Liquid ring vacuum pumps
They are extremely simple, durable and dependable. Designed to operate in demanding environments like the paper, power, mining and chemical process industries, these pumps offer durability and reliability at a low cost of operation.
These durable pumps can handle excess liquid carryover without any difficulty, even if it arrives as massive slugs. Constructed of L stainless steel, the series offers excellent corrosion resistance and can be outfitted with a variety of mechanical seals. It also includes a patented gas scavenging feature. With four models ranging from - CFM and vacuum levels as low as 1" HgA, the AT's are an ideal choice when you need a rugged and long lasting machine to handle your saturated process gases.
Marine Duty Vacuum Pumps NASH has been providing vacuum pumps and packages in shipboard priming applications for over 50 years and continues to offer a wide range of classic products for this service.
The liquid-ring pump compresses gas by rotating a vaned impeller located eccentrically within a cylindrical casing. Liquid usually water is fed into the pump and, by centrifugal acceleration, forms a moving cylindrical ring against the inside of the casing.
This liquid ring creates a series of seals in the space between the impeller vanes, which form compression chambers. The eccentricity between the impeller's axis of rotation and the casing geometric axis results in a cyclic variation of the volume enclosed by the vanes and the ring. Gas, often air, is drawn into the pump through an inlet port in the end of the casing. The gas is trapped in the compression chambers formed by the impeller vanes and the liquid ring.
The reduction in volume caused by the impeller rotation compresses the gas, which reports to the discharge port in the end of the casing. Compressed gas on discharge of pump contains certain amount of working liquid which is usually removed in vapor—liquid separator. The earliest liquid-ring pumps date from , when a patent was granted in Germany to Siemens-Schuckert. US Patent 1,,, for liquid-ring vacuum pumps and compressors, was granted to Lewis H.
Around the same time, in Austria, Patent was granted to Siemens-Schuckertwerke for a similar liquid-ring vacuum pump. Liquid-ring systems can be single- or multistage. Typically a multistage pump will have up to two compression stages on a common shaft.
In vacuum service, the attainable pressure reduction is limited by the vapour pressure of the ring-liquid. As the generated vacuum approaches the vapour pressure of the ring-liquid, the increasing volume of vapor released from the ring-liquid diminishes the remaining vacuum capacity. The efficiency of the system declines as a result. Single-stage vacuum pumps typically produce vacuum to 35 Torr mm Hg or 47 millibars 4.
Some ring-liquid is also entrained with the discharge stream. An internal passage joins the openings from the pump inlet to an inlet port in the cone. There's also a passage from the cone discharge to the discharge connection on the head. Some NASH pumps have a port plate configuration rather than conical, but the principle is the same. This diagram demonstrates what the rotor and body do while the pump is in operation.
The spinning of blue liquid forms a ring due to centrifugal force. Because the rotor axis and body axis are offset from each other, the liquid ring is not concentric with the rotor. Air or gas traverses the internal passage to the cone inlet port. As the white dots indicate, the gas is drawn into the rotor chambers by the receding liquid ring, similar to the suction stroke of a piston in a cylinder.
The liquid ring does the job of pistons, while the rotor chambers play the part of cylinders.