Standard No.:	GB/T 9239.21-2019
English Name:	Mechanical vibration—Rotor balancing—Part 21: Description and evaluation of balancing machines
Chinese Name:	机械振动 转子平衡 第21部分：平衡机的描述与评定
Chinese Classification:	N73    Mechanical vibration, impact equipment and dynamic balancing machine
Professional Classification:	GB    National Standard
ICS Classification:	21.120.40 21.120.40    Balancing and balancing machines 21.120.40
Issued by:	SAMR and SAC
Issued on:	2019-10-18
Implemented on:	2020-5-1
Status:	valid
Superseding:	GB/T 4201-2006 Description verification and evaluation of balancing machines
Language:	English
File Format:	PDF
Word Count:	23000 words
Price(USD):	570.0
Delivery:	via email in 1 business day

GB/T 9239 consists of the following parts, under the general title Mechanical Vibration — Rotor Balancing: — Part 1: Introduction ; — Part 2: Vocabulary ; — Part 11: Procedures and Tolerances for Rotors with Rigid Behaviour ; — Part 12: Procedures and Tolerances for Rotors with Flexible Behaviour ; — Part 13: Criteria and Safeguards for the In-situ Balancing of Medium and Large Rotors ; — Part 14: Procedures for Assessing Balance Errors ; — Part 21: Description and Evaluation of Balancing Machine ; — Part 23: Enclosures and Other Protective Measures for the Measuring Station of Balancing Machines ; — Part 31: Susceptibility and Sensitivity of Machines to Unbalance ; — Part 32: Shaft and Fitment Key Convention . This part is Part 21 of GB/T 9239. This part is drafted in accordance with the rules given in the GB/T 1.1-2009. This part replaces GB/T 4201-2006 Description Verification and Evaluation of Balancing Machines in whole. The following main technical deviations have been made with respect to GB/T 4201-2006 (the previous edition): — modification of the standard name; — modification of some parameters of proving rotors type C for outboard tests on horizontal machines (see Table 5; Table 5 of Edition 2006); — modification of the some parameters of shafts of proving rotors type C for outboard tests on horizontal machines (see Table C.1; Table C.1 of Edition 2006); This standard is identical with International Standard ISO 21940-21:2012 Mechanical Vibration — Rotor Balancing — Part 21: Description and Evaluation of Balancing Machines. The Chinese documents consistent and corresponding with the normative international documents in this part are as follows: — GB/T 6444-2008 Mechanical Vibration — Balancing — Vocabulary (ISO 1925:2001, IDT). This part was proposed by China Machinery Industry Federation. This part is under the jurisdiction of SAC/TC 122 (National Technical Committee 122 on Testing Machines of Standardization Administration of China). The previous editions of standards replaced by this part are as follows: — GB/T 4201-1984, GB/T 4201-2006. — GB/T 7662-1987. Mechanical Vibration — Rotor Balancing — Part 21: Description and Evaluation of Balancing Machines 1 Scope This part of GB/T 9239 specifies requirements for evaluating the performance of machines for balancing rotating components by the following tests: a) test for minimum achievable residual unbalance, Umar test; b) test for unbalance reduction ratio, URR test; c) test for couple unbalance interference on single-plane machines; d) compensator test. These tests are performed during acceptance of a balancing machine and also later, on a periodic basis, to ensure that the balancing machine is capable of handling the actual balancing tasks. For periodic tests, simplified procedures are specified. Tests for other machine capacities and performance parameters, however, are not contained in this part. For these tests, three types of specially prepared proving rotors are specified, covering a wide range of applications on horizontal and vertical balancing machines. An annex describes recommended modifications of proving rotors prepared in accordance with the original national standard. Moreover, this part also stresses the importance attached to the form in which the balancing machine characteristics are specified by the manufacturer. Adoption of the format specified enables users to compare products from different manufacturers. Additionally, in an annex, guidelines are given on the information by which users provide their data and requirements to a balancing machine manufacturer. This part is applicable to balancing machines that support and rotate rotors with rigid behaviour at balancing speed and that indicate the amounts and angular locations of a required unbalance correction in one or more planes. Therefore, it is applicable to rotors with rigid behaviour as well as to rotors with shaft-elastic behaviour balanced in accordance with low-speed balancing procedures. It covers both soft-bearing balancing machines and hard-bearing balancing machines. Technical requirements for such balancing machines are included; however, special features, such as those associated with automatic correction, are excluded. This part does not specify balancing criteria; such criteria are specified in ISO 1940-1 and ISO 11342 (only low-speed balancing procedures apply). 