Material: High-strength aluminum alloy

• Gear Material: Alloy steel, case-hardened

• Mounting Flange: SAE A type, two-bolt flange

• Rotation: Clockwise (CW, standard) / Counter-clockwise (CCW) optional

• Fluid Type: Petroleum-based hydraulic oil

• Viscosity Range: 6–300 cSt (recommended 10–100 cSt)

• Weight: Approx. 3.0 kg

Model-Specific Specifications

ALP2-S-30

• Model Code: ALP2-S-30

• Displacement: 21.1 cc/rev

• Max. Working Pressure: 180 bar

• Max. Speed: 3,200 rpm

• Theoretical Flow (@1,500 rpm): 31.6 L/min

• Rotation: Counter-clockwise (left-hand)

• Shaft: Tapered 1:8

• Mounting Flange: European flange, pilot diameter 36.5 mm

• Inlet Port: Flange connection D40×D19×M8

• Outlet Port: Flange connection D40×D19×M8

• Weight: Approx. 3.0 kg

ALP2-D-34-FG

• Model Code: ALP2-D-34-FG

• Displacement: 23.7 cc/rev

• Max. Working Pressure: 180 bar

• Max. Speed: 3,000 rpm

• Theoretical Flow (@1,500 rpm): 35.5 L/min

• Rotation: Clockwise (right-hand)

• Shaft: Tapered 1:8

• Mounting Flange: European flange, pilot diameter 36.5 mm

• Inlet Port: 3/4″ GAS threaded

• Outlet Port: 1/2″ GAS threaded

• Weight: Approx. 3.0 kg

ALP2-D-16-FG

• Model Code: ALP2-D-16-FG

• Displacement: 11.5 cc/rev

• Max. Continuous Pressure (P1): 230 bar

• Max. Intermittent Pressure (P2): 250 bar

• Max. Peak Pressure (P3): 270 bar

• Max. Speed: 4,000 rpm

• Theoretical Flow (@1,500 rpm): 16.4 L/min

• Rotation: Clockwise (right-hand)

• Shaft: Tapered 1:8

• Mounting Flange: SAE A type, two-bolt flange

• Inlet Port: 3/4″ GAS threaded

• Outlet Port: 1/2″ GAS threaded

ALP2-D-20-FG

• Model Code: ALP2-D-20-FG

• Displacement: 14.1 cc/rev

• Max. Continuous Pressure (P1): 230 bar

• Max. Intermittent Pressure (P2): 250 bar

• Max. Peak Pressure (P3): 270 bar

• Max. Speed: 4,000 rpm

• Theoretical Flow (@1,500 rpm): 20.1 L/min

• Rotation: Clockwise (right-hand)

• Shaft: Tapered 1:8

• Mounting Flange: SAE A type, two-bolt flange

ALP2-D-22-FG

• Model Code: ALP2-D-22-FG

• Displacement: 16.0 cc/rev

• Max. Continuous Pressure (P1): 210 bar

• Max. Intermittent Pressure (P2): 225 bar

• Max. Peak Pressure (P3): 240 bar

• Max. Speed: 4,000 rpm

• Theoretical Flow (@1,500 rpm): 22.8 L/min

• Rotation: Clockwise (right-hand)

• Shaft: Tapered 1:8

• Mounting Flange: SAE A type, two-bolt flange

Key Technical Advantages

1. High-Strength Aluminum Alloy Body with Precision-Ground Alloy Steel Gears

The pump body, flange, and end covers are die-cast from special pressure-resistant aluminum alloy, delivering exceptional strength and wear resistance. Gears are manufactured from alloy steel with case-hardening treatment, paired with precision needle bearings to ensure low friction and extended service life. The aluminum body also provides excellent heat dissipation for effective oil temperature control.

2. Superior Pressure Capability

The ALP2 series delivers 250 bar continuous working pressure and 290 bar peak pressure on smaller displacement models (4.5–14.1 cc/rev). Even on larger displacement models (21.1–35.2 cc/rev), it maintains 180 bar continuous working pressure. This pressure performance is among the best in its class.

3. High-Speed Operation with Substantial Flow Output

Maximum speed reaches 4,000 rpm. High-speed capability delivers greater flow output in a compact package. The ALP2-D-34-FG, for example, produces 35.5 L/min at just 1,500 rpm, maximizing hydraulic system power density.

4. Low Noise and High Volumetric Efficiency

Optimized gear tooth profiles combined with precision manufacturing significantly reduce operating noise. Precision-machined gear pairs ensure minimal internal leakage, delivering exceptional volumetric efficiency. High volumetric efficiency translates to lower power loss and reduced oil temperature rise.

5. Excellent Self-Priming and Wide Viscosity Range

The pump features excellent self-priming capability—no pre-filling required before startup. Internal automatic lubrication is achieved using the hydraulic fluid being pumped—no additional lubricant is needed. Stable operation across a wide viscosity range of 6–300 cSt (recommended 10–100 cSt).

6. Modular Design with Flexible Configuration

The modular design allows flexible accessory integration, including relief valves and check valves to simplify system design. The standard SAE A two-bolt flange mounting interface enables easy integration into various hydraulic systems. Available in both clockwise (CW) and counter-clockwise (CCW) rotation to suit different installation requirements.

Application Areas

• Mobile hydraulic equipment: Forklifts, loaders, telescopic handlers

• Agricultural machinery: Tractor hydraulic systems, combine harvesters, implement hydraulics

• Construction equipment: Mini excavators, skid steer loaders, road rollers

• Industrial hydraulic power units: Medium to high-pressure systems

• Material handling: Stackers, scissor lifts, platform elevators

• Municipal and construction equipment: Street sweepers, aerial work platforms

• Marine hydraulic systems: Deck machinery, steering gear

• Industrial lubrication systems: Centralized lubrication for large equipment

Expert Maintenance Tips

1. Rotation Direction Verification: Confirm pump rotation matches system requirements before installation. “S” in the model code indicates counter-clockwise (left-hand) rotation; “D” indicates clockwise (right-hand) rotation. Incorrect rotation swaps suction and pressure ports, potentially damaging the pump.

2. Coupling Alignment: Maintain shaft concentricity within 0.05 mm. Excessive misalignment causes premature needle bearing wear and shaft seal leakage, significantly reducing service life.

3. Inlet Line Negative Pressure: Inlet absolute pressure must not fall below 0.8 bar (vacuum not exceeding -0.2 bar). Use piping no smaller than the inlet port size and minimize elbows to prevent cavitation damage.

4. First-Start Priming: Fill the pump cavity with hydraulic oil from the outlet port before first start-up. Running dry or with trapped air will cause severe gear and bearing damage.

5. Fluid Cleanliness: Maintain system fluid cleanliness to ISO 4406 18/16/13 or better. Install a suction filter with minimum 100 μm rating and a return-line filter with 10 μm rating.

6. Regular Inspection: Inspect pump operating condition every 2,000 operating hours. If system pressure drops, flow decreases, or abnormal noise occurs, promptly inspect gear pairs and bearing wear.