1. definitions (1) Static balance A correction balance is carried out on a correction surface of the rotor, and the remaining unbalanced amount after correction is used to ensure that the rotor is within the specified range of allowable unbalanced amount at static time, which is also called single side balance. (2) Dynamic balance In order to ensure that the rotor is in the specified range of allowable unbalance, it is also called double-sided balance. Choice and determination of 2. rotor balance How to choose the balance mode of rotor is a key issue. Its choice has such a principle: as long as satisfied with the rotor balance after the use of the premise, can do static balance, do not do dynamic balance, can do dynamic balance, do not do static balance. The reason is very simple, static balance is easier to do than dynamic balance, dynamic balance is easier to do than static balance, save work, labor and cost. So how to determine the rotor balance type? It needs to be determined from the following factors and bases: (1) The geometry and structural dimensions of the rotor, in particular the diameter of the rotor D the ratio of the distance between the rotor and the b of the front of the rotor, and the support spacing of the rotor. (2) Working speed of the rotor. Technical standards relating to technical requirements for rotor balance, such as GB3215、API610 eighth edition, GB9239 and ISO1940. Conditions 3. static balancing of rotor According to the GB9239-88 balance criterion, the condition for static balancing of a rigid rotor is defined as :" If the support spacing of the disk rotor is large enough and the axial runout of the disk position is small while rotating, thus the even imbalance (dynamic balance) can be neglected, a correction surface can be used to correct the imbalance, i.e. one side (static) balance, which must be verified for the specific rotor. After balancing a large number of certain types of rotors in one plane, the maximum residual even imbalance can be obtained and divided by the supporting distance. if this value is not greater than half of the allowable remaining imbalance in the most adverse case, one-sided (static) equilibrium is sufficient? quot; from this definition, it is not difficult to see that the conditions for the rotor to do only one-sided (static) balance have three main aspects: one is that the rotor geometry is disk-shaped; the other is that the rotor has a large support spacing when balancing on the balancer; and the other is that the end runout of the calibrated front is very small when the rotor rotates. The above three conditions are described below: (1) What is a discoid rotor The diameter of the rotor D the ratio of the distance dimension b between the two calibrated front of the rotor. When specified in API610 eighth edition standard D/b<6, the rotor can only do one-sided balance; D/bD/b<6 can be specified as the condition of whether the rotor is a disc rotor, but can not be absolute, because what kind of balance the rotor does must also consider the operating speed of the rotor. (2) Large support spacing There are no specific parameters specified, but the ratio b the rotor correction front spacing ≥ more than 5 is considered as the support spacing is large enough. (3) Axial runout of the rotor It mainly refers to the end runout of the front when the rotor rotates, because any rotor doing balance test is finished, after processing has guaranteed the rotor hole and the calibration front between the behavior tolerance, the end runout is very small. On the basis of the above conditions for single-sided (static) balancing of the rotor, combined with the relevant technical standards for pumps (e.g. GB3215 and API610 version 8), the conditions for the rotor to do static balancing are as follows: (1) For the rotor of single-stage pump and two-stage pump, if the working speed <1800 rpm, no matter D/b<6 or D/bD/b<6 only do static balance. but if require to do dynamic balance, must ensure D/b<6, otherwise can only do static balance. (2) For the rotor of single-stage pump and two-stage pump, if the working speed ≥1800 rpm, if D/b≥6 only do static balance. but the remaining imbalance after equilibrium should be equal to or less than 1/2 of the allowable imbalance. If the dynamic balance is required, it depends on whether the balance of the two school fronts can be separated on the balancer, and if the separation is not open, it can only be done static balance. (3) For some open impeller and other rotors, if the two ends can not be supported, only static balance can be done. Because the two ends can not be supported, the cantilever is bound to be carried out, so it is dangerous to do the dynamic balance on the balance machine, and only one side (static) balance static) balance. Conditions for 4. rotor dynamic balance According to the GB9239 standard :" Where a rigid rotor can not meet the conditions of a disc rotor for static balance, two planes are required to balance, that is, dynamic balance. "Rotor conditions for static balance only are as follows (level G0.4 of equilibrium is the highest precision, and in general the dynamic balance of pump impeller is selected G6.3 or G2.5): (1) For the rotor of single-stage pump and two-stage pump, whenever the working speed ≥1800 rpm, a dynamic balance shall be made at 6 D/b<. (2) For multistage pumps and combined rotors (stage 3 or above), the dynamic balance of the combined rotors shall be made regardless of the operating speed.