2 Normative References The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 1925 Mechanical Vibration — Balancing — Vocabulary 3 Terms and Definitions For the purposes of this document, the terms and definitions given in ISO 1925 apply. 4 Capacity and Performance Data of the Balancing Machine 4.1 General The manufacturer shall specify the data listed in 4.2 for horizontal or 4.3 for vertical balancing machines, as applicable, and in a similar format. Note: Information provided by the user to the balancing machine manufacturer is summarized in Annex A. 4.2 Data for horizontal balancing machines 4.2.1 Rotor mass and unbalance limitations 4.2.1.1 The maximum mass of a rotor, m, which can be balanced shall be stated over the range of balancing speeds (n1 , n2 , ...). The maximum moment of inertia of a rotor with respect to the shaft axis, mr2, where m is the rotor mass and r is the radius of gyration, which the machine can accelerate in a stated acceleration time shall be given for the range of balancing speeds (n1 , n2 , ...) together with the corresponding cycle rate (see Table 1).   Table 1 Data for horizontal balancing machines Manufacturer: ………………………………………… Model: ………….……………………………………….. Balancing speeds or speed ranges (see 4.2.3.1) n1 n2 n3 n4 … Rotor mass kg (see Note 1) Maximum Minimum Occasional overload force per support N (see Note 1) Maximum negative force per support N (see Note 1) Maximum rotor moment of inertia with respect to the shaft axis kg·m2 (see Note 2) Cycle rate (see Note 2) Maximum unbalance g·mm/kg or g·mm (see Note 3) Measurable value Permissible value a) For inboard rotors Minimum achievable residual specific unbalance, emar g·mm/kg (see Note 4 and Clause 6) Maximum mass 0.2 × maximum mass Minimum mass Corresponding deflection of analogue amount-of-unbalance indicator, mm; or Number of digital units (see Note 4) Gross vehicle mass 0.2 × maximum mass Minimum mass b) For outboard rotors Minimum achievable residual specific unbalance, emar g·mm/kg (see Note 4 and Clause 6) Gross vehicle mass 0.2 × maximum mass Minimum mass Corresponding deflection of analogue amount-of-unbalance indicator, mm; or Number of digital units (see Note 4) Gross vehicle mass 0.2 × maximum mass Minimum mass Note 1: The occasional overload force is only stated for the lowest balancing speed. It is the maximum force per support that can be accommodated by the machine without immediate damage. The negative force is the static upward force resulting from a rotor having its centre of mass outside the bearing support. Note 2: Cycle rate for a given balancing speed is the number of starts and stops which the machine can perform per hour without damage to the machine when balancing a rotor of the maximum moment of inertia. Note 3: In general, for rotors with rigid behaviour with two correction planes, one-half of the stated value pertains to each plane; for disc-shaped rotors, the full stated value holds for one plane. Note 4: Limits for soft-bearing machines are generally stated in gram millimetres per kilogram (specific unbalance, g·mm/kg), since this value represents a measure of rotor displacement and, therefore, motion of the balancing machine bearings. For hard-bearing machines, the limits are generally stated in gram millimetres (g·mm), since these machines are usually factory calibrated to indicated unbalance in such units (see Clause 6). For two-plane machines, this is the result obtained when the minimum achievable residual unbalance is distributed between the two planes. 4.2.1.2 Production efficiency (see Clause 7) shall be stated, as follows. 4.2.1.2.1 Time per measuring run: a) Time for mechanical adjustment: s b) Time for setting indicating system: s c) Time for preparation of rotor: s d) Average acceleration time: s e) Reading time (including time to stabilize): s f) Average deceleration time: s g) Relating readings to rotor: s h) Other necessary time: s i) Total time per measuring run [a) to h) in the preceding]: s 4.2.1.2.2 Unbalance reduction ratio, URR, for inboard rotors: % 4.2.1.2.3 Unbalance reduction ratio for outboard rotors: % 4.2.2 Rotor dimensions 4.2.2.1 Adequate envelope drawings of the pedestals and of other obstructions, such as belt-drive mechanism, shroud mounting pads, thrust arms and tie bars, shall be supplied to enable the user to determine the maximum rotor envelope that can be accommodated and the tooling or adaptors required. A combination of large journal diameter and high balancing speed can result in an excessive journal peripheral speed. The maximum journal peripheral speed shall be stated. When belt drive is supplied, balancing speeds shall be stated for both the maximum and minimum diameters over which the belt can drive, or other convenient diameter. The manufacturer shall state if the axial position of the drive can be adjusted. 