The Shortcomings Of Using Pump Suction Specific Speed Alone To Avoid Suction Recirculation Problems

Abstract

There is a mistaken belief in the pump industry (fueled by many publications) that the best way to avoid suction recirculation problems is to design and/or apply only pumps having low suction specific speed values (below 8,500 to 11,000). Attempts are made to correct this overly simplified treatment of a complex problem, which if used alone, can still lead to field problems, or, unnecessary and expensive over design. A more accurate, but still simple, method is presented as an alternative for identifying pumps which may be susceptible to suction recirculation problems (damage) during reduced capacity operation. Pump type, impeller inlet tip speed, impeller vane overlap and fluid specific gravity have been added to pump suction specific speed to greatly improve the prediction process.