GB/T 11348.2-1997 Measurement and evaluation of radial vibration of rotating machinery shafts Part 2: Large steam turbine generator sets installed on land
Some standard content:
GB/T11348.2—1997
This standard is one of the series of standards for the measurement and evaluation of radial vibration of rotating shafts of rotating machinery. It is equivalent to the international standard IS7919-2:1996 "Mechanical vibration of non-reciprocating machines--Measurement and evaluation criteria for rotating shafts Part 2: Land-mounted steam turbine generator sets".
This standard is consistent with IS07919-2 in terms of main technical content. However, for the convenience of users and in combination with my country's national conditions, this standard has made specific explanations and recommendations on some contents based on IS07919-2. For example, this standard recommends the use of non-contact sensors and composite sensors: it is recommended to install the shaft vibration sensor at 45° on both sides of the vertical centerline of the upper half of the bearing; regarding the provisions of vibration limits, the limits for zone A are completely consistent with the recommended limits of ISO7919-2, and the limits for zones B and C refer to the provisions of IFC89/77015 and ISO7919-2, giving a limit range and proposing some guiding opinions on the selection of specific unit vibration limits. This standard was proposed by the Ministry of Machinery Industry of the People's Republic of China. This standard is under the jurisdiction of the National Technical Committee for Mechanical Vibration and Shock Standardization. The drafting units of this standard are: Zhengzhou Machinery Research Institute, Thermal Engineering Research Institute of the Ministry of Electric Power, Shanghai Power Generation Equipment Complete Design Institute, Beijing Dianfang Construction Research Institute, Harbin Large Electric Motor Research Institute. The main drafters of this standard are: Jiang Yuanfeng, Huang Xiuzhu, Zhang Hanying, Zhou Xueye, and Jiang Shangchong. 156
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ISOForeword
ISO (International Organization for Standardization) is a federation of national standardization organizations (ISO member states) around the world. The preparation of international standards is usually carried out by ISO technical committees. Any member state has the right to propose proposals to a technical committee for a project for which a technical committee has been established. International organizations that are in coordination with ISO, whether governmental or non-governmental, also participate in this work. ISO) and the International Electrotechnical Commission work closely together and maintain consensus in all areas of electrotechnical standards. The draft international standard is sent by the technical committee to the member states for their opinions. To be officially published as an international standard, at least 75% of the member states must vote in favor.
International Standard IS()7919-2 was proposed by ISO/TC108 Technical Committee (Mechanical Vibration and Shock) Subcommittee SC2 (Measurement and evaluation of mechanical vibration and shock in machinery, vehicles and structures). The general title of IS7919 is: "Mechanical vibration of non-reciprocating machines - Measurement and evaluation of rotating shafts" and it consists of the following parts: Www.bzxZ.net
Part 1: General
- Part 2: Large steam turbine generator sets installed on land...·Part 3: Coupled industrial machines
- Part 4: Gas turbine sets
Part 5: Hydroelectric power plants and pumping station sets Appendix A is the main body of this part of IS7919. 157
National Standard of the People's Republic of China
Measurement and evaluation criteria of rotating shaft radial vibration of rotating machinery Part 2: Large land-based steam turbine generator sets1Scope
GB/T 11348.2-- 1997
eqv ISO 7919-2:1996
This standard specifies the measurement method and evaluation criteria of the radial vibration of the rotating shaft of large land-based steam turbine generator sets. This standard is applicable to land-based steam turbine generator sets with a rated power greater than 50MW and a rated speed range of 1500 to 3600r/min. Generally speaking, the vibration state of the steam turbine generator set should be evaluated from two aspects: the vibration of the rotating shaft and the vibration of the bearing seat. The general principles of the measurement and evaluation of the rotating shaft vibration involved in this standard refer to GB11348.1-89. This standard applies to the measurement and assessment of the vibration of the rotating shaft of a steam turbine generator set located at or near the bearing under normal operating conditions. This standard does not apply to the assessment of the vibration state of the shaft system under non-steady-state conditions, such as starting, shutting down, overspeeding and passing through critical speed. This standard does not apply to the measurement and assessment of the torsional vibration and axial vibration of the shaft system of a steam turbine generator set. 2 Referenced standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB11348.1-89 Measurement and assessment of radial vibration of rotating shafts of rotating machinery Part 1: General GB11347-89 On-site measurement and assessment of vibration intensity of large rotating machinery 3 Definitions
This standard adopts the following definitions.
