Reactor Charge

Reactor Feed Pump

Roth Pump Co. recently supplied a a reactor charge pump for a Midwestern polymer chemicals plant. Many years ago the service was handled with a Roth regenerative turbine pump. In recent times the plant had used a gear pump for the job. However, the gear pump did not last long in service. The fluid was a water-based solution.

When a call was received for a new Roth pump, the plant was making do with an air-diaphragm pump. Hose nuisance and operating costs were a problem. Since the reactor typically operated at 10-15 psig, it seemed that this was not much of a turbine pump application.

However, on a visit to the plant, it was learned that:

The reactor pressure varied from vacuum to 15 psig during the time that the pump was needed to add about 100 gallons of solution to the reactor. There may be an occasional “worst case” of 30 psig in reactor.
There were multiple reactors. Some were close to the charge pump and some were a distance away from the pump. It was necessary to look at the “worst case” condition, which was a distance of 88 ft. plus fittings. Flow was through a 1 inch line. At 64 feet, the friction head was significant.
There were 2 check valves in the line - one at 25 psi, and one at 5 psi.
Thus the total head for the application was 168 feet.

With a desire to have 20 to 25 gal/min flow rate, this was now a suitable service for a turbine pump.

With the variation in reactor pressures, and the variation in friction head, a centrifugal pump would likely need a control valve to modulate the flow, so that the flow rate was similar in all circumstances. The Roth turbine pump is able to pump a flow rate suitable for the service without the use of a control valve.

What can be learned?

There may be more to an application than initially meets the eye.
The ability to pump at a relatively unvarying flow rate against a varying head can give the regenerative turbine pump a major advantage over a centrifugal pump.