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Double-Acting Reciprocating Pumps

KRYTEM VHV-Type Pumps featuring forced push-action cylinder filling were designed to pump cryogenic media in circumstances where single-acting low-temperature pumps (such as pumps of the TL-type or SA-type) are ill-suited for the sort of tank connection available. This particularly relates to the net positive suction head (NPSH) value available at the level of the piston inside the pump when the pump is connected to a tank mounted horizontally or just above the ground, but also to the delivery of liquids having a temperature above boiling point due to heat absorption from the outside.

VHVX 50 on test bench

The process fluid enters from below and circulates in the pump head due to natural convection and the movement of the piston. During the return stroke of the piston rod, a larger amount of fluid is trapped by the rear suction piston. As the piston moves toward bottom dead centre, this amount of liquid is forced, free of gas, through the suction valve integrated in the piston rod and into the pressure cylinder.

An integrated relief valve prevents over-compression inside the pressure cylinder during the process. The medium is discharged via a pressure valve located centrally at the front. The frictional heat caused by the oscillation of the piston is removed from the pump head by natural convection via the gas return feed fitted to the top. The robust, wear-resistant design of the pressure-valve results in low maintenance costs and superior operating reliability.

VHV pumps can be used for the bottling of liquefied gases and as process pumps. Standard VHV-Pumps are capable of achieving ultimate pressures of up to 420 bar. Intended to be used for pumping media at temperatures as low as -196°C, they are equipped with a very effective vacuum-insulation. VHV-Pumps feature a 60mm stroke Type DF belt-driven eccentric drive. A twin-headed or triple-headed pump configuration makes it possible to achieve high discharge rates even at high ultimate pressures.

VHV pumps are available with speed controllers, and with explosion-protection for applications involving flammable or explosive media. Together with all relevant accessories, the pumps are mounted on welded frames made from galvanised steel sections.

Design features

  • Forced filling of the pressure cylinder by a suction piston, thus facilitating the delivery of boiling liquid or delivery at NPSH = 0;
  • the pump head is isolated from the drive to prevent physical contact between the discharge medium and lubricants;
  • a shear ring coupling between pump head and drive shields the pump against unacceptable mechanical stress;
  • heated piston rod seals allow shutdown and restart without pressure relief or suction side warm-up;
  • a PTFE bellow protects the piston rod against ice formation caused by moisture in the ambient air;
  • a temperature-controlled warning system is integrated in the pump head to protect against unacceptable spreading of cold due to leaks;
  • flow monitoring via a temperature sensor inside the pressure line;
  • a pulsation damper reduces vibration caused by pressure pulsation;
  • complete control set including automatic start routine (automatic valve control on suction side), stuffing box temperature control and dry-running protection.