Air Release vs. Combination Air Valves in Petrochemical Applications: What’s the Difference?

Quick Summary: The Key Difference

1. What Is an Air Release Valve?

Function:
An air release valve is designed to automatically discharge small volumes of trapped air that accumulate at high points in a pressurised pipeline during normal operation.

In petrochemical applications, where seawater is pumped continuously through fire suppression lines, even minor trapped air can cause:

• Flow reduction or surging
• Pressure drops
• Corrosion due to oxygen exposure

Air release valves help maintain system efficiency and reduce these risks by expelling air pockets before they become problematic.

Limitations:
They do not handle large volumes of air, making them unsuitable for startup, shutdown, or vacuum-breaking functions on their own.
 

2. What Is a Combination Air Valve?

Function:
A combination air valve integrates the functionality of both an air release valve and a kinetic air valve (also known as a large-orifice valve).

This allows it to:

• Expel large volumes of air quickly during pipeline filling
• Admit large volumes of air during draining or sudden shutdown (to prevent vacuum)
• Continuously release small pockets of air during operation

Ideal for petrochemical pipelines, especially long or elevated systems, where sudden changes in flow conditions or pressure are common—such as when activating firewater systems.

Benefits:

• One valve handles all air-related functions
• Reduces risk of vacuum collapse and surges
• Ideal for critical systems that must remain fully operational and air-free

3. When to Use Each Valve Type

4. Considerations for Petrochemical Environments

In harsh petrochemical conditions, especially those involving corrosive seawater, the material of construction is just as important as valve type. Both valve types are available in corrosion-resistant materials like:

• Super Duplex Stainless Steel
• Titanium
• 6Mo (254 SMO)
• Hastelloy
• Aluminium Bronze

At GA Valves, we specialise in providing both air release and combination air valves specifically designed for seawater fire-fighting systems in petrochemical plants.

Conclusion: Choose Based on System Needs

To sum up:

• Use air release valves where you need ongoing micro-air management during normal operation.
• Use combination air valves where you need full protection during filling, draining, and running cycles—especially in long or complex pipe networks.

If you’re unsure which valve best suits your system, our team can help with specification, sizing, and material compatibility based on your operating conditions.