Vacuum pumps drive a large number of laboratory processes, from distillation to drying, lyophilization, the transfer of hazardous chemicals within vacuum manifolds, flash chromatography, and others. Some of these applications are critical, some are not, but they all share one characteristic: If the pump goes down, so does the process.
Vac Aero (Burlington, Ontario, Canada), which specializes in large industrial processes that rely on dependable pump performance, suggests instituting a formal pump maintenance program to prevent pump failure. In a 2016 blog post outlining its philosophy of maintenance to optimize a lab’s investments in vacuum technology, the company noted that “In a pump’s normal operating life, nearly all unexpected vacuum pump failures can be prevented, and when carefully maintained, a vacuum pump will provide years of reliable service.”
The right pump for the job
The first step in avoiding pump problems is to select the right pump for your specific application. “Freeze dryers, gel dryers, centrifuges, rotary evaporators, and vacuum ovens all require different vacuum levels,” notes Dave Rolph, president of Mass-Vac (North Billerica, MA).
An oil-lubricated, two-stage rotary vane vacuum pump, for example, runs comfortably below 100 millitorr. “This type of pump is suitable for freeze dryers, but not for the other mentioned applications that typically require a vacuum level in the torr or inches-of-mercury pressure range. A twostage, oil-lubricated rotary vane pump running in the torr range for extended periods will get extremely hot, throw oil mist out the exhaust, and eventually fail prematurely.”
By contrast, single-stage, oil-lubricated rotary vane vacuum pumps are designed to run comfortably in the torr or inches-of-mercury pressure range.
“These pumps are used successfully on centrifuges and vacuum ovens, while dry-running diaphragm vacuum pumps are used successfully on gel dryers and rotary evaporators, which require a much higher pressure,” Rolph says.
Keeping it running
Once you’ve chosen the right pump, your goal should be protecting and maintaining your investment. “Vacuum pumps in many laboratories are exposed to all sorts of chemicals that can destroy your vacuum pump in short order,” Rolph says. Organic solvents, acid, water vapor, and particulate matter are of particular concern. “Using a vacuum pump inlet trap to [catch] contaminants before they enter your pump is critical.”
Vacuum inlet traps are available with replaceable media that adsorb organic solvent vapors, neutralize acids, or remove particulates, water vapor, or oils. Mass-Vac touts its traps as devices that protect pumps from contaminants and the laboratory environment from the pump’s oil vapors. Several vendors, including Mass-Vac, offer transparent trap housings that allow visual examination of trap media.
Many laboratory pumps use oil to lubricate moving parts. For these, Rolph advises checking the oil regularly for signs of contamination. “Contamination that degrades or thins your vacuum pump oil will lead to increased pressure and eventually vacuum pump failure. Changing the oil frequently will help ensure a long vacuum pump life.”
Users can tell whether their vacuum pump’s oil needs to be changed by observing the oil’s color. “Vacuum pump oil should be the color of honey. If it changes to the color of maple syrup, you should change it.” If it’s coffee-colored, you probably should have changed it a month ago.
Users should never assume a pump’s oil doesn’t require changing because they’re using a vacuum inlet trap or because the trap itself looks OK. “Even when using a vacuum inlet trap, trace amounts of contamination can build up in the oil over time and begin to degrade the oil,” Rolph warns. “Oil may be the least-expensive component of your vacuum pump, but it’s definitely the single most important one.”
As vacuum pump oil ages during its duty cycle, it concentrates any gaseous or vaporized contaminants from its environment, thereby becoming a hazardous material. “When performing routine maintenance on industrial vacuum equipment, it is critical to use proper personal protective equipment,” says Cassie Carlson, marketing manager at DEKKER Vacuum Technologies (Michigan City, IN). “It is also crucial to dispose of air filters, oil, and other parts or accessories properly, as you would any other hazardous waste.”
For additional resources on vacuum pumps, including useful articles and a list of manufacturers, visit www.labmanager.com/vacuum-pumps