GB/T 9239-1988 Determination of allowable unbalance for balancing quality of rigid rotors
Some standard content:
National Standard of the People's Republic of China
Balance quality of rigid rotors
Determination of permissible residual unbalance
Balance quality of rigid rotorsDetermination of permissible residual unbalanceUDC 62. 253:62-755
GB9239—88
This standard is equivalent to ISO1940/1-1986 (E) "Mechanical vibration-Requirements for the balance quality of rigid rotors-Part 1: Determination of permissible residual unbalance".
Balancing is a process of improving the mass distribution of the rotor to ensure that the vibration or vibration force caused by the imbalance when the rotor rotates in its bearing is reduced to an allowable range. The unbalance of the rotor can be reduced to a fairly small range using existing measuring instruments, but it is uneconomical and unnecessary to have too high a requirement for the balance quality. Therefore, it is necessary to determine to what extent the unbalance should be reduced, so as to solve the relationship between technical possibility and economic rationality.
This standard applies to rigid rotors. For the determination of the allowable unbalance of quasi-rigid rotors and flexible rotors, please refer to GB6558-86 "Evaluation Criteria for Flexible Rotor Balance" and GB6557-86 "Mechanical Balance of Flexible Rotors". This standard specifies 11 levels of balance quality, and gives the minimum specified values for the balance quality of various commonly used rotors; if the balance quality of the rotor is selected according to the specified values, the rotor can be operated safely and smoothly to a large extent, and serious omissions or excessive requirements for balance requirements can be avoided. In some special cases, it is necessary to accurately determine the required balance quality through measurements in the laboratory or on-site, and the above levels can be used as the basis for verification. For some rotors that have some deviations from the values specified in this standard due to the particularity of their structure or geometric dimensions, and for rotors for which the balance quality level has not yet been specified, the manufacturer and the user can negotiate and determine it according to the methods specified in this standard and report it to the relevant departments for certification. The provisions of this standard on rotor balance quality levels will continue to be supplemented. 1 Terminology
For the definitions of terms related to the field of balance technology involved in this standard, please refer to GB6444-86 "Balance Vocabulary". For the definitions of vibration-related terms involved in this standard, see GB2298-80 "Terms and Terms of Mechanical Vibration and Shock". 2 Imbalance and Correction
2.1 Representation of Imbalance
The same unbalance state of a rigid rotor can be represented by the different methods shown in Figures 1a to f. Most rotor unbalances are measured in the manner shown in Figures 1a to c, and the correction of unbalance is also carried out in this way. In special cases, the representation method shown in Figures 1d to f can also be used.
2.2 Effects of Imbalance
An unbalanced rotor not only causes its support and foundation to bear dynamic loads, but also causes vibration of the machine. At a given speed, the extent of these two effects mainly depends on the geometric dimensions of the machine and rotor, the mass distribution, and the stiffness of the support and foundation. In most cases, static unbalance is the main one compared to even unbalance, that is, two equal unbalances in the same phase on different planes are more harmful than two unbalances of equal size and opposite direction. In some cases, even unbalance is more harmful. For example, for a rotor with cantilevered discs at both ends, the support spacing is smaller than the spacing between the two correction planes, and the dynamic load caused by the even unbalance is greater than the dynamic load caused by the same pair of same-phase unbalance. Approved by the State Machinery Industry Commission on May 12, 1988 104
Implementation on January 1, 1989
2.3 Rotor with single correction plane
GB9239—88
If the support spacing of the disc-shaped rotor is large enough and the axial runout of the disc-shaped part during rotation is quite small, so that the even unbalance can be ignored, then one correction plane can be used to correct the unbalance, that is, single-plane (static) balancing. It is necessary to verify whether these conditions are met for a specific rotor. For a large number of rotors, after completing single-plane balancing, the maximum residual unbalance should be measured and divided by the support span; if the unbalance obtained in this way is still allowable in the worst case, then single-plane balancing is sufficient. 3.15
Correction plane II
Orthogonal plane
Note: There is one unbalance vector on each correction plane I and II. Correction plane I
Note: There are two unbalance components on each correction plane I and II. 71.6Www.bzxZ.net
Figure 1 Different manifestations of the same unbalance state of a rigid rotor 105
Note: There is one unbalance loss on each of the other two correction planes. GB923988
Note: The position of the unbalance vector synthesized by a synthetic unbalance vector and a pair unbalance located on the two correction planes I and I can be selected, for example, at a certain point in the middle of the two correction planes, the pair unbalance The size depends on the position of the resultant unbalance vector. Continued Figure 1
GB9239-88
Note: Special case of d: The resultant unbalance vector passes through the center of mass of the rotor, and there is another even unbalance. 5
Note: Special case of d: The resultant unbalance vector passes through the center of unbalance, and the even unbalance is minimum at this time. Continued Figure 1
2.4 Double correction plane rotor
If the rigid rotor cannot meet the conditions of the disc rotor described in Article 2.3, two correction planes are required. The balancing process corresponds to the single-sided (static) balancing described in Article 2.3, and is called double-sided (dynamic) balancing. The rotor must rotate during double-sided balancing, otherwise Then the residual unbalance cannot be detected.
