GB/T 45055-2024Turbine compressors for large air separation plant (English PDF)

1 Scope

This document specifies the classification, technical requirements, test methods, inspection rules, packaging, transport and storage of turbine compressors for large air separation plants.

This document applies to the manufacture of axial compressors and centrifugal compressors for large air separation plants.

Note: the large air separation plants to which this document applies are plants with an oxygen output greater than 40 000 m3/h (standard conditions).

3 Terms and definitions

The terms and definitions given in GB/T 10606, JB/T 2977, JB/T 4113 and ISO 10439-1, together with the following, apply to this document.

3.1 compressor process section. The combination of compressor stages for which the inlet and outlet parameters, such as flow, pressure and temperature, are explicitly specified in the process scheme. Note: the interstage parameter requirements for instrument air extraction are not treated as a separate process section.

3.2 aerodynamic performance calibration. Comparison of the aerodynamic performance figures of the compressor running on site with the guaranteed design values.

3.3 main air compressor. The feed air compressor whose inlet medium is the local atmosphere.

3.4 booster compressor. The compressor whose inlet medium is high pressure air or high pressure nitrogen.

4 Symbols and abbreviations

4.1 Symbols. Av is the radial vibration displacement (peak to peak), expressed in micrometres (µm). Nmc is the maximum continuous speed, expressed in revolutions per minute (r/min).

4.2 Abbreviations. CCS: compressor control system. DCS: distributed control system. ESD: emergency shutdown device. MCC: motor control center.

5 Classification

5.1 Air separation process schemes. According to the way the oxygen is compressed, the process scheme of an air separation plant is either external compression or internal compression. The scheme and the equipment shall comply with GB/T 36227. Note 1: in the external compression scheme the low pressure oxygen produced by the air separation equipment is raised by an oxygen compressor to the pressure required. Note 2: in the internal compression scheme the liquid oxygen drawn from the main cold box is pumped by a liquid oxygen pump to the pressure the user requires; because of its high safety and reliability and its good overall economics, internal compression is widely used in the large air separation plants of the petrochemical and coal chemical industries.

5.2 Turbine compressors for air separation plant. The turbine compressors of an air separation plant (referred to below as compressors) are mainly the feed air compressor, the air booster and the nitrogen booster. The main compressor of an air separation plant is usually a single-shaft centrifugal compressor, a combined axial and centrifugal compressor or an integrally geared centrifugal compressor, and the booster is usually an integrally geared centrifugal compressor. The medium handled by the main air compressor is natural atmospheric air, containing oxygen, nitrogen, argon, moisture, carbon dioxide, dust and traces of hydrocarbons. The medium handled by the booster is air purified through the molecular sieve system, or pure nitrogen. The feed air of an air separation plant is available without limit and free of charge, so the running cost of the compressor train is essentially energy consumption; the factors that affect it are the energy consumption of the driver, the electricity consumed by the oil station, the pressure drop of the gas coolers, the pressure drop of the inlet filter and the pressure drop of the pipes and fittings.

5.3 Compressor train configuration. In the internal compression scheme, different air separation processes require different discharge pressures: the discharge pressure of the main air compressor is usually 0.55 MPa(A) to 0.8 MPa(A), and the discharge pressure of the booster falls mainly into two classes, the 5 MPa(A) class and the 7 MPa(A) class. The main combinations of compressor and driver in an internal compression air separation plant are: a) the main air compressor driven by its own motor or steam turbine and the booster driven by its own motor or steam turbine; b) the main air compressor and the booster driven by one steam turbine, also called a one drives two train, the turbine being designed with a shaft extension at each end; c) the main air compressor and the booster designed as one machine driven by a single motor or steam turbine, which is common where the booster discharge pressure is below 5 MPa(A).

6.1 General requirements

Where the technical requirements of ISO 10439-1, ISO 10439-2, ISO 10439-3 and ISO 10441 conflict with this document, this document prevails; technical requirements not covered by this document shall meet the technical requirements defined in ISO 10439-1, ISO 10439-2, ISO 10439-3 and ISO 10441. If specified, the compressor equipment, its components, the technology used, the raw materials and the manufacturing methods shall have been proved in actual service.

The compressor shall be provided with active noise reduction measures; if specified, passive measures shall also be provided, including the supply and installation of the noise reduction equipment. Note 1: active noise reduction means reducing noise by optimising the mechanical design of the compressor, including but not limited to lowering gas velocities and increasing casing thickness. Note 2: passive noise reduction means fitting noise reduction equipment such as acoustic hoods, jackets or acoustic fencing outside the casings of the compressor, the driver and the gearbox in order to lower the environmental noise.

