Relay Pumping Operations

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Relay Pumping Operations

• Sugar Land Fire Department
• Driver/Operator-Pumper Academy
• Spring 2003

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Relay Pumping Operations
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Hoses Appliances

• Medium diameter Hose (MDH)
• Large diameter Hose (LDH)
• Pressure Relief Valves
• Intake pressure relief valves

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Hoses Appliances

• Bleeder valves on the intake pressure relief
  valve
• In-line relay valves
• Discharge manifold

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Relay Considerations

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

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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.

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Restrictions

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

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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

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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

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Relay Pumping Operations
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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.

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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.

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Modifications

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

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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

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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

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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.

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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.

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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.

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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.

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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.

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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.