Oil flooded compressors and turbo expanders are widely used in oil field applications. Screw pumps are used for the lubrication of this rotating equipment.
The lubrication oil circulates in the compressor and expander, the pressure loss is low. System pressure of the lube oil can be up to 100 bar and pressure drop is only around 5 bar. The inlet pressure at the screw pump is only a bit lower than the outlet pressure. This high inlet pressure can cause a too high load to the bearing of the main spindle of the screw pump.
The screw pump is driven by an electrical motor which is connected to the shaft of the main spindle. The spindle shaft is lead through the pump casing. The shaft must be sealed to prevent leaking. The common sealing is a mechanical seal. All screw pump manufacturers balance the load on the suction and the pressure side of the pump to compensate axial load to spindles. There should be no force to move the spindles from the pressure to the suction side, because if there would be such a force, it must be taken from the pump casing. Each well designed pump is balanced.
In a high pressure applications for compressors and expanders this balance is difficult. The high inlet pressure and the bit lower outlet pressure cause a force to the spindles in direction to the mechanical seal and the bearing. To prevent the mechanical seal and the bearing, extensive designs of liquid channels and mechanical stabilizers are necessary.
The KRAL AG offers a pump with magnetic coupling for compressor and expander lubrication. The magnetic coupling is a complete different sealing technology than the mechanical seal. Because a pump with magnetic coupling has no mechanical sealing, the risk of damaging the seal is completely eliminated. In addition, the balancing of suction and pressure side is much easier.
As a result, the KRAL magnetic coupled pump is a highly recommended cost-efficient replacement for mechanical seal pumps, which need an expensive strengthening.
For more informatiuon, visit www.engineerlive.com/iog
Thomas Flauger is with KRAL AG is based in Lustenau, Austria. www.kral.at