Liquid seal ring compressors

Rotary compressors are classified into three general groups sliding vane, helical lobe, and liquid-seal ring. 

Figure 8.8 Liquid-seal ring rotary air compressor...

The liquid film seal uses metallic sealing rings and is liquid buffered to maintain a fluid film in the clearance area and thereby preclude gas leakage. It is not unusual in the screw compressor to find the radial bearing and seal combined. 

Figure 12-50C. The seal oil system supplies filtered oil to the liquid film rings or to mechanical-type seals at the correct pressure and temperature. The system is basically designed in accordance with API 614 and is suitable for continuous compressor operation. (Used by permission Bui. PROM 526/I-5/95-II. Nuovo Pignone, Florence, Italy New York Los Angeles and Houston, Texas. All rights reserved.)...

Jets have been partially replaced by liquid ring-seal pumps. These are really positive-displacement compressors. The gas is squeezed between the vanes of the compressor s rotor and a pool of liquid in the compressor s case. Liquid ring-seal pumps are not interesting. They have no character. They are not as complex as steam jets. Anyway, I will discuss positive displacement compressors in later chapters. 

Figure 76. Liquid film shaft seal with nlindrkwl hushing lor a high-pressure centrifugal compressor a) Shaft b) Bearing c) Pressure side d) Ambient side e) Floating seal rings f) Sea) oil surge vessel g) Sea) oil h) Lube oil i) Drain to gas-oil separaior k) Drain lo lube oil tank l) Elevation for seal oil head...

The vacuum at the top of the flash column is often produced by a sequence of three elevated steam-jet eductors with intermediate and final surface condensers to remove the steam. A liquid-ring compressor can be substituted for one or more eductors to conserve steam. Mechanical vacuum pumps are seldom used because of the corrosive nature of the off-gas. The noncondensible sour compressed gas and condensate are led away through a water seal for safety in case of steam system failure. The seal pot is equipped to skim off condensed oil continuously. 

Applications and uses medical implants, sealing rings, bearings, piston parts, pumps, high pressure liquid chromatography (HPLC) columns, compressor plate valves, and cable insulation. 

In dry compressors, shaft end seals are generally one of five type.s. These are labyrinth, restrictive ring, mechanical contact, liquid film, and dry gas seal. The labyrinth type is the most simple but has the highest leakage. The labyrinth seal is generally ported at an axial point between the seals in order to use an eductor or ejector to control leakage and direct it to the suction or a suitable disposal area. Alternatively, a buffer gas is used to prevent the loss of process gas. Appendix D presents a calculation method for use with labyrinth seals. 

Figure 7.19. Some rotary positive displacement compressors, (a) A two-lobe blower, (b) Performance of a two-lobe blower (Rools-Connersville Co.), (c) A screw pump with one power and two idle rotors (Kristal and Annett, 1940). (d) Performance of 3.5" screw pump handling oils at 1150 rpm against 325 psig (Kristal and Annett, 1940). (e) Principle of the liquid ring seal compressor (Nash Engineering Co.). (0 A sliding vane blower (Beaeh-Russ Co.).

Figure 11.25 also shows pressure relief on the column. The normal design pressure for vessels containing liquid chlorine is 15-20 atmospheres. The suction chiller, however, is connected directly to the compressor suction, where the pressure rating is much lower. The relief system on the suction chiller must also protect the compressor. Standard construction is a reverse-buckling Monel rupture disc in combination with a safety valve having Monel internals and a PTFE O-ring seal. 

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