4.2.2.2 Rotor envelope limitations shall be stated (see Figure 1). 4.2.2.3 Rotor diameter: a) Maximum diameter over bed: mm b) Maximum diameter over which belt can drive: mm c) Minimum diameter over which belt can drive: mm 4.2.2.4 Distance between journal centrelines: a) Maximum: mm b) Minimum: mm c) Maximum distance from coupling flange to centreline of farthest bearing: mm d) Minimum distance from coupling flange to centreline of nearest bearing: mm Key: 1 — shaft; 2 — rotor; 3 — support; 4 — bed. If the left-hand support is not a mirror image of the right-hand support, separate dimensions shall be shown. The profile of the belt-drive equipment shall be shown, if applicable. Figure 1 Example of a machine support drawing illustrating rotor envelope limitations 4.2.2.5 Journal diameter: a) Maximum: mm b) Minimum: mm Maximum permissible peripheral journal speed m/s 4.2.2.6 Correction plane limitations (consistent with the statements in 5.4) shall be stated. 4.2.2.7 Correction plane interference ratios (consistent with the statements in 5.4 and based on the proving rotor) shall be stated. 4.2.3 Drive 4.2.3.1 Balancing speed Rated torque on rotor r/min N·m n1 n2 n3 n4 n5 n6 n7 n8 or steplessly variable or steplessly variable From To From To 4.2.3.2 Torque: a) Zero-speed torque: ................................. % of rated torque on rotor b) Run-up torque adjustable from ......... % to .......... % of rated torque on rotor c) Peak torque .......................................................... % of rated torque on rotor Note: In most cases, maximum torque is required for accelerating a rotor. However, in the case of a rotor with high windage or friction loss, maximum torque can be required at balancing speed. When there is axial thrust, it is necessary that provisions be made to take this into account. 4.2.3.3 Type of drive to rotor: …………………………………………. Examples: End drive by universal joint driver, end drive by band, belt drive, magnetic field, driven bearing rollers, air jet. 4.2.3.4 Prime mover (type of motor): …………………………………………. a) Rated power: ………………………………………….kW b) Motor speed: ………………………………………….r/min c) Power supply, voltage/frequency/phase: ……………/………………/……………… 4.2.3.5 Brake: a) Type of brake: …………………………………………. b) Braking torque adjustable from ........... % to .......... % of rated torque c) Can the brake be used as a holding device? Yes / No 4.2.3.6 Motor and controls in accordance with the following standard(s): ……………… 4.2.3.7 Speed regulation provided: Accurate or constant within .................. % of ................. r/min, or .................. r/min 4.2.4 Couple unbalance interference ratio: ………………………………g·mm/(g·mm2) Note: This value is only applicable for single-plane balancing machines. It describes the influence of couple unbalance in the rotor on the indication of resultant unbalance. 4.2.5 Air pressure requirements: ................. Pa, ............m3/s 4.3 Data for vertical balancing machines 4.3.1 Rotor mass and unbalance limitations 4.3.1.1 The maximum mass of a rotor, m, which can be balanced shall be stated over the range of balancing speeds (n1, n2, ...). The maximum moment of inertia of a rotor with respect to the shaft axis, mr2 , where m is the rotor mass and r is the radius of gyration, which the machine can accelerate in a stated acceleration time shall be given for the range of balancing speeds (n1, n2, ...) together with the corresponding cycle rate (see Table 2). Table 2 Data for vertical balancing machines Manufacturer: Model: Balancing speeds or speed ranges (see 4.3.3.1) n1 n2 n3 n4 … Rotor mass kg (see Note 1) Maximum Minimum Occasional overload force up to N (see Note 1) Maximum rotor moment of inertia with respect to the shaft axis kg·m2 (see Note 2) Cycle rate (see Note 2) Maximum unbalance g·mm/kg or g·mm (see Note 3) Measurable value Permissible value Minimum achievable residual specific unbalance, emar g·mm/kg (see Note 4 and Clause 6) Maximum mass 0.2 × maximum mass Minimum mass Corresponding deflection of analogue amount-of-unbalance indicator, mm; or Number of digital