All gas discharged from the compressor train to the atmosphere shall comply with GB 31571. The technical specification of the compressor shall state the spare parts list for installation and for the individual machine test run.

6.2 Mechanical construction

6.2.1 Pressure casing. The maximum allowable working pressure of each pressure casing shall be not lower than the set pressure of the relief valve of the compressor process section concerned. The casing design pressure shall meet the settle-out pressure of its process section. If a horizontally split casing is used, the joint face shall be a metal-to-metal design and a machined groove with an added sealing ring shall not be used. All fasteners of casing sealing faces and of external connection flanges shall be studs; if specified, hexagon head bolts or screws may be used. Lifting eyes or lifting columns shall be provided on the upper half of a horizontally split casing for lifting and turning it over.

6.2.2 Pressure casing connections. Standard mating flanges with the associated gaskets and fasteners shall be supplied as a set with the piping. The design of the suction and discharge nozzles shall not adversely affect the performance of the volute. Recommended values shall be given for the minimum straight length of the compressor inlet and outlet process piping, and the effect on compressor performance of site conditions that do not provide that straight length shall be assessed. No pressure-carrying connection on the casing shall be threaded.

6.2.3 Stationary parts. The first stage of each compressor process section shall be fitted with adjustable inlet guide vanes. The inlet guide vane shaft of the booster shall be well sealed so as to reduce gas leakage to atmosphere. Where necessary the internal labyrinth seals shall be of abradable design. Note: the abradable material meets the design temperature of the compressor. If specified, the split face of a horizontally split diaphragm shall have a groove with an inlaid sealing strip. Note: the material and properties of the sealing strip need to meet the design temperature of the compressor or the corrosivity of the medium.

6.2.4 Rotating parts. The thrust collar on the compressor rotor shall be integral with the shaft. Unless otherwise specified, impeller blanks shall be forged and impellers shall be welded or machined from solid. Unless otherwise specified, impellers shall be located axially by a sleeve or by a shaft shoulder.

6.2.5 Bearings and bearing housings. The bearing housing of the main air compressor shall be designed so that its upper half is separate from the upper casing. A chamber vented to atmosphere shall be provided between the bearing housing and the casing so that oil mist does not enter the casing. If the bearing housing is inside the compressor flow path, it shall be designed with an oil mist barrier to keep oil mist out of the flow path; where a double-wall construction is used, a vent to atmosphere shall be provided in the isolating chamber. For hydrodynamic radial bearings whose maintenance weight exceeds 20 kg, process holes shall be designed to make dismantling, fitting and adjustment easier. Where the compressor rotor weighs more than 6 t, the support bearings shall have a high pressure oil lift arrangement and the lifting equipment shall be provided. Note: the lifting equipment includes the motor, the high pressure oil pump, the instruments and the connecting parts.

6.3 Aerodynamic performance

Unless otherwise specified, the compressor shall satisfy all operating conditions, including running at off-design points under extreme conditions such as extreme summer conditions, extreme winter conditions and site start-up test conditions. The technical specification shall state the complete design interface input conditions, including inlet relative humidity, flow, pressure, temperature and cooling water conditions. If specified, the pressure loss limits of the coolers, valves, flow meters, piping and fittings shall be stated.

The performance guarantee condition of the compressor shall be the operating point expected to run for the longest time. When running at the guarantee point (normal condition) there shall be no negative deviation of head or of flow, and under those conditions the shaft power shall not exceed 102 percent of the design value at the guarantee point (normal condition). If specified, the technical specification shall state the long-term operating conditions of the compressor. Unless otherwise specified, the compressor shall be designed with the average condition of the hottest summer month as the performance guarantee point. Note: the average condition of the hottest summer month includes but is not limited to the compressor inlet parameters and the cooling water conditions.

The compressor shall meet a flow turndown range of 75 percent to 105 percent at the performance guarantee condition. The expected performance curves shall cover all the conditions specified in the data sheet, and shall include at least the annual average condition, the average condition of the hottest summer month and the average winter condition; if specified, they shall also include the extreme summer and extreme winter conditions. Compressor performance shall be regulated by inlet guide vanes or adjustable stator vanes. If specified, the performance regulation shall accommodate changes in the air separation process conditions, in the atmospheric environment and in the circulating water conditions.

