Oil-free diaphragm pumps have earned a reputation for environmental- friendliness for low- to medium-pressure applications. At the low-pressure end, pumps do not continuously send water down the drain as do aspirators and there is no contaminated oil to deal with. The pumps have a long operational life with minimal maintenance and DC voltage models are said to be more energy efficient.
High foreline pressure tolerance permits the use of a smaller, lowcost backing pump. “Turbomolecular pumps cannot discharge directly to the atmospheric pressure, only up to 10 mbar absolute pressure at its outlet, hence the need for a backing pump,” explains Mauro Nebiolo, director of global marketing for vacuum products at Agilent.
The turbomolecular pumps are suitable for achieving high vacuum and ultra-high vacuum, with operating pressure ranging from 10-1 to 10-11 mbar inlet pressure.
High vacuum may also be achieved through a diffusion pump, which is not as clean as the turbomolecular design, or cryogenic pumps. “The latter are far less flexible, however, due to the required regeneration cycles,” Mr. Nebiolo says.
Ultra-high vacuums may otherwise be reached using sputter ion pumps, titanium sublimation pumps, and getter pumps. The latter rely on a “non-evaporable getter,” an aluminum-zirconium alloy that soaks up gases by forming non-evaporable or non-sublimable compounds with them.
Vacuum pumps are commonly specified both by ultimate vacuum and by flow rate. The flow rate is also known as pumping speed (the “volume flow rate” at the inlet, measured in volume per unit time) or free air displacement (the volume of air that flows into the pump, per unit time, when inlet and outlet are at atmospheric pressure). Ultimate vacuum is the deepest vacuum the pump can reach, the point at which the effective pumping speed is zero.
“The problem is that the pump can’t move any vapor at ultimate vacuum, and at a specified pumping speed, the pump is working as a fan, not a vacuum pump. No one uses a vacuum pump to work at either of these conditions,” says Peter Coffey, vice president of sales and marketing at Vacuubrand (Essex, CT).
Pumps with identical specifications for flow rate and ultimate vacuum can perform very differently between these two end points. “So if you only use these terms to select a pump, you don’t know what performance you will get out of the pump under actual lab conditions,” he says.
In other words, users need to know how the pump behaves between these two end points— when the pump is both creating the vacuum and moving vapor.
There are two ways to determine pump performance at the vacuum pressure you need. One is to ask your vacuum pump vendor while the other is to rely on vacuum pump performance curves that all reputable vendors will provide on request.
Depending on pump engineering, the actual pumping speed falls off at a greater or lesser rate as the pressure approaches the ultimate vacuum. The better the pump, the more the specified pumping speed is preserved closer to the ultimate vacuum.
4UHV Ion Pump Controller
- Able to power, control and monitor independently up to four ion pumps, with capacities ranging from 20 to 500 liters per second each
- Eliminates or shrinks electrical noise filters in critical applications
- Shares its communication protocol with Agilent’s other controllers for turbomolecular and pre-vacuum pumps, so less engineering work is required
Dolphin LX B series
- Rugged and reliable
- A good fit for wet process applications
- Multiple configurations available
- High-efficiency, single-stage pumps provide end vacuum levels comparable to most twostage designs
MV Visi®Trap Vacuum Pump inlet Trap
- Prevents users from contaminating a central source vacuum system
- Features clear 9.5” sumps for visually monitoring filter condition
- Can be supplied with replaceable copper or stainless steel gauze, molecular sieve, Sodasorb®, activated charcoal, activated alumina and Polypro 2-, 5- and 20-μm filter elements
- Provides vacuum and pressure in just one unit
- Has a noise level of only ~ 60 dB
- Maintenance-free because of the oil-free design
- Comes with guaranteed operation of two-years or 3000 working hours of free service parts (excluding the moisture filter)
New Star Environmental