units (see Note 4) Gross vehicle mass 0.2 × maximum mass Minimum mass Note 1: The occasional overload force is only stated for the lowest balancing speed. It is the maximum force per support that can be accommodated by the machine without immediate damage. Note 2: Cycle rate for a given balancing speed is the number of starts and stops which the machine can perform per hour without damage to the machine when balancing a rotor of the maximum moment of inertia. Note 3: In general, for rotors with rigid behaviour with two correction planes, one-half of the state value pertains to each plane; for disc-shaped rotors, the full stated value holds for one plane. Note 4: Limits for soft-bearing machines are generally stated in gram millimetres per kilogram (specific unbalance, g·mm/kg), since this value represents a measure of rotor displacement and, therefore, motion of the balancing machine bearings. For hard-bearing machines, the limits are generally stated in gram millimetres (g·mm), since these machines are usually factory calibrated to indicated unbalance in such units (see Clause 6). For two-plane machines, this is the result obtained when the minimum achievable residual unbalance is distributed between the two planes. 4.3.1.2 Production efficiency (see Clause 7) shall be stated, as follows. 4.3.1.2.1 Time per measuring run: a) Time for mechanical adjustment: s b) Time for setting indicating system: s c) Time for preparation of rotor: s d) Average acceleration time: s e) Reading time (including time to stabilize): s f) Average deceleration time: s g) Relating readings to rotor: s h) Other necessary time: s i) Total time per measuring run [a) to h) in the preceding]: s 4.3.1.2.2 Unbalance reduction ratio, URR: % 4.3.2 Rotor dimensions 4.3.2.1 If the machine is equipped with two or more speeds, the information on rotor dimensions shall be stated for each speed. If the machine is equipped with steplessly variable balancing speeds, then the information shall be given in the form of a table, formula or graph. Adequate drawings of the support surface of the spindle or mounting plate and of obstructions, such as drill heads and electrical control cabinets, above the mounting plate shall be supplied to enable the user to determine the maximum rotor envelope that can be accommodated and the tooling or adaptors required. 4.3.2.2 Maximum diameter: mm a) Maximum overall height: mm b) Maximum height of centre of gravity: mm at 100 % of maximum mass: mm at 50% of maximum mass: mm at 25% of maximum mass: mm 4.3.2.4 Rotor envelope limitations, including machine spindle or mounting plate interface, shall be stated (see Figure 2). 4.3.2.5 Correction plane limitations (consistent with the statements in 5.4) shall be stated.   4.3.3 Drive 4.3.3.1 Balancing speed Rated torque on rotor r/min N·m n1 n2 n3 n4 n5 n6 n7 n8 Key: 1 — rotor; 2 — adaptor; 3 — protractor; 4 — spindle; 5 — upper correction plane; 6 — centre of mass plane; 7 — lower correction plane; 8 — mounting holes for adaptor; 9 — spigot diameter. Figure 2 Example of vertical machine mounting interface illustrating rotor envelope limitations 4.3.3.2 Torque: a) Zero-speed torque: ....................................% of rated torque on rotor b) Run-up torque adjustable from ........... % to ............ % of rated torque on rotor c) Peak torque .......................................................... % of rated torque on rotor Note: In most cases, maximum torque is required for accelerating a rotor. However, in the case of a rotor with high windage or friction loss, maximum torque can be required at balancing speed. 4.3.3.3 Prime mover (type of motor): ........................................................................ a) Rated power: ........................................................................kW b) Motor speed: ........................................................................r/min c) Power supply, voltage/frequency/phase: ................./................./................. 4.3.3.4 Brake: a) Type of brake: .................................................................... b) Braking torque adjustable from .......... % to .......... % of rated torque c) Can the brake be used as a holding device? Yes / No 4.3.3.5 Motor and controls in accordance with the following standard(s):................. 4.3.3.6 Speed regulation provided: Accurate or constant within .................. % of ................. r/min, or .................. r/min 4.3.4 Couple unbalance interference ratio: ..................................g·mm/(g·mm2) Note: This value is only applicable for single-plane balancing machines. It describes the influence of couple unbalance in the rotor on the indication of resultant unbalance. 