Q1: How noisy are these pumps? I’m not sure I want noisy vacuum pumps in my lab.
A1: Pumps used in VACUU•LAN® networks typically operate at 45-50 dBA. For reference, common reference materials describe face to face conversation as 60 dBA. This means that you will never have to shout over a VACUU•LAN® network pump. In fact, it is much quieter than the typical fume hood, so it is entirely likely that you will not realize that the pump is operating, even without a sound insulating cabinet. Watch our pump noise video to get a sense of how quiet a vacuum pump can be.
Q2: You report all of your vacuum performance on VACUU•LAN® networks in millibar and Torr. We use inches of mercury. How do these units compare?
A2: Millibar and Torr are units of pressure that are on an “absolute” scale. That is, they begin at zero pressure and get larger as pressure builds – all pressure is positive. Because they have an absolute reference point, these scales are favored in many scientific applications. When using these absolute scales, “vacuum” means simply pressure that is below normal atmospheric conditions. “Inches of mercury” are widely used in North America to represent vacuum in the construction professions (architecture and engineering). This is a relative scale where the zero point is atmospheric pressure as represented on a gauge. It is often reported as “in. Hg gauge”. The rising numbers on this scale correspond to decreasing pressure (increasing vacuum). Since scales have different zero points and run in opposite directions, conversion between these scales for communication between scientific and engineering specialists can be complicated. Adding to the confusion is that local atmospheric pressure differs from sea level to mountain locations, with the result that there can be a 15% difference in the absolute pressure represented by the zero point on a gauge scale. As a result, gauge pressures are not reliable indicators of actual conditions for scientific reporting. Tools like our handy vacuum unit conversion calculator and our unit conversion slide chart exist to help with converting among the wide range of standard vacuum units. If you’d like to receive a free vacuum unit conversion tool, please contact us to request one.
Q3: Can I attach this to my copper piping with conventional lab vacuum ball valves?
A3: You can attach a VACUUBRAND oil free diaphragm pump to your current copper piping, but that will not deliver the advantages of a VACUU•LAN® vacuum network. The copper piping networks used for central vacuum system distribution are high-flow piping that is designed to be supported by large central vacuum pumps with very high pumping speeds. The high pumping speeds compensate for the vacuum losses that occur when the uncontrolled vacuum valves on traditional systems are opened. Attaching a lab scale pump—even a high-performance VACUUBRAND pump—to such a tubing network will result in inadequate gas flowrates and the likelihood of interference among users of the system. The result will be performance comparable to a large vacuum manifold, not the performance of a network that protects adjacent users from interference from others on the same network.
In contrast, a VACUU•LAN® network relies on the presence of VACUU•LAN® valves that control vapor flow. As a result, a lab-scale pump can provide adequate pumping speed to operate multiple vacuum applications at once while minimizing interference. The performance of a VACUU•LAN® network derives from the combined operation of the VACUUBRAND corrosion-resistant diaphragm pump with the VACUU•LAN® valves and tubing.
Q4: What is meant by “interference” among users of a vacuum system?
A4: A central vacuum system (CVS) is designed to serve a number of users who are connecting and disconnecting from the CVS unpredictably. When they do, this creates sudden pressure changes. An example is that, when a filtration is completed, air can flow freely through the filter and into the vacuum system because the liquid no longer serves to “plug” the vacuum port. In essence, it creates a leak into the vacuum system that persists until the port is closed. Since a vacuum system with a leak is not very effective at providing vacuum, this condition reduces the vacuum available on the CVS for other users, interfering with their work. The same effect occurs when boiling begins in an evaporative application. The sudden flow of vapor reduces the vacuum level within the system. For other users of the network, the changes from desired conditions can cause “bumping” and possible sample loss, or less than optimal vacuum conditions. It is even possible for cross-contamination to occur. Cross-contamination happens when gas or chemical vapor drawn into the vacuum system at one port actually flows out of the vacuum system at an adjacent port that has been operating at a lower pressure (greater vacuum) than that available in the lines after another port is open, or evaporation begins at another location. Clearly, this poses a risk to the integrity of the work of scientists using a CVS. This video demonstrates the potential risk of cross-contamination in a traditional lab vacuum system.