6.4 Rotordynamics

The compressor design shall include an undamped critical speed analysis of the rotor on rigid supports, with a separation margin of not less than 20 percent between each critical speed and the running speed range of the train. Note: for rotors with overhung impellers or heavy couplings, or certain long slender and highly flexible rotors, the rigid-support critical speeds need a sufficient separation margin so as to reduce the vibration risk of the actual product.

From the stability analysis of the train rotor, allowing for the excitation of all seal gas flows, the logarithmic decrement shall be not less than 0.12. For rotors with overhung impellers, a synchronous thermal instability assessment shall be carried out to ensure that dynamic instability does not occur.

For the torsional vibration assessment of the shaft system of a motor-driven train, if within a band of +/-10 percent around the running speed range the frequency of the principal coupling mode interferes with the speed-synchronous or the electrical excitation frequency, a torsional vibration response analysis shall be carried out to ensure that the shaft system components meet the life requirement under the pulsating torque of the motor.

6.5 Materials

6.5.1 General requirements. Fasteners, washers and similar items of the compressor equipment in direct contact with feed air carrying acid gases or salt spray shall meet the corrosion resistance requirements of the medium. If specified, the parts of the compressor casing related to the process gas and the fasteners and washers used on the piping shall meet the design temperature of the casing. Unless otherwise specified, the lubricating oil system piping and flanges shall be of stainless steel and graphite-based gaskets shall not be used. It shall be stated whether anti-seize compound is needed on all fasteners and, if so, the grade shall be given. Note: where anti-seize compound is used, the tightening torque of the fastener differs with the compound.

6.5.2 Coating materials. If specified, the inlet guide vanes (IGV) and the first two stages of adjustable stator vanes of an axial compressor shall be given an additional anti-corrosion coating. The surfaces of the parts in the gas path of a booster shall not be coated, except at the abradable positions of the seals.

6.6 Painting

The painting requirements for the surfaces of the compressor equipment shall be determined from the material of the equipment, the working temperature, the atmospheric conditions of the site and similar factors. For equipment exposed to the atmosphere without ultraviolet radiation, the durability of the surface paint shall be maintained for at least 5 years; within that minimum durability period the paint shall show no blistering, cracking, peeling or other abnormality. A clear painting scheme shall be provided for review and confirmation, covering surface preparation, type of paint, surface colour and method of application.

6.7 Auxiliary equipment

6.7.1 General requirements. The selection and design of the auxiliary equipment shall meet the site utility conditions of the air separation plant, and shall meet the requirements of running under the specified ambient conditions. Note: ambient conditions usually include the installation position of the equipment (indoors, outdoors, coastal, high altitude), the maximum and minimum ambient temperature (with or without heating), humidity, dust and corrosion. The design and selection of the auxiliary equipment shall assure the safety and reliability of the train during normal start-up and shutdown and under all the conditions given in the compressor data sheet.

6.7.2 Lubricating system. The lubricating system shall comply with GB/T 42601.1 and ISO 10438-2. One lubricating system shall provide the complete pressurised lubricating oil and cooling for the compressor, the driver, the gearbox if fitted, the clutch if fitted and the other associated equipment. Where the main air compressor and the booster share one driver, they shall share one combined oil station. Where each has its own driver, each shall have its own oil station; if specified, where each has its own driver they may still share one combined oil station. The motors used in the lubricating system shall be squirrel cage induction motors complying with GB/T 755, with an efficiency class not lower than class 2 of GB 18613. Both the main and the auxiliary oil pumps shall be driven by their own motors; a shaft-end pump design shall not be used. The design flow of the emergency oil pump shall be not less than 35 percent of the normal lubricating oil quantity of the train, and its delivery pressure shall meet the normal lubrication of the train.

6.7.3 Mounting arrangements. If specified, the compressor and the prime mover shall have their own separate baseplates or soleplates, including levelling pads, adjusting screws and stainless steel shims. The baseplate or soleplate shall have dedicated lifting lugs or lifting eye holes. Assembly and site installation of the baseplate or soleplate shall use vertical adjusting and positioning screws or wedges. The cumulative tolerance on the positions of all foundation bolt holes of the baseplate shall be not more than +/-2 mm. The safety factor on the strength of all structural parts, other than lifting eyes and shackles, shall be not less than 2.0. The baseplate shall be given an overall stress relief treatment in the works in accordance with GB/T 25712. All piping within the limits of the baseplate shall be terminated at the edge of the baseplate; all instruments within those limits, including the wiring of junction boxes, shall be run to an open instrument panel on the baseplate, and shall be trial fitted in the works. If the unit is transported as a complete skid, the strength of the baseplate shall meet the requirement of lifting it as one. Where the compressor itself weighs more than 45 t, it shall be designed with an alignment arrangement that allows hydraulic jacks to be used, the equipment supports shall be of concrete type and soleplates shall be provided. Note: the compressor itself includes the rotor, the stator and the bearings.

