KRACHT KF-F Fuel Gear Pump Series

Overview

The KRACHT KF-F is the fuel-duty version of the KRACHT KF external gear pump family, developed specifically for pumping fuels and in particular marine fuels. Modern low-sulphur distillates such as MGO and DMA gas oil have poor lubricity, and lubricity cannot be judged from viscosity alone, so a pump that is perfectly sound on lubricating oil can wear quickly on them. The KF-F range, offered in nominal sizes 2.5 to 630 with geometric displacements from 2.55 to 622.5 cm³ per revolution, is built to stay fatigue-resistant on fuels whose lubricity is as low as the minimum allowed by ISO 8217.

Seven Star LLC supplies the KRACHT KF-F to shipyards, marine service companies, power generation sites and fuel-handling contractors in Oman and the wider GCC. Our engineers in Muscat help match the nominal size and valve option to a given fuel, flow rate and drive speed, and confirm that the lubricity of the fuel stays inside the limit stated by the manufacturer.

Operating Principle

Like every pump in its family, the KRACHT KF-F displaces a fixed geometric volume on each revolution of two helical gear shafts that mesh in a close-fitting housing. Fuel enters on the suction side, travels in the tooth gaps along the housing wall and leaves on the pressure side, so delivery is proportional to shaft speed. In the KRACHT KF-F the direction of delivery follows the direction of rotation seen from the shaft end: clockwise rotation delivers from left to right.

What distinguishes the KF-F is how it copes with thin, low-lubricity fuels. The manufacturer measures lubricity with the HFRR test to ISO 12156, expressed as wear scar diameter (WSD), where a higher value means poorer lubricity. KF-F pumps are rated fatigue-resistant up to a WSD of 520 µm, the minimum lubricity of MGO and DMA under ISO 8217, and they remain highly efficient at high speed. Because pressure capability depends on viscosity, the maximum pressure is 12 bar for viscosities below 12 mm²/s and 25 bar at 12 mm²/s and above.

Engineering Design of the KRACHT KF-F

For KRACHT KF-F fuel service the housing is made of spheroidal cast iron EN-GJS-400-15, the gear sets are case-hardened steel 1.7139, and the gears run in multi-layer plain bearing bushes; the plastic and white metal bushes offered on standard KF pumps are not part of the KF-F programme. Seals are FKM, rated for media temperatures from −20 to 150 °C, and the shaft can be sealed with single, double or triple radial lip-type seals, a mechanical seal, or a magnetic coupling for hermetic duty.

Mounting follows the DIN flange pattern with a short cylindrical shaft end with feather key to ISO R775. Pipe connections on sizes 2.5 to 25 are Whitworth thread or SAE flange, and larger sizes use SAE flange connections. A directly controlled pressure relief valve of type D can be mounted on the pump to protect it from pressure peaks, but it may only open briefly, because a continuous bypass would overheat the pump; for permanent discharge, a valve with an external outlet is required. Explosion-protected versions under directive 2014/34/EU are available for gas and dust zones.

Key Features

Buyers specifying the KRACHT KF-F for fuel duty benefit from the following design points:

• Fatigue resistance of the KRACHT KF-F is stated up to a lubricity value of 520 µm WSD, covering low-sulphur MGO and DMA fuels.
• Viscosities for the KRACHT KF-F run from 1.2 to 20,000 mm²/s are permitted, which is wider at the thin end than the standard family.
• Speeds of 200 to 3,600 rpm on sizes up to 63 allow compact, high-flow arrangements on fast drives.
• All materials in contact with the fuel are chosen for fuel service, including FKM seals and spheroidal cast iron housings.
• KRACHT KF-F sound pressure levels are 65 to 80 dB(A) at 1 m, depending on nominal size and pressure.
• Single, double and triple lip seals, mechanical seals and a magnetic coupling cover most leakage and quench requirements.
• Motor-pump units can be built with IEC, ATEX or marine-approved motors for engine rooms and fuel skids.
• Without a quench connection the pump can be mounted in any position, which gives installers freedom in tight engine rooms and skids.

Industrial Applications

The principal use of the KRACHT KF-F is fuel delivery, particularly marine fuels, together with the supply of fuel to diesel engines and burners where the lubricity of the product is low. For Oman this means bunkering and day-tank transfer at the ports, fuel supply skids for diesel generators and boilers at power and desalination plants, and fuel forwarding at industrial sites in Sohar and Salalah. Offshore support vessels, tugs and workboats running on MGO are a further natural fit.

A complete fuel system often combines several products, and Seven Star LLC supplies them together. The KRACHT KF80RF2-D15 gear pump shows a typical mid-size KF build with a mounted relief valve, the KRACHT VCM gear flow meter can measure the delivered fuel volume downstream of the pump, and the KRACHT SPV 10 L1G 1 A 12 pressure relief valve can protect a line once fluid compatibility has been confirmed with the manufacturer.

For lubricating oil and other media, see the KRACHT KF series modular gear pump.

Technical Specifications

Key data for the KRACHT KF-F are collected below from the manufacturer catalog for KF and KF-F gear pumps.

Request a Quote for KRACHT KF-F

If your project involves transferring marine or diesel fuel, send Seven Star LLC the fuel grade, lubricity data, viscosity range, flow, pressure and drive speed for the KRACHT KF-F. We will prepare a formal RFQ for Oman and the GCC, confirm current availability and lead time and provide the KRACHT catalog so that your engineers can verify the size, seal and valve options before ordering.