Common accidents in the laboratory
December 30, 2021
3 min read
When it comes to using vacuum pumps, there are some common mistakes that can happen in the laboratory. University labs, where graduate students rotate out every few years, are particularly prone to these types of mistakes. A lot of vacuum knowledge can be lost as older, more senior grad students leave and new students take over. If they haven't had time to learn best practices and get proper training on the equipment, accidents are more likely to happen. However, these accidents can happen in any lab where proper procedures aren't being followed when using vacuum pumps.
Oil pumps
When they aren't handled properly, oil-sealed pumps can experience oil backstreaming (also called suck back) from the pump into the chamber. This is a good reason to upgrade oil pumps to dry pumps.
This type of accident happens when you have oil in the pump and there's a power outage or the system is shut down improperly. If the chamber itself and the vacuum line leading to the pump are still under vacuum when everything is turned off, the vacuum can pull oil from the pump up into the chamber and the vacuum lines. This contaminates your chamber, your pump, and sometimes the components that you have in your chamber. It's difficult to clean all that oil out of the system, so this can be detrimental to productivity and vacuum cleanliness.
Often oil pumps do have anti-suck back valves built into the pump to prevent this from happening, but not all pumps do. Adding in safety valves is one possible solution, but the valves can fail. This type of failure can still happen even with those precautions. Obviously, a fool-proof solution is to not have oil at all in the system and instead use a dry pump. With a dry pump, even if a valve breaks, there's no oil that can contaminate the system.
Turbopumps
Turbopumps can fail when the pump experiences a sudden inrush of gas, which can happen if you have the turbopump running at full speed when your chamber is still at atmospheric pressure. If you accidentally open the valve between them, you can have a sudden inrush of atmospheric pressure onto the pump, which can cause the pump to crash. This type of accident can cause serious damage to the turbo rotors and blades that run inside the pump, as well as to the bearings.
This is a fairly common accident in vacuum labs. It's called shock venting to the atmosphere. Proper training is essential to avoid this type of accident. You should always be careful about how you run the pump. You can use an automated system to make sure the chamber is down to a specific pressure using a gauge. Another method is to have the turbopump connected to the chamber so the chamber is being pumped down through the turbopump. This ensures the chamber is at a good pressure when the turbopump is turned on.
Some turbopumps are being manufactured to help avoid these types of mistakes. Leybold pumps are particularly robust in resisting damage from shock venting.
Best practices to avoid vacuum-related lab accidents
In addition to training on the proper use of vacuum pumps, the following best practices can help avoid mistakes in the laboratory:
Ensure the pressure on all ion pumps is down to the appropriate level using gauges before the ion pumps are turned on, or the system could be damaged.
Always wear gloves when working with high or ultra-high vacuum systems to avoid getting fingerprints inside the chamber.
Keep everything scrupulously clean around vacuum pumps.
