Brown & Sharpe BSM No.3 Rotary Gear Pump

Brown & Sharpe BSM No.3 Rotary Gear Pump

The Brown & Sharpe BSM No.3 Rotary Gear Pump (widely designated across marine technical registries as the BSM 3 / 3-S series) is an industrial-duty, positive displacement external gear pump engineered for continuous hydraulic, fuel oil service, and lubrication circulation. Featuring close-tolerance, precision-hobbed spur gears encased in fine-grain high-tensile cast iron, this unit handles clean fluids across broad kinematic viscosity bands—from light distillate diesel (MGO/MDO) up to heavy lubricating oils and viscous thermal fluids (32 SSU to 100,000 SSU).

The BSM No.3 operates efficiently at direct motor speeds up to 1,725 / 1,800 RPM while maintaining volumetric efficiency against differential head pressures reaching 200 PSI (13.8 bar). Standard configurations include replaceable iron sleeve bushings that self-lubricate via the handled medium, case-hardened steel shafts, and an optional integrated spring-loaded bypass/relief valve to protect drive trains and discharge piping from over-pressurization.

Model Details

• Manufacturer: BSM Pump Corp. (formerly Brown & Sharpe Mfg. Co.)
• Model Series: No. 3 Series / Model 3-S (High-Speed Rotary Gear)
• Base MPN / Standard Part Numbers:
  • 713-30-2 (Foot-Mounted, 3/4″ NPT Ports, Mechanical Seal)
  • 713-30-1 (Foot-Mounted, Packing Gland Seal)
  • 713-930-7 / 713-30-RV (Foot-Mounted with Integral Relief Valve)
  • 713-33-2 (Flange-Mounted, C-Face Motor Adapter)
• Pump Type: External Rotary Spur Gear, Positive Displacement
• Mounting Configuration: Base Foot Mount or NEMA/IEC Flange C-Mount

Technical Details:

Compatible Equipment

• Marine Main & Auxiliary Engines: Compatible as pre-lube, priming, and boost pumps for diesel engines (e.g., Caterpillar 3500 series, Wärtsilä 20/26 auxiliaries, Daihatsu, Yanmar, and Cummins KTA series).
• Marine Separator & Purifier Modules: Feed and booster supply pumps for Alfa Laval, Westfalia (GEA), and Mitsubishi Heavy Industries (MHI) centrifugal purifiers handling MDO and lube oil.
• Machine Tool & Industrial Machinery: Coolant high-pressure transfer, central spindle lubrication skids, press hydraulics, and gear box circulation units.
• Burner & Boiler Skids: Fuel feeding and booster injection for Aalborg, KangRim, and Saacke auxiliary marine boilers.

Frequently Asked Questions

What is the maximum operating pressure of the Brown & Sharpe No.3 pump?

The BSM No.3 rotary gear pump is rated for a continuous operating discharge pressure of up to 200 PSI (13.8 bar). For long-term duty life in continuous marine service, maintaining operating pressures between 50 and 150 PSI delivers optimal bearing life and mechanical seal longevity.

Can the BSM No.3 pump run in reverse?

Yes. The pump can mechanically rotate clockwise or counter-clockwise. However, the fluid discharge port always corresponds to the side toward which the top of the drive shaft turns. If your unit includes an integral pressure relief valve, the valve mechanism must be matched to the selected rotation.

What is the difference between BSM No.3 and BSM No.3-S?

The “S” designation denotes high-speed construction designed for direct electric motor coupling at 1,150 to 1,725 RPM. Older legacy No.3 pumps were designed for lower speed limits (typically up to 900 RPM under the standard “B-Series”). The 3-S incorporates specialized porting and tighter bearing tolerances optimized for modern 4-pole motor direct drive.

How do I select the right motor horsepower for this pump?

Horsepower requirements depend on liquid viscosity and differential pressure. At 1,725 RPM and pumping light oil (300 SSU), delivering 16.2 GPM at 50 PSI requires approximately 0.92 HP, while operating at the full 200 PSI pressure limit requires approximately 3.1 HP. A 3.0 HP or 5.0 HP motor is standard for full-envelope industrial duty.

What causes low flow or reduced discharge pressure in service?

The primary cause of flow loss in rotary gear pumps is internal slip caused by increased gear face and bushing clearances. If abrasive contaminants enter the pump, wear occurs across the side wear-plates and tooth tips. Inspect your suction strainers (we recommend 60 to 100 mesh suction filtration) and verify that the relief valve spring has not loosened or fatigued.