Liquid Ring Vacuum Pumps, Compressors and Systems

Transcription

1 Helmut Bannwarth Liquid Ring Vacuum Pumps, Compressors and Systems Conventional and Hermetic Design Translated by Christine Ahner WILEY- VCH WILEY-VCH Verlag GmbH & Co. KGaA

2 XIII Foreword VII Preface IX Preface of the first edition in German language in 1991 XI 1 Gas Physics and Vacuum Technology The term "vacuum" Application of vacuum technology Basic operations in process engineering Basic fields and worked-out examples for the application of vacuum technology Overview of the most important vacuum processes Basic designs of apparatus for mass transfer and mass combination Limits to the application of vacuum in process engineering Operating ranges and measuring ranges of vacuum Vacuum pressure ranges Vapor pressure curve of water in vacuum Vacuum operation ranges, temperature pressure table Total pressure measuring Pressure meters Definition of terms for vacuum measuring devices Gas flow and vacuum ranges Vacuum ranges and types of flow Mean free path Reynolds number Gas flow, suction power, suction capacity Flow losses in pipework Effective suction capacity of vacuum pumps Gas-inflow and outflow on a vacuum chamber Practice oriented application of the gas flow calculation Physical states of matter The terms gases, vapors, vacuum 44 Liquid Ring Vacuum Pumps, Compressors and Systems. Helmut Bannwarth Copyright 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim ISBN:

3 XIV Physical basic principles of ideal gases Standard temperature and pressure Real gases and vapors Phase transitions and their descriptions Mixtures of ideal gases Mass composition Molar composition Volumetric composition Ideal gas mixtures and general equation of gas state Gas mixtures and their calculation Density of an ideal gas mixture Molar mass of gas mixture Gas constant of an ideal gas mixture Relation between mass proportions and volume percentage Gas laws and their special application in vacuum technology Discharge of gases and vapors General state equation of gas Real gas factor Z General gas constant The special gas constant depending on the type of gas Thermal state equation for ideal gases Suction of dry gases and saturated air-water vapor mixture by liquid ring vacuum pumps Gases in mixtures with overheated vapors Condensation and cavitation Change of gas state during the compression process The isothermal compression The adiabatic compression Adiabatic exponent K Especially distinguished changes of state Names and definitions in vacuum technology Machines for Vacuum Generation Overview of vacuum pumps ill 2.2 Description of vacuum pumps and their functioning Gas transfer vacuum pumps Gas binding vacuum pumps Operating fields of pumps ace. to suction pressure Suction pressure and suction capacity of different pump designs Usual designs and combinations of vacuum pumps Sliding vane vacuum pump Multi cell vacuum pump Liquid ring vacuum pump Rotary plunger vacuum pump Trochoidal vacuum pump 131

4 XV Roots pump Jet pump Vacuum pump units and their control The three phases of evacuation Vacuum pumps in series Names and definitions of vacuum pumps and their accessories Liquid Ring Vacuum Pumps and Liquid Ring Compressors Liquid ring vacuum pumps and compressors with radial flow Liquid ring machines with axial flow Liquid ring pump with lateral channel Liquid ring pump with eccentric screw wheel Liquid ring machines with elliptic casing Liquid ring compressors Liquid ring machines with eccentrically installed impeller The operating liquid Influence of the operating temperature of the ring liquid on suction capacity and suction pressure of the pump Operating behavior at different densities of the operating liquid Influence of the viscosity of the operating liquid on the discharge behavior of the pump Solubility of gases in the operating liquid The quantity of operating liquid The behavior of liquid ring vacuum pumps in case of liquid being carried simultaneously The carrying of contaminants The condensation effect Characteristic curves of liquid ring machines at different compression pressures and suction pressures The similarity law for liquid ring gas pumps Pump performance and power consumption of liquid ring machines Characteristic curves of liquid ring vacuum pumps and compressors Cavitation Cavitation protection Gas ejector in combination with the liquid ring vacuum pump Operating range of a vacuum pump with gas ejector Operation mode of gas ejectors Operating modes, supply of operating liquid Operation without liquid recirculation (fresh liquid operation) Operation with liquid recirculation (combined operation) Operation with closed circulation (circulating liquid operation) Materials for liquid ring machines Sealing of liquid ring vacuum pumps and compressors 224

