>From NFPA 20, 1999 2-9.3 Suction Size. The size of the suction pipe for a single pump or of the suction header pipe for multiple pumps (operating together) shall be such that, with all pumps operating at 150 percent of rated capacity, the gauge pressure at the pump suction flanges shall be 0 psi (0 bar) or higher. The suction pipe shall be sized such that, with the pump(s) operating at 150 percent of rated capacity, the velocity in that portion of the suction pipe located within 10 pipe diameters upstream of the pump suction flange does not exceed 15 ft/sec (4.57 m/sec). The size of that portion of the suction pipe located within 10 pipe diameters upstream of the pump suction flange shall be not less than that specified in Table 2-20.
11-2.6.2 Flow Tests. 11-2.6.2.1* The minimum, rated, and peak loads of the fire pump shall be determined by controlling the quantity of water discharged through approved test devices. Exception: If available suction supplies do not permit the flowing of 150 percent of rated pump capacity, the fire pump shall be operated at maximum allowable discharge to determine its acceptance. This reduced capacity shall not constitute an unacceptable test. ---------------------------------------------------------------------------- ------------------------------------------ 2-9.3 requires suction size to be such that suction pressure is minimum 0 psi at 150% flow. Then 11-2.6.2.1 seems to permit the usage of a pump at its maximum allowable discharge if suction supplies are not adequate. Aren't these two contradictory? Or am I missing something? What I have is a 100 gpm fire pump to supply a class 2 standpipe system (which requires 100 gpm flow). The existing underground supply is 2". The suction supply is fine for 100% of the reated capacity. But at 150% it will cause cavitation. Can I use this pump as the requirement is only 100 gpm? The owner wants a diesel fire pump, but the smallest listed diesel I have found is 250 gpm. Anyone has come across one smaller? Also, extending the previous question, can the 250 gpm pump be used if the required flow is 100 gpm (at which the suction is adequate), even though inadequate for higher flows? Tony _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum
