Vacuum Pump Evolution
Despite the maturity of vacuum pump designs, manufacturers show even in well-established technologies key innovations are there for the taking.
Vacuum pumps are the veteran workhorses of the laboratory, providing the mechanical force for a host of research-related tasks that require precise atmospheric control. Over the last 100 years, a number of well-established pump designs have come to dominate the market. And for decades, many varieties of pumps have seen just incremental changes. This is not for lack of competition. More than 450 vacuum pump companies now operate globally. Because of this competition, vacuum pump vendors must invest in new technology when it becomes practical, or when development dollars are available.
At KNF Neuberger, Trenton, N.J., the diaphragm pump is one of their key products. A couple of years ago, the company launched a new type of diaphragm that features a level of control not typically seen in a standalone vacuum pump. Earlier this year, prompted by the success of their prior launch, the company released a new pump that elevated power, reduced footprint size, and improved the desirable control features.
For Pfeiffer Vacuum, Nashua, N.H., rotary vane pumps are a big component of their business, and the company markets several lines to suit different needs for pumping speed, power, and relative cost. One of these pump lines has recently adopted a revised type of drive coupling that preserves performance while lowering operating costs.
Remote control for vacuum pumps
Controller-managed vacuum pump systems have become an increasingly regular sight in the laboratory. Enabled by rugged electronics and touch-activated interfaces, wireless control systems offer the ability to manage vacuum equipment efficiently and quickly. Less fiddling with analog controls saves the researcher time and often improves results.
“Originally, laboratory pumps were standalone units,” says Dan McDougall, senior manager of Laboratory Products at KNF Neuberger. “Over time, there became a market need for controlling the vacuum process. This was accomplished first with a simple gauge and regulator with some electronics and a two-point controller. You would set your desired end vacuum and allowable tolerance.”
A few years ago, the company launched its first-ever remotely controlled wireless diaphragm pump system: the SC920. The usual features of the KNF Neuberger diaphragm line were available, and with this new system came four different operating modes: vessel evacuation with adjustable pump capacity, constant pressure control, automatic detection of a sample’s vapor pressure, and intelligent regulation of process pressure using a user-defined pressure curve. But the key innovation was a simplified wireless touchscreen and control knob interface that could be used remotely.
Expanding its line of wireless controlled systems, KNF more recently launched a new speed-regulated pump system, the SC950. Improving on the SC920’s 20-L/min pumping capacity, the SC950 offers 50-L/min pumping. According to McDougall, the SC950 eliminates what was once necessary for multihead pump systems—either placing the heads in parallel to create faster flow, or putting them in series for deeper end vacuum. With a newer design, the SC950 is able to provide both high flow and a deeper end vacuum in a small package with low noise level.
The benefits of wireless remote control may not be obvious. However, utilizing wireless control eliminates many installation concerns. The vacuum system can be placed under the bench, on a shelf, or under a fume hood and controlled with the handheld unit, thus freeing up scarce benchtop space. Compared to the SC920, the newest pump in the line is also a more efficient player even when located on the benchtop. Though it is 2.5 inches taller than the SC920, it is just 9.7 inches wide, nearly five inches narrower, thus saving precious benchtop space.
KNF Neuberger has not compiled statistics on how much energy the use of a SC920 or SC950 pump system might save when used regularly in a fume hood; but when operating in a sash-closed position, HVAC efficiency typically increases substantially. Another environmentally friendly feature of these pump systems is the revised inlet/outlet condenser, which reduces solvent emissions.
The DC motor also contributes to efficiency. As opposed to AC motors, the DC unit can be adjusted precisely by the controller, optimizing power consumption required to maintain the target vacuum level. Such control also allows the operator to select a vacuum level and walk away confident that the process will proceed as desired.
Sealing in the energy savings
Pfeiffer Vacuum is best known for inventing the turbomolecular pump in 1958. But its experience in displacement pumps is even deeper. In the 1990s, it made a major improvement in its rotary vane pump line with the introduction of the DuoLine pumps, which feature magnetically coupled sealing. Compared to the traditional cap-seal shaft ring, the magnetic coupling seal offered a more complete and less complex seal that preserved more of the pumps operating fluid, or pump oil.
Whether they’re used in accelerator systems, mass spectrometry, or preparation chambers, these pumps may run the better part of 365 days a year, 24 hours a day.
The new seal design was therefore a welcome change for high-demand users, and the coupling offered up to 30% savings in energy costs while still delivering high pumping speeds. Over time, the magnetic coupling has been improved, and now appears in the revised DuoLine pumps launched earlier this year. Only now, says Michael Parry, product manager of Primary Vacuum Pumps at Pfeiffer, the advantages of saving energy, reducing maintenance costs, and preventing downtown are even more pronounced.
Pfeiffer’s rotary vane pumps are offered in two configurations: a single-stage pump system with a cover inlet pressure range of 1,000 to approximately 0.5 mbar, and a two-stage serial pump system (like the DuoLine) that have an expanded inlet pressure in the high-vacuum range of up to 0.005 mbar. This allows the DuoLine to support critical processes and serve as backing pump to turbomolecular applications. The current lineup (Duo 1.6, 3, 6, and 11) offers pumping speeds ranging from 1.25 to 11 m3/h.
The key feature of the DuoLine pumps is the use of a new contactless, magnetically coupled drive, which helps save energy by hermetically sealing the pumps. This drastically reduces oil leakage potential and improves both the environmental impact and the service life of the pump. It also minimizes maintenance requirements, leading to cost savings per pump and extended maintenance intervals. The new design also lightens the pump relative to its similarly performing DuoLine of the previous year.
A completely sealed wet pump is a significant advance, in part because all wet rotary vane pumps require pump oil. It fulfills three important functions in a rotary vane pump, according to Parry. It seals, lubricates valves and bearings, and guides the compression and friction heat over the aluminum casing to the outside to cool the pump. Maintaining the oil level is an important preventative step; if the level drops too low, the pump system can be blocked due to lack of lubrication, leading to rapid failure. Low oil also allows compression heat to build, which ages the fluid that is there. In addition to shortening pump and component life, the formation of oil carbon can also cause performance problems.
Normally, users of wet rotary vane pumps must change the oil every 12 months as a preventative measure. With the new DuoLine, that period has been extended.
In addition to the new coupling design, an integrated, hydraulically controlled high-vacuum safety valve increases operational reliability. This valve disconnects the pump from the vacuum recipient in the event of intentional or unintentional standstill, using the displaced gas to vent the pumping system and prevent operating fluid from rising into the exhaust gas.
In addition to internal mechanical improvements, the development team was also able to reduce the footprint of the pump. New placement of the vacuum connections on the top side of the pump is intended to improve the ability of users to integrate the unit with other pumps or systems.
“These pumps offer reliable operation as a standalone pump or as a backing pump in turbomolecular pumping stations,” says Parry. The pumps are also offered with a conventional radial shaft sealing ring.