DBR Pumpen NHG-2.5-3 / DHG 3.0 FM Marine Lub Oil & Fuel Oil Transfer Gear Pump

DBR Pumpen NHG-2.5-3 / DHG 3.0 FM Lub Oil & Fuel Oil Transfer Gear Pump

The DBR Pumpen NHG-2.5-3 (Designation: DHG 3.0 FM) is a positive displacement rotary gear pump engineered for continuous service in harsh marine engine room and industrial process environments. Purpose-built to handle viscous hydrocarbons—ranging from marine gas oil (MGO) and low-sulfur marine gas oil (LSMGO) to heavy fuel oil (HFO) and high-viscosity lubricating oils—this pump delivers stable, non-pulsating volumetric displacement across high operating backpressures.

Featuring precision-machined, case-hardened helical gear profiles housed within a rigid spheroidal graphite iron (nodular cast iron) casing, the NHG-2.5-3 minimizes fluid slip and internal shear while operating at reduced noise levels. The pump integrates a dual-bushing hydrodynamic journal sleeve bearing arrangement lubricated directly by the pumped medium, alongside an internal, adjustable spring-loaded safety bypass valve to safeguard discharge pipework, couplings, and motor windings from sudden downstream pressure spikes.

Model Details

• Manufacturer: DBR Pumpen
• Model Series: NHG / DHG Series
• Model Number: NHG-2.5-3
• Secondary / Casting Designation: DHG 3.0 FM
• Manufacturer Part Number (MPN): DBR-NHG2.5-3-FM
• Product Classification: External Meshing Helical Rotary Gear Pump
• Mounting Configuration: Flange-Mounted (FM) / Horizontal Foot-Bracket Adaptable

Technical Details

Features

1. Hydrodynamically Balanced Gear Geometry: Precision-cut, case-hardened helical gears eliminate axial thrust imbalances, lowering mechanical wear on gear flanks and maintaining laminar, low-noise fluid displacement.
2. Integral Full-Flow Relief Valve: Factory-fitted adjustable spring-loaded internal bypass circuit redirects overpressure directly into the suction chamber, protecting against valve closures or discharge line blockages.
3. Heavy-Duty Casing Construction: Cast from graded ductile iron (GGG-40 / QT450) to absorb cyclical pipeline vibration and high hydraulic shocks encountered in dynamic marine vessel piping networks.
4. Medium-Lubricated Journal Bearings: High-lead bronze / carbon composite sleeve bushings operate immersed in the process fluid, eliminating secondary lubrication lines and extending MTBF during continuous transfer cycles.
5. Standardized IEC / Marine Flange Interface: Designed to ISO/DIN dimensional standards for direct drop-in replacement on common marine auxiliary skid bedplates.

Compatible Motor & Skid Interfaces

• Electric Motors: Fits standard IEC marine-duty motor frames (IEC 80M, 90S, 90L; IP55 / IP56 enclosures) across 380V/440V 50Hz/60Hz configurations.
• Coupling Types: Flexible jaw couplings (Lovejoy, Rotex 19/24, or equivalent claw couplings with 92/98 Shore-A elastomeric spiders).
• Separator Modules: Compatible with fuel and lube oil purifier modules manufactured by Alfa Laval, GEA Westfalia, and Mitsubishi Kakoki Kaisha (MKK).

Frequently Asked Questions

Can the DBR Pumpen NHG-2.5-3 pump run dry?

No. The internal shaft journal sleeve bearings are lubricated exclusively by the pumped media. Running the pump dry—even for brief intervals over 30 to 45 seconds—will cause severe thermal expansion of the bushings, shaft galling, and seal failure. Always pre-fill the pump housing with clean oil prior to initial startup.

What is the difference between the NHG-2.5-3 and DHG 3.0 FM model markings?

NHG-2.5-3 and DHG 3.0 FM designate the same hydraulic pump frame across DBR Pumpen product catalogs. NHG refers to the internal factory series code, while DHG denotes the marine application line, where “FM” explicitly indicates a Flange-Mounted arrangement engineered for close coupling to IEC standard motors.

Can this pump handle low-sulfur marine gas oils (LSMGO / MGO)?

Yes, provided the viscosity remains above 2.0 to 3.0 cSt at the operating temperature. For ultra-low viscosity fuels with poor inherent lubricity, operating differential pressure should be kept below 0.3 MPa to prevent hydrodynamic lubrication breakdown at the gear journals.

How do I adjust the integrated pressure relief valve?

Remove the hex protective acorn nut located on the valve cap of the pump casing. Loosen the lock nut and rotate the internal slotted adjusting screw clockwise to increase cracking pressure, or counter-clockwise to lower it. Always use an accurate, calibrated pressure gauge on the discharge line during calibration, and re-tighten the lock nut firmly with a fresh copper sealing washer.

Is the pump bi-directional?

Standard factory units are assembled for unidirectional rotation (typically clockwise when viewed from the motor drive shaft end). Reversing rotation requires disassembling the front cover, inverting the internal gear set, and swapping the internal relief valve flow channel orientation. Operating in reverse without internal modification will pressurize the mechanical seal chamber and blow out the seal faces.