Pump & Piping
Many pumps are installed with inappropriate piping arrangements, resulting in premature pump failures as we covered in our latest eBook, 36 Ways to Kill Your Pump. If you were installing a pump in a new system, where would you turn for guidelines on proper pump piping arrangements?
Knowledge and resources are extremely limited on this topic, except what you may find in the Installation, Operation and Maintenance (IOM) manual (which is minimal). By following 5 simple rules, you can avoid premature pump failure and related pump piping pitfalls.
1. KEEP SUCTION PIPING AS SHORT AS POSSIBLE
Include a straight run pipe length equal to 5 to 10 times the pipe diameter between the pump inlet and any obstruction in the suction line. Note: Obstructions include valves, elbows, "tees", and etc.
Keeping the suction piping short ensures that inlet pressure drop is as low as possible. The straight run pipe gives you a uniform velocity across the pipe diameter at pump inlet. Both are important to achieving optimal suction.
2. PIPE DIAMETER ON SUCTION SIDE SHOULD BE EQUAL OR ONE SIZE LARGER THAN PUMP INLET
Suction piping velocities should be limited to 7 to 8 feet per second or less.
3. ELIMINATE ELBOWS MOUNTED ON OR CLOSE TO THE INLET NOZZLE OF THE PUMP
Include 5 to 10 pipe diameters of straight run pipe between the pump inlet and elbow. This helps to eliminate "side loading" of the pump impeller and creates uniform pump axial bearing loading.
4. ELIMINATE POTENTIAL FOR AIR ENTRAPMENT IN THE SUCTION PIPING
Maintain adequate levels in supply tanks to eliminate vortices from forming and air entrapment.
Avoid high pockets in suction piping, which can trap air
Keep all pipe and fitting connections tight in suction vacuum conditions to prevent air from getting into the pump.
5. ENSURE THE PIPING ARRANGEMENT DOES NOT CAUSE STRAIN ON THE PUMP CASING
Pumps should never support the suction or discharge piping. Any stress on the pump casing by the piping system greatly reduces pump life and performance.
Keep in mind that increasing the performance of the pump will help to make up for piping mistakes made on the discharge side of a pump. Problems on the suction side, however, can be the source of repetitive failures, which could cause problems for years to come if not addressed appropriately.