6.7.4 Instrumentation. If specified, the flow, temperature and pressure instruments needed for anti-surge control of the compressor, together with the anti-surge valves including the blow-off valve, shall be supplied with the compressor as a package. If specified, the process flow diagrams related to the compressor shall be planned together with the layout of the instruments, valves and process piping associated with the compressor control. The flow capacity of the anti-surge valve shall meet not only the needs of anti-surge control but also the requirements of the start-up and shutdown sequences. The selection of the anti-surge valve shall meet the process conditions and the interface conditions of the upstream and downstream piping; several anti-surge valves may be used in parallel. Where a blow-off valve is used in parallel with an anti-surge valve, the total design flow of the two in parallel shall be not less than 110 percent of the design condition.

6.7.5 Couplings and guards. The coupling shall be of the non-lubricated flexible type; the half coupling may be connected to the shaft by a key, by a hydraulic interference fit or by an integral flange, and a keyed connection may be used in non-hazardous areas. If specified, a gear type coupling may be used. If specified, an equivalent simulation block for the coupling shall be supplied. The coupling guard shall have a drain connection of not less than DN50 with a sight glass on the drain line; a vent of not less than DN50 shall be provided at the top of the guard with an oil deflector plate beneath it, and the radial and axial flanges of the guard shall prevent leakage of oil and gas. If specified, equipment shall be provided outside the coupling guard to prevent contact by persons. If specified, the coupling guard may have an intermediate stainless steel expansion joint, and a non-sparking arrangement shall be provided between the expansion joint and the rotating parts. If specified, the guard shall have oil return sight glasses on both sides for observation. Note: the sight glass material needs to resist corrosion and high temperature. Where a guard that is not fully enclosed is used, the axial gap between the end face of the guard and the equipment shall be not more than 10 mm.

6.7.6 Driver. The driver shall be selected according to the utility conditions of the air separation plant and shall meet the severe conditions of the operating environment. The driver shall satisfy all the operating conditions of the compressor, its power characteristic shall match the load characteristic, and its power shall be at least 1.1 times the power of the compressor at the rated condition; where there are special requirements, the value taken for the driver power factor shall at least meet the requirement of running the compressor at the rated condition. Where a turbine compressor is driven by a steam turbine, the turbine shall comply with GB/T 28574. Where it is driven by a motor, the motor shall comply with GB/T 755; if specified, the motor shall also comply with GB/T 3836 (all parts). The separation margin between the critical speeds of the driver rotor and the running speed range of the train shall be not less than 20 percent.

6.7.7 Gearbox. The design, manufacture and inspection of the gearbox shall comply with ISO 13691. The tooth form shall be involute. The continuous running time of the gearbox shall be not less than 40 000 h and its service life not less than 20 years.

6.7.8 Piping. Pressure piping shall comply with GB/T 20801 (all parts). Auxiliary piping connected to the equipment shall have removable spool pieces so that the equipment can be maintained and moved. The load imposed on the compressor by the process gas piping shall not exceed the requirements of the manufacturer. The installation of the process gas piping shall meet JB/T 6896.

6.7.9 Intercoolers and aftercoolers. The main air compressor coolers shall have a continuous drain recessed gate valve so that liquid can be drained away. Inside the main air compressor coolers there shall be a gas-liquid separation unit and a drain device that removes effectively the condensate that separates out after the air is cooled. The drain point shall be close to the discharge side of the cooler. For the main air compressor, with the utility design conditions unchanged and unless otherwise specified, the drain device of the cooler shall meet the drainage duty for a compressor inlet relative humidity of 100 percent. The number of coolers shall be set from the requirements of the compressor system, with one cooler or one bank of coolers between stages or between sections. Cooling shall be by water, by air or by a similar method; if specified, another liquid or gaseous coolant available on site may be chosen. The cooler shall be of the shell and tube, plate or air cooled type; unless otherwise specified a shell and tube cooler shall be chosen. The heat transfer area margin of the cooler at the compressor design condition shall be not less than 10 percent. The design of the cooler shall meet the operating parameters of the compressor under extreme conditions, and its design pressure shall meet the settle-out pressure of the piping system in which it sits. Cooler types include composite tube, plate, U-tube and packed-box; unless otherwise specified the tube bundle shall be designed to be removable.

