Tips & tricks
Small but mighty: Gas ballast is a clever feature in many vacuum pumps for preventing condensate.
© VACUUBRAND
Are you familiar with the little helper integrated with your diaphragm or rotary vane pump? Gas ballast – often overlooked, but indispensable. When used correctly, it prevents condensation, protects the pump, and extends its service life. We'll show you how to use it effectively in daily operation – for less maintenance and reliable processes.
Gas ballast is a small but powerful feature in many vacuum pumps – from rotary vane pumps and diaphragm pumps to HYBRID pumps. Yet many users don't even realize how crucial it can be in daily lab work.
Why do you need gas ballast?
Especially when pumping large amounts of condensable vapor or drying moist substances, gas ballast makes all the difference. It ensures that your pump operates more efficiently and lasts longer.
Applications that particularly benefit from gas ballast:
- Rotary evaporation
- Distillation
- Drying
What happens without gas ballast?
Many applications generate significant loads of vapor or moisture towards the vacuum pump. Without protective measures, these can condense inside the pump when the saturation vapor pressure is exceeded (the pressure at which a vapor becomes liquid).
Even after the application process is completed, there is still a risk of condensation: If the vacuum pump is shut down too early, warm vapors that have not been fully evacuated remain in the system. These vapors cool down and condense into droplets.
The consequences range from reduced process quality and increased maintenance requirements to complete pump failure. Risks that can be avoided with properly used gas ballast.
The risks without gas ballast
Reduced vacuum performance:
When condensate accumulates inside the pump during operation, re-evaporation occurs. The resulting vapor pressure of the medium works against the pump's vacuum performance. The result is a significant reduction of the pump's achievable ultimate vacuum.
Contaminated oil in rotary vane pumps:
Residual condensate can lead to contaminated oil, altered lubrication properties, and corrosion damage. Possible consequences: expensive oil changes, costly disposal, and even complete pump failure.
Increased wear and tear in diaphragm pumps:
Condensate droplets can cause mechanical wear in the pump heads when they "shoot" through the pump chamber at high velocity during startup, potentially damaging valves in the worst case. Additionally, condensate accumulation in the pump head can lead to diaphragm wear due to increased mechanical stress. The result: loss of vacuum performance and rising maintenance costs.
What does gas ballast actually do?
In short: It allows ambient air flow into the vacuum pump in a controlled manner. This additional air ensures that the saturation vapor pressure in the pump is not exceeded. The vapors remain gaseous and are expelled from the system – liquid condensate doesn't form in the first place.
And should condensate droplets occasionally form due to excessive pumped vapor loads, the additional airflow ensures that they are immediately "purged" from the pump heads.
Benefits of gas ballast:
- Greater process reliability
- Longer service life
- Less maintenance
How do I use gas ballast correctly?
“Gas ballast purge“
One of the most effective tips – whether for rotary vane or diaphragm pumps – is to open the gas ballast immediately after a moisture- or vapor-related application run:
- End the process
- Close the inlet port of the pump
- Open the gas ballast
Let the pump continue running for up to 30 minutes, depending on pump type
This purge cycle gives the pump enough time to expel any accumulated condensate or residual vapor. This keeps the pump clean and dry, protects it, and extends its service life.
Practical gas ballast tips for different vacuum pump types
- When do I activate the gas ballast?
- How long should the gas ballast run after the process?
- Can the gas ballast remain open permanently?
- Does gas ballast affect the ultimate vacuum?
Below we answer these frequently asked questions in a compact and practical way.
Rotary vane pumps
- Do not keep gas ballast open permanently to avoid oil loss.
- Ideally, open at the end of the application for approximately 30 minutes.
- Particularly important for substances prone to condensation, e.g., due to a high boiling point.
Diaphragm pumps
- Gas ballast can remain open permanently – if you don't require the maximum ultimate vacuum. The additional air flow through pump leads to a slight reduction in achievable vacuum performance.
- Otherwise, open at the end of the application for approximately 15–30 minutes.
HYBRID pump
- Combination of rotary vane pump and diaphragm pump that evacuates the oil reservoir.
- Gas ballast is permanently open on the diaphragm side to protect the rotary vane pump oil.
- Only operate the rotary vane side with gas ballast when needed to avoid oil loss.
VACUU·PURE® 10C screw pump
Screw pump VACUU·PURE®
Show more
Show less
Is the air intake through gas ballast safe?
Introducing ambient air through the gas ballast brings oxygen into the system. In combination with certain solvents, explosive mixtures can form depending on the concentration. The solution: supply gas ballast with inert gas (e.g., nitrogen or argon) via an adapter. The effect remains, the risk disappears.
Conclusion: Small feature, big impact
Gas ballast is not an "add-on" but a clever default tool that needs to be used strategically. Those who understand how it works extend the service life of their vacuum pump, reduce maintenance costs, and ensure reliable processes.
Whether rotary vane, diaphragm, or HYBRID pump: What matters is not the feature alone – but that you know it and use it optimally. This is how you ensure efficiency and safety in daily lab work.
