Relay Pumping Operations Sugar Land Fire Department Driver/Operator-Pumper Academy Spring 2003

Relay Pumping Operations

Hoses & Appliances –Medium diameter Hose (MDH) –Large diameter Hose (LDH) –Pressure Relief Valves –Intake pressure relief valves

Hoses & Appliances –Bleeder valves on the intake pressure relief valve –In-line relay valves –Discharge manifold

Relay Considerations Amount of water required at the emergency scene Distance from emergency scene to water source

Mo Water –Increase the size of the hose –Increase the number of hoselines –Increase the pump discharge pressure of relay pumpers. –Increase the number of pumpers in the relay.

Restrictions –Increasing the size of the hose or number of hoselines –Increasing the pump discharge pressure –Increasing the number of pumpers in the relay

Relay Considerations –Increasing the size of the hose or number of hoselines –Increasing the pump discharge pressure –Increasing the number of pumpers in the relay

Relay Considerations –Increasing the size of the hose or number of hoselines –Increasing the pump discharge pressure –Increasing the number of pumpers in the relay

Relay Pumping Operations

Constant Pressure Relay Establishes the maximum flow available from a particular relay setup by using a constant pressure in the system Depends on a consistent flow being provided on the fireground Attack pumper maintains constant flow rate by using an open discharge or securing a waste line to handle the excess beyond the flow being used in the attack lines.

Advantages Speeds relay activation. Each driver/operator knows exactly how much hose to lay out and how to pump it without awaiting orders. Requires no complicated calculations on the emergency scene. Reduces radio traffic and confusion between pump operators. Allows attack pumper driver/operator to govern fire lines with greater ease. Simplifies pressure regulation as driver/operator in the relay only have to guide and adjust pressure to one constant figure.

Modifications –Variations in relay pumper spacing –Severe elevation differences between source and fire –Increases in needed fire flow –Large diameter hose

Putting a Relay in Operation A relay pumping operation always begins with the source pumper Generally, the largest capacity pumper is used at the water source The maximum capacity of the relay is determined by the capacity of the smallest pump and the smallest hoseline used within the relay. Failure to keep water moving through the pump could result in a loss of prime, thus delaying the operation

Putting a Relay in Operation The relay pumper should be waiting for water with the dump line or discharge open and the pump out of gear. If the waiting period for receiving water from the source pumper or another relay pumper is only a few minutes, the pump on the in-line relay pumper may be engaged before receiving the water. Sometimes the relay can be started, or the hoselines filled with water from the apparatus water tank. It is most desirable to maintain an intake pressure of 20 to 30 psi

Putting a Relay in Operation If the relay pumper is receiving an intake pressure greater than 50 psi, the valve to the dump line on the relay pumper must be adjusted to limit residual pressure to the 50 psi maximum. Because pump discharge pressure increases as the throttle setting on the relay pumper is increased, the valve to the dump line must be gated down to maintain the 50 psi residual pressure and prevent cavitation.

Putting a Relay in Operation Once the pump discharge pressure on the relay pumper has reached the desired pressure with the water being discharged, this portion of the relay has been established and no further adjustments should be necessary. When water reaches the attack pumper, the operator should bleed air from the line by opening the bleeder valve on the intake being used. When one of the attack lines is shut down, an alert attack pumper operator can open the dump line to allow water to flow, thus preventing a dangerous pressure buildup in the relay.

Few Facts… Once the relay is in operation and water is moving, all pump operators set their automatic pressure control devices to an appropriate level. If the intake relief valve is readily adjustable, it should be set to discharge at 10 psi above the static pressure of the water system it is attached to or above discharge pressure of the previous pumper in the relay. Small variations in pressure are not significant and as long as the intake relay pumper pressure does not drop below 10 psi or increase above 100 psi, no attempt should be made to maintain exact pressures.

Few Facts… If the attack pumper is equipped with a readily adjustable intake relief valve, it should be set between 50 and 75 psi to establish a stable operating condition. At no time should the relief valve be set for a higher amount than the safe working pressure of the hose. The auxiliary cooler can be adjusted as necessary to maintain the proper engine operating temperature over the extended periods of time that are often necessary during a relay.

Few Facts… Radios must be used cautiously: too much radio usage in establishing a relay can hamper fire fighting activities and efforts to establish water supply If additional radio frequencies are available, one channel should be dedicated to coordination of the water supply operation. When pumpers are within sight of each other, hand signals can be used or messengers can be sent on foot.

Few Facts… Once the water is moving, a minimum of communication should be required. Portable radios may be used if relay units are equipped with incompatible radios. Radio-equipped ambulances or utility units that are not otherwise occupied can be used to establish communications throughout the relay. Relay operations should be shut down from the fire scene first. If the source pumper is shut down while the rest of the relay is still operating, cavitation can result.