Vacuum is an integral part of many laboratory processes, but costs associated with generating a vacuum, such as process costs, user costs and cost to the environment, have never really been considered seriously. Although technology has advanced to provide smaller, cleaner and quieter options, not many people are taking advantage of it. “Vacuum pumps last a long time and many people go through their careers without actually buying one,” says Peter Coffey, vice president of sales and marketing at Vaccubrand Inc. “Hence, people tend to replace their vacuum pumps with what they have used before and not take the time to find out about the alternatives.”
Vacuum pumps used in laboratories can be classified into two main types—rotary vane pumps, sometimes referred to as oillubricated pumps, and dry (oil-free) pumps. They operate in different ways to create vacuum and aspirate fluids. Centrifugal pumps use centrifugal force to push the fluid through an outlet; metering pumps, such as diaphragm, peristaltic, piston and syringe pumps, pull fluid into a chamber and then push it through the outlet valve; while positive displacement pumps use bellows, piston, rotary lobe and rotary vane to push fluid through a cavity, leaving a vacuum that pulls in more fluid.
Oil-lubricated pumps have been around for many decades, while the oil-free diaphragm pumps are a more recent addition. Although oil-free pumps tend to be one and a half to two times more expensive than oil pumps, there are a lot of advantages to their use as well as significant lifetime savings. First of all, no oil is used, and therefore there is no cause for oil contamination and no necessity for oil change or disposal. Oil-free pumps can be built to be corrosion resistant and hence do not require regular maintenance. “Service intervals on better oil-free pumps exceed 10,000 operating hours,” says Coffey. “If you use your vacuum pump 20 hours a week, 50 weeks a year, that’s 10 years before the first scheduled service!”
The other misunderstanding that leads to the choice of an oillubricated pump is that people think that more vacuum is always better. Oil-free diaphragm vacuum pumps can provide vacuum levels from atmosphere to below 0.5 mbar/torr, whereas oil-lubricated pumps offer high capacities and higher vacuum levels up to 10-3 mbar/torr. “What is more important is matching the vacuum to the application, and almost any application can now be performed using an oil-free pump, with the exception of freezedrying,” says Coffey.
For certain applications he also recommends considering buying a pump with controls that provide a good balance of speed and control. “Even manual controls are better than none, but electronic controls offer huge productivity advantages,” he says. “In many applications, the type of vacuum control used will determine how much scientist time is needed for oversight and how fast the application proceeds.”
It is often very helpful to talk to someone from a vacuum pump company, who can recommend a pump and offer a demonstration about what will be right for your application and budget. There are also interactive online vacuum pump selection guides available that ask a few questions about the planned use for the pump and recommend a series of pumps to satisfy a range of budgets. “It is not a glamorous technology but it is one that can affect the costs, comfort and convenience of your laboratory,” says Coffey.
.