DOSING/RETURN VALVE (DRV)
With the option Dosing return valve (DRV) it is possible to practice and test dosing rate without consuming the concentrate. This feature gives substantial savings over many years with no cost for cleaning or destruction of the solution after the test. A Pressure relief valve (PRV) is included to avoid the risk for overpressure if the return line is closed when DRV is open. The respective water and concentrate flows should be measured with two independent flow meters to calculate accurate dosing rate.
THE ACCURATE WAY OF VERIFYING DOSING RATE
Verifying dosing rate equals to verifying the correct volumetric function of both the water motor and dosing pump with two independent flow meters and calculate to below formula, In accordance with EN 13565-1, NFPA 11, and FM 5130:
Concentrate Flow ________________________________ x 100 = Dosing rate %
Water Flow + Concentrate Flow
On request we supply the complete hardware, incl two inductive flow meters, for a Dosing rate test system according to EN 13565-1, NFPA 11, FM 5130 described above.
REVOLUTION COUNTER METHOD - THE LIMITS
The revolution counter method which is also presented on the market assumes the correct working of the water motor, this means it gives only an estimate of water flow and therefore it cannot be used to correctly verify the dosing rate, as the dosing rate is directly dependent on the performance of the water motor.
The revolution counter method is not an approved method to verify dosing rate as described by EN 13565-1, NFPA 11, FM 5130. Quote from FM Approval guide: ”...may be used to provide a general estimate of the extinguish water flow..."
REVOLUTION COUNTING WITH HANDHELD TACHOMETER
The estimated water flow can be measured with handheld tachometer (contact or non-contact) to ensure that the unit is not over-speeding, i.e working within the upper rpm = flow limit specified in the Data sheet of each FIREMIKS model.
FLOW CHART WITH OPTION DOSING RETURN VALVE (DRV)
FLOW DIRECTION ON INSTALLATION
Standard flow direction is from left to right seen from pump side. Reversed water flow direction (right to left) or Vertical flow direction (upwards or downwards) is optional if specified when ordered.