KRAL - Three screw pump (L Series)

The KRAL L-series medium-pressure pump is a compact three-screw pump designed for pressures up to 63 bar and flow rates from 5 to 85 l/min. Manufacturer: KRAL, Austria. The working mechanism consists of one driving screw and two driven screws; the model designation corresponds to the flow rate in litres per minute at 1,450 rpm, so the L 55 delivers approximately 55 l/min.

How does the L series differ from the K and C series?

The three KRAL series cover three different ranges, and it is costly to confuse them.

K Series — these have high flow rates at pressures of up to 16 bar. The L series, on the other hand, has low flow rates of up to 85 l/min, but the pressure is four times higher. C Series It raises the pressure to 100 bar and provides a higher flow rate, but the dimensions and price are also different.

Rule of thumb: if you need a pressure of between 16 and 63 bar at a flow rate of several tens of litres per minute, this falls within the L range.

On the principle of operation of a screw pair — how a screw pair works.

Technical Specifications of the KRAL L Series

The data is taken from the manufacturer’s catalogue, edition 05/2011. The lower viscosity limit of 1.5 mm²/s in the catalogue is accompanied by a footnote — when operating near this limit, the value should be verified for the specific medium.

Five types of sealing — and what each one offers

The seal in the L series determines the maximum fluid temperature. The permissible pressure at the suction flange depends not so much on the type as on the version.

Pressure at the suction flange: 6 bar for face and radial seals, 20 bar for a balanced end-mounted pump. If the pump is situated beneath the tank or downstream of the booster, this figure determines the model.

Performing LFI, LFT, LVI and LVT

The series comprises four models: the LFI and LFT — flanged, for splicing into a pipeline; and the LVI and LVT — mounted on a support, for installation on a tank. The hydraulic system is the same across all four models; the choice depends on the layout of the installation.

Certificates and explosion protection

There are no certificates listed in the 05/2011 catalogue. According to the product series page on the manufacturer’s website: classification societies ABS, BV, CCS, DNV, GL, LRS, MRS, NK, RINA, KR; ATEX II 2 GD b/c explosion protection, Group II, Category 2. The specific set is confirmed upon ordering.

Current models — on the manufacturer’s website KRAL.

Where are L-series pumps used?

The industry catalogue does not list them. According to the relevant page on the manufacturer’s website, these include the maritime sector, the oil and gas industry, the energy sector, mechanical engineering and the chemical industry.

Typical applications include the delivery of clean lubricating fluids, greases and fuels in circuits where pressures higher than those achievable by the K series are required, but flow rates remain moderate.

Selection and service from Steiner Ukraine

The L series is selected with maintenance in mind: its compact design and minimal number of wearing parts are only effective when the size and seals are matched to the actual operating conditions, rather than being chosen with a margin of safety. We specify the discharge pressure, inlet back pressure, viscosity at operating temperature and the system configuration, and use these to determine the model and variant. Next — service and spare parts. Steiner Ukraine has been operating in the industrial equipment market since 2006.