Lewa: Safe pumping of sour crude oil

SauerölpumpeCritical applications of conveying mixtures of acidic hydrocarbon/water to the washing system are a challenge for any pump manufacturer. This was also the case in one recent project Lewa handled in the Emirate of Abu Dhabi. Lewa have designed and supplied 16 pumps to a major construction company in Abu Dhabi specifically designed to handle this critical application. Two processes required to pump

  • liquid hydrocarbons from the flare knock-out drum or the blow-down drum respectively and
  • convey the acidic hydrocarbon/water mixture back into the oil line to the washing system

Since the differences in these two processes are only minor, it was possible to supply 16 mechanically identical pumps of the Ecoflow series, driven by 55 kW electric motors.

To ensure high reliability in operating the system, despite the project’s difficult conditions, the customer defined a series of strict selection criteria. The critical fluid characteristics that had been taken into consideration while designing the pumps are: high content of sulfur of about five percent, high chlorine content, high temperatures and highly humid conditions under which even stainless steel corrodes. Since the medium conveyed is very volatile and extremely hazardous, Lewa selected hermetically tight diaphragm pump heads made of superduplex stainless steel. The diaphragm itself, due to the eroding effect of the particles in the corrosive liquid, is made of wear-resistant PTFE.

Special suction valves ensure a low NPSHr value
While designing the pumps, it was also necessary to take into consideration that the mixing ratio of water to hydrocarbons in the liquid phase varies significantly and that the pressure can vary between 20 and 45 bar. The pumps have to handle a flow rate between 0.5 and about 15 m³/h of the acidic mixture. To ensure that the pumps work reliably despite the changing flow rate, the net positive suction head of the system (NPSHa) also had to be kept higher than that required at the pump suction (NPSHr). So special suction valves are integrated into the pump to keep the suction pressure requirements low and satisfy all process conditions.

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