Rotary Pump Troubleshooting

The next series of blog posts will focus on what operators can do to reduce the time it takes to develop troubleshooting skills.  These comments are related to their rotary positive displacement pump technology.

Trouble shooting rotary pumps in systems is a skills that takes some time to develop.  We are often contacted about a 'pump problem' without users providing sufficient consideration to changing system dynamics.   In almost any pumping system, the pump is the most vulnerable component.  However, engineers and operators should be aware that systems dynamics are more frequently the cause of the problem.  'Pump problems' are usually caused by a system component malfunction, inadequate control of the liquid or a change in operating requirements, which burdens the system or pump with conditions in which it cannot perform.   Today's post will focus on flow loss or low flow conditions.  In future posts will talk about loss of suction and low discharge pressure.

In a positive displacement pump, flow loss is normally accompanied by a reduction in system pressure.  Either the pump is delivering less flow, or the system is bypassing it - such as through a defective or worn relief valve or pressure control valve.  The pump could be worn and internally bypassing (slipping) flow so that less flow reaches the system.  In that event, pump repair will be necessary.  A partial inspection of the pump internals will usually provide a good indication of wear condition.  Also, if the operating viscosity of the liquid has been reduced (new liquid or higher operating temperature), a rotary pump's rated flow will be slightly reduced and even more so for higher pressure operation.