APCO Sewage Air Release Valves (ASR)

Because sewage media generates large quantities of gas, the potential for air entrapped with sewage pipelines is even greater than in water lines. It is recommended that each high point be protected with a Sewage Air Release Valve. The elongated body of the Sewage Air Release Valve minimizes clogging by permitting use of a much longer float stem to prevent the sewage from fouling up the mechanism.

Why Do You Need an Air Release Valve in a Pipeline?

Air in a pressurized closed-pipeline system can have many effects. When air is present in a hydraulic pipeline, flows are erratic, unpredictable and have high head losses. Air may enter a piping system in many ways:

1. Air in the pipeline when initially filled may not be completely purged.
2. Air may be drawn in at a pump inlet by entrainment if the liquid level falls below the inlet elevation.
3. Air in solution (about 2% by volume) will be released at points in the pipeline where the pressure is reduced, especially where the line elevation is close to the hydraulic gradient.
4. Gas created from digested sewage.
5. Air may be drawn in through the packing, seals and flanged joints.
6. Air may enter by vortexing at the pump.

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 APCO Air Release Valves on pipeline high points.

Sewage Air Release Valves (ASR) Specifications