When this is not possible, adequate vent lines must be installed to allow manual or automatic removal of air or gas. Eight pipe diameters of straight piping before the pump are recommended after a short radius elbow; three pipe diameters are recommended after a long radius elbow. Placing an elbow immediately in front of a pump should be avoided, if possible.
If larger piping is used compared to the pump’s suction connection size, then the suction valves should be of the larger size. A suction side valve must never be used to control system flow. Suction isolation valves must be fully open during pump operation. If a valve must be throttled to control system flow, it should always be accomplished with a discharge side valve.
A check valve should never be used on the suction side of a pump. Butterfly valves must never be used when pumping liquids containing solids, as the solids can collect on the butterfly disk and block flow.
Mix Fluid & Solids in a Pit
Mixing of pits with water and floating debris (for example, bark or plastic debris in pits) has proven to be effective at keeping the system functioning properly as the pit is pumped down.
Homogenizing the pit contents prior to pumping may be the difference between the system working or not. Mixing can be accomplished by building a recirculation nozzle into the pump or discharge piping and locating it below liquid level to avoid aeration.
Examine Different Pump Configurations
Some pumping applications call for self-priming chopper pumps. Some call for submersible or vertical wet-well chopper pumps. Some call for pedestal or horizontal chopper pumps.
Sometimes when a user has had trouble with one type of pump configuration, it may be time to consider a change to something that may work more reliably.
Make sure a chopper pump supplier can provide a full range of pump configuration options.
Compare Initial & Total Lifetime Costs
Power costs, history of wear and parts replacement, and the reliability of the chopper pump to do the pumping job without plugging or overloading the motor during cutting all contribute to the lifetime costs of ownership. The maintenance costs of unplugging pumps on a regular basis can be overwhelming. Get plenty of references and talk to more than one chopper pump company and their customers.
Look for a Technical Partner
Some chopper pump companies provide significant help in understanding the pitfalls of approaching your specific type of application. Look for the expertise inside the chopper pump company to help keep the user out of trouble.