Laboratory vacuum pumps are machines that create vacuums in enclosed spaces for use in laboratories. A vacuum is a space where no physical matter is present. While no perfect vacuums exists (it is also impossible to create a perfect vacuum), machines can create partial vacuums by removing atmosphere from enclosures.
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In laboratories that conduct tests on the electric conductivity of gasses, near vacuum conditions are required to avoid the interference of air molecules during tests. Electron microscopes require near vacuum conditions in order to scan objects effectively. Experiments that produce hazardous gasses require the evacuation of those gasses; many laboratory pumps are designed to be chemical-resistant and capable of removing harmful gasses from enclosed spaces of various sizes. Some laboratory pumps feature vacuum concentrators and gas drying systems; traps and aspirators remove moisture, expelling clean, particle-free air. Vacuum pumps are usually made of heavy-duty stainless steel because of the material's strength and resistance to contamination. Because air pressure affects the state of all materials, pump system accessories like gaskets and seals must be strong enough to retain their shape despite exposure to variable and extremely low pressures.
Rotary vane pumps are commonly used in laboratories, but scroll pumps, piston pumps, diaphragm pumps, liquid ring pumps, momentum transfer pumps, cryopumps and other vacuum pump varieties are also used. There are three main categories of vacuum pumps: positive displacement, momentum transfer and entrapment pumps. Positive displacement pumps enlarge one cavity within a chamber while compressing another to create a vacuum. Momentum transfer pumps treat gases like liquids by bringing them into contact with solid surfaces to create momentum that carries the molecules out of the vacuum chamber and through the exhaust. Entrapment pumps rapidly heat or cool the collected molecules to compress and trap them in a solid or absorbed state. Pump varieties can be further distinguished from each other based on whether they are wet or dry. Wet pumps are oil sealed or lubricated or, like liquid ring pumps, they require liquid within their pump enclosures. Because of most liquid seals' high level of effectiveness, wet vacuum pumps are generally capable of generating lower-pressure vacuums than dry vacuums. However, oil-contamination of the vacuum enclosure or other areas is a possibility with wet vacuum pumps, so they are often paired with devices to prevent oil leaks. Dry pumps make no use of any liquids, oil or otherwise. For this reason, they can be more suitable in laboratory settings, because they are guaranteed not to contaminate workspaces.
