Air in your Pipes? Choosing the Correct Air Valves For Your System. Presented by John Skalla DeZURIK, Inc.

Transcription

1 Air in your Pipes? Choosing the Correct Air Valves For Your System Presented by John Skalla DeZURIK, Inc.

2 Air in Pipelines Air is present in all pipelines Three primary sources: Water contains up to 2% by volume of entrained air Pump Startup Pipelines contain air which must be exhausted during filling Air can enter into the pipeline through equipment (pumps, gaskets, fittings, valves, etc.) when vacuum condition occurs

3 Harmful Effects of Air in Pipelines Pipeline Efficiency will suffer because air pockets create a restriction in the pipeline. This restriction results in addition head loss that was not calculated during the pipeline design Corrosion in the pipe can occur when pipe is exposed to air pockets, potentially causing premature pipeline or equipment failure System Operation A sudden change in velocity (surge) can occur when air pockets move from one high point to another

4 When Things Go Wrong

5 When Things go Wrong

6 Using the Right Air Valve Traditional Sewage Air Valve Installed Saves Energy High Performance Sewage Combination Air Valve Installed

7 Air Valve Types

8 Air Release Valves (ARV) Air Release Valves release air pockets that collect at high points of a fully pressured pipeline The orifice opens when air displaces water and lowers the float The leverage frame provides mechanical advantage to open the orifice against pressure After air is released, water rises to lift the float and close the valve

9 Air Release Valves (ARV) Fractional orifice (3/32", 1/8", 3/16" etc.) located at the outlet (top) provides the ARV performance Inlet size does not dictate performance Plug located on cover for pressure gauge or petcock

10 Two Functions: Air/Vac Valves (AVV) Air Exhaust Lets out large quantities of air while filling the pipeline Vacuum Protection Admits large quantities of air to prevent pipeline collapse during regular pump shutdowns, pipeline breaks or power failures

11 Air/Vac Valves (AVV) Choosing the right valve size is critical for proper vacuum protection The large discharge outlet is equal in size to the inlet Rising water causes the internal float to close the valve. Pressure holds it closed. The float will not lower until a vacuum (negative pressure) occurs.

12 Combination Air Valves (CAV) Combines features of Air/Vac Valves and Air Release Valves Installed on high points of systems where dual function Air/Vac and Air Release Valves are needed to vent and protect the pipeline Available in Single Body and Double Body configurations

13 Traditional Sewage Air Valves Air Release (SARV) Air/Vacuum (SAVV) Combination (SCAV)

14 High Performance Sewage Combination Air Valves High performance on dirty, greasy sewage Simplicity in design of the body, cover, float and float linkage means minimal or no maintenance is required If maintenance is required, features such as bolted top cover and lifting lugs make the job easy

15 Locations for Air Valves

16 Typical Air Release Locations

17 Typical Air/Vac Locations

18 Typical Combination Locations

19 Sizing Air Release Valves

20 Pumping Condition Sizing Air Release Valve ARV CAV Air release = ¼ Orifice for 70 psi Need to Know: Flow Rate (GPM) Pressure (PSI) Valve capacity varies by orifice size, valve style and manufacturer Normal Pumping Condition: 24 15,000 GPM & 70 psi

21 Sizing Air Release Valves Air Release Valve: Small Orifice Under Sizing does not allow the proper amount of air to be released and the valve cannot catch up. This may cause air to collect below the air release valve inlet and be passed to the next high point in the pipeline. Oversizing may not allow the Air Release Valve to open under the stated operational pressure.

22 Determine Orifice Size Need to Know: Flow Rate (GPM) Working Pressure (PSI) 15,000 GPM at 70 psi ¼ Orifice

23 Air Release Valve Selection ¼ Orifice at 70 psi Model 200A

24 Sizing Air/Vac Valves

25 Filling Pipe 2 Exhaust 2 Exhaust 3 2 Exhaust Filling the pipeline at 1 FPS is recommended to prevent surges in the line Air should be vented at the same volumetric rate as the pipeline is being filled 2 psi or less differential pressure is recommended, or 5 psi if slow closing devices are used

26 Draining Pipe Slope CAV Exhaust & Inflow Slope The pipe slope and size determines the air volume inflow required to prevent excessive vacuum Orifice is sized to allow negative pressure at the allowable negative pressure of chosen pipe or 5 psi, whichever is less

27 Gravity Flow: Sizing Air/Vac Valves Most small and medium size pipes can withstand a complete vacuum. Low stiffness, large diameter pipes may collapse from negative internal pressures The orifice must be sized to allow the required inflow of air to replace the water in the pipeline with minimum pressure differential

28 Sizing Air/Vac Valves Air/Vac Valves: Large Orifice Under Sizing Exhaust can cause premature closing due to high velocity air discharge Under Sizing Intake can cause destructive vacuum on pipeline Oversizing Exhaust and/or Intake will not be a problem, but will create unnecessary costs and require more space.

29 Determine Slope of Pipe 33 cfs 49 cfs

30 Sizing for Air Exhaust and Vacuum Protection Slope CAV 0.04 Slope Exhaust & Inflow 49 cfs Inflow = 6 AVV (May require 8 for plastic pipe) Exhaust = 15,000 GPM, or 33 cfs Inflow = 49 cfs (using.04 slope) 24 Pipe

31 Determine Air Inlet Rate Need to Know: Slope of Pipe Pipe Diameter 24 Slope 49 cfs

32 Need to Know: Air Inlet Rate (cfs) Allowable Vacuum Differentiable Pressure (PSI) typically 5 psi Valve Size Selection 49 cfs 6

33 Vertical Turbine Pumps Special Consideration

34 Vertical Turbine Pump Air Valves Vents air before rapidly rising column of water during pump startup Slow closing feature protects the air valve Works as an air release valve once pump is running normal

35 Vertical Turbine Pump Startup

36 Pump Performance Data No Head Flow Rate

37 Selecting Air/Vacuum Valves for Vertical Turbine Pumps

38 Questions?

39 Air in your Pipes? Choosing the Correct Air Valves For Your System Presented by John Skalla DeZURIK, Inc.