6.7.10 Inlet air filter and silencer. For a compressor whose inlet medium is atmospheric air, if specified, a dry, self-cleaning, multi-stage, high efficiency air filter suitable for outdoor installation shall be provided at the compressor inlet. If specified, the inlet filter shall have a silencing unit. Unless otherwise specified, the air filter shall be shipped knocked down and assembled on site. The air filter shall comply with GB/T 14295 and shall be fitted with remote reading differential pressure instruments. While the train is running, the air filter shall be capable of on-line cleaning of the elements and on-line replacement of the primary filtration elements. The design pressure drop through the air filter elements shall be not more than 500 Pa. The flow capacity of the air filter shall be not less than 150 percent of the compressor design flow. If specified, a dehumidifying device may be fitted downstream of the air filter.

6.7.11 Blow-off silencer. If specified, a blow-off silencer shall be provided for the compressor. A tower type silencer is preferred and its internals and connecting bolts shall be supplied; the main air compressor and the booster may share one tower type silencer. The noise reduction of the silencer shall be not less than 30 dBA, and the gas velocity at the silencer inlet flange shall be not more than 40 m/s.

6.7.12 Impeller inlet water wash system. If specified, wash nozzles and connecting piping shall be provided in the inlet piping or the inlet casing at the impeller inlet of the main air compressor. If specified, wash nozzles and connecting piping shall also be provided at the impeller inlets between stages. If specified, an inlet water injection panel shall be provided. Note: the water injection panel includes the filter, flow meter, control valve, check valve, pressure gauge and the necessary piping. The water used to wash the impellers shall be desalinated and softened.

6.7.13 Check valves. The check valve shall be of the wafer, swing, axial flow or butterfly type. If specified, in order to reduce the pressure loss of the check valve, the valve shall have an assisted opening function.

6.8 Automatic control and remote monitoring

6.8.1 General requirements. The automation of the compressor train shall have the following features: automatic sensing; automatic control; monitoring and diagnosis; adaptation and optimisation; interaction and cooperation; interconnection and integration; digital design and delivery. The basic automation capability of the train includes the service functions of the individual items of equipment, the aerodynamic performance of the compressor, the reliability of the train, its maintainability and its safety.

6.8.2 Automatic sensing. The types of data sensed automatically shall include but are not limited to: a) physical data, such as process gas temperature, pressure and flow, train speed, the bearing temperatures of the main items of the train and the shaft vibration values of the train; b) chemical data, such as gas composition and gas molecular mass. The sensed data packages shall be collected through reliable probes and shall be timely, complete, accurate, trustworthy and stable. The data obtained by instrument monitoring shall be processed promptly, and the processed result shall be consistent with the transmission.

6.8.3.1 Control system automation. The CCS shall manage as a sequence the bringing into service of each auxiliary item before the compressor starts, and shall show the operating record in a database. The control functions of the CCS shall include at least: start-up of the train; shutdown sequence control; speed and load control; inlet guide vane regulation; anti-surge control; alarm and interlock protection; drive system control; mechanical condition monitoring; data acquisition and storage; clock synchronisation of the control system; protection of the auxiliary systems; and data exchange with the DCS over a local area network. Transfer of the train between local and remote control shall be bumpless and may be done by a software or hardware switch; the transfer shall not be allowed to change the running state of the train. In automatic operation the control logic is linked to the key protection parameters associated with load change, which act as boundary conditions so that the train does not trip on protection; when a state parameter reaches its high alarm the train shall stop automatic operation, the system shall raise a parameter alarm and send it to the DCS display for the guidance of the remote operator, and the load change command shall be issued again once the parameter leaves the alarm band. All ESD control shall be fail-safe, and the ESD control loops shall have fault diagnosis able to detect and alarm open and short circuits automatically; the CCS control program shall prevent an ESD pushbutton from triggering the ESD program spuriously when energised. If specified, a data calculation model shall be built from the original works performance curve data of the compressor and adjusted automatically from the site data collected, the collated data being fed into the CCS for calculation to obtain the true compressor performance curve as a basis for predictive maintenance. If specified, a dynamic simulation analysis report of the compressor system shall be provided, covering the response during start-up, normal shutdown, emergency shutdown, starting at settle-out pressure (SOP) and load change. If specified, a torque meter shall be fitted to measure the torque transmitted between driver and compressor while the train runs.