VACUU·LAN® networks are likewise designed to accommodate a number of simultaneous users who are connecting and disconnecting from the network unpredictably. However, VACUU·LAN® networks are designed to minimize the pressure variations within the network when users open and close vacuum ports. Besides providing stable vacuum to scientists, this also minimizes the potential for interference between users and cross-contamination.
Q5: How is a VACUU·LAN® network different from a Central Vacuum System or other in-lab vacuum system?
A5: Basically, they are different because they are designed differently. Central Vacuum Systems and other in-lab vacuum systems are designed to allow uncontrolled flow through the vacuum turrets. They generate vacuum by simply pumping air and other gases/vapors out faster than gases/vapors can flow in to the system. As long as that happens, the system will stay under vacuum. But while that’s happening, the vacuum level can vary quite substantially. Those pressure variations also lead to the cross-contamination/interference issues discussed in Question 4.
In contrast, a VACUU·LAN® network is designed to control flow into the system through the vacuum ports. This not only mitigates the cross-contamination and interference issues, but it also allows for VACUU·LAN® networks to provide vacuum that is much deeper and much more stable than Central Vacuum Systems or in-lab vacuum systems which use standard copper pipe and standard vacuum turrets. VACUU·LAN® networks can provide vacuum as deep as 2 mbar (or 1.5 torr or about 29.9 in. Hg) – vacuum sufficient to support nearly all of the common evaporative or drying applications in a lab. In contrast, a good central system will only get down to 100 mbar (76 torr or 25 in. Hg), and many new vacuum systems operate at only 250 mbar (190 torr, 22.5 in. Hg). With a Central Vacuum System, these evaporative applications would require dedicated vacuum pumps to supply the deeper vacuum needed. And the stable vacuum provided by a VACUU·LAN® network makes lab applications like filtration, aspiration, or solid phase extraction go more smoothly and consistently.
Q6: You say that VACUU•LAN® vacuum networks are “modular.” What does that mean?
A6: VACUU•LAN® networks are modular in several ways. One aspect of modularity is that the vacuum needs only be installed where the need exists today. A VACUU•LAN® network can be installed as needed today, with additional vacuum capacity added after the fact when a need for vacuum is determined in a new location. This contrasts with central vacuum systems, which are inherently inflexible. Central vacuum systems are plumbed using large diameter piping located behind walls and between floors. That means that piping needs to be plumbed to every possible room where vacuum may (or may not) one day be needed, with pumps and piping diameters selected to accommodate the highest possible future flows. This overbuilding is expensive initially, and leads to higher than necessary operating costs for the life of the building.
Another aspect of the VACUU•LAN® networks’ modularity is in the performance options for each vacuum workstation. Each port has a common mounting base that can accept a range of controls from a simple on/off ball valve, to a manual valve that provides variable flow control, to a solenoid valve that can be operated with a VACUUBRAND electronic controller for full programmable control of individual ports on the network. Ports can be upgraded or traded among locations in a laboratory as needs change, based on the modularity of the vacuum port design.
Q7: How many vacuum valves can I put on the network?
A7: That depends on several factors, including what applications the network is used to support, the diversity factor (the percentage of open ports at any given time), and of course the size of the pump specified. With regard to the applications which the network will support, some applications place a high flow demand on the network while others impose a relatively low aggregate flow demand. For example, vacuum drying ovens tend to impose a high demand on the network whereas filtration and rotary evaporation impose lower flow demands (when done properly). Similarly, a low diversity factor means that many ports are closed, and thus imposing no demand on the network pump; this allows for a relatively high number of valves to be installed on a single network. And the opposite is true as the diversity factor approaches 100% – relatively fewer valves can be installed on a network with high simultaneous utilization. And of course the size of the pump itself has a large influence on the number of ports that are installed on a network. We offer a wide range of pumps so we can accommodate anywhere from 4 to 40 active vacuum ports. Talk with us about your intended use of your networks, and we can advise you how to ensure that you have sufficient vacuum for your needs without overbuilding.
Q8: Can I mix vacuum applications on a network?
A8: Absolutely. An advantage of a VACUU•LAN® vacuum network is that it can serve a range of vacuum applications at once, while preserving the performance of each port on the vacuum network. We suggest some care in applying this rule. Certain vacuum applications — such as rotary evaporation of complex samples that are subject to bumping and foaming — may be better served with a dedicated pump designed for such applications, such as the VACUUBRAND line of VARIO® pumps. VACUUBRAND’s VARIO® pumps offer self-regulating, continuously optimizing vacuum management of individual applications. Other applications — such as large vacuum ovens with very wet samples and therefore high vapor flow rates — may consume a substantial portion of the network pumping speed such that they can interfere with other users. Most routine lab vacuum applications can be operated simultaneously on a VACUU•LAN® vacuum network with other types of applications.