4.3.5 Air pressure requirements: ................. Pa, ............m3/s   5 Machine Features 5.1 Principle of operation An adequate description of the principle of operation of the balancing machine shall be given, e.g. motion measuring, force measuring, resonance, compensation. 5.2 Arrangement of the machine 5.2.1 The manufacturer shall describe the general configuration of the balancing machine and the principal features of design, e.g.: — horizontal or vertical axis of rotation; — soft- or hard-bearing suspension system; — resonance-type machine with mechanical compensator. 5.2.2 The manufacturer shall provide details of the following, as applicable. 5.2.2.1 Components designed to support the rotor, e.g.: — V blocks; — open rollers; — plain half bearings; — closed ball, roller or plain bearings; — devices to accommodate rotors in their service bearings; — devices to accommodate complete units. Details of bearing lubrication requirements shall be given, where applicable. 5.2.2.2 The mechanical adjustment and functioning of the means provided to take up axial thrust from the rotor (horizontal machines only). 5.2.2.3 Type(s) of transducers used to sense unbalance effects. 5.2.2.4 The drive and its control. 5.3 Indicating system 5.3.1 General A balancing machine shall have means to determine the amount of unbalance and its angular location; such means shall be described, e.g.: — wattmetric indicating system; — voltmetric indicating system with phase-sensitive rectifier (including systems with frequency conversion); — voltmetric system with stroboscope and filter; — voltmetric indicating system with marking of angular position on the rotor itself; — compensator with mechanical or electrical indication. 5.3.2 Amount indicators The manufacturer shall describe the means of amount indication provided, e.g.: — wattmetric or voltmetric component meters; — wattmetric or voltmetric amount meters; — wattmetric or voltmetric vector meters; — mechanical or optical indicators; — analogue or digital readout. 5.3.3 Angle indicators The manufacturer shall describe the means of angle indication provided, e.g.: — wattmetric or voltmetric component meters; — wattmetric or voltmetric vector meters; — direct angle indication in degrees on a scale meter; — oscilloscope, stroboscopic indicators; — mechanical or optical indicators; — analogue or digital readout. 5.3.4 Operation of the indicating system The manufacturer shall describe the procedure by which readings are obtained, taking into account at least the following aspects. a) How many measuring runs are required to obtain: — the two readings for single-plane balancing; — the four readings for two-plane balancing. b) Is an indicator provided for each reading or is it necessary to switch over for each reading. c) Are readings retained after the end of the measuring run. d) Is an individual plus-and-minus switch provided for each plane which permits the indication of a heavy or light spot. 5.4 Plane separation system 5.4.1 This subclause is not applicable to single-plane balancing machines, for which see 5.4.2. The manufacturer shall state whether plane separation is provided. If it is provided, at least the following details shall be given. a) How is it operated for single rotors of a type not previously balanced. b) How is it operated for single rotors in a series, with identical dimensions and mass. c) The limits of rotor geometry over which plane separation is effective shall be defined with the effectiveness stated on the basis of the correction plane interference ratio, stating the following. — the ratio of bearing distance to plane distance for which plane separation is effective; — whether either or both correction planes can be between or outside the bearings; — whether the centre of mass can be between or outside the two selected correction planes or bearings. d) Whether the indicator system can also be used to measure directly resultant unbalance and couple unbalance. 5.4.2 For single-plane horizontal or vertical machines, the manufacturer shall state to what extent the machine is able to suppress effects of couple unbalance (see 11.8). 5.5 Setting and calibration of indication 5.5.1 General The manufacturer shall describe the means of setting and calibration and the means provided for checking these. The manufacturer shall state whether setting is possible for indication in any desired unit, whether practical correction units or unbalance units. The manufacturer shall state: — the number of runs required for calibrating the balancing machine for single-plane balancing; — the number of runs required for calibrating the balancing machine for two-plane balancing. The manufacturer shall state the maximum permissible change, in percentage terms, in repeatability of speed during calibration and operation. 