6.8.3.2 Auxiliary system automation. The MCC shall be able to collect and measure the operating data of the main incoming supply and of all electrical equipment, including voltage, current, power factor, active and reactive power and energy metering, and shall be able to transmit the data signals over a communication link. If specified, the MCC shall have an electrical fire monitoring system which does not interfere with the normal working of the power supply and does not cut the supply automatically, but sends the alarm and fault information to the electrical fire monitor and displays it there; the system shall meet the requirement of being connected to the low voltage electrical fire system master unit of the station.

6.8.4 Monitoring and diagnosis. If specified, the compressor train shall be equipped with a condition monitoring and fault diagnosis system. The system shall be able to carry out its monitoring task under the specified service conditions and under multiple operating conditions, and shall keep the rate of false alarms and of missed alarms low. It shall be able to indicate accurately, for predictive maintenance, planned maintenance and breakdown maintenance, the time of maintenance, the part concerned and the maintenance measures.

6.8.5 Adaptation and optimisation. The compressor train shall keep its preset functions in a complex application environment and, through optimisation and control, shall run stably under different conditions. The preset functions include the system anti-surge function and the interlock control function. The CCS shall, within an acceptable time, gather information and adjust the running state quickly so as to keep the functions of the train stable. If specified, the train shall compensate automatically, within acceptable limits, for changes in the external environment such as ambient temperature or process changes and for changes in its internal state such as increased seal clearance after long running, so as to keep performance stable and reliable. The train shall have fault-tolerant technology to guard against hardware faults and software errors caused by changes in the external environment and in the internal state; this includes but is not limited to redundant configuration of the CCS and redundant probes on the key interlocks.

6.8.6 Interaction and cooperation. The CCS shall be able to exchange information effectively with the other equipment on site, and shall have a sufficient level of security protection and a synchronisation mechanism so that information can be exchanged and work coordinated with other systems safely and promptly.

6.8.7 Interconnection and integration. The CCS shall transfer data between itself and the subordinate control systems through standard data structures and open interface data. The CCS hardware shall support common mechanical and electrical interfaces. The CCS shall have a control unit providing an interface for higher-level applications. The technical specification shall state the type of communication protocol.

6.8.8 Digital design and delivery. Three-dimensional models shall be provided for the compressor and its auxiliary equipment, and the file format and size of the models shall be specified. If specified, the collected data on the key information of the equipment shall be provided. If specified, the drawings and documents shall meet the requirements of digital delivery.

6.9 Evaluation of mechanical performance

6.9.1 Shaft radial vibration. The grades of shaft radial vibration of the compressor are given in Table 1. The table works on the shaft radial vibration displacement (peak to peak) and distinguishes three grades. Where the maximum continuous speed is not above 12 000 r/min the limits are 15 µm for grade 1, above 15 µm and up to 20 µm for grade 2, and above 20 µm and up to 25.4 µm for grade 3; where the maximum continuous speed is above 12 000 r/min the same three limits are scaled by the ratio of 12 000 to the maximum continuous speed. Note 1: Av denotes the radial vibration displacement (peak to peak), expressed in micrometres (µm). Note 2: Nmc denotes the maximum continuous speed, expressed in revolutions per minute (r/min).

6.9.2 Bearing temperature. The bearing temperature of the compressor shall be lower than the allowable temperature limit of the bearing.

7.1 Test methods - general requirements

Before the compressor leaves the works it shall be tested in accordance with ISO 10439-1 or JB/T 4113 and witnessed by the purchaser or by a third party. The test plan and procedure documents shall be reviewed and confirmed beforehand. Before the works test, the test equipment and instruments shall be calibrated and all calibration records kept. The works test report shall be supplied with the compressor. If specified, the compressor shall undergo a performance test in the works, complying with GB/T 25630.

7.2 Aerodynamic performance calibration

7.2.1 Time limit. Unless otherwise specified, the aerodynamic performance calibration of the compressor shall be completed within 72 h of loaded running.

