Vacuum rotary piston

In 1840 a hydrauHc power network, which involved large reciprocating pumps that were driven by steam engines, suppHed fluid power to London. However, concurrent technology in steam (qv) turbines and the electric generators outmoded such networks until hydrauHc systems were improved with the use of rotary pumps and oil. The rotary piston pump marked the transition from use of water to oil as the hydrauHc fluid (4). The use of vacuum-distilled, refined mineral oils were instmmental in the success of rotary axial piston pumps and motors such as the Waterbury variable speed gear... 

The most used mechanical vacuum pumps or compressors are reciprocating, liquid-ring, rotary-vane, rotary blower, rotary piston, and diaphragm. 

Huff [23] found that reciprocating and rotary piston pumps were the most economical mechanical systems for their range of application. Obviously, the economic discussions are dependent on the vacuum expected and the local utility costs, plus the cost of maintenance. 

Vacuum capacities and operating ranges, table, 344, 355 Ejectors, 344, 357 Integrated systems, 344 Liquid ring pumps, 344 Rotary lobe blowers, 344 Rotary piston pumps, 344 Rotary vane pumps, 344 Vacuum equipment, 343 Applications diagram, 352 ASME Code, 344 Pumps, 382 Steam jets, 357 Vacuum flow,... 

Vacuum pumps reciprocating piston type decrease the pressure to 1 Torr rotary piston down to 0.001 Torr, two-iobe rotary down to 0.0001 Torr steam jet ejectors, one stage down to 100 Torr, three stage down to 1 Torr, five stage down to 0.05 Torr. 

Like Roots pumps, claw pumps belong to the group of dry compressing rotary piston vacuum pumps (or rotary vacuum pumps). These pumps may have several stages their rotors have the shape of claws. 

A clean and dry vacuum system (qpy = 0) with V = 2000 I (as in example 1) is to be pumped down to a pressure of Pend - 10 tAbar. Since this pressure is smaller than the ultimate pressure of the rotary piston pump (Sg max ... 

N cuum technology acceptance specifications for rotary piston vacuum pumps Part 1 - Rotary piston and vane type rotary vacuum pumps in rough and medium vacuum range Part 2 - Roots vacuum pumps in medium vacuum range ... 

Rotary piston pump studies made by Sadler12 demonstrated that the above attributes of piston pump design helped them outperform vane design pumps both in speed and vacuum achieved (Sadler compared pumps of comparable size). On the other hand, piston pumps had greater vibration. 

A rotary-piston pump is an oil-sealed, positive-displacement vacuum pump. The oil both lubricates the pump and seals the discharge from the suction side of the pump. As the piston rotates, gas enters a chamber, as shown in Figure 5.2. Then, the inlet port closes, and the gas is compressed in the chamber until the discharge valve opens, exhausting the gas to the atmosphere. Possible contamination of the oil with condensable vapors, usually water, is a problem. One way condensation can be avoided is by reducing the partial pressure of the condensable gases by allowing air to leak into the cylinder, which is called a gas ballast. 

The mechanical vacuum pump consists of an eccentrically mounted rotor driven inside a cylindrical housing. Two types of mechanical pumps are constructed (a) the rotary piston type, where the rotor comes in close contact with the housing and thus makes the seal between intake and exhaust compartments, and (b) the vane type pump where two vanes, spring-mounted in the rotor, make contact with the walls of the housing and thereby divide the space between the rotor and the housing. Typical construction is shown in Figs. 2 and 3. 

Rotary piston oil-sealed vacuum pump, 0.015 kPa-abs, with base plate, drip proof... 

Rotary piston vacuum pumps are based on the rotational action of an eccentric cam — not a piston producing a reciprocating action in a linear direction. Like linear piston pumps, it is the piston in this pump which is exposed to the material being removed from the work chamber. 

Figure 2.12 Arrangement of Components in a Rotary Piston Vacuum Pump...

P. Systems that initially remove air with vacuum and later remove solvent with vacuum are referred to as vacuum-to-vacuum systems within the EPA NESH/ P literature. It is perfectly possible, and some firms have done or are doing so, to use more than one type of vacuum pump in an enclosed cleaning machine. For example, some firms use rotary piston pumps to remove air from the work chamber These pumps require oil changes and mist eliminators. But they don t contaminate the cleaning solvent with seal oil because solvent never contacts the pump. 

Positive displacement pumps diaphragm vacuum pumps, liquid ring vacuum pumps, rotary vane and rotary piston vacuum pumps as well as Roots vacuum pumps (dry compressing claw and screw pumps are not yet mentioned here but also belong to this group of pumps). 

LRVPs, similar to all rotary piston displacement compressors, are characterized by small vibrations and low-pulsation delivery. Nevertheless, if the operating performance does not meet the requirements of the customer, the vibration and sound emissions can be reduced by more or less extensive measures. On behalf of the most cost-effective solution possible, it requires well-founded knowledge of the procedures in the vacuum pump. 

There is also a much more compact and low-cost option - based on the pump manufacturer concept . This concept has been tried and tested for decades in oil-lubricated rotary piston vacuum pumps - so why not in LRVPs. There is no need for extensive frame constructions for mounting system components. Costintensive pipes required for manufacturing previous units, as well as throughout the service life, are no longer required. Components can be retrofitted easily. 

Figure 3.38 Arrangement of a combination of rotary piston and iiquid ring vacuum pump.

It is to be taken into account that with the employment of rotary piston vacuum pumps, the temperature of the fluid fed to the liquid ring compressor is higher than with the other combinations. In addition, this heat is to be dissipated by the ring liquid, so that the temperature of the liquid ring will be higher and with it the suction capacity will be lower. 

Figure 5.6 Working principie of a rotary piston vacuum pump. (With permission from Oer-likon Leyboid Vacuum, Coiogne, Germany.)...

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