3.1 Run-out
Non-vibration deviation caused by mechanical, electromagnetic and material factors, such as eccentricity, bending, non-roundness and local defects of the measured shaft section, residual magnetism, material inhomogeneity, surface residual stress, etc. 3.2 Baseline
Representative and repeatable normal vibration value of the unit under steady-state operation, generally obtained by the statistical average of multiple measurements of the specific unit during previous normal operation.
4 Measurement method
Measure the relative vibration of the shaft or the absolute vibration of the shaft. 4.1 Selection of sensor
For the vibration measurement of the shaft of a large steam turbine generator unit, a contact sensor can be used to measure the absolute vibration of the shaft (shaft relative to the ground), or a non-contact sensor can be used to measure the relative vibration of the shaft (shaft relative to the bearing seat), or a composite sensor composed of a non-contact sensor and an inertial sensor can be used to measure the absolute vibration of the shaft. When using contact sensors, the contact should be considered. Approved by the State Administration of Technical Supervision on June 6, 1997 458
Implemented on January 1, 1998
GB/T11348.2--1997
Surface contact, limited by factors such as shaft surface speed: When using eddy current sensors, the influence of electromagnetic pulse interference should be considered. This standard recommends the use of contact sensors or composite sensors. 4.2 Measurement point arrangement
Two shaft vibration sensors are installed perpendicular to each other in the radial direction in the same transverse plane at or near each bearing and perpendicular to the axis of rotation. For all bearings, the orientation of the sensor installation should be as similar as possible. This standard recommends installing the sensor at 45° on both sides of the straight center line of each bearing ten-length bushing. The manufacturer should provide conditions for installing shaft vibration sensors when designing the new machine structure. For vibration monitoring of long-term operation of the unit, it is also possible to install only one shaft vibration sensor at each bearing. However, due to the anisotropy of the bearing oil film stiffness, damping, and dynamic stiffness of the support in the circumferential direction, the values of the shaft vibration measured in different vibration measurement directions are also different. Only one shaft vibration sensor is installed at each bearing. This can only be done after sufficient experience has been accumulated. During unit acceptance, new machine commissioning, or vibration fault diagnosis, temporary vibration measurement points can be added as needed. 4.3 Measurement parameters
4.3.1 Displacement
The measurement parameter of the shaft vibration of a large steam turbine generator set is the peak-to-peak value of the full-frequency vibration displacement, in microns (um). The so-called full-frequency vibration refers to the wide-band vibration within the specified frequency band. The shaft vibration at each bearing is evaluated based on the larger of the peak-to-peak values of the displacement measured in two mutually perpendicular directions. In some applications, it may also be necessary to measure the axis trajectory, axis position, or maximum axis offset value.
The frequency band of the shaft vibration measurement of a large steam turbine generator set should be wide enough, and the upper limit frequency of the frequency band should be at least 160Hz. For fault diagnosis, the frequency range needs to be wider.
4.3.2 Phase
Vibration displacement is a loss. In some cases, such as shaft system dynamic balancing and fault diagnosis, the vibration phase of the relevant frequency components should be measured simultaneously.
4.4 Shaft deflection
The deflection signal will be mixed into the vibration signal. The total deflection value should not exceed 25% of the allowable vibration displacement value. If the deflection is within this range, its influence can be ignored in the shaft vibration measurement. If the deflection exceeds this range, the cause should be analyzed and compensation or other measures should be taken.
