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Relay Pump Operations: Who Says It's Just for the Long Lay?

Paul Shapiro

Flow Test #6

The final flow test involved the use of 300 feet of 4” LDH ATTACK HOSE with a maximum allowed operating pressure of 275 psi and an Akron HRV. The hydrant system used was strong in volume and pressure with a 100 psi static pressure. Three tests were done in this operation. The first test was a forward lay using the Akron HRV and supplied from hydrant pressure only. The receiving pumper throttled up until he ran out of water reaching a flow of 1029 GPM while leaving 80 psi hydrant residual pressure. There was plenty of water left.

The second part of the tests was the relay pump operation utilizing the Akron HRV with a single supply line from the valve to the pump and a single relay line between the pumpers. The flow was measured when the receiving pumper ran out of water delivering 1305 GPM. The hydrant still had water left as was noted by the 70 psi hydrant residual pressure.

For the final test we utilized the hydrant to the max by connecting a second 4” line from the hydrant directly to the large intake of the pumper and a second 4” discharge line from the hydrant pumper to the receiving pumper. The engines throttled up until the receiving pumper ran out of water and would you believe we moved 2371 GPM. There was a gain of 1066 GPM by adding a second line to the pumper at the hydrant. The hydrant residual pressure was at 50 psi indicating that there was still water available.