VARIABLE VOLUME RATIO Two forms of variable volume control are available. 1. ADJUSTABLE VOLUME RATIO (MVI) 2. AUTOMATIC VARIABLE VOLUME RATIO (AVI) Compressor selections need to take account of the peak operating conditions likely to be encountered. However, actual operating conditions may vary, resulting in lower efficiencies. Control of capacity and volume ratio can maintain high efficiency levels. The Howden variable Vi concept, coupled to slide valve capacity control, offers alternative control methods. Where the pressure ratio across the compressor is consistently high or changes in pressure ratio are infrequent (e.g. the change from winter to summer conditions) then the MVi manually adjustable system will be entirely satisfactory. With lower pressure ratios, or where condensing conditions vary frequently, the Howden automatic control AVi system can be offered.
howden xrv 204 manual
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READ CAREFULLY BEFORE INSTALLING AND STARTING YOUR COMPRESSORThese instructions have been prepared to ensure that yourcompressor gives long and satisfactory service. Detailedinstructions for carrying out an annual inspection or overhaulprocedure is included for the following range of compressors:MK1G-1K/WRV163 MK6-6D/WRV204 MK6-6D/WRVi255 MK6-6C/WRVi321MK1/WRVi365 The entire manual should be read before reverting toany one section for specific information. One copy should be givento the personnel responsible for installing and operating thecompressor. All requests for information, services or spares shouldbe directed to: HOWDEN COMPRESSORS Compressor Business Unit 133Barfillan Drive Glasgow G52 1BE UK Telephone: Fax: E-mail: Website:or HOWDEN COMPRESSORS LLC 1850B North Gravers Road Plymouth MeetingPA 19462 USA
FIRST START Installation of the compressor will have beencarried out in accordance with Section 3 of this manual. TheCommissioning Engineer should however ascertain that the correctprocedures have been followed, in particular the coupling alignmentmust be checked, then proceed as follows: 1. Disconnect thecoupling between the drive and the compressor and check that thedirection of rotation is correct to drive the compressor in aclockwise direction, looking on the compressor input shaft.(Anti-clockwise if compressor MRV model). Fill the oil tank withlubricating oil of the correct grade to the required level asindicated on the tank level sight glass. Ensure that the manifoldand oil pipes to the compressor are clean then start thelubricating pump motor to circulate the oil and clean the system.The lubricating oil pressure differential control valve should beset to give a 30 psi (2 kg/cm) oil manifold differential pressurefor a standard range compressor and 40 psi (2.7 kg/cm) oil manifolddifferential pressure for an H designated compressor at correctoperating temperature, with clean oil filter elements fitted. Checkthe operation of any safety trips fitted by running the drive unitdisconnected from the compressor and mechanically operating thetrips, check that the actual settings are in accordance with thecontract specification. The lubricating oil differential pressuretrip can be set at 12 psi (0.85 kg/cm) on a standard rangecompressor and 22 psi (1.54 kg/cm) on H designated compressors bypartially closing the oil filter outlet isolation valve and therebyreducing the differential oil pressure. As the filters become dirtythe differential oil pressure will drop to these figures, which arethe minimum accepted value. Check that the compressor turns freelyby hand and reconnect the coupling between the drive unit and thecompressor. Check that the cooling water is turned on to thelubricating oil cooler, if fitted. Check that all gas inlet andoutlet isolating valves are open. Start the lubricating oil pumpmotor. NOTE: The compressor should be unloaded prior to start up.If the compressor is started without first being unloaded a higherstarting torque will be required. 11. 12. Start the drive unit andcheck that all gauges are indicating correctly. Run the compressorfor 30 minutes at minimum gas flows and check that all readings arenormal, then operate the capacity control valve to the requiredposition. This position will be indicated on the dial mounted onthe hydraulic cylinder. If possible, check the slide valve controlover the full range of capacity.
Notes about Dismantling and Re-assembly The dismantling andassembly method varies slightly between the WRV163 & WRV204compressors and the WRVi255, WRVi321 & WRVi365 compressors dueto differences in construction. It is, therefore, essential thecorrect procedure is used for the size of compressor involved.Reference should always be made to the Sectional Arrangementdrawing supplied. Use only proper locknut spanners to avoid damageto the locknut slots. Special tools to facilitate assembly anddismantling operations can be supplied on request. A list ofspecial tools is located in Section 9.3 of this manual. Alllockwashers, tabwashers, O rings and PTFE seals must be renewed onassembly. All lockwashers must be assembled according to theprocedure as described per Section 9.2. All fasteners should betorqued to the specified values as stated under Section 9.1.
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