If the shaft deflection needs to be measured, it should be done at low speed when the bearing oil film has been established and stabilized. However, it should be noted that measuring the shaft deflection at a slow speed may be affected by factors such as temporary bending of the shaft, irregular movement of the journal in the bearing, and axial movement of the shaft. Certain measures should be taken to reduce the errors caused by the above factors. In addition, it should be ensured that the low-frequency characteristics of the measurement system meet the requirements. Note 1: For example, the following measures can be taken: the unit runs under load for a period of time, and after the thermal expansion is normal, it is shut down, and the turning device is started until the shaft wobble returns to normal, and then the speed is increased to the minimum speed at which the bearing oil film is established in the hot state and the shaft runout is measured when it is stable, and then the multiple measurement results are averaged. 5 Influence of foundation
The foundation of large steam turbine generator sets has an important influence on the unit shaft vibration and bearing seat vibration. The coupling vibration characteristics between the unit and the foundation should be considered to avoid resonance near the rated speed. 6 Measuring instruments
The instruments used for measuring the shaft vibration of large steam turbine generator sets should comply with the requirements of GB11348.1. The shaft vibration measurement system should be calibrated regularly.
More detailed and specific requirements and indicators for shaft vibration measuring instruments will be further specified in the national standard for shaft vibration measuring instruments. 7 Evaluation criteria
This standard specifies the following two criteria for evaluating the radial vibration of the shaft of large steam turbine generator sets. These criteria are applicable to the measurement and evaluation of the shaft vibration of the unit under steady-state conditions within the rated speed and load range or under normal and slow changes in electrical load. 459
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Note 2: For steam turbine generator sets with power greater than 50MW and less than 200MW, it is generally required to measure only the bearing seat vibration and to certify it according to G111347. When necessary (such as specified in the contract or during unit commissioning, fault diagnosis and analysis), the shaft vibration can be measured at the same time and evaluated according to the standard. 7.1 Criterion I: Vibration amplitude
Under the specified steady-state operating conditions and rated speed, the maximum shaft vibration amplitude (peak-to-peak value of the full-frequency vibration displacement) measured at or near any bearing should not exceed a certain specified limit and be The vibration amplitude is divided into four evaluation areas. 7.1.1 Evaluation Areas
Area A: The vibration of newly commissioned units is usually within this area. Area B: Units with vibrations within this area are generally considered qualified and can operate for a long time. Area (. Units with vibrations within this area are generally considered unqualified for long-term continuous operation. ...-Generally speaking, the unit can operate in this state for a limited period of time before there is a suitable opportunity to take remedial measures. Area D: Vibration amplitudes within this area are generally considered dangerous and are severe enough to cause unit damage. 7.1.2 Shaft vibration limits in evaluation areas
The vibration limit of the shaft should be consistent with the allowable dynamic load of the bearing, the radial clearance between the fixed and rotating parts of the machine, and the allowable vibration transmission rate to the supporting structure and foundation. The vibration limit values of the shaft of steam turbine generator sets above 50MW recommended by this standard are shown in Table 1 and Table 2. If the vibration limit values in Table 1 and Table 2 are used as acceptance specifications, they should be agreed upon by the manufacturer and the user. Table 1 Relative vibration displacement limit values of the shaft in each region Rated speed/(r·min\l)
Regional limit value
Regional limit value
120～200
200~～320||tt ||Peak-to-peak value of relative vibration displacement of rotating shaft/μm
120~185
185~290
120165
180～260
Table 2 Limit values of absolute vibration displacement of rotating shaft in each region Rated speed/（r·min?）
170~240
265~385
Peak-to-peak value of absolute vibration displacement of rotating shaft/μm
160~220
265~~350
150~～200
250320
120-- 150
180~~210
145~~180
245~~290
The recommended shaft vibration limits in the table are based on the accumulated experience of the Datao Group's shaft vibration measurements. In some cases, the machine may have special performance that requires the use of different zone boundary values (higher or lower). For example, with tilting pad bearings, alternative vibration limits may need to be specified. In the case of elliptical bearings, the vibration limits can be different for the maximum and minimum bearing clearance directions. In particular, it should be noted that the vibration limits are related to the journal diameter, because generally speaking, the running clearance will be larger for bearings with larger point diameters. In the same shaft system, the vibration limits can also be different for shaft vibrations measured at bearings of different diameters. In this case, the reasons are usually stated, especially to ensure that the unit or components will not be damaged when operating with larger vibration limits. If the vibration measurement point is not at the bearing but at other locations and in non-steady-state conditions, such as starting and stopping (including passing through the boundary zone 160
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area), a higher vibration limit value can be allowed. In addition, for rotors with lighter bearing loads, such as exciter rotors, their vibration limits can be specified according to the specific design of the machine.
