Rim and face method shaft alignment

 Rim and face method shaft alignment

Why does alignment need to rotating equipment?

  • Every attempt should be made to reduce shaft misalignment and coupling when two rotating items of equipment are joined by a shaft connection. Energy consumption, vibration, temperature, and failure of the bearing, shaft, and connection can all be decreased by proper alignment. A proper alignment also increases the lifespan of the equipment between scheduled maintenance periods. Take into account the alignment constraints of every system component, not only the connection, when determining the required level of precision in the alignment. Excessive misalignment cannot be justified by a flexible coupling.

Shaft misalignment: what is it?

  • The shaft center lines of two shafts must coincide for them to be referred to as "aligned". There is either parallel misalignment or angular misalignment if these center lines do not form a single line when taken together. furthermore, because misalignment can occur in several directions, it is customary to characterize the misalignments in the vertical and horizontal planes in order to specify the entire alignment condition that is present.
  • Axial misalignment is another kind of alignment that is frequently disregarded. many factors, including heat expansion, thrust forces from connected equipment, modifications to the pump volute gap, and sleeve bearing motor end float, might affect the linked shaft axial position. In addition, misalignment, speed, and applied torque can cause some couplings to produce thrust forces. Make sure that are operating within the declared axial working limitations of the coupling and that the right kind is being utilized for the application.

Alignment types: 

  1. Rim and face alignment
  2. Reverse dial indicator/laser
  3. Across the flex element
We'll take the example of a motor coupled to a pump to demonstrate the three suggested alignment techniques. You need to adjust the alignment in both the horizontal and vertical planes, regardless of the technique employed.
  • Shimming under the equipment feet is the first step toward correcting the vertical misalignment.
  • Second, move the equipment from side to side to adjust the horizontal alignment.

Rim and face alignment method:

Step 1: First in order to address the pre-alignment concerns.

Step 2: Ascertain which equipment is "movable" and which is "fixed". Generally speaking, you will only be moving one piece of machinery, which is usually the drive motor but might be anything else.

Step 3: Equipment arrangement lay down the piece of equipment that has to be aligned on a graph paper sheet. the following distances must be measured and plotted:
  • The distance measures the front foot center of the engine from where the indicator rides radially on the pump hub. This is 15" in this instance.
  • The diameter of the pump hub flange is where the face indication is mounted. This is a 10" in the example.
  • The distance is measured between the motor's front and back foot centers. this is a 25" in this instance.
Step 4: Install brackets and use the vertical solution to sweep readings. Rotate the shaft in 90-degree increments while the indicator is mounted on the motor, and readings are obtained from the pump hub face. any end play will cause the face readings to be distorted. Therefore, be sure that both aligning shafts are axially constrained.

Step 5: Translate the vertical solution for face reading is to measure +.005 a the bottom of the face at a diameter of 10 inches. this indicates that the indicator stem was crushed by.005 inches for every 10 inches of length. This only possible when the centerline extension of the motor shaft is smaller than that of the pump shaft.

Step 6: Plot-face interpretation (vertical approach) Along the outlined pump centerline, extend the 10 inch face-measuring diameter. plot the inch that is.005 below the centerline of the pump using a vertical scale where one little square equals.0001. the line that was drawn beyond the motor foot plane and between the plotted point and the center of the pump flange. this line illustrates the motor shaft centerline's angular orientation exclusively with respect to the pump shaft centerline.

Step 7: Adjust to fix angular misalignment (vertical approach) count the squares below the shaft centerline to the motor shaft centerline extension at the locations of the front motor feet (A) and the back motor feet (B). Shim the front motor foot in order to align the motor shaft angularly in the vertical plane.0075 inches, then shift the rear feet. inch is .0020

Step 8: Slide the indicator from the face to the rim. place the indicator stem on the outside rim of the pump hub while the motor bracket is still fastened to the motor hub.

Step 9: Sweep-rim measurements take readings, zero the dial indicator on top, and spin it in ninety-degree increments.

Step 10: Accurate reading of the bottom rim (vertical solution) of the indicator regarding the bottom dial was +.010 inches. However, this measurement needs to be adjusted to account for the indicator sag. the real value is +.015 [(.010-(-.005)=+.015] after correcting the reading by deducting the indicator sag reading (-.005) from the bottom dial indicator reading (+.010).

Step 11: Reading the plot rim (vertical solution) this is two times the actual shaft-to-shaft proportion since it is a T.I.R (total indicator reading). +0.0075 is the difference between the motor shaft centerline extension and the pump shaft centerline at the pump hub. calculated as +0.015/2. A corrected positive reading at the bottom indicates that the dial indicator stem was squeezed, which can only happen if the motor shaft centerline is high in relation to the pump shaft centerline, given that the pump has been set as a stationary piece of equipment. Plot this location on a graph with a scale of one small division equal to 0.001 inches. By taking out the shims that are positioned beneath are front and rear motor feet by 0.0075 inches, the parallel offset or rim misalignment alone might be fixed.    

Step 12: Angular or face solution (Horizontal): The same process is applied to the horizontal (side-to-side-) results. subtract this reading from the "near" and "far" measures to zero on one of the side readings. you may disregard the indicator sag since it cancels out. plot these readings so that the graph's findings may be seen.


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