©2005 Armstrong International, Inc.

Water HammerWater HammerWater HammerWater Hammer

““Expect many Expect many enjoyable experiencesenjoyable experiences!”!”David M. ArmstrongDavid M. Armstrong

““Expect many Expect many enjoyable experiencesenjoyable experiences!”!”David M. ArmstrongDavid M. Armstrong

2

Where Water Hammer OccursWhere Water Hammer OccursWhere Water Hammer OccursWhere Water Hammer Occurs

• In any water supply line, hot or cold

• Will be more pronounced in biphase* systems

• Examples of biphase applications are heat exchangers, tracer lines, steam mains, condensate return lines, and pump discharge lines

*Systems that carry water in two states, as a liquid and as a gas

““Expect many Expect many enjoyable experiencesenjoyable experiences!”!”David M. ArmstrongDavid M. Armstrong

““Expect many Expect many enjoyable experiencesenjoyable experiences!”!”David M. ArmstrongDavid M. Armstrong

3

Damaging Effects of Water HammerDamaging Effects of Water HammerDamaging Effects of Water HammerDamaging Effects of Water Hammer

Thermostatic Elements

Overstress Gauges

Crack Trap Bodies

Rupture Fittings

Collapse Floats

Over time repeated stress on the pipe will weaken to the point of rupture

““Expect many Expect many enjoyable experiencesenjoyable experiences!”!”David M. ArmstrongDavid M. Armstrong

““Expect many Expect many enjoyable experiencesenjoyable experiences!”!”David M. ArmstrongDavid M. Armstrong

4

Conditions causing water hammerConditions causing water hammerConditions causing water hammerConditions causing water hammer

• Hydraulic ShockHydraulic Shock

• Thermal ShockThermal Shock

• Differential ShockDifferential Shock

““Expect many Expect many enjoyable experiencesenjoyable experiences!”!”David M. ArmstrongDavid M. Armstrong

““Expect many Expect many enjoyable experiencesenjoyable experiences!”!”David M. ArmstrongDavid M. Armstrong

5

Hydraulic ShockHydraulic ShockHydraulic ShockHydraulic ShockVisualize what happens at home when a faucet is open

• 100 Pounds of Water

• Moving 10 feet per second

• Equaling 7 miles per hour

• Shut Suddenly…. Equaling

• 100 Pound Hammer Stopping

• “Bang” “Bang” “Bang”

• 600 psi Shock Wave

• Reflecting Back to Forth until energy is dissipated

““Expect many Expect many enjoyable experiencesenjoyable experiences!”!”David M. ArmstrongDavid M. Armstrong

““Expect many Expect many enjoyable experiencesenjoyable experiences!”!”David M. ArmstrongDavid M. Armstrong

6

Thermal ShockThermal ShockThermal ShockThermal ShockThis Kind of Shock is Temperature Related

• Flash Steam Bubbles become Trapped in Pools of Condensate

• Flooded Main, Tracer Line, Heat Exchanger Tubing or Pumped Condensate Return

• Condensate will be below saturation causing immediately collapse

• 1 pound of steam equals 1,600 times volume of water

• Causing a vacuum in all directions

““Expect many Expect many enjoyable experiencesenjoyable experiences!”!”David M. ArmstrongDavid M. Armstrong

““Expect many Expect many enjoyable experiencesenjoyable experiences!”!”David M. ArmstrongDavid M. Armstrong

7

Differential ShockDifferential ShockDifferential ShockDifferential ShockSteam flowing over condensate can create waves

• Velocity of Steam is 10-100 times greater than the velocity of liquid

• Steam moving over the condensate will start manufacturing waves

• Waves will grow until they block the pipe completely forming a “Slug”

• Steam cannot flow through the sealed condensate wall, thus causing positive to negative pressure zone from the back to front of the “Slug”

• Stopping only when suddenly impacted by equipment, tee, elbow, valve, or any bend in the piping