In summary, the vibration limit values of specific units should be determined based on the unit design, shaft vibration measurement characteristics, and the long-term operation experience of the inner and outer peripheral types of units, with reference to the recommended values and various instructions of this standard. For example, the vibration limit values of 300MW and above units manufactured with imported technology at this stage are the smaller values in Table 1 or Table 2. 7.2 Inference: Changes in vibration amplitude
Under steady-state conditions, the changes in the frequency-broadband vibration amplitude from the pre-specified baseline value are evaluated using this criterion. Significant changes in the shaft vibration amplitude may be instantaneous or develop gradually over time and may indicate damage to the unit, a symptom of a fault, or a warning of some irregular change.
If the vibration amplitude of the rotor shaft changes significantly and its change from the baseline value exceeds 25% of the upper limit of Region B, whether the vibration amplitude increases or decreases, steps should be taken to find out the cause of the change. If any action is to be taken, it should be made after considering the maximum vibration amplitude and whether the unit is stable under the new conditions. When applying criterion 1, vibration measurements must be made and compared at the same sensor position and orientation and under approximately the same unit operating conditions.
It should be noted that criterion 1 considers changes in the amplitude of the general vibration. Its application is limited because in some cases, significant changes in amplitude only occur on individual frequency components and may not be reflected in the wide-band general-frequency shaft vibration signal or may be insensitive. For example, the expansion of a rotor crack may cause multiple frequency vibration components of the rotation frequency to gradually change, but their amplitudes may be small relative to the amplitude of the rotation frequency component per revolution. Therefore, it may be difficult to identify the effect of crack growth by only observing the changes in broadband vibration. In some applications, it may be necessary to perform vibration spectrum analysis to determine the change trend of each frequency component in the vibration signal. However, the description of these works is beyond the scope of this standard.
8 Setting of alarm and trip values
For long-term operation of the unit, it is common practice to specify alarm and trip values during steady-state operation. Alarm: An alarm is triggered when the vibration reaches a certain specified amplitude or the vibration changes significantly. In this case, it may be necessary to take remedial measures. Generally speaking, if an alarm occurs, the machine can continue to operate for a period of time to conduct research to identify the cause of the vibration change and determine what remedial measures to take
Tripping: A vibration amplitude is specified. If the machine continues to operate beyond this value, it may cause damage. If the trip value is exceeded, measures should be taken immediately to reduce the vibration or shut down the machine.
For different measurement positions and directions, the dynamic load and support stiffness are reflected differently, and the alarm and trip values during operation are also specified differently
8.1 Setting of alarm value
For different units, the alarm value may vary greatly. The alarm value is usually set relative to the baseline value. Setting of alarm value:
a) "baseline value + 25% of the limit value of zone B" and the smaller value of the limit value of zone B; b) baseline value + 25% of the upper limit value of zone B.
If the vibration amplitude of the shaft exceeds the range specified in a) and b), an alarm will be issued. In the case where no baseline value is established, for example: for a new unit, the initial alarm value can be set based on the experience of other similar units or with reference to the vibration limit value of zone B of this standard. After running for a period of time, a steady-state baseline value can be established, and then the alarm value setting can be adjusted accordingly.
If the steady-state baseline value changes (for example, after the unit is overhauled), the alarm value setting can be modified accordingly. For different bearings in the unit, the alarm value setting may also be different due to different dynamic loads and bearing support stiffness. 161
8.2 Setting of tripping value
GB/T11348.2-1997
The tripping value is generally related to the mechanical firmness of the machine and depends on the design characteristics of the unit to withstand abnormal dynamic loads. Therefore, the tripping value setting is generally the same for all similar units and is usually unrelated to the steady-state baseline value used to set the alarm. Generally speaking, the tripping value will be in area C or I), and is usually set according to the upper limit of area C. However, for units with different designs, the tripping value may be different.
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