Krytem Pump Technology
Pump Head / Cold End
Low-boiling point liquids tend to form gas bubbles due to local evaporation caused by small differences in temperature and pressure. When conditions on the suction side are unfavourable, therefore, gas can enter the displacement chamber along with the liquid and reduce the degree of admission into the cylinder. This reduces also the effective discharge rate of the pump in comparison to geometric discharge volume. The collapse of the bubbles during the push stroke causes considerable noise and wear to the valves, piston and seals.The Krytem pump head design minimises heat absorption and pressure loss of the medium flowing into the cylinder. Heated or evaporated medium is fed out of the pump head without entering the displacement chamber.
A vacuum mantle effectively isolates the cold pump components from the warmth of the environment. The cylinder is surrounded by the discharge medium to conduct away heat generated inside the pump by friction. The movement of the piston displaces the medium in the direction of discharge through the pressure valve and circulates the surrounding fluid at the same time. Warmed medium can expand in the gas return feed and, in the case of a suitable tank installation, reach the tank under natural convection.
The piston rod seals consist of an active spring-loaded rod packing, which utilises the pressure of the gas-producing medium to increase its tightness. Heating the end of the packing on the side of the transmission makes it possible for the pump to remain primed even for long periods of non-operation without leaks occurring due to ice forming on the piston rod or seals. The bright-chrome plated piston rod reduces friction and increases the working life of rod packing seal. An elastic gaiter made from PTFE protects the exposed end of the piston rod against contamination and moisture from the atmosphere.
The mean pump head maintenance interval is 1000 to 2000 operating hrs depending on the actual load and operating conditions.
For oxygen sevice the medium wetted pump head components can be manufactured from monel 400.
Drive Units
Krytem pumps for high pressures and/or high discharge rates are driven by 45 mm stroke Type F or 60 mm stroke Type DF eccentric drive units via a V-belt or toothed-belt transmission and an electric motor. Pumps with 2 or 3 pump heads connected to coupled Type DF drive units are available for large discharge volumes. For smaller discharge volumes and/or lower operating pressures we provide eccentric drive units with integrated reduction gears and stroke that can be adjusted up to 30 mm.
The standard V-belt transmission unit damps the hydraulic shock and pulsation pulses due to its elasticity thus protecting the electrical drive unit and - if applicable - the electronic control devices at the same time.
With high operating pressures large forces must be transmitted by the eccentric drive unit. Effective lubrication is necessary to achieve a reasonable service life. The spatial separation between the pump head and the oil-proof drive housing, due to an open space and the gaiter seal on the end of the rod packing, also facilitates the safe use of efficient standard hydrocarbon-based lubricants when delivering oxygen or other oxidising media. If demanded oxygen-compatible lubricants can be applied.
A shear coupling (fracture ring) protects the transmission from unacceptable loading due to situations such as those caused by the maximum pressure being exceeded or the pump head being blocked mechanically by foreign objects or ice.
When using F or DF Type drives, the whole pump unit, including the motor, transmission, belt safety cover, eccentric drive, pump head and connection accessories is mounted on a weather-resistant galvanised steel frame.