7.2.2 Method. The calibration shall be based on the actual process conditions of the site piping. It shall be carried out with the mechanical performance stable, that is the train speed, the bearing temperatures and the rotor vibration. For a variable speed compressor the expected figures may be reached or approached by changing the speed; for a compressor with adjustable inlet guide vanes, by changing the vane angle. Before calibration the correct connection of the test piping and the correct setting of the measuring instruments shall be assured. Test data shall be recorded when all running values are steady. Calibration shall be carried out at the specified conditions, and during calibration no adjustment shall be made that could affect the performance at the operating condition. During calibration, only results obtained from accurate measurement of the compressor at the guarantee condition may be compared directly with the guaranteed values. Where the test conditions differ from those specified for the guarantee condition, the test data shall be converted to the guarantee conditions and the converted result compared with the guaranteed value. Away from the process, the compressor may be adjusted through the anti-surge valve or the blow-off valve, and if conditions allow the running parameters may be brought into line with the guarantee point. Where the process cannot be adjusted to the required condition, data are collected at a single test point and compared with the guarantee point, and that point shall meet the class A or class B test conditions of GB/T 25630. Assuming constant gas efficiency, the coupling power converted to the guarantee conditions is the value obtained by converting to the inlet volume flow and the pressure ratio at the guarantee conditions, as shown in Figure 1, and is calculated from formula (1). The symbols are: the coupling power converted to the guarantee point conditions, in kW; the coupling power converted to the test conditions, in kW; the guarantee point volume flow, in m3/s; the volume flow converted to the test conditions, in m3/s; the specific compression work at the guarantee point, in kJ/kg; the specific compression work converted to the test conditions, in kJ/kg; and the mechanical loss power converted to the guarantee point conditions, in kW. Figure 1 also identifies the coupling power, the coupling power at the guarantee point and the deviation between the coupling power converted to the guarantee point conditions and the coupling power at the guarantee point, all in kW, together with the volume flow in m3/s and the specific compression work in kJ/kg. The volume flow at the test point during performance calibration shall lie between 96 percent and 104 percent of the guarantee point flow. If the calibration result is invalid because of a problem in the gas circuit or in the test instruments, the calibration shall be repeated.

7.2.3 Efficiency correction. Where the performance calibration is carried out beyond 72 h of loaded running, an efficiency correction shall be made according to the running time and the degree of deterioration of the equipment; the factors considered include but are not limited to increased seal clearance, fouling or dust deposition and wear. The reference data for the efficiency correction are given in Annex A.

8 Inspection rules

8.1 General requirements. The compressor shall undergo non-destructive testing, hydrostatic test, overspeed test, dynamic balancing and mechanical running in accordance with ISO 10439-1 and ISO 10439-2. The inspection plan and procedure documents shall be reviewed and confirmed before inspection, the measuring equipment and instruments calibrated, and all calibration records kept.

8.2.1 Pressure casing. If specified, the welds of the pressure casing shall be radiographed to NB/T 47013.2, ultrasonically tested to NB/T 47013.3 or penetrant tested to NB/T 47013.5. For low temperature service the parent material of the pressure casing shall undergo low temperature impact testing and the report shall be provided. Cast casings shall be non-destructively tested in accordance with GB/T 5677, GB/T 7233.2, GB/T 9443 and GB/T 9444. If specified, the foundry shall provide a mechanical property test report for the cast casing together with test blocks poured from the same melt. For the hydrostatic test, the test pressure shall lie between 25 percent and 75 percent of the range of the pressure gauge, the gauge shall be of accuracy class 0.5 or better and within its calibration period. The pressure casing shall be sealed with tooling, and after a satisfactory test the internal cavity and other areas that cannot be seen shall be thoroughly drained and cleaned; if specified, they shall be purged and dried with dry air.

8.2.2 to 8.2.3. The butt welds of all piping within the limits of the baseplate shall be root run by argon arc welding, free from slag, and butt joints shall be fully penetrated; socket welding shall not be used. The clearances of the sealing parts shall be checked and recorded before and after the mechanical running test, and material certificates shall be provided for abradable seals. The sealing groove in the split face of the diaphragm shall be even and smooth in appearance and free from sharp corners that could damage the sealing ring, and the fit between groove and sealing ring shall be checked. Inlet guide vane forgings shall be ultrasonically tested to NB/T 47013.3, and the machined vanes shall be magnetic particle tested to NB/T 47013.4. After assembly with the compressor, the inlet guide vanes, the actuator and the transmission mechanism shall undergo a mechanical function test, and the range of vane opening shall meet the regulation requirements of the train.

8.2.4 Rotating parts. The parent material of the impellers, the shaft and the spacer sleeves of the rotor shall be ultrasonically tested in accordance with NB/T 47013.3 and the report provided. For low temperature service they shall also undergo low temperature impact testing, with the report and with test blocks from the same melt for mechanical property testing. Impellers shall be overspeed tested at not less than 115 percent of the maximum continuous speed, for not less than 3 min for three-dimensional impellers and not less than 1 min for two-dimensional impellers. The key dimensions of the impeller, such as the bore, the eye ring and the outside diameter, shall be measured and recorded before and after each overspeed run, and the distortion of the bore shall not exceed the design tolerance. After the overspeed test the impeller shall be liquid penetrant tested.