5 XVI 3.17 Drives for liquid ring machines Electric motor drive Hermetic drive systems Explosion protection on canned motor machines according to the European Standard "EN" Double walled security in hermetic drives (DWS) Control and monitoring devices for machines with double tube/double can Compression of explosible gas-vapor mixtures with liquid ring compressors Safety standards for rotating machines Characteristics and fields of applications of liquid ring vacuum pumps and compressors Vacuum and Compressor Plants with Liquid Ring Machines Demands on pump systems in process engineering Basic combinations of liquid ring vacuum pumps and equipment in compact plants Control of liquid ring pumps and pump systems Electronic vacuum control for distillation in laboratories Liquid ring vacuum pump system with automatic suction pressure control Control of coolant consumption for heat exchanger and immission cooler Optimal evacuation with liquid ring vacuum pumps Pump unit designs and possibilities for the application of liquid ring machines with design examples Vacuum systems for condensate recovery Pump systems with hermetic liquid ring vacuum pumps and compressors Vacuum pump unit of special design for the suction of polluted process gases Steam jet liquid ring vacuum system of corrosion-resistant design Selection of application examples for liquid ring machines Electric heating and insulation on pumps and plants Names and definitions - vacuum systems, components and equipment Components for Pump Units with Liquid Ring Vacuum Pumps and Compressors General criteria Liquid separators Vessel arrangements Auxiliary appliances for vessels and pipework 293

6 XVII Inflow control unit Outflow control unit Injection segments Purging equipment Aeration and ventilating facilities Sieves for liquids Gas cleaning devices Chamber separator Impact plate separator Centrifugal separator Aero-cyclones Filters Heat transfer devices Heat transition Contamination of transfer surfaces Designs of heat exchangers Condensers Surface condensers Co-condensers Condensate discharge Exhaust gas condenser Temperature controllers Flowmeters Shut-off instruments Check valves and ball check valves Safety valves Vacuum ventilation valves Flanges in vacuum technology Fast flange connections, small flange connections in vacuum technology Surface condition of sealing surfaces Sealing materials in vacuum technology Vacuum greases Design of Vacuum Pumps and Pipework Leakages in vacuum systems Evacuation time and suction capacity of the pump Graphical determination of the evacuation time of vessels in the rough vacuum range Determination of suction capacity of vacuum pumps from the leakage of the vessel Leak rate values in practice Determination of the leak rate by measuring on an existing plant Determination of the pump suction capacity according to the apparatus volume 338

7 XVIII 6.5 Vacuum loss of vessels with different designs Arithmetic determination of volume flows, mass flows and partial pressures Calculation of gas-vapor mixtures Flow velocities of liquids, vapors and gases Assembly and Testing of Vacuum Pumps and Systems Installation of machines and devices Pipework General notes regarding installation Cleaning of the pipework Characterization of the pipework according to the flow media Leakage tests and pressure tests of devices and pipework in the overpressure range The leak test The pressure test Leak detection methods on components and plants in the range of vacuum and overpressure The leak detection Leak detectors Integral leak test Leak localization on test units under vacuum or with test gas overpressure Leak test methods with helium leak detectors on vacuum plants Test leak Acceptance and performance tests on liquid ring machines Acceptance rules Similar experiment on liquid ring vacuum pumps Acceptance test for liquid ring vacuum pumps Electrical components and cables Insulation Putting into operation Closing down Materials, Surface Treatment and Safety-at-work in Vacuum Engineering Criteria for the selection of materials Surface treatment Vacuum hygiene Corrosion and corrosion protection Treatment of metal surfaces for corrosion protection by means of inorganic coats Formulas for chemical or electrolytic pickling and electrolytic polishing of metals Paint coats 385

8 XIX 8.3 Health and safety protection at the workplace during maintenance and operation of vacuum plants Danger through implosion Auxiliary materials for operation and maintenance of vacuum pumps and plants Explosion Protection and Explosion-proof Electrical Equipment General Danger of explosion and measures to prevent the ignition of explosion-prone atmospheres Zoning of explosion-prone areas Classification of explosion-proof electrical equipment into the main groups I and II Ignition protection classes Temperature classes Standardized symbols for electrical equipment in explosion-prone areas ace. to EN to EN Examples of explosion protection symbols Comparison of symbols for explosion protection and firedamp protection according to the old and new standard Protection classes ace. to DIN IEC 34, part 5/VDE 0530, part Motor power rating Three-phase A.C. motors in VIK-design "ATEX 100a" according to EU-Directive 94/9/EG Application for liquid ring vacuum pumps Regulations outside of CENELEC member states Electric motors for explosion-prone areas ace. to the American NEC-Rules Classes and hazardous locations Group classification Temperatures for Class I and Class II in "hazardous locations" Application of motors according to American regulations Identification of motors Protection classes ace. to NEMA in comparison to IEC Internationally common power supply systems Appendix International system of units (SI) SI basic units Derived SI units Additional SI units Decimal multiples and parts of SI units Units outside the International System of Units Units of measurement and their conversion Summary of physical and technical units 434

9 XX 10.4 National and international standards, recommendations and regulations Graphical symbols used in the vacuum and process technology Graphical symbols and call letters for measuring control and regulation (MCR) in process engineering Physical call values of liquids and gases Tables and diagrams 470 Index 487