WPH PZ2-K-25-P Hydraulic Gear Pump

WPH PZ2-K-25-P External Hydraulic Gear Pump (25 cm³/rev, Clockwise)

The WPH PZ2-K-25-P is an external hydraulic gear pump manufactured by Wytwórnia Pomp Hydraulicznych (WPH Wrocław / Hydrotor Tuchola). Engineered for continuous duty under severe dynamic loads, this displacement unit features a high-tensile cast-iron end-cover assembly paired with an extruded, pressure-balanced aluminum alloy housing.

Operating at a nominal displacement of 25.0 cm³/rev, the PZ2-K series provides hydrostatically balanced axial clearance compensation. This mechanism maintains volumetric efficiency exceeding 91% under fluctuating operating temperatures and high discharge back-pressures up to 200 bar (20 MPa). Designed specifically for commercial marine power units, vessel deck machinery, and heavy mobile industrial systems, the unit utilizes standard European 4-bolt mounting flange geometries with an integrated conical shaft interface.

Technical Details

Features

1. Hydrostatic Axial Pressure Compensation: Employs dynamic PTFE-backed bronze pressure balance plates that seal the gear gear-face clearances under load, preventing internal slip and boosting volumetric efficiency past 91%.
2. High-Load Journal Bearing Assemblies: Fitted with DU composite lead-bronze slide bushings designed to absorb cyclic radial side-loads from drive coupling misalignment without premature galling.
3. Optimized Tooth Profile Geometry: Features 12-tooth precision case-hardened steel gears running inside tight-tolerance gear chambers to damp micro-vibrations and keep fluid displacement pulsation under 3%.
4. Bimodal Pressure Capability: Sustains 160 bar continuous baseline pressure while handling up to 200 bar intermittent peak pressure for valve changeover spikes in heavy winch circuits.
5. Corrosion-Resistant Industrial Coating: Treated with zinc-phosphate primer and high-grade anti-corrosive industrial enamel to protect against saltwater, wash-down spray, and humid engine room environments.

Targeted Hydraulic Circuits

• Constant-flow pilot control circuits for marine hydraulic manifolds.
• Cooling loop recirculation and primary low-to-medium pressure lube delivery.
• High-cycle steering gear accumulator charging systems.
• Bilge, ballast valve, and hydraulic remote-control valve actuator circuits.

Frequently Asked Questions

What does the model code “PZ2-K-25-P” signify?

The alphanumeric designation breaks down as:

• PZ2: Gear pump frame Group 2 (European 4-bolt rectangular mount, 50 mm centering spigot).
• K: 1:5 tapered conical drive shaft with standard Woodruff key and retaining locknut.
• 25: 25.0 cm³ geometric displacement per single shaft revolution.
• P: Right-hand (Clockwise) rotational direction viewed facing the drive shaft end (P = Prawe in Polish).

Can I run the WPH PZ2-K-25-P in counter-clockwise (CCW) rotation?

No. The PZ2-K-25-P is an asymmetric, single-rotation pump. Operating this pump counter-clockwise will reverse the suction and pressure ports, immediately subjecting the low-pressure shaft lip seal to full hydraulic discharge pressure. This will rupture the shaft seal within seconds. If your prime mover rotates counter-clockwise, you must order the left-hand version: PZ2-K-25-L.

What hydraulic oil viscosity should be used with this pump?

The pump operates best with mineral-based hydraulic oils (HLP/HVLP) matching ISO VG 32, VG 46, or VG 68. The permissible working viscosity range is 20 to 150 cSt, with an optimal operating viscosity of 35 to 46 cSt. For cold-start scenarios, absolute maximum startup viscosity is 1,000 cSt at reduced RPM.

What is the maximum continuous working pressure for the PZ2-K-25-P?

The nominal continuous working pressure is 16.0 MPa (160 bar / 2,320 PSI). The unit can handle intermittent shock loads or valve switching pressure peaks up to 20.0 MPa (200 bar / 2,900 PSI) for durations shorter than 6 seconds, provided the duty cycle stays under 10%.

How do I check if my existing pump flange matches the PZ2-K-25-P?

Check your mounting pad against standard Group 2 dimensions: 4-bolt rectangular mounting pattern measuring approximately 71.4 mm × 96.0 mm on center, with an exact Ø50.0 mm centering register/spigot, and an input shaft exhibiting a 1:5 taper with an M12×1.25 threaded tip.