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Foam pump systems NFPA 20

Question asked by dmdennym on Jul 5, 2017

Foam concentrate pumps, their controls, and general piping arrangements now follow the requirements of Nfpa 20 and I have related questions:

1. In main/reserve, dual pump, installations, is an individual control valve required for each pump on the discharge side of the pump check valve even if there is a shutoff valve on the common discharge to the ratio controller?

2. Sensing lines occur in both fire water pump systems and foam pump systems. Water pump systems utilize sensing lines for requirements of pressure drop starting. Foam pumps, with listed and Nfpa recognized controls, can be started much the same way. Sensing lines are also necessary for a balanced pressure pump system for sensing the incoming water pressure to the ratio controller and sensing that water pressure signal to the balancing valve where it adjusts the foam liquid pressure from a like sensing line on the foam pump discharge.  Nfpa 20 dictates sensing lines to be of metallic construction and no less than 1/2" size. Should this requirement be applicable to balance pressure sensing lines on foam pump applications? Should a manufacturer be allowed to use what they consider "equivalency" under Nfpa #11, section 1.5, if it doesn't meet all the criteria established in that paragraph?

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