Ch. 12 Relay Pumping Operations

Question 1

Relay Apparatus and Equipment

Answer 1

• Any type of apparatus equipped with adequate size pump can be used
• Water supply pumper (source pumper)- Takes water from hydrant or source and pumps to next apparatus
  -Should be apparatus with largest pumping capacity
• Relay pumper- Receives water from pumper or another relay pumper, raises the pressure, then supplies water to next apparatus
  -Can be smaller capacity
• Fire attack pumper- Pumping apparatus located at the fire
  -Pumper supplying attack lines
• Hose Tenders- Assist in relay pumping operation
  -May be equipped with fire pump
  -Carry mile or more of large diameter hose

Question 2

Relay Pumping Operational Considerations

Answer 2

• 2 requirements to consider:
  -The amount of water required at an incident
  -Distance between the incident scene and water source
• To increase the amount of flow one of three things must happen
  -Diameter of supply hose or number of hose lines must increase
  -Pump discharge pressure of pumpers must increase
  -More pumpers added to overcome friction loss
• Longer the hose lay, the more friction loss will be encountered
• Centrifugal pumps are rated to pump their max volume at 150 psi
• Elevation pressure is not affected by amount of water being moved, only by the topography
• Discharge pressures must not exceed pressure at which hose or appliances have been service tested
• Place additional pumpers in system to operate at lower pressures and maximize flows
• When relaying long distances hose lays between pumpers should be equal

Question 3

Putting a Relay into Operation

Answer 3

• Begins with largest capacity pumper working from water source
• Source pumper may need to developed a higher pump discharge pressure
• Overall capacity of system is determined by the smallest pump and smallest diameter of hose is used in relay
• Relay pumpers maintain an intake pressure of 20-30 psi
• As water reaches each pumper bleed line to release air
• Pressure governors- Serve in safety of a relay operation pressure increases when changes in flow occurs
  -Should be set in pressure mode

Question 4

Operating the Relay

Answer 4

• Once water is flowing at desired pressure attack pumper should set pressure governor
  -attack pumper - pressure mode
  -relay pumper - RPM mode
• Relay pumpers equipped with adjustable intake relief valve they should be set 10 psi above static pressure of water system attached or 10 psi above discharge pressure of previous pumper in relay
• Attack pumpers should be set between 50 -70 psi
• Line shut down or discharge changes friction loss in supply line decreases and residual pressure increases
• Attack pumper should expect small variations in pressure
  -DO NOT attempt to correct as long as intake pressure doesn’t drop below 20 psi

Question 5

Shutting Down the Relay

Answer 5

-Begin with attack pumper (Fire scene)
-Slowly decrease the throttle
-Open dump line valve
-Disengage the pump

Question 6

Open Relay Method

Answer 6

-Provide an alternate water supply system
-Consist of deploying portable folding drop tanks at each intake for pumpers
-Requires no adapters or other appliances to connect to intake
-Place the hard sleeve and supply hoses at opposite ends
-Eliminates pressure surges when operating from portable folding drop tanks
-This helps to avoid turbulence
-Task force to initiate operation are independent of companies operating at scene

Question 7

Closed Relay Method

Answer 7

-Variety of hose diameters
-When using medium size hose 2 ½ or 3-inch multiple hose lines are laid
-Large diameter hose 4, 5-inch requires only one supply line

Question 8

Pressure Relief Valves

Answer 8

• Reduce damage to pump
• Incoming pressure exceeds preset level valve opens and dumps excess pressure/water
• Two basic types of intake pressure relief valve
  -Supplied by pump, is an integral part of pump intake manifold
  -Add-on device that is screwed onto the pump intake connection
• Many of screw-on intake relief valves are also equipped with gate valve that allows water supply to the pump to be shut off
• Bleeder Valve- Allows air to bleed off as the incoming supply hose is charged
• Inline relay valve
  -Placed along length of supply hose
  -Pumper can connect to valve to boost pressure
  -Later pumpers can tie in and boost pressure without interrupting water supply
• Discharge manifold may be used to break down LDH into two or more hose lines that may then be connected to different pumpers