Air Valves in Piping Systems

While many are familiar with air release valves designed to expel trapped air from pipelines, it's important to recognize that various other air valve types exist, each with unique functions and designs tailored for wastewater applications, with sizes reaching up to NPS 20. Ensuring piping systems are protected from air-related issues necessitates properly selecting and installing appropriate air valves.

If you're seeking additional information, please visit Disai.

Different Types of Air Valves

According to the American Water Works Association (AWWA) Standard C512, there are three primary air valve types utilized in water and wastewater systems:

• Air-Release Valves
• Air/Vacuum Valves
• Combination Air Valves

These AWWA-standard air valves are typically made from iron or stainless steel with corrosion-resistant trims for longevity in water and wastewater services. It's crucial to note that these air valves serve different purposes than pressure and vacuum relief valves, which are installed atop gas or steam pressure vessels and liquid storage tanks to prevent overpressure. Relief valves have set points for pressure protection and fall outside this discussion's scope. The air valves discussed here automatically regulate air or gas flows in and out of liquid piping systems under all operating conditions.

Description of Air Release Valves

Air release valves are essential for expelling small pockets of air that accumulate in pressurized liquid piping systems. If not released, these air pockets can reduce efficiency and increase energy consumption.

Functions of Air/Vacuum Valves

Air/vacuum valves primarily serve applications involving vertical turbine pump discharges. Upon shutdown, air fills the piping between the pump and the check valve. When the pump starts again, it quickly raises the water column, necessitating the expulsion of trapped air before the water can open the check valve. These valves are ideal for this task, rapidly expelling large volumes of air and effectively sealing when fluid enters.

Additionally, a slow-closing device can be used alongside air/vacuum valves in pipeline applications where column separation might happen. This device helps manage high exhaust rates and prevents water hammer or air valve damage by controlling the air valve's exhaust rate. It is typically mounted on clean water valve inlets and wastewater air valve outlets under column separation or vacuum conditions.

The combination air valve, encompassing both air release and air/vacuum functions, is available in single-body or dual-body designs. A single-body design integrates both components into one unit, providing cost efficiency, while a dual-body design offers flexibility in orifice sizing and independent function performance, making it suitable for varied applications.

Strategic Installation of Air Valves Along Pipelines

Strategically installing air valves in liquid piping systems helps exhaust air or gases and prevents vacuum conditions and air-related surges. The AWWA Air Valve Manual outlines recommended installation points, such as high spots, long pipeline runs, near mainline valves, downstream from pumps, and where pipe slope changes exist. Utilizing valve manufacturer-provided software can aid in the precise placement and sizing of air valves.

Proper installation methods are paramount to air valve functionality (AWWA, 2016). Optimal results are achieved when the valve is mounted directly atop the pipe. However, in cases where pipelines run beneath roadways, placing the air valve in a separate vault may be necessary. Here, the connecting pipe must be appropriately sized and sloped upward to the air valve. Extended piping could amplify surges, necessitating a transient analysis to assess potential impacts.

For maintenance ease, all air valve installations should include a shutoff valve underneath. A larger riser pipe than the air valve inlet helps collect air traveling along the pipeline (Figure 8). Annual checks via a drain valve can verify the air valve’s functionality; if air is expelled, the air release part may need maintenance. Observing the air valve during pump operations can ensure it efficiently exhausts air and closes without excessive leakage.

Exercise caution during air valve inspection or maintenance, as significant volumes of air under pressure or vacuum conditions can be dangerous. Maintenance requires closing the shutoff valve beneath the air valve. Nevertheless, pressurized air trapped in the valve could still pose risks. Carefully vent the air via a drain valve or pipe plug before removing the air valve cover.

Top Brand Gate Valve, Brass, FNPT Connection Type, ...
Specifying Ball Valves for Hydrogen Applications Q&A

For additional information on Types Of Air Valves, feel free to get in touch with us.

Featured content:
The difference between cast iron and cast steel gate valves

CONCLUSION

Air accumulation in pressurized pipelines can reduce efficiency and lead to significant system damage. Understanding the various types of air valves enables system designers to make informed decisions regarding air valve selection and installation, thereby safeguarding liquid piping systems.

JOHN V. BALLUN, P.E. is the president and CEO of Val-Matic Valve & Mfg. Corp. (www.valmatic.com). Ballun has significantly contributed to valve standards development for the American Society of Safety Engineers, AWWA, and Manufacturers Standardization Society (MSS), where he also served as past president. Reach him at jvb@valmatic.com.

References

1. American Water Works Association, VALVE Magazine, "Why Air Valves are Needed in Water Applications," Spring, 2017, pp. 32-34

2. American Water Works Association, AWWA C512-2015, Air Release, Air/Vacuum, and Combination Air Valves for Water and Wastewater Service

3. American Water Works Association, AWWA M51, 2nd ed., Air Valves: Air Release, Air/Vacuum, and Combination, 2016

RELATED CONTENT

• The Future of Valve Manufacturing is Already Here

  Companies in the valve and control products industry are adapting to various transformative forces in manufacturing, including automation, agility, and digitalization.

• An Overview of Butterfly Valves

  Butterfly valves offer a key advantage by reducing system space and weight compared to other options like ball, check, globe, or gate valves.

• Ancient Roman Valves

  The story of water supply in the ancient Roman Empire is fascinating and grand.

I'm curious about how important air valves are for a steam system's efficiency. After experimenting with various air valves and upgrading to Gorton valves based on their guide, I noted a significant performance improvement in my system. Have others experienced underperformance with cheaper valves in otherwise well-designed systems?

0

For more check valve leaking information, please contact us. We will provide professional answers.