Note that two sets of face readings are taken across each flexing point in the coupling. One of the first shaft- alignment patents filed in the United States embodied this technique, although relatively few people use this method in the field. Although usually not as accurate as the shaft to coupling spool method, there are occasions where this method must be used instead.
The accuracy of this technique increases propor- tionally with the diameter on which the face readings are measured.
The larger the diameter, the more accurate this method becomes. There are some interesting applications of this technique when adapted to measure off-line to running machinery movement as explained in Chapter Advantages Better set up if the brackets cannot be attached to the machinery shafts as in the shaft to coupling spool method but can be attached to the spool piece.
In the event that the shafts are not to be directly in line with each other but have an intentional centerline offset designed into the drive system, this method is better suited than the shaft to coupling spool method. Disadvantages Not as accurate as the shaft to coupling spool method assuming the readings were taken on a relatively small diameter assuming the shafts are to be aligned colinearly.
It is interesting to note that the bracket can be clamped on the shaft or on the coupling spool. The principles applied to the face—rim technique also apply here, in that, the larger the diameter on which the face readings are taken, the more accurate the technique becomes.
To plot the position of the two shafts and the spool piece, the T bar overlay will be used twice once at each end of the spool piece or drive shaft. The distance from the outboard feet to the inboard feet bolting planes of the first machine. The distance from the inboard bolting plane of the first machine to the flexing point between the shaft and the coupling spool or drive shaft on the first machine.
Note that the point where the bracket is clamped on the shaft or on the coupling spool is not relevant. Again, the larger this diameter on which the face readings are taken, the more accurate this technique becomes. The diameter on which the face readings were taken at the flexing point between the first machine and the spool piece or drive shaft. The distance from the flexing point between the shaft and the coupling spool or drive shaft on the first machine to the flexing point between the shaft and the coupling spool or drive shaft on the second machine.
The diameter on which the face readings were taken at the flexing point between the second machine and the spool piece or drive shaft. The distance from the flexing point between the shaft and the coupling spool or drive shaft on the second machine to the inboard bolting plane of the second machine.
The bracket could also be attached to the spool piece and the indicator reading the coupling hub face if desired. Accurately scale the distances along the length of the drive train onto the graph centerline and the diameters on which the face readings were taken at each flexing point onto the T bar overlays. The procedure for plotting the face—face technique is as follows: 1. Draw the coupling spool or drive shaft on top of the graph centerline, extending from flexing point to flexing point.
It is suggested that you also draw a face diameter line at each end of the coupling spool or drive shaft to aid in pitching the T bars. Start with the top to bottom face dial indicator readings or side to side face dial indicator readings if you want to plot the top view taken across the flex point on the first machine to the spool piece.
At the intersection of the graph centerline and the point where the flexing occurs between the first machine shaft and the spool piece, pitch or rotate the T bar overlay to reflect the difference in gap between the top and bottom or side to side readings.
If the bottom or side reading was negative, pitch the T bar clockwise by the full amount of the bottom or side readings across the diameter on which the face readings were captured.
If the bottom or side reading was positive, pitch the T bar counterclockwise by the full amount of the bottom or side readings across the diameter on which the face readings were captured.
The base of the T represents the centerline of rotation of the first machine. If you are going to use the T bar again at the other flexing point, draw in the position of the shaft so it lines up with the base of the T. Next, start at the intersection of the graph centerline and the point where the flexing occurs between the second machine shaft and the spool piece, pitch or rotate the T bar overlay to reflect the difference in gap between the top and bottom or side to side readings.
If the bottom or side reading was positive, pitch the T bar clockwise by the full amount of the bottom or side readings across the diameter on which the face readings were captured. If the bottom or side reading was negative, pitch the T bar counterclockwise by the full amount of the bottom or side readings across the diameter on which the face readings were captured. The base of the T represents the centerline of rotation of the second machine.
Again, draw in the position of the second machine shaft so it lines up with the base of the T. Again, the clockwise or counterclockwise pitch of the T bar noted above assumes that you took front side face readings similar to the set up shown in Figure If you took back side face readings, the pitch of the T bar would be opposite the rotation indicated above. With the advent of the microprocessor chip, silicon photodiodes, and the semiconductor junction diode laser, new inroads have been forged in the process of measuring rotational centerlines that utilize these new electronic devices.
The shaft alignment systems shown in Chapter 6 utilize dial indicators as the shaft position measuring device. This chapter will explore the other currently used types of electronic measuring devices that have been employed to measure shaft alignment. The sensor is, in effect, a mechanically actuated, electronic dial indicator. This system is shown in Figure The MAC10 system is based on the reverse indicator method as explained in Chapter A bracket is attached to each shaft.
The operator then rotates the shafts to measure one shaft position. A built in inclinometer device to measure the shaft rotation angle keeps track of angular position of the assembly. As the stem of the optical encoder is plunged in or retracts outward, the amount of movement observed by the sensor is sent to the operator keypad via cables.
Once measurements have been taken on one shaft, the span bar and inclinometer are reversed and the operator again rotates the assembly to capture the measurements on the other shaft. The operator display then solves for the corrective vertical and lateral moves required for the machine designated as the movable machine.
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By author John Piotrowski. Free delivery worldwide. Expected delivery to Germany in business days. Not ordering to Germany? Click here. Order now for expected delivery to Germany by Christmas. Description Rotating machinery is the heart of many industrial operations, but many engineers and technicians perform shaft alignment by guesswork or with limited knowledge of the tools and methods available to accurately and effectively align their machinery.
Two decades ago, John Piotrowski conferred upon the field an unprecedented tool: the first edition of the Shaft Alignment Handbook. Two editions later, this bestselling handbook is still the most trusted and widely embraced guide in the field. The third edition was reorganized, updated, and expanded to be more convenient, intuitive, and to reflect the latest developments in the area.
Dedicated chapters now discuss the basics of alignment modeling, each of the five basic alignment methods, and electro-optic methods. Significant new material reflects recent findings on detecting misalignment, machinery movement from offline to running conditions, multiple element drive trains, and specific information on virtually every type of rotating machinery in existence.
Entirely new chapters explore bore and parallel alignment.
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