Hengshun Machinery 3.5 VP 75 Air Motor

Hengshun Machinery 3.5 VP 75 Air Motor | Marine Pneumatic Drive

The Hengshun Machinery 3.5 VP 75 is a positive-displacement rotary air motor engineered for offshore, shipboard deck machinery, and hazardous operating environments. Rated at 3.5 HP (2.6 kW) with a nominal governed output speed of 750 RPM under a working pressure of 6.0 kg/cm² (0.59 MPa / 85.3 PSI), this motor delivers high starting torque, smooth low-to-mid-speed modulation, and intrinsically safe operation where conventional electric motors pose ignition risks.

The 3.5 VP 75 excels under severe duty cycles involving frequent stalling, dynamic load reversal, and saturated, saline marine ambient conditions. Its self-cooling pneumatic design prevents thermal degradation during sustained heavy-load cycles on vessel gangways, mooring tensioners, hose reels, and chemical cargo pump room drives.

Model Details

• Manufacturer: Hengshun Machinery
• Model Designation: 3.5 VP 75
• Standard Manufacturer Part Number (MPN): HS-3.5VP75
• Serial / Production Lot Example: MFG No. 250332 Series
• Pneumatic Mechanism: Rotary Vane / Planetary Reduction Configuration
• Mounting Standard: Multi-hole flange mounting (compatible with international marine deck drive interfaces)

Part Number Cross-References

• Samgong Machinery: SAM-3.5-PE-300 / SAM-3.5-PE-300DR / SAM-4.5 Series (verify gearing ratio for nominal shaft RPM)
• Shin Myung (SMC Korea): SM-3.5P / SM-7P series deck motor equivalents
• Japan Air Motor (JAM): JAM-3.5PE / JAM-4.5PE-1200S class replacements
• Huangshi / BTM Series: BTM-3.5PE / BTM-5.5PE series platform dimensions

From the Desk of a Marine Chief Engineer:

1) Purge the Line Before Bolt-Up: Most air motor failures on deck machinery happen in the first 10 minutes of operation. Shipboard service air mains accumulate moisture, rust flakes, and scale over time. Always blow out the supply hose at full blast for 30 seconds away from the motor before securing the G 3/4″ inlet line.

2) Mandatory FRL Rigging: The 3.5 VP 75 must never be run on dry, raw ship’s service air. Always verify your Filter-Regulator-Lubricator (FRL) pack is located within 3 to 5 meters of the motor inlet. Set the drip rate on your sight glass to 2 to 4 drops per minute of an approved pneumatic oil (ISO VG 32 or SAE 10W non-detergent). Dry vane operation causes friction-glazing and rapid drop in starting torque within weeks.

3) Avoid Exhaust Line Throttling: If you pipe the exhaust away from the working deck or pump room bilge, make sure your exhaust run diameter is at least one pipe size larger than the exhaust port (step up from 1″ to 1-1/4″). Vane motors cool rapidly by adiabatic gas expansion; backpressure in an undersized exhaust line creates rapid icing and chokes motor performance down to 50% rated output.

4) Long-Term Stoppage Procedure: If the deck machinery will sit idle during an ocean transit or cold layup, pour 30–50 ml of turbine oil directly into the air inlet port, turn the output shaft by hand two revolutions to coat the vane pockets, and plug both ports with threaded brass plugs.

Frequently Asked Questions

Can the Hengshun 3.5 VP 75 air motor be throttled for precise winch positioning?

Yes. Speed regulation is executed by adjusting an inline pressure regulator or proportional air control valve. Reducing the air pressure modulates torque, while adjusting volume (CFM) directly alters shaft RPM, allowing slow, controlled inching of heavy loads.

What is the maximum permitted air pressure for this motor?

The motor is engineered for optimal performance at 6.0 kg/cm² (~85 PSI). While it can operate comfortably across 4.0 to 7.0 kg/cm², operating continuously above 7.0 kg/cm² increases mechanical wear on the vane tips and internal bearings without generating commensurate work efficiency.

What should I do if the motor loses speed or exhibits hard starting?

Check three primary failure modes: First, verify whether the inline lubricator has run dry; dry rotor vanes cannot seat against the cylinder wall to create a tight chamber. Second, check the exhaust port for ice formation or silencer clogging. Third, check supply air pressure with an inline gauge while the motor is running to identify excessive dynamic line pressure drop.

Is the motor bi-directional, and how is direction switched?

The 3.5 VP 75 is fully reversible. Reversal is accomplished by directing supply air into the alternate side port while allowing the primary port to vent through a standard 4-way, 3-position (4/3) hand-lever or pilot-actuated marine pneumatic valve.

Can this motor be installed vertically?

Standard units are engineered for horizontal flange or foot mounting. If your installation requires a vertical shaft orientation (e.g., agitator drive or vertical capstan), ensure internal thrust bearings and oil-mist drainage ports are verified for vertical shaft-down or shaft-up duty to prevent oil accumulation inside the rotor chamber.