5.5.2 Soft-bearing machines The manufacturer shall state how calibration is accomplished on the first rotor of a particular mass and configuration (e.g. whether the rotor has to be balanced by a trial-and-error procedure or whether a compensator is provided, whether calibration masses are required), and whether total or partial recalibration is required when changing the balancing speed. If a compensator is provided, the limits of initial unbalance, of rotor geometry and speed for which compensation is effective shall be stated. 5.5.3 Hard-bearing machines The manufacturer shall state whether the balancing machine is permanently calibrated and can be set according to the rotor or whether it requires calibration by the user for different balancing speeds, rotor masses and dimensions. 5.6 Other devices Special devices which influence the efficient functioning of the balancing machine shall be described in detail, e.g.: — indication in components of an arbitrary coordinate system; — indication of unbalance resolved into components located in limited sectors in more than two correction planes; — correction devices; — devices to correlate the measured angle or amount of unbalance with the rotor; — suitable output for connection to a computer, printer or other peripherals. 6 Minimum Achievable Residual Unbalance The minimum residual unbalance that can be achieved with a balancing machine shall be specified in terms of specific unbalance, in gram millimetres per kilogram (g·mm/kg), together with the corresponding amount-of-unbalance indication. This minimum achievable residual specific unbalance, emar, shall be stated for the full range of rotor masses and balancing speeds of the machine. In achieving the stated residual unbalance, the manufacturer shall consider whether the accuracy of the following is adequate for this purpose: — amount indication; — angle indication; — plane separation; — scale multiplier; — drive, bearings, etc. It should be noted that the stated minimum achievable residual unbalance value applies to the balancing machine as delivered, but if out-of-round journals, excessively heavy or loose adaptors, or other tooling are employed by the user, the minimum achievable residual unbalance can be affected. 7 Production Efficiency 7.1 General Production efficiency is the ability of the machine to assist the operator in balancing a rotor to a given residual unbalance in the shortest possible time. It shall be assessed by using a proving rotor or, alternatively, a test rotor to be specified by the user. To find the production rate for a specific rotor (number of pieces per time or the reciprocal of the floor-to-floor time), the time per measuring run, the necessary number of runs, the time for loading, unbalance correction and unloading have to be taken into consideration. The necessary number of measuring runs depends on the average initial unbalance, the balance tolerance and the unbalance reduction ratio (URR).

Foreword III 1 Scope 2 Normative References 3 Terms and Definitions 4 Capacity and Performance Data of the Balancing Machine 4.1 General 4.2 Data for horizontal balancing machines 4.3 Data for vertical balancing machines 5 Machine Features 5.1 Principle of operation 5.2 Arrangement of the machine 5.3 Indicating system 5.4 Plane separation system 5.5 Setting and calibration of indication 5.6 Other devices 6 Minimum Achievable Residual Unbalance 7 Production Efficiency 7.1 General 7.2 Time per measuring run 7.3 Unbalance reduction ratio 8 Performance Qualifying Factors 9 Installation Requirements 9.1 General 9.2 Electrical and pneumatic requirements 9.3 Foundation 10 Proving Rotors and Test Masses 10.1 General 10.2 Proving rotors 10.3 Test masses 11 Verification Tests 11.1 Requirements for performance and parameter verification 11.2 Duties of manufacturer and user 11.3 Requirement for weighing scale 11.4 Test and rechecks 11.5 Test speed 11.6 Test for minimum achievable residual unbalance, Umar 11.7 Test for unbalance reduction ratio, URR 11.8 Test for couple unbalance interference on single-plane machines 11.9 Compensator test 11.10 Simplified tests Annex A (Informative) Information Provided by the User to the Balancing Machine Manufacturer Annex B (Informative) URR Limit Diagrams Annex C (Informative) Shafts of Outboard Proving Rotors Type C Annex D (Informative) Modifications of Proving Rotors Prepared in accordance with the Original National Standard to This Part Bibliography