Q9: Does VACUU•LAN® technology only work in big-budget professional research laboratories?
A9: Not at all. Many VACUU•LAN® local vacuum networks are installed in small teaching laboratories with only four to eight vacuum ports. We even have installed VACUU•LAN® networks in high school labs. Networks can be a very economical way to provide vacuum to a small number of users with simple vacuum requirements.
Q10: How difficult is installation of a VACUU•LAN® local vacuum network?
A10:A VACUU•LAN® network is much easier to install than the rigid copper or stainless tubing networks of a central vacuum system. All VACUU•LAN® network connections are compression fittings that can be made with simple hand tools and minimal training. (We know of one VACUU•LAN® network installed by a college sophomore chemistry class!) No welding or brazed connections are required. Visit the Installation section of this website for an illustrated guide to making VACUU•LAN® tubing connections. Or contact us to request a copy of the full installation instructions.
We do make one recommendation to ensure a vacuum-tight network and avoid rework. The network can be tested as installed by connecting the pump first, and then adding the most remote port on the network. By testing each vacuum port as installed, using a vacuum gauge like the cordless DVR2 gauge by VACUUBRAND, you can ensure that each connection is tight and the entire network will provide performance that is up to specification when the network is complete. Tracking down an imperfect connection after the entire network is installed is a much more complicated job that can be avoided by simply testing as you go.
Q11: What is the longest tubing run that I can plan into a VACUU•LAN® network?
A11: We recommend a limit of 30 meters (100 feet). For networks with a large number of vacuum workstations, shorter runs are advisable, and the pump should be installed near the center of the network to optimize performance.
Q12: What about service? Isn’t it a lot harder to service distributed vacuum than central vacuum?
A12: VACUUBRAND oil-free, chemical-resistant pumps used in VACUU•LAN® networks have a recommended service interval of 15,000 operating hours. In a lab using vacuum intensively, say, 40 hours per week, the pumps are in use only about 2000 hours per year. Network pumps should be expected to operate many years without service. Should the pumps need service because of misuse (e.g., sucking liquids or particulates into the networks), service on individual pumps is simple, and leaves other vacuum users in a building unaffected during the service operation.
Q13: How big are the pumps?
A13: The pumps vary in size depending on the capacity chosen, but most have a footprint just a little over a square foot, and even our largest pumps will fit under fume hoods or in cabinet space in most lab furniture.
Q14: Do I need to provide for exhaust from the network pumps?
A14: Yes. In some applications, the exhaust from the pumps is expected to be innocuous. The problem is that lab uses change over time, and scientists using vacuum ports assume that noxious vapors are carried away safely. It is always a better plan to exhaust the network pumps through the building exhaust system – either directly or through a fume hood – rather than assume that all vapors or waste gases from vacuum operations are harmless.
Q15: Do pump cabinets need mechanical ventilation to remove heat?
A15: VACUU•LAN® pumps have motors that draw between 250 and 530 watts. This will generate heat in a closed cainet, but the heat can be easily managed by planning for convective airflow past the pumps. A common solution is to remove the cabinet backs to permit airflow into the service chase behind benches and fume hoods, and permitting entry of cool room air by way of louvers on doors or recessed cabinet floors to admit air behind doors. Cabinet temperatures should be kept below 40 degrees C (104 F) in order to prevent pump overheating.
One additional note is that pumps equipped with variable speed motors draw much less than rated power in normal lab operations. This significantly reduces heat generation in cabinets.
Q16: Can I test a VACUU•LAN® network with water or compressed air?
A16: No. Using water or compressed air are effective tests for a pressurized system, but are not appropriate for a system with connections and valves designed to work under vacuum. It is very important not to test with water. Water in a vacuum system must be completely removed in order to restore the full vacuum capacity of the system, since water in the lines will evaporate when vacuum is applied, and limit the ultimate vacuum of the system to the vapor pressure of water at room temperature (24 mbar/18 Torr) until all of the water is removed. This could take two days of continuous pumping.