Basic Hydraulics

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SOUTHERN AREA WILDLAND ENGINE ACADEMY

• Basic Hydraulics

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Objectives

• Discuss and describe how hydraulics affect pump
  operations under various conditions.
• Solve various hydraulics problems under simulated
  conditions. Note Students are allowed a 5 PSI
  confidence interval.

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• Dont Panic!

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Hydraulics

• How the pump operator calculates an adequate
  water supply to the nozzle at an effective
  pressure
• This session teaches one of several methods for
  calculating friction loss
• Not foolproof - some solutions may not work in
  real life - wont know until you try it!

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Engine Pressure

• Hydraulics problems solve for Engine Pressure
  (EP) - this is what you are looking for!
• Pressure indicated on the pressure gauge of a
  discharge orifice (PSI)
• The major controlling factor determining nozzle
  pressure and volume of discharge
• Changed by adjusting the pump throttle

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Engine Pressure Formula

• EP NP H FL (remember this!)
• EP Engine Pressure (PSI)
• NP Nozzle Pressure
• H Head Pressure
• Head - nozzle elevation is above pump
• - Head - nozzle elevation is below pump
• FL Friction loss per 100 feet of hose

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Information needed for calculations

• Total amount of hose in lay
• Size of hose
• Number of appliances
• Size of tips or GPM rating of nozzles
• Elevational difference between pump and nozzle
• Desired nozzle pressure

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Information needed for calculations

• The previous six items will be needed in all
  situations to solve for EP
• FL is always computed using 100 ft. lengths of
  hose

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Nozzle Pressure (NP)

• Solid stream (50 PSI)
• supplies large concentrations of water to a
  specific area and used where a long reach is
  required
• Fog stream (100 PSI)
• produces the most water surface for heat
  absorption, but has shorter range
• Forester nozzle (always 50 PSI)

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Nozzle Pressure (NP)

• Nozzle Pressure must be added in all hydraulics
  problems
• EP NP H FL

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Head Pressure (H)

• Generated by the weight of water in a vertical
  column - measured in feet
• One foot of head is equivalent to a column of
  water one foot high
• One foot of water exerts a pressure of 0.434 PSI
  (we will approximate at 0.5)
• Head pressure depends on the height of the liquid
  in the column, not the shape of the vessel

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Calculating Head Pressure

• If the hoselay is LOWER than the pump, SUBTRACT
  the head pressure
• For each 1 loss in elevation between the pump
  and the nozzle, subtract 0.5 PSI
• If the hoselay is HIGHER than the pump, ADD the
  head pressure
• For each 1 gain in elevation between the pump
  and the nozzle, add 0.5 PSI

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Calculating Head Pressure
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Friction Loss (FL)

• Measured in water flow (GPM)
• Loss in energy caused by the water rubbing
  against the lining of the hose
• An eddy effect develops inside the hose as the
  water near the hose liner moves at a slower rate
  than the water in the center of the hose (see
  diagram)
• This results in a decrease in the total flow

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Friction Loss (FL)

• The greater the amount of water forced through a
  given size hose, the greater the friction loss
  (greater volumemore turbulence)
• For this method of calculating hydraulics
  problems, we will measure FL in terms of 100 feet
  lengths of hose

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Facts about Friction Loss

• The smaller the diameter of the hose, the greater
  the friction loss
• 3/4 hardline has 4 times the friction loss of 1
  hose
• 1 hose has 6 times the friction loss of 1½ hose
• Friction loss is higher when pumping retardant or
  any additive that thickens water

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Reducing Friction Loss

• Reduce the nozzle pressure
• reduces discharge, but can you do the job?
• Reduce the nozzle size
• reduces discharge, but can you do the job?
• Lay parallel hose lines
• 2 parallel lines have 1/4 the FL of a single line
• 3 parallel lines have 1/9 the FL
• 4 parallel lines have 1/16 the FL
• Use a hydropac

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Friction Loss in Appliances

• EP NP H FL A
• A drop in pressure will occur any time an
  appliance is added to the hoselay.
• Examples include wye, siamese, Ts
• (Does NOT include nozzles)
• ADD 5 PSI per appliance
• Even if equation doesnt include A you must
  remember it!

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Hydraulics Calculations

• Favors process-oriented people
• We will go slow as a group
• If you want to work ahead, go for it, but save
  questions until the class catches up with you
• Calculators are allowed
• Watch your addition!

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Hints for doing hydraulics problems

• Develop a set system and stick to it
• do problems the same way every time
• Write down the formula and fill it in
• Start calculations at the end of the hoselay and
  work back to the pump
• Note FL GPM next to each hose length
• Note H next to the elevational change
• Show your work for partial credit
• All answers are judged 5 PSI

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Using the Friction Loss Calculator

• Part 1
• Inputs
• Output
• Part 2
• Inputs
• Output

• Nozzle pressure
• Nozzle bore (tip size)
• US gallons flow per minute
• US gallons flow per minute
• hose size
• Pounds pressure FL per 100 hose

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Remember
Don't Panic!
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Objectives

• Discuss and describe how hydraulics affect pump
  operations under various conditions.
• Solve various hydraulics problems under simulated
  conditions. Note Students are allowed a 5 PSI
  confidence interval.