The allowable unbalance on each of the two correction planes depends on the correction plane spacing and the support spacing and the relative position relationship between the two, and is also related to the phase between the residual unbalance on the two correction planes. Chapter 5 will give three methods to determine the allowable unbalance of the rotor, and Chapter 6 will introduce the method of allocating the allowable unbalance of the rotor to the correction plane. 2.5 Assembled combined rotor
The rotor can be balanced as a single part or as an assembled assembly. The imbalance of each part in the assembled combined rotor should be added according to the loss method, and the imbalance caused by assembly errors should also be included in the total imbalance; special attention should be paid Pay attention to the impact caused by the difference between the final assembly position of the parts and the installation position when balancing on the balancing machine. GB9239—88
If the balancing quality of the assembled rotor cannot be met by balancing each part separately, the assembled rotor must be balanced as a whole.
If each part is balanced separately, the ownership of the connecting parts such as bolts and keys should be clarified first so that they can be considered in the balancing process. 3 Rotor mass and allowable unbalance
Generally speaking, the larger the rotor mass, the larger the allowable unbalance. Therefore, the allowable unbalance eper defined by the following formula: eper
To express the relationship between the permissible unbalance Uper and the rotor mass m. (1)
In special cases, that is, when the rotor unbalance can be simplified into an equivalent system of a single unbalance in a cross section and the even unbalance is zero, the permissible unbalance eper can be equivalent to the permissible mass eccentricity of the rotor mass center from the axis. In all general cases that can be represented by Figure 1, after the double-sided balancing reaches the permissible value, the equivalent mass eccentricity e is less than the permissible unbalance eper. 4 Relationship between balancing quality level, operating speed and permissible unbalance Experience shows that, in general, for the same type of rotor within the speed range of each balancing quality level shown in Figure 2, the permissible unbalance is inversely proportional to the maximum operating angular velocity of the rotor, that is:
eperαconst
The theoretical basis of this relationship is that for rotors with similar geometric shapes, at equal circumferential speeds, the rotor and its bearings are subjected to the same stress due to the residual unbalanced centrifugal force. Therefore, the balancing quality grade G is expressed by the product of the permissible unbalance epe (um) and the rotor's maximum operating angular velocity w (rad/s) divided by 1000 (mm/s): G
eper te
The balancing quality grade is specified as 11 grades (see Table 1). According to the actual work of the rotor or the needs of the balancing process, if more precise control of the permissible unbalance is required, each professional standard can make a more detailed division within a certain grade. If a new grade is indeed needed, it can be based on the common ratio between the grades of 2.5 is expanded.
Table 1 Balancing quality grade table
Balancing quality grade
Balancing quality grade value
≤1600
The balancing quality grades of various commonly used rigid rotors and the maximum allowable unbalance corresponding to each balancing quality grade are listed in Table 2 and Figure 2 respectively. Table 2 gives an example of balancing quality grades of rigid rotors based on domestic and international practices. It stipulates the minimum limits of balancing quality grades of various types of rotors. 108
GB9239-88
Each professional standard may make more detailed provisions for the balancing quality grades of various types of rotors. Similar rotors not listed in Table 2 can be implemented as a reference.
