Vacuum Breaker Valve: Working Principle and Benefits in Steam Systems

When the steam supply to a system is shut off or a control valve throttles down, the steam inside the equipment condenses and its volume shrinks dramatically. As a result, a vacuum can form inside a heat exchanger, coil or tank. A vacuum breaker valve senses this vacuum and admits air from outside to equalise the pressure, keeping condensate draining and protecting the equipment.

This article covers the working principle of vacuum breakers, their benefits, applications, technical data and installation points.

What Is a Vacuum Breaker Valve?

A vacuum breaker works much like a check valve. It stays closed while system pressure is above atmospheric pressure; when a vacuum starts to form and the pressure difference between the outside and the system reaches the opening value, it opens automatically and lets air in.

Working Principle

1. Steam shut-off or cooling: When steam use stops or the system cools down, the steam condenses and its volume falls.
2. Vacuum formation: Condensation creates a pressure below atmospheric (vacuum) inside the system.
3. Valve opens: When the difference between outside and inside pressure reaches the opening value, the vacuum breaker opens.
4. Air inlet: Incoming air equalises the pressure and eliminates the vacuum.
5. Closing: When steam is supplied again and pressure rises, the valve closes automatically.

Benefits

• Continued condensate drainage: A vacuum holds condensate inside the equipment and prevents the steam trap from discharging it. The vacuum breaker lets condensate drain to the trap by gravity.
• Lower risk of water hammer and corrosion: Condensate trapped in equipment leads to water hammer, corrosion of heat transfer surfaces and damage. Preventing the vacuum prevents this build-up.
• Equipment protection: Prevents thin-walled tanks and vessels from collapsing or deforming under vacuum.
• Automatic operation: Senses the vacuum and acts without any power supply or control signal.
• Easy installation: Its compact design fits easily into the pipework; it is usually installed vertically.

Applications

• Coil systems
• Heat exchangers
• Ends of steam lines
• Steam headers
• Steam boilers
• Autoclaves
• Sterilisers

Technical Data

Installation

The vacuum breaker must be connected to the steam space where the vacuum forms; for heat exchangers, for example, on the steam inlet between the control valve and the exchanger or on the top of the exchanger shell. It is usually installed vertically as specified by the manufacturer, with the air inlet positioned where it will not become contaminated.

Frequently Asked Questions

Conclusion

Vacuum breaker valves prevent condensation-induced vacuum in steam systems, keeping condensate draining and protecting equipment. Browse our vacuum breakers product group to find the right model, or contact ORFA at [email protected] for technical support.