Difficult to convey

Jon Lawson

When it comes to conveying difficult substances cleanly, a positive displacement pump can be used to empty tankers without interruption

Emptying tankers can cause problems for many pumping processes. The difficulties involved are air pockets that cannot be avoided when attaching a pipe.

The gas bubbles initially lead to reduced performance and irregular running until the product flow stalls as the gas inflow further increases.

After repeated breakdowns, a major detergent manufacturer converted its conventional pump for surfactant supply to a T.Proc rotary lobe pump from Netzsch Pumps & Systems.

The product flow used to repeatedly stall during the emptying of the surfactant with the centrifugal pump that was used before.

The pump was intended to convey the basic material of the detergent from a road tanker to the company’s production facility. However, problems arose as early as the suction phase: air that got into the pipe during connection of the tank formed air pockets in the medium. This led to slumps in performance and also to frequent stalling of the product flow. The pump kept on breaking down and had to be recommissioned, many pumping processes.

To put an end to this situation, in October 2013 avoided when attaching a pipe. The the company changed to a positive displacement pump gas bubbles initially lead to reduced that promised higher reliability.

The T.Proc is part of the Tornado T2 series, which is designed for maximum robustness, long service life and full service in place. It handles substances from 1 mPas to 50,000 mPas and air pockets in the medium pose no problems whatsoever in terms of conveying performance due to the conveying chambers that are used to transport the medium. This means the tank is also emptied leaving virtually no residue.

The surfactant being conveyed was diluted with a solvent in this application. Most plastics are not resistant to solvents and elastomer swells in contact with them and impairs pump performance. For this reason, the stainless steel, all-metal model of the T.Proc was installed.

As the pump operates in an explosion protection area 1, it must not ever run dry. For this reason, both pressure and dry running protection were integrated so that the pump automatically switches off in the event of a fault. The double mechanical seal is always provided with the necessary fluid via the attached quench supply. This allows the safety of the pump to be increased.

In addition, a heated pump cover was fitted to improve the fluidity of the medium as the surfactants are conveyed at around 60°C. It was possible to lower the required heating temperature somewhat in comparison to the previous centrifugal pump, because viscosity is no longer critical with the positive displacement pump. This means the customer also makes a considerable saving in terms of energy and operating costs.

The pump has now been running trouble-free since October 2013 and conveying 15 to 20m3 of surfactant per hour at a pressure of 4 bar. Meanwhile, there is no longer any need for supervisory staff during the emptying of the tanker and drivers can easily start the process themselves and complete it within the scheduled timeframe. Additional costs for waiting times, production downtimes and the staff effort involved in recommissioning the centrifugal pump are a thing of the past.  

For more information, visit www.engineerlive.com/process 

 Erwin Weber is with Netzsch.  

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