8.2.5 to 8.2.7. The bond between bearing alloy and bearing body shall be inspected in accordance with GB/T 18329.1 and GB/T 18329.3; the mechanical properties and chemical composition of the bearing alloy shall comply with GB/T 1174; the alloy shall be firmly bonded to the bearing body or pad body, shall be checked ultrasonically and shall show no debonding; the interference between the outside diameter of the bearing body and the bearing cap or gland shall be 0 mm to 0.05 mm; the bearing housing shall be liquid penetrant tested in accordance with NB/T 47013.5 with a liquid depth of not less than 100 mm held for not less than 2 h, and if it leaks it shall be weld repaired and tested again. After the labyrinth seals have been fitted, the clearances shall be checked with feeler gauges or by the lead wire method and shall meet the clearance requirements. The inspection of the aerodynamic performance of the compressor shall comply with 7.1.5.

8.2.8 to 8.2.10. The main rotor parts (impellers, shaft, balance drum and the like) shall be dynamically balanced individually before assembly to at least grade G1 of GB/T 9239.1-2006; the equivalent simulation block shall likewise be balanced individually to at least grade G1; the coupling assembly shall be balanced separately and inspected in accordance with ISO 10441. A mechanical running test procedure document shall be provided in accordance with ISO 10439-1; if specified, test seals shall be used for the mechanical running test, and their construction shall effectively prevent lubricating oil from entering the compressor casing. The inspection of the painting of the compressor equipment shall comply with GB/T 37400.12.

9 Packaging, transport and storage

9.1 Packaging. A packing plan shall be drawn up and confirmed according to the construction of the compressor, the transport route and the site conditions. The equipment shall be packed in cases or bare, and packing cases shall be of good quality timber or of steel. Where the compressor is shipped completely packed and does not have to be opened for inspection on site, it shall be confirmed before start-up that the sealing adhesive is within its shelf life, and the effect on the process medium of the rust preventive oil the manufacturer has chosen for the internal parts shall be assessed. The equipment lifting diagram shall include the key information of the lifting points, the weight and the centre of gravity of the packing case. Before packing, every component shall be thoroughly cleaned internally and externally, freed of swarf, rubbish, weld slag, scale, tools and other foreign matter, and thoroughly dried.

9.2 Transport. The rotor and the stator of an axial compressor shall be packed and shipped to site separately. Unless otherwise specified, the booster, including rotor, stator and gear casing, shall be packed and shipped to site as one. Reasonable protective measures shall be set out according to the delivery condition and the mode of transport, including protection against corrosion, damp and impact. Note: where measures such as coating the equipment surface with a preservative are used, the method of removing the preservative is to be stated together with whether the removal process is harmful to persons or to the environment. During transport all flange connections shall be protected and sealed with metal blanks fitted with gaskets or with plastic caps, so that the sealing faces are not damaged and moisture does not get in; if specified, key components shall be protected under nitrogen.

9.3 Storage. Within the storage period the appearance and condition of the packing cases shall be checked once a month, the desiccant and the rust preventive renewed periodically, and records kept. Rotors stored horizontally for a long period shall be turned through 180° every three months and a record kept; rotors stored vertically in metal nitrogen-filled cases do not need periodic turning.

A Annex A (informative) Reference data for compressor efficiency correction

A.1 The measured efficiency of the compressor should be corrected for deterioration of the equipment.

A.2 Efficiency correction for deterioration of axial blades or centrifugal impellers. After long running, fouling or dust deposition on the surface of the axial blades or the centrifugal impellers increases the flow losses, reduces the flow capacity and increases the surface roughness, so that friction losses, secondary flow losses and wake losses all rise. The correction curve of efficiency against axial blade roughness is given in Figure A.1 and the correction curve of efficiency against the roughness of the flow surfaces of a closed impeller in Figure A.2. The data of Figures A.1 and A.2 come from the performance test results of a combined axial and centrifugal compressor and of an integrally geared centrifugal compressor for a large air separation plant.

A.3 Efficiency correction for seal deterioration. As the compressor runs for a long period, the impeller eye seals and the balance drum seal are scoured by the gas flow, so that the clearance increases, leakage increases, efficiency falls and energy consumption rises. The correction curve of efficiency against the change in clearance of the eye seal of a closed impeller is given in Figure A.3.