Seals rotary pumps

Figure 13-17 shows a balanced, single, rotary dement seal mounted onto the pump shaft, pressed against the stationary face and gland, mounted in the seal chamber. Note the individual component parts of the rotary element. 

Standard 682 Shaft Sealing Systems for Centrifugal and Rotary Pumps... 

API Std 682 Shaft sealing systems for centrifugal and rotary pumps ... 

Instead of rotary pumps, large water jet, steam ejector, or water ring pumps can be used. For batch evacuation, and the production of hydrocarbon-free fore vacuum for sputter-ion pumps, adsorption pumps (see Section 2.1.8.1) are suitable. If the use of oil-sealed rotary vane pumps cannot be avoided, basically two-stage rotary vane pumps should be used. The small amount of oil vapor that backstreams out of the Inlet ports of these pumps can be almost completely removed by a sorption trap (see Section 2.1.4) Inserted In the pumping line. 

Vacuum pumps acceptance specifications Part 1 (Oil-sealed rotary pumps and Roots pumps) 28426 1979... 

Brake, hydraulic, and recoil-cylinder fluids fall in much the same field of operating conditions. These are employed in systems in which operating units are exposed to low temperatures, and in practically all cases the connecting tubing lines are so exposed. Temperatures are not likely to go very high, but for aviation, temperatures as low as —70° F. may be frequent. Practically all brake systems and many hydraulic systems employ reciprocating units packed with synthetic rubbers. Hydraulic systems employ rotary pumps and often rotary motors these cannot be soft packed but are only capillary-sealed—i.e., close clearances. These pumps and motors drop in volumetric efficiency as viscosity falls. 

A. Rotary Oil-Sealed Pump Designs. All of the commercial oil-sealed mechanical pumps are based on a rotor inside a cylindrical stator. These individ-... 

B. Troubleshooting and Mounting a Mechanical Pump, it will be noted in Fig. 6.2 that gas from a rotary pump is exhausted through an immersed flapper valve. For this valve to make a good seal it must be covered with oil. One common cause of the loss of ultimate vacuum performance in these types of pumps is a low oil level, and this should be the first item to be checked when a pump is not performing well. A telltale sign of low oil is a change in the sound of the pump. 

Fig. 6.4. Cross-section of a metal diffusion pump. The upper stage in this pump has a wide annular opening (A) which provides a good ultimate vacuum. The lower stage has a small annular opening (A ) so the pump will operate against a high fore pressure. (B) High-vacuum connection to the low-temperature trap and vacuum line. (C) Connection to rotary oil-sealed pump. This pump is cooled by means of water tubes (D). Air-cooled versions have fins in place of these tubes and a fan is installed to blow air over these fins. (E) Electrically heated oil reservoir.

VACUUM PUMPS (ROUGH-MEDIUM VACUUM RANGE) 3.2.1 Oil-sealed Rotary Pumps... 

With oil-sealed rotary pumps, it is possible to achieve values of k of 105 to 106. 

Figure 3.2 RGA of components at the inlet of an oil-sealed rotary pump contaminated with pump oil. Masses 28, 41 and43, 55 and 57,67 and 69 etc. are due to hydrocarbon fragments occurring at mass intervals 14 ( CH2 ) Mass 28 is frequently due to N2from air-inleakage...

Ethanol is to be pumped with an oil-sealed rotary pump with an exhaust pressure of 1.3 bar. Calculate the vapour tolerance to ethanol if the pump temperature is about 60 °C and atmospheric pressure is 1000 mbar. 

A mixture of water vapour and air is to be removed from a vessel using an oil-sealed rotary pump. If the exhaust temperature is 65 °C and the pump is not fitted with an exhaust filter, calculate the critical partial pressure ratio which should not be exceeded if condensation is to be prevented. 

This pumping speed is achievable using a two-stage oil-sealed rotary pump. If a dry pump, such as a hook-and-claw pump is required, then a Roots + dry pump combination would have to be used because of the limited pult of the dry pump (see Figure 3.3). 

To maintain 10 1 mbar, Smin for the backing pump should be 76.1 Ls-1 (-275 m3h-1). This is achievable with, say, a Roots + two-stage oil-sealed rotary pump combination e.g. >SRoots = 500 m3 h 1, SIotaiy = 60 m3 h 1. 

Moisture is to be removed, in a drier, from compacted material with a microcrystalline structure. The drier, fitted with a heating jacket and a regulator to maintain a constant temperature, is charged with 100 kg product containing 30% water. The final product must have a residual moisture of 0.1% or less. Because of the nature of the product, its temperature should not exceed 50 °C and, to achieve the required dryness, a pressure of 2 mbar is required. It is proposed to carry out the process with a single-stage oil-sealed rotary pump (Seff = 100 m3 hr1, water vapour tolerance = 50 mbar at 40 °C and pult (with gas ballast) = 1 mbar). 

Chapter 3 summarised initially the various types of vacuum pump available and the pressure ranges in which they normally operate. Subsequent sections dealt specifically with types of pump and, in some cases, to support calculations, reviewed the operating principles and characteristics. For example, aspects of oil-sealed rotary pump operation were discussed (Examples 3.1-3.5) and Roots pumps, widely used in applications where large gas loads at pressures in the rough-medium range have to be handled, were examined (Examples 3.7-3.9). 

Oil-sealed rotary pump 0.25 to 500 760 to 2x10 2(1 stage), 760 to 5xl0-3 (2 stage)... 

---