Balancing quality grades of various commonly used rigid rotorsTable 2
Balancing quality grade
G4 000
eper·a
Examples of rotor types
Crankshaft drives of rigidly mounted low-speed marine diesel engines with an odd number of cylindersCrankshaft drives of rigidly mounted large two-stroke enginesCrankshaft drives of rigidly mounted large four-stroke enginesCrankshaft drives of elastically mounted marine diesel enginesCrankshaft drives of rigidly mounted high-speed four-cylinder diesel enginesCrankshaft drives of high-speed diesel engines with six or more cylinders"Crankshaft drives of (petrol or diesel) engines of automobiles, trucks and locomotives3) Automobile wheels, rims, wheel assemblies, drive shaftsCrankshaft drives of high-speed four-stroke (petrol or diesel) engines with six or more cylinders elastically mountedCrankshaft drives of engines of automobiles, trucks and locomotivesDrive shafts with special requirements (propeller shafts, universal transmissions) Shaft) pulverizer parts
Individual parts of (petrol, diesel) engines for automobiles, trucks and locomotives Special requirements for six-cylinder or more cylinder engine crankshaft drive parts Parts of continuous process machines in metallurgical, chemical, petroleum and other refineries Ship (merchant ship) main turbine gear Centrifugal separator drum Paper machine roller, printing press roller Fan, ventilator, blower Aircraft gas turbine rotor parts Flywheel Pump rotor parts or impellers
Machine tool and general machinery parts
General medium and large motor rotors (axis center height exceeds 80mm) Mass-produced small armatures whose installation conditions are not sensitive to vibration or have vibration isolation devices Special requirements for engine parts Supercharger rotors Gas and steam turbines, including ship (merchant ship) main turbine Rigid turbine generator rotors
Calculation Machine storage drum or disk
Turbine compressor rotor
Machine tool drive
Medium and large motor rotors with special requirements Small armature turbine drive pumps that do not meet one of the two conditions of G6.3 level
Tape recorder and record player drive
Grinding machine main transmission and armature
Small armature with special requirements
Precision grinding machine spindle, grinding wheel and armature gyroscope Note: ① If the unit of speed n is r/min and the unit of is rad/s, then α=2 yuann/60~%. ② For the allocation of allowable unbalance to the correction plane, refer to Chapter 6. 109
GB9239-88
1) This standard refers to low-speed diesel engines with a piston speed of less than 9m/s, while high-speed diesel engines refer to engines with a piston speed of less than 9m/s. High-speed diesel engine refers to a machine with a piston speed greater than 9m/s. 2) The crankshaft drive device is a combination of components, including crankshaft, flywheel, clutch, pulley, shock absorber, connecting rod rotating part, etc. The scope of the balanced parts in the crankshaft drive device can be specified in detail in the professional standards (see Article 2.5). 3) The mass of the rotor in the engine is the sum of the masses of all the parts of the crankshaft drive device mentioned in the above Note 1). 5 Determination of balancing quality
The required balancing quality of the rotor can be determined by the following three methods: The first method is the empirical balancing quality grade based on the practical experience of rotor balancing and operation; the second method is the experimental method, which is often used to determine the balancing quality of rotors produced in large quantities or with special requirements; the third method is to determine the balancing quality based on the rated allowable bearing load. The choice of specific methods should be determined by negotiation between the manufacturer and the user. 5.1 Determine the balancing quality according to the established grades The balancing quality grades established on the basis of Chapters 3 and 4 can be used to classify the balancing quality of the rotor. Each balancing quality grade in Table 1 includes a permissible unbalance range from an upper limit to zero. The upper limit of the balancing quality grade is determined by the product eper· in mm/s. The balancing quality grade G is represented by the value of this product. The common ratio between the grades is 25. In some cases, more detailed classification can be made, especially when precise balancing is required. In Figure 2, the upper limit of eper is plotted corresponding to the maximum operating speed. After knowing the eper value, the permissible rotor unbalance Uper is: Where: m-rotor mass, kg;
eper——permissible unbalance, gmm/kg; Uper—permissible unbalance, g?mm. Uper - eper · m
Note: ①Grades G1 and GO.4 take into account the relationship between technical requirements and practical possibilities. The selected limit values are related to the minimum unbalance state that can be reasonably reproduced.
