KRACHT DT DuroTec Gear Pump for Abrasive Fluids

Overview

The KRACHT DT DuroTec® is an external gear pump developed specifically for abrasive and poorly lubricating fluids that need to be pumped at high working pressure. KRACHT GmbH, the Werdohl-based pump manufacturer in the Atlas Copco Group, began developing gear pumps for these difficult media in 1990 and has refined the design continuously since then. The KRACHT DT range comprises two frame sizes, DT 3 with 63, 100 and 125 cm³/rev and DT 5 with 150, 200 and 250 cm³/rev, for working pressures up to 100 bar, viscosities from 500 to 50 000 mm²/s and media temperatures up to 150 °C. The gear set is surrounded by a silicon carbide bearing bush and protected by a hard-material coating, and solid particles below 50 µm with a Vickers hardness below 2 500 are accepted in the pumped medium.

Seven Star LLC supplies the KRACHT DT to polyurethane processors, chemical producers and equipment builders across the Sultanate of Oman and the GCC, with engineering support in Muscat. We help users confirm whether a DuroTec pump is the right answer for a filled or crystallising fluid, select the displacement and drive, and quote either the bare pump or a complete motor-pump assembly for delivery to Muscat, Sohar, Duqm or Salalah.

Operating Principle of the KRACHT DT

Like every external gear pump, the KRACHT DT moves liquid in the spaces between the teeth of two meshing gears, carrying it from the suction port around the housing wall to the discharge port. The challenge addressed by DuroTec is that standard gear pumps rely on the pumped fluid to lubricate their bearings and gear flanks. KRACHT notes that the limit of conventional gear pumps is reached when the medium lacks the lubricity needed for proper function while a high working pressure is required at the same time. Typical problem fluids are sodium silicate, and isocyanates and polyols containing hard fillers as used in polyurethane technology, which can also crystallise when exposed to air or humidity and make the lubrication problem worse.

To overcome this, the KRACHT DT combines a hard-material coated steel gear set, hardened and nitrided steel sliding plates and silicon carbide bearings. As general engineering background, silicon carbide is among the hardest engineering ceramics and keeps its shape and surface finish under abrasive attack, while hard coatings on the gear teeth resist the micro-cutting caused by filler particles. KRACHT also takes heat treatment and surface geometry into account when applying the coating, so that the gear set remains rigid and wear-resistant in service.

Engineering Design of the KRACHT DT

The housing and flange cover of the KRACHT DT are cast in grey iron EN-GJL-300. DT 3 pumps use a four-hole flange to DIN ISO 7653, while DT 5 pumps use an SAE-C two-hole flange, and both have a cylindrical 32 mm shaft. Inlet ports are SAE 1½, 2 or 2½ inch flanges and outlet ports SAE 1¼ or 2 inch flanges, depending on displacement. The shaft is sealed by a mechanical seal with a quench chamber and quench tank, which keeps moisture away from the seal faces and prevents crystallising media such as isocyanate from building up at the seal. The pumps are installed horizontally, accept inlet pressures up to 20 bar and operate at ambient temperatures from -20 to 60 °C.

KRACHT also supplies the pump as a motor-pump assembly with bell housing and coupling, using 4-, 6- or 8-pole motors from frame size 132 S up to 225 M for DT 3 and from 160 M up to 250 M for DT 5. Pump weights range from about 25 kg for the DT 3/63 to about 57 kg for the DT 5/250.

Key Features of the KRACHT DT

The DuroTec concept gives the KRACHT DT the following advantages over a standard gear pump on difficult fluids:

• Designed for abrasive and poorly lubricating fluids at the same time as high working pressure.
• Working pressure up to 100 bar and inlet pressure up to 20 bar.
• Six displacements of 63, 100, 125, 150, 200 and 250 cm³/rev in the DT 3 and DT 5 frames.
• Hard-material coated steel gearing, hardened and nitrided sliding plates and silicon carbide bearing bushes.
• Accepts solid particles below 50 µm with a Vickers hardness below 2 500.
• Mechanical seal with quench chamber and tank for crystallising media such as isocyanates.
• Viscosity range from 500 to 50 000 mm²/s, with higher viscosities on request, and media temperatures up to 150 °C.
• Available as a bare pump or as a complete motor-pump assembly with bell housing and coupling.

Industrial Applications

KRACHT identifies multi-component systems in polyurethane technology as the main field for the KRACHT DT, particularly wherever polyols with hard fillers must be handled and standard gear pumps do not achieve a satisfactory service life. Other suitable media include sodium silicate and similar silicate solutions. In Oman and the GCC these duties arise in insulation panel and pipe-in-pipe foaming lines, spray foam and casting systems, sandwich panel plants supplying the construction sector, and chemical blending units in the Sohar and Salalah free zones.

Seven Star LLC supplies the KRACHT DT together with motors, couplings and spares and can combine it with accurate flow measurement such as the VCA aluminium gear flow meter for ratio control. Where the fluid is clean and lubricating, a conventional pump such as the KF Series modular gear pump or the KP Series internal gear pump may be the more economical choice, and our engineers will advise accordingly.

Technical Specifications

Key data from the manufacturer datasheet:

How to Order

Send Seven Star LLC your fluid description, filler content, viscosity, flow, discharge pressure and temperature to receive a formal quotation for the KRACHT DT. Our team in Muscat will confirm the displacement and drive, advise on a motor-pump assembly and arrange delivery to your plant in Oman or elsewhere in the GCC. The manufacturer datasheet with dimensions and motor-pump assembly data can be downloaded from this page.