Consider a typical ANSI-dimensioned 1x1.5-6 pump, as discussed in the P&S August article. The performance curve showed the BEP flow at around 100 gpm. The ANSI designation 1x1.5 means that the discharge flange is 1 in and suction 1.5 in. Why and how do manufacturers select such dimensions for a particular flow rating? Why did they not select and base their performance coverage charts on a 3x4-8 size for the 100 gpm?
Proper pipe (and the pump flange to match) sizing should begin with the approximation rule on suction and discharge velocity limits. These are empirical (and suction sizing differs from discharge). We are challenging you to figure out what these limits are exactly, or what a rule of thumb should be. Applying these rules, you can determine if a selected pump size will work for the intended flow.
After determining the limits, determine if you could hook up a supply tank to the 1.5 in pump suction flange of this 1.5x1-6 pump to handle 100 gpm. Similarly, is its 1 in flange sized well for 100 gpm?
The person with the best answer receives a ticket to an upcoming Pump School.
Pumps & Systems, November 2009