1 Air Separators. 2 3 AIR IN THE SYSTEM WHAT DOES IT DO Annoying noises Gurgling and falling water...
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Transcript of 1 Air Separators. 2 3 AIR IN THE SYSTEM WHAT DOES IT DO Annoying noises Gurgling and falling water...
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Air Separators
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AIR IN THE SYSTEM WHAT DOES IT DO
• Annoying noises
• Gurgling and falling water
• Reduced pump head and failure
• Water/air mixture becomes compressible
• Catastrophic pump failure
• Disturbed water flow
• Foam in the piping/loss of conductivity
• Corrosion
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Air Management
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50o 100o 150o 200o 250o 300o
5%
20%
15%
10%
25%
5 PSI
10 PSI
150 PSI
25 PSI
0 PSI
50 PSI
75 PSI
100 PSI
125 PSI
Nitrogen Solublein Water
Expressed in % ofWater Volume
@ 0 PSI & 32 oF
Temperature oF
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Air Management
Hot Water Coil
Velocity
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Example: Full Flow
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Example: Half Flow
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Air Elimination
Hot Water Coil
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Pipe Sizing• Velocities high enough to carry air to the
point of separation.– Above 2 ft/sec will carry air bubbles with liquid stream– Below 0.5 ft/sec will allow bubbles to rise by buoyancy
in spite of the downward flow
• Need effective air control.– Maximum velocity limits assume that air is not
present.
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Air Air< 0.5 fps > 2 fps
Water Water
Water velocities greater than 2 feet per second will move entrained air downward. Air will rise in downward water flows at velocities of 6 inches per second or less.
(Gil Carlson. 1981. The design influence of air on hydronic systems. ASHRAE TRANSACTIONS 87(1):1293-1300.)
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Air Separation• Initial fill, remove gross air by:
– Venting– Purging
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System purging
City
Water
Drain
Hose to drain
Open
Closed
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Air Separation• Operation, remove entrained air
using:– High temperature– Low pressure– Low velocity– Centrifugal action– Coalescence
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AIR SEPARATIONEFFECT of PRESSURE and
TEMPERATURE
• Lowest pressure /highest temperature: this is the Point of lowest solubility
• Example at 40 psig (ie: right out of faucet)
• At 60 degrees F = 8% air by volume
• Now heat the water up...
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AIR SEPARATIONEFFECT of PRESSURE and
TEMPERATURE
• Lowest pressure /highest temperature: this is the Point of lowest solubility
• Example at 40 psig
• At 60 degrees F = 8% air by volume
• RESULT: At 195 degrees F = 4% air by volume....where did the air go?
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AIR SEPARATIONEFFECT of PRESSURE and
TEMPERATURE• Lowest pressure /highest temperature: this is the Point of
lowest solubility• Example at 40 psig• At 60 degrees F = 8% air by volume
• RESULT: At 195 degrees F = 4% air by volume....where did the air go? RELEASED INTO THE SYSTEM
• Means 100 gallons of water yields 4 gallons of air with a 135 degree F rise at start up
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CHILLED WATER SYSTEMS
• Lower temperatures so air pockets are less likely to lockup system
• Corrosion still a concern
• Air removal device is recommended
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Enhanced Air Separator
Diffuser
StraightThrough
Inlet
Coalescing Brush
Outlet
Angle PatternInlet
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Effective Air Separators
• Enhanced Air Separator (EAS)
Coalescing Air Separator
System Outlet
Alternate System Inlet
System Inlet
To vent or tank
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Enhanced Air Separator
• Brush filaments collect entrained air
• Excellent for radiant loop systems
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In Line Air Separators
OutletSystem Inlet
To StandardTank or Vent
To Pre-Charged Tank
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Effective Air Separators
• In-Line Air Separator (IAS)
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In Line Air Separators
• In-Line Air Separator (IAS): collects large air pockets; not as effective on entrained air as the EAS. Low Cost. Also known as an Air PURGER
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Rolairtrol Centrifugal Air Separator
System Inlet
System Outlet
To Standard (compression) Tank or Vent
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System Inlet
System Outlet
To Standard Tank or Vent
Rolairtrol
Centrifugal Air Separator
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Rolairtrol Centrifugal Air Separators
• Rolairtrol: For 2” thru 24” pipe; ASME Code construction; spinning water stays to outside of vessel, the lighter air rises through middle. The percent of entrained air removed per pass is published (air elimination efficiency)
• Choose size based on flow rate, NOT line-size; approx. 1psi pressure drop, or less, for 90%+ air elimination efficiency
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Buffer Tank / Air Separator
Boiler
BufferTank