Custom diluent injection pumps

Paul Boughton

Thomas Böhme shares a case study that showcases a smart solution devised for a major energy transporter

With a goal of reaching the highest operational efficiencies at the storage facility, a customer was looking to install a pumping system that would take the heavy crude oil from the tanks and blend it with diluents to lower the viscosity of the crude oil to be pumped to the main pipeline for distribution. 

As the crude oil sits in storage tanks over a long period of time, lighter product settles to the top and the heavier product goes to the bottom. Crude oil is drawn off the bottom of the tanks first and this is where most amount of diluent injection is required. As the product changes in viscosity there is a constant need to adjust the amount of diluent being used. Netzsch approached the design of this pumping system with progressing cavity pumps to take care of operating issues associated with constantly changing viscosity.

Custom pump design 
A critical design issue was the extremely cold operating temperatures during the winter months. With ambient conditions of -30 to -40°C and diluent temperatures as cold as -22 to -25°C, Netzsch engineers needed to carefully consider the elastomer selection for this application. Because the company’s progressive cavity pumps would operate outdoors, it was determined to use a reduced wall stator with heat tracing to insure that a -5 to 0°C operating temperature was maintained within the elastomer. In addition, three resistance temperature detectors (RTD) were to be mounted in each pump to provide feedback data to the control system.

To compensate for the cold temperatures, Netzsch designed a rotor that is slightly oversized to keep the interference fit at sub-zero temperatures. This presented an additional hurdle at assembly time. The solution for assembling a stator on an oversize rotor was to pack the stators in ice in order to make assembly possible.
By using four custom-designed progressing cavity pumps piped to a common header, Netzsch was able to provide the customer with the level of diluent injection control that he was looking for. With the new system, the customer has the ability to run from one to all four pumps and with the use of VFDs, he will have complete control over the diluent injection. The large pump size also allows the customer to run the pumps slower for a greater life cycle – a critical maintenance advantage in the extremely cold operating environment.

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Thomas Böhme is with Netzsch in Germany

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