Triple Screw and Positive Displacement Pumps for Oil Transfer and Hydraulic Power

How Wenzhou buyers specify triple screw, gear, axial piston, and triplex piston pumps for lubrication, fuel transfer, and hydraulic power units.

What this family is for

Positive displacement pumps move a fixed volume each revolution. That is why they remain the default choice when a plant must push lubricating oil, residual fuel, hydraulic fluid, or a measured water slug against a rising head. WanGuan builds this group in Wenzhou for export packages that ship to Europe, the Middle East, and Southeast Asia, and the four catalog units below cover the duties that show up most often on RFQs.

The triple screw pump is the quiet workhorse for viscous oil. Two idler screws mesh with a power rotor inside a close-clearance liner, so flow is almost pulseless and shear stays low. Gear pumps sit on hydraulic power units where the fluid is thinner and the circuit needs a compact aluminum housing. Variable displacement axial piston pumps take over when the same HPU must hold pressure while flow changes. Horizontal triplex piston pumps are specified when the buyer needs high discharge pressure on water, emulsion, or light process liquid rather than oil.

Triple screw pump: lubrication and fuel oil

Specify a triple screw pump when the liquid is lubricating oil, hydraulic oil, or residual fuel in the range where a centrifugal would cavitate or run far off its curve. Typical plant rooms use it on main-engine lube circulation, burner fuel supply, and gearbox lubrication. Because the rotors are hydraulically balanced, bearing loads stay modest and noise is lower than a comparable gear pump at the same viscosity.

When you send an inquiry, list viscosity at pumping temperature, suction lift or flooded suction, discharge pressure, and whether the oil is clean or carries fine carbon. WanGuan machines the rotors for a defined clearance band; too thin an oil at high temperature will slip, and too cold a start will overload the motor. Ask for a curve at the actual centistoke value rather than a water curve. Mechanical seal faces and elastomers should match the oil additive package. For outdoor skids in the Gulf, confirm tropicalization of the motor and a heating jacket if winter pour point is a risk on European sites.

Aluminum hydraulic gear pump

The aluminum hydraulic gear pump in the catalog is a compact external-gear unit for mobile and industrial HPUs. Aluminum keeps mass down on OEM frames; the gear set is intended for mineral hydraulic oil in a filtered circuit. Use it as a fixed-displacement source on log splitters, small presses, dock equipment, and lubrication carts where the duty is intermittent and the pressure is in the medium range.

Do not treat it as a chemical pump. Water glycol, phosphate ester, and aggressive solvents need a different housing and seal set. Inlet vacuum must stay within the maker limit or the gears will cavitate and pit. Pair the pump with a suction strainer, a return filter, and a relief valve set below the housing rating. If the power unit also needs load-sensing or constant pressure, move the duty to the axial piston pump instead of oversizing the gear unit.

Variable displacement axial piston pump

Variable displacement axial piston pumps change swashplate angle so flow falls as system pressure approaches the compensator setting. That is the right architecture for injection machines, marine deck machinery, and test stands that spend much of the hour holding load rather than dumping oil over a relief valve. Energy use and oil temperature both drop compared with a fixed gear pump on the same cycle.

RFQ notes should include maximum displacement, rated and peak pressure, through-drive needs, and the control type: pressure compensation, load sensing, or electric proportional. Confirm the case drain line is piped independently to tank and that the inlet is flooded. WanGuan can discuss shaft options and mounting flanges that match common European HPU frames. Always state ISO viscosity grade and expected oil temperature; piston pumps are unforgiving of aeration and of cold oil at high speed.

Horizontal triplex reciprocating piston pump

The horizontal triplex piston pump uses three plungers on a crankshaft to deliver high pressure with a manageable residual pulse. Buyers use it for high-pressure cleaning, hydrostatic test, descaling, and some process injection duties. Unlike the screw and gear units, this pump is usually applied on water or water-based fluids, so packing, valve seats, and corrosion allowance matter as much as flow.

Give NPSH available, maximum discharge pressure, stroke rate, and whether the fluid carries solids. A pulsation dampener on the discharge and a suction stabilizer on long inlet lines are not optional on export skids. If the duty is oil rather than water, say so clearly; packing and lubrication of the power end change. For 24-hour process service, ask for a spare fluid-end kit and a documented packing adjustment procedure in English.

How to write the RFQ so the quotation matches the photo

WanGuan lists these four pumps as separate catalog items because the hardware is not interchangeable. Attach the duty: liquid name, viscosity or specific gravity, temperature, suction condition, discharge pressure, flow, and hours per day. Note motor voltage and frequency for the destination country, and whether you need a bare pump, a baseplate set, or a full skid with coupling guard.

Documentation typically requested by European and Middle East EPCs includes outline drawing, sectional drawing, performance curve, material list, and a packing list in English. ISO 9001 factory control and CE-related files can be discussed per model; do not assume every size carries the same file set. Send the inquiry to the WanGuan export desk with the product names as they appear on the website. The application team will map the duty to one of the four units above rather than forcing a centrifugal onto an oil line.