1 Air Separators

2

3 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

4 Air Management

5 50 o 100 o 150 o 200 o 250 o 300 o 5% 20% 15% 10% 25% 5 PSI 10 PSI 150 PSI 25 PSI 0 PSI 50 PSI 75 PSI 100 PSI 125 PSI Nitrogen Soluble in Water Expressed in % of Water 0 PSI & 32 o F Temperature o F

6 Air Management Velocity

7 Example: Full Flow

8 Example: Half Flow

9 Air Elimination

10 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.

11 Air < 0.5 fps > 2 fps 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 The design influence of air on hydronic systems. ASHRAE TRANSACTIONS 87(1): )

12 Air Separation Initial fill, remove gross air by: –Venting –Purging

13 System purging City Water Drain Hose to drain Open Closed

14 Air Separation Operation, remove entrained air using: –High temperature –Low pressure –Low velocity –Centrifugal action –Coalescence

15 AIR SEPARATION EFFECT 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...

16 AIR SEPARATION EFFECT 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?

17 AIR SEPARATION EFFECT 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

18 CHILLED WATER SYSTEMS Lower temperatures so air pockets are less likely to lockup system Corrosion still a concern Air removal device is recommended

19 Enhanced Air Separator Diffuser Straight Through Inlet Coalescing Brush Outlet Angle Pattern Inlet

20 Effective Air Separators Enhanced Air Separator (EAS) Coalescing Air Separator System Outlet Alternate System Inlet System Inlet To vent or tank

21 Enhanced Air Separator Brush filaments collect entrained air Excellent for radiant loop systems

22 In Line Air Separators Outlet System Inlet To Standard Tank or Vent To Pre-Charged Tank

23 Effective Air Separators In-Line Air Separator (IAS)

24 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

25 Rolairtrol Centrifugal Air Separator System Inlet System Outlet To Standard (compression) Tank or Vent

26 System Inlet System Outlet To Standard Tank or Vent Rolairtrol Centrifugal Air Separator

27 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

28 Buffer Tank / Air Separator Boiler Buffer Tank