- Industry / Applications
Why do we need Air Release Valves for Pipelines ?
Air in a pressurized closed-pipeline system can cause problem. When air is present in a hydraulic pipeline, flows are erratic, unpredictable and have high head losses.
How does unwanted Air enter a piping system ?
- Air may not be completely purged when the pipeline is initially filled.
- Air may be drawn in at a pump inlet if the liquid level falls below the inlet elevation.
- Air is always present in solution (about 2% by volume). This air will be released where the pressure is reduced in the pipeline, especially where the line height is close to the hydraulic gradient.
- Gas created from digested sewage.
- Air may be drawn in through the packing, seals and flanged joints.
- Air may enter during pump vortexing.
An air pocket will decrease the cross-sectional area and increase frictional pressure loss. The combined loss for two-phase flow (air and water) is always greater than the pressure loss for each phase flowing alone. Thus, air in a pipeline increases system flow resistance and increases system head against which pumps must operate.
Air in piping tends to collect at high points in the line when flow velocities are low. If the air pocket formed is large, part of it will be removed when the velocity increases. This partitioned air may or may not go through the system, depending on velocity, pipe size, and pipe down-slope. Air may only move into the sloping straight section and then return to the summit when the velocity decreases.
While it is impossible to totally prevent accumulation of air (or gases) within the piping system, the volume can be greatly minimized by installing Air Release Valves on pipeline high points. DeZURIK offers several kinds of Air Release Valve types. The most popular air valve is the APCO 55.
What is an Air Release Valve ?
An Air Release Valve is used to eliminate small air pockets that form at the high points of a pipeline and restrict flow. Air pockets reduce pipeline capacity and increase the amount of energy required to pump fluids. Air quick release valves are a critical piece of equipment on process systems.
Air/Vacuum Valves are used to protect pipelines from damage by expelling or admitting large quantities of air. Air/Vacuum Valves expel air when filling the pipeline and admit air to relieve a vacuum when draining the pipeline.
DeZURIK manufactures two main styles of APCO Air Release & Air/Vacuum Valves:
- ARV Clean Water Air Release Valves
- ASR Sewage Air Release Valves
Combination Air Valves
Combination Air Valves perform the functions of an Air/Vacuum Valve with an Air Release Valve. Combination Air Valves, in either single to dual body types, are typically installed on all high points of a system where it has been determined that the functions of both an Air/Vacuum Valve and an Air Release Valve are needed to vent and protect a pipeline.
DeZURIK manufactures four main types of APCO Combination Air Valves:
- ASU Single Body Combination Air Valves
- AVC Single Body Combination Air Valves
- AVV Dual Body Combination Air Valves
- ASC Single Body Sewage Combination Air Valves
Vacuum Relief/Air Inlet Valves
Vacuum Relief/Air Inlet Valves are normally closed. If the system pressure becomes negative, the Vacuum Relief/Air Inlet Valve will immediately admit air into the system and prevent a vacuum from forming. When system pressure returns to positive, the Vacuum Relief/Air Inlet Valve closes air tight.
Surge Check Air Valves
A Surge Check Air Valve is used to prevent critical shock conditions from occurring in installations where the operating conditions cause a regular air valve to slam open and/or closed. The Surge Check Air Valve reduces the rate of flow of water into the air valve by means of throttling orifices in the disc, thereby preventing water hammer. This Surge Check Air Valve provides this slow closing feature and is mounted on the inlet of the Air/Vacuum Valve.
Double Acting Air Throttling Device
Air/Vacuum Valves can efficiently discharge air from deep well pump columns when combined with a Double Acting Air Throttling Device. The Double Acting Air Throttling Device is fitted on the discharge orifice of the Air/Vacuum Valve. Because the pipeline media does not contact the Double Acting Air Throttling Device, it can be used on pipelines containing dirty fluids.
Carotek can assist with your air release valve selection and help you determine air release valve sizing, where to put air release valves and installation requirements.