IMO ACF 100K4 NVBO Triple Screw Pump

IMO ACF 100K4 NVBO Triple Screw Pump (Year: 2005)

The IMO ACF 100K4 NVBO is a self-priming, positive displacement three-screw pump engineered specifically for continuous duty in marine propulsion, power generation, and critical industrial fluid loops. Featuring IMO’s cycloidal screw profile, this pump delivers smooth, pulse-free laminar flow with zero internal hydraulic shock, eliminating the emulsification of delicate oils and extending the lifespan of in-line instrumentation, valves, and filter elements.

The ACF 100K4 NVBO incorporates an internally balanced triple-screw assembly: a central power rotor driven directly via a flexible shaft coupling that drives two symmetrically positioned idler rotors. Fluid chambers formed between the interlocking threads advance axially, transferring media under consistent volumetric displacement without turbulence. Equipped with an integral internal relief/bypass valve configured for low-to-medium differential pressure regulation (up to 10 bar spring envelope) and high-temperature FKM (Viton) elastomers, the NVBO configuration is purpose-built to handle lube oils, fuel oils, and hydraulic media at operating temperatures up to +130°C.

Model Details:

• Manufacturer Part Number (MPN): ACF 100K4 NVBO (Mfg. Year: 2005)
• Series (ACF): Low-to-medium pressure industrial & marine screw pump with DIN flange standard
• Rotor Outer Diameter (100): 100 mm power rotor frame size
• Rotor Lead (K): Low lead displacement (769 cm³/revolution volumetric displacement)
• Design Generation (4): Generation 4 engineering revision with integrated shaft-seal deaeration porting

Technical Details:

Frequently Asked Questions

What does the “NVBO” designation mean on an IMO ACF pump?

The NVBO code defines the material construction and internal components of the pump. “N” signifies a Nodular Cast Iron (Ductile Iron) casing; “V” designates Viton (FKM) dynamic seals and O-rings; “B” specifies a standard bellhousing-face flange mounting configuration; and “O” indicates an integral pressure relief valve calibrated for low-pressure bypass adjustment up to 10 bar.

Can the IMO ACF 100K4 be mounted vertically?

Yes. The ACF series can be mounted either horizontally or vertically using standard intermediate bellhousings and direct-drive foot/tripod brackets. For vertical installations, ensure the motor sits directly above the pump assembly to avoid oil ingress into the motor bearings in the event of an undetected shaft seal failure.

What is the difference between K-lead and N-lead on IMO ACF 100 pumps?

“K” and “N” define the pitch (lead angle) of the rotor screws. The ACF 100K4 has a low lead with a displacement of 769 cm³/rev, delivering up to 67 m³/h. The ACF 100N4 features a normal (steeper) pitch lead with 895 cm³/rev displacement, providing higher flow rates (up to ~78 m³/h) at identical operating RPM.

How do I adjust the integrated pressure relief valve on this pump?

Remove the protective threaded end cap on the valve cover to reveal the internal adjusting screw and locknut. Loosen the locknut and rotate the spindle clockwise to increase the opening pressure, or counterclockwise to lower the relief threshold. Always monitor an accurate downstream gauge during adjustment, and never exceed 10 bar for “O” spring configurations.

What is the recommended maintenance interval for the shaft seal and bearings?

Under clean, non-abrasive operating conditions with well-filtered lube oil, the internal ball bearing and Viton mechanical seal have an expected service life of 20,000 to 30,000 operating hours. We recommend replacing the G050 shaft seal and G057 gasket kit during every standard 5-year drydock overhaul cycle.