Viking Pump HL 75M-3N706 Motor Speed Gear Pump

Viking Pump HL 75M-3N706 Motor Speed Cast Iron Hydraulic Internal Gear Pump

The Viking Pump HL 75M-3N706 is a heavy-duty, close-coupled positive displacement internal gear pump engineered for direct motor-speed operation. As part of Viking’s proven 75 Series General Purpose motor-speed line, the HL 75M eliminates the footprint, alignment complexity, and mechanical maintenance associated with intermediate speed reducers, gearboxes, or belt-drive configurations. Designed to mount directly to standard NEMA C-face electric motors, it drives a balanced rotor-and-idler gearset to provide uniform, non-pulsating fluid delivery up to 30 GPM (6.8 m³/h / 114 L/min) at operating speeds up to 1800 RPM.

Manufactured with a Class 30 gray iron casing, an induction-hardened rotor and idler, and an integral pressure relief valve, this pump is optimized for clean-to-semi-clean lubricating liquids, hydraulic fluids, diesel/MGO booster circuits, and lube oil circulation systems. The compact “M” drive mounting configuration utilizes an internal lip-seal arrangement with a factory-calibrated suckback channel that relieves pressure from the shaft seal area back to the suction chamber, dramatically extending seal life in high-hour marine and industrial installations.

Model Details

• Manufacturer: Viking Pump (An IDEX Corporation Company)
• Model: HL 75M-3N706 (also cataloged as HL75M / HL 75 M)
• Manufacturer Part Number (MPN): HL75M-3N706
• Displacement Class: “HL” Frame Size (30 GPM nominal @ 1800 RPM)
• Design Series: Series 75 Motor Speed (Close-Coupled Direct Drive)
• Casing Material: Cast Gray Iron (ASTM A48 Class 30B)
• Drive Interface: Close-coupled hollow-shaft rotor for direct slide-on NEMA C-Face mounting

Key Features

1. Direct Motor-Speed Close-Coupling: Operates at standard 4-pole (1450/1750 RPM) and 6-pole (1150 RPM) motor speeds without external gearboxes, timing belts, or alignment-critical couplings, reducing skid footprint by up to 60%.
2. True Non-Pulsating Positive Displacement: Precision-meshed internal gear crescent geometry guarantees smooth, shear-sensitive fluid flow, preventing emulsification in lube oil reservoirs and hydraulic circuits.
3. Internal Lip Seal with Suckback Relief: Incorporates dual opposed radial lip seals backed by a factory suckback port directed to the suction chamber to prevent seal pressurization and premature weeping.
4. Built-In Overpressure Protection: Fitted with an internal, adjustable spring-loaded bypass relief valve mounted directly on the pump casing to safeguard downstream piping and motor windings against deadheading.
5. Bi-Directional Pumping Capability: Delivers full hydraulic capacity in either clockwise or counter-clockwise rotation simply by repositioning the internal crescent head and setting the relief valve orientation.

Technical Specifications

Compatible Prime Movers

• NEMA Frame Motors: 143TC, 145TC, 182C, 184C, 182TC, 184TC (with standard Viking C-face drive adapters).
• IEC Frame Adapters (with conversion kit): IEC 90L, 100L, 112M B5/B14 flanges.

Compatible Engine & Skid Applications

• Marine Main Engine & Genset Auxiliary Modules: Caterpillar 3500/3600 Series, Wärtsilä 20/26 Lube Pre-Lubrication Skids, Yanmar, Daihatsu auxiliary engines.
• Separators & Filtration Systems: Alfa Laval, GEA Westfalia, and Mitsubishi fuel/lube oil conditioning units.
• Reduction Gears: Renk, Reintjes, ZF, and Twin Disc marine transmission pre-lube and circulation loops.

Applications

• Marine Diesel Pre-Lubrication & Circulation: Continuous oil circulation and pre-lube duty for heavy-duty marine diesel engines and propulsion gearboxes.
• Fuel Oil Booster & Unloading: High-reliability transfer of Marine Gas Oil (MGO), Marine Diesel Oil (MDO), and Light Fuel Oil (LFO) through centrifugal purifiers and booster units.
• Industrial Hydraulic System Circulation: Low-pressure, high-volume hydraulic fluid loop supply, hydraulic filtration loops, and reservoir kidney-loop filtration.
• Turbine & Compressor Bearing Flush: Constant non-pulsating hydrodynamic bearing lubrication on centrifugal gas compressors, generators, and steam turbines.
• General Fluid Transfer: Pumping transformer oils, heat transfer oils, gear lubricants, and industrial cutting fluids across machining centers.

Frequently Asked Questions

What does the “M” signify in the Viking HL 75M model designation?

The “M” designates a close-coupled, motor-speed mounting configuration. The pump is designed with a direct-mount casing that bolts directly onto an electric motor face via an adapter bracket, featuring a hollow rotor bore that accepts the motor’s keyed drive shaft directly without an external flexible coupling.

Can the HL 75M pump be converted to a mechanical seal later?

Yes. The Series 75 lip seal casing and Series 475 mechanical seal casing share identical external and internal machining dimensions. By removing the lip seal set and installing the Viking mechanical seal kit, sleeve, and retaining snap ring, the unit can be upgraded to a mechanical seal configuration without replacing the pump casing or rotor.

What is the difference between Series 75 and Series 475 pumps?

Series 75 units are factory-fitted with dual lip seals and rated for operating pressures up to 50 PSI (3.4 Bar). Series 475 pumps are factory-equipped with component mechanical seals and can operate at pressures up to 100 PSI (6.9 Bar).

Is this pump self-priming?

Yes. Viking internal gear pumps are positive displacement units capable of self-priming under standard suction lifts, provided the internal pumping elements (rotor and idler) are wetted with liquid prior to initial commissioning to create an effective hydraulic seal against the crescent.

Can the Viking HL 75M handle high-temperature thermal oils?

The standard HL 75M handles operating temperatures up to 350°F (177°C) when fitted with high-temperature fluorocarbon or PTFE lip seals and standard internal clearances. Applications exceeding these temperatures require high-temperature mechanical seals and enlarged internal gear clearances.