Relay Pumping Operations

TOPIC: RELAY PUMPING OPERATIONS TIME REQUIRED: ONE HOUR MATERIALS: APPROPRIATE AUDIO VISUAL SUPPORT REFERENCES: PUMPING APPARATUS DRIVER/OPERATOR HANDBOOK, FIRST EDITION, IFSTA PREPARATION: MOTIVATION: OBJECTIVE (SPO): 1-1


      c. Devices preset to allow set amount of pressure into fire pump

      d. If incoming pressure exceeds preset level; valve activates and dumps excess pressure/water until

          water entering pump at preset level

      e. Valves set within 10 psi of static pressure of water system supplying pumper or 10 psi above

         discharge pressure of previous pumper in relay

     f. Most screw-on intake pressure relief valves equipped with manual shut-off valve

     g. Bleeder valves on intake pressure relief valve allow air to be bled off as incoming supply hose

       charged

    h. Particularly important when using devices in conjunction with LDH

    i. Large amount of air pushed through hose until solid column of water reaches valve

   j. Bleeder valves located directly in intake piping to pump itself.

I. Relays dependent upon later-arriving companies set up initial relay of lesser volume and greater spacing with in-line relay valves in relay line for incoming pumpers

J. Valves allow late-arriving pumpers to hook up after relay operating and boost pressure (and corresponding volume) without interrupting operations

K. If LDH relay pumping operation intended to support more than one attack pumper, discharge manifold used to break down LDH into two or more hoselines then connected to attack pumpers

 

II. RELAY PUMPING OPERATIONAL CONSIDERATIONS (EO 1-2)

A. Relay operation based on two things

  1. Amount of water required at emergency scene

  2. Distance from emergency scene to water source

B. Relay must supply total water necessary to complete fire fighting operation

C. Relay used to supplement inadequate municipal water supply system

D. Amount of water needed to flow has major impact on design of relay

E. Longer relay distance, more hose necessary

F. More hose equates to more friction loss

G. Desirable to increase amount of flow through relay, one of three things necessary

  1. Increase size of hose or number of hoselines used in relay

  2. Increase pump discharge pressure of pumpers operating in relay

  3. Increase number of pumpers in relay

H. Generally impractical to shut down existing relay to replace hose being used with larger hose

I. Possible to have engine or hose tenders not already committed to pumping in relay to lay additional hoseline between relay pumpers

J. Each pumper may have additional hoseline attached to pump and begin flowing hose when all pumpers ready

K. Possible to have pumpers increase pump discharge pressure, not necessarily mean that volume of water through relay increased

L. Pumpers rated to pump maximum volume capacity at net pump discharge pressure of 150 psi

M. Depending on length of hose lay and volume of water being flowed, eventually get to point where increasing pressure will not increase volume

N. When considering increasing pressure, limited by pressure to which fire hose annually tested

  1. At no time should discharge pressures exceed maximum operating pressure for hose being used

  2. Hose pumped at pressures do not exceed 90 percent of annual service test pressure

O. Elevation pressure factor in relay pumping operations

  1. If relay operation pumping uphill, pressure loss on system greater than caused simply by friction

      loss

  2. Reverse true if operation going downhill

  3. Elevation pressure not affected by amount of water moved, only by topography

P. Increasing flow in relay accomplished by placing additional pumpers in relay

  1. By shortening length of hose each pumper has to supply, maximum pressures and flows maintained

      within hose assembly

  2. If in-line relay valves not placed in hose lay from outset, necessary to shut down relay when

      additional pumper(s) added

Q. In situations where low flow rates required and LDH available, required spacing between pumpers so great that exceeds amount of hose carried on each pumper

R. In cases may be necessary to call pumpers solely to lay hose but not actually participate in pumping process

 

III. TYPES OF RELAY PUMPING OPERATIONS (EO 1-3)