②These two balancing quality grades can only be achieved when the rotor journal and bearing accuracy are sufficient. G1 grade usually requires balancing in the working bearing of the rotor, generally using belt drive, air drive or self-drive. GO.4 grade is usually balanced in the rotor working base and bearing and under the working environment and temperature, usually requiring self-drive. 5.2 Determine the balance quality by experiment
Determine the required balance quality by experiment is usually used in the balancing process of mass-produced rotors. Obtaining data through experiments and determining the appropriate balance quality is conducive to improving the technical and economic level of mass-produced rotors. Rotors with special requirements sometimes also need to be tested to determine their balance quality. The experiment is generally carried out under the working support state of the rotor. In some cases, if the characteristics of the balancing machine are basically the same as the installation working conditions of the rotor, it can also be carried out on the balancing machine. The allowable unbalance on each plane is determined by adding different test masses to each plane one by one by experimental methods. The selected judgment basis should be given by the most representative factors (such as vibration, force or noise caused by imbalance). When balancing on both sides, the different effects of the unbalance amount and unbalanced force couple in the same phase must be considered. In addition, environmental changes or rotor changes that may occur during the working process should also be taken into account. 5.3 Determination of the balancing quality based on the rated permissible support load The influence of the unbalanced forces transmitted from the bearing to the support is an important factor and the limits for these unbalanced forces must be determined. The determination of the permissible unbalance must take this factor into account. The permissible unbalance on each bearing plane can be derived directly from the maximum permissible load caused by the unbalance on each bearing plane. If the rotor is balanced on a balancing machine that measures the residual unbalance on the bearing plane, these values can be used directly. If the residual unbalance is measured on other planes, the permissible unbalance on these planes can be calculated using the method described in Chapter 6, defining Uper as the sum of the permissible unbalance on the bearing planes. NOTE The determination of the permissible unbalance on each bearing plane from the maximum permissible unbalance force on each bearing depends on many factors, including the operating speed, the distribution of the rotor mass and the rigidity of the bearing support. However, for the special case of a rigid rotor supported on a rigid support, the permissible unbalance on each bearing plane is equal to the maximum permissible unbalance force on each bearing divided by the square of the maximum operating angular velocity. 110
100000
5 000
Normal
GB9239-88
5001000
2 0005 00010 000
Maximum operating speed
100200
50 000 100 000 r/min
5001 000 2000r/s
Figure 2 Maximum permissible unbalance corresponding to each balancing quality level 6 Distribution of permissible rotor unbalance to correction planes The required balancing quality of the rotor can be determined by one of the three methods described in Chapter 5. Among them, Article 5.2 determines the required balancing quality based on the maximum permissible value of the residual unbalance on each correction plane, so no further judgment is required. However, Articles 5.1 or 5.The method of clause 3 must use the value of the permissible unbalance Uper.
As a general rule, Uer should be distributed to each correction plane in the following way, even if the ratio of the residual unbalance on each support plane is in the same proportion as the ratio of the permissible dynamic load on the working support. Accordingly, if the rotor is balanced on a balancing machine, and the balancing machine measures the unbalance on the support plane, the above rules can be directly applied. However, the balancing machine usually measures the residual unbalance on a plane other than the support plane. In addition, some special requirements (such as vibration transmission, noise, and limit fatigue) require that the permissible unbalance be distributed to the two support planes in different proportions. This chapter specifies the method of using Uper to determine the permissible unbalance on each correction plane. Note: The permissible dynamic load of the working support can be found from the bearing sample, or derived from the conditions such as the permissible specific load, length and diameter of the bearing. 6.1 Single-plane balancing
For rotors with one correction plane, the permissible unbalance measured on this plane is equal to Uper. 6.2 Double-plane balancing
6.2.1 Simple approximate methods
This clause proposes three simple methods. They can reasonably and appropriately distribute the permissible unbalance to each correction plane in various practical applications, so that when the unbalance of the two correction planes is in any phase relationship, the maximum dynamic load on the two supports is consistent with the ratio of the static load on the supports distributed by mass. Although these simple methods are approximate, they have been successfully applied to many rotors. If the rotor meets the following conditions, these methods can give satisfactory results for most rotors. 6.2.1.1 Correction plane spacing is less than the support spacing The rotors involved in this clause shall meet the following conditions (see Figure 3): The center of mass is located within the middle third of the support spacing; a.
The correction plane spacing is greater than one-third of the support spacing and less than the support spacing; b.
The correction plane is basically equidistant from the rotor center of mass. For this type of rotor, each correction plane should take half of the allowable unbalance Uper, that is: Upet I = Uper I:
If the working conditions meet the above a. and b., but the correction planes are not basically equidistant relative to the center of mass, the allowable unbalance on the correction planes should be distributed as follows:
The sum of the allowable unbalance on each correction plane is equal to Uper; a.
b. The allowable unbalance of each correction plane is inversely proportional to the distance from each correction plane to the center of mass. A larger residual unbalance is allowed on the correction plane closer to the center of mass. However, in any case, the ratio of the above-mentioned larger and smaller allowable unbalance amounts should not exceed 0.7/0.3, that is:
0. 3U g< Ur I = UT
<0. 7Uper
Correction plane 1
Correction plane II
Figure 3 Geometric dimensions of the rotor applicable to the simple method 112
GB9239--88
0. 3U per
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