What is the difference between a gas ballast and non-return valve?

Gas ballasts and non-return valves are two different components found in vacuum systems, and they serve different purposes. Gas ballasts are used within a vacuum pump to prevent the condensation of vapors by introducing a non-condensable gas, while non-return valves are used to prevent backflow and maintain a vacuum in a system when the pump is not in operation. They are both important for the proper operation of vacuum systems but function in very different ways.

Gas Ballast:

• The gas ballast is a feature found on many vacuum pumps, particularly rotary vane pumps.
• Its purpose is to prevent the condensation of vapors inside the vacuum pump.
• When a vacuum pump operates, it can generate a vacuum that may cause vapors within the pump to condense into liquids. This can be problematic because many vacuum pumps are designed to handle gases, not liquids.
• The gas ballast admits a controlled amount of air or another non-condensable gas into the pump during the compression phase, which helps to keep the vapor phase above its dew point, thus preventing condensation.
• This helps in maintaining the efficiency of the pump and extends its lifespan by preventing the accumulation of condensed fluids that can cause corrosion or damage.

Non-Return Valve (Check Valve):

• A non-return valve, also known as a check valve, is designed to allow a fluid (liquid or gas) to flow through it in only one direction.
• It is typically used in piping systems to prevent backflow, which could damage equipment or upset process conditions.
• In vacuum systems, a non-return valve prevents the backflow of air or gas from the process into the vacuum pump when it is turned off. This is crucial for maintaining a vacuum when the pump is not running and for protecting the vacuum system from atmospheric pressure.
• Non-return valves are often spring-loaded and open when the pressure differential across them is in the forward direction and close when the pressure attempts to reverse.