Blower Vacuum Pumps: These are positive displacement pumps that operate by pulling air through a pair of meshing lobes not unlike a set of stretched gears. Air is trapped in pockets surrounding the lobes and carried from the intake side to the exhaust. The most commonly used type is called the Roots Blower Pump.
Things to Consider: Volume flow versus pressure, Suction volume, Speed, Power requirements, Dimensions, Weight, Materials of construction, Warranty.
Dry Mechanical Vacuum Pump: Dry screw vacuum pumps operate without oil or water in the pumping chamber, and with their straight-through design, they can handle both condensable vapors and some solids without leaving residue. There is no metal-to-metal contact inside the pumping chamber, so wear is greatly reduced.
Things to Consider:Pump capacity, Materials of construction, Suction, Discharge, Motor power, Cooling water capacity, Dimensions, Weight, Warranty.
Jet Vacuum Pump: Also known as an ejector pump, works by converting pressure energy of a moving fluid into velocity energy as it flows through a relatively small nozzle. The lowered pressure of the moving fluid creates suction in a mixing chamber, into which process fluid is drawn from the vessel being evacuated. The process fluid mixes with the moving fluid stream and is removed from the system.
Things to Consider: Mass flow rate and molecular weight of each component present in the process fluid to be evacuated, Pressure and temperature at the inlet to the vacuum-producing system, Motive fluid type, Motive fluid temperature, Motive fluid max/min available pressure, Vapor pressure for each component in process fluid, If motive fluid is steam quality must be specified, Pressure against which device will discharge, Dimensions, Weight, Warranty.
Liquid Ring Vacuum Pump: A rotating positive displacement pump. Its function is similar to a rotary vane pump except that the vanes are part of the rotor and churn a rotating ring of liquid to form the compression chamber seal. Because the rotor is the only moving part, they generate low friction. These pumps are typically powered by an induction motor. The liquid ring pump compresses gas by rotating a vaned impeller within, and eccentric to, a cylindrical casing.
Things to Consider: Pumping speed versus inlet pressure, Water consumption versus inlet pressure, Nominal pumping speed, Ultimate end pressure, Ultimate vacuum, Motor size, Motor rotational speed, Maximum sound level, Weight, Dimensions (LWH), Dimensions (inlet/outlet), Materials of construction, Warranty.
Once-Through Oil Vacuum Pumps. These pumps, also called OTO pumps, are the sliding-vane type that uses once-through oil to seal clearances and lubricate moving parts. Vanes are in slots in a rotor, mounted eccentrically to the pump chamber. As they rotate, centrifugal force pushes the vanes against the chamber walls, creating pockets whose size varies. This size variation creates suction which draws process gas into the pump from the vessel being evacuated. Compression occurs as the vanes rotate toward the discharge side of the device, decreasing the area and forcing the gas and lubricating oil against the discharge valve. The discharge valve opens slightly above atmospheric pressure. These pumps can handle acidic or otherwise corrosive vapors, because the once-through oil continuously flushes the vapors out. OTO pumps are usually found in pharmaceutical plants and chemical plants, for drying, evaporation, distillation or other vessel evacuation tasks.
Things to Consider: Pumping speed versus inlet pressure curve, Nominal pumping speed, Free air displacement, End vacuum, Motor size 3 phase, Motor rotational speed, Inlet connection, Outlet connection,Sound level at one meter, Standard sealant capacity, Sealant usage rate (min/max), Cooling water consumption, Shipping weight, Dimensions (LWH), Warranty.