Coupling alignment method

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Coupling alignment is also known as centering. After the pump and motor have been installed, the final task is to align the pump with the motor, that is, to ensure that the axes of the pump and the prime mover are on the same line, so as to prevent vibration during operation. When aligning a newly installed pump, the radial and axial errors of the coupling can present one of the following four situations: Method 1 – For ordinary pumps (water pumps, small oil pumps), a straight edge or feeler gauge can be used for rough measurements, but precise measurements are required for most equipment, which are carried out using a dial indicator. The levelness of the pump is generally already adjusted; by using the coupling of the pump as a reference, the coupling of the motor is measured and adjusted to ensure that the axes of the motor and the pump are aligned. Note: a1, a2, a3, a4 represent the radial clearances, while S1, S2, S3, S4 represent the axial clearances. During measurement, first determine the radial clearance a1 and the axial clearance S1 when the dial indicator is at 0°; then measure the radial and axial clearances at 90°, 180°, and 270° respectively, and record them inside and outside the circles shown in the figure above. When the measurement returns to 0°, it must match the original reading; otherwise, the cause must be identified, which is usually due to shaft play or loose foundation bolts. Finally, the measured data must also meet the following conditions to indicate that the calculation is correct. Method 2: Alignment using two gauges. Place the dial indicator at the pump end and zero it. Rotate the coupling by one full turn; a value is obtained at every 90 degrees. When the dial indicator returns to its initial position, it must be zeroed again. The sum of the readings from the left and right should equal the sum of the readings from the top and bottom. Then, the relative spatial position of the two axes is analyzed based on the readings, and appropriate adjustments are made according to the deviation values. First, adjust the left-right deviation of the coupling to the allowable value, and then adjust the height to be within the standard range. Alignment formula: S1 = ±(axial difference between the mating wheels (absolute value of the opening) × distance from leg 1 to the measurement point) ÷ diameter of the measurement point ± radial insertion (difference) value / 2 ； S2= ±(difference in wheel axis alignment × distance from foot 2 to the measurement point) ÷ diameter of the measurement point ± circular radial insertion (difference)/2. First ±: If the opposite wheel is in the upper open position, use the “+” sign ； If it is opening downward, then using the “-” sign can be understood as moving from top to bottom ； Second ±: Take the value when the motor is at a low level“+” ； When the motor speed is high, select “-”; this means reading from top to bottom – a positive value indicates a positive direction, while a negative value indicates a negative direction. If S1 is positive (the mouth is open upward and the motor is positioned low), it indicates that shims are needed; the value of S1 represents the thickness of the shims required. Note: The diameter of the measurement point is the rotation diameter of the measuring probe, not the diameter of the coupling. Adjusting left and right is similar. The calculation method for adding or removing pads is as follows: a represents the axial gauge reading, D represents the diameter of the back wheel, L1 represents the distance from the back wheel to the front foot of the motor, L2 represents the distance from the front foot to the rear foot of the motor, and S represents the radial gauge reading. The result obtained gives the number of pads that need to be added to the front and rear feet of the motor. Using two tables for alignment is good, but it can be difficult to control the axial displacement sometimes. A beginner might take half a day to do it by luck, while an experienced person can finish it in just over ten minutes thanks to their experience! It is best to add another axial gauge at 180°. The so-called three-table alignment!