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Practical Solutions to Machinery and Maintenance Vibration Problems

Chapter 15, Improvement Routines

Section 1, New Machinery

1. Have your own company's vibration specifications for new machinery before requesting quotations.

2. Indicate not only vibration amplitudes but also where readings are to be taken, such as on the bearing caps, shaft readings, etc. Indicate whether the pickup should be seismic or proximity-type.

3. Arrange to have your company representative witness the balancing of any expensive rotor, expensive machine rotor, or machine crucial to your plant's operation.

4. If possible to arrange, have the same representative witness final assembly and the final running tests at the vendor's plant.

5. After the machine passes the vendor's vibration tests, recheck using your own instruments (as a precaution against error caused by wide variations in instrument calibration).

6. Some companies require certain rotors be removed and separately packaged for long distance hauling (to prevent brinneling of bearings and rotor bending). To prevent excess cost, the relative merits of this procedure should be decided machine by machine, as no one rule can apply in all cases.

7. If the rotor is shipped in a separate container, the rotor should be checked on a local balancing machine. In most cases, this also allows a relatively fast trim balance.

8. When machinery is on the job site and ready to run, run the drive unit alone with coupling disconnected if possible. Record all vibration readings including phase. Use this record to compare with vibration at all points after the machine is recoupled and run as a complete assembly.

9. Complete assembly by connecting drive belts or coupling. Measure vibrations, including phase, while machine has been running only a short time and is relatively "cold." Record the time when the readings were measured.

10. Recheck vibration levels, including phase, when machine has been running long enough to have all the piping, base, structure, etc. up to full operating temperatures.

11. Check for possible resonances of pipes, bases, reducer pipes, ductwork and so on. If resonance is found, make arrangements to have it at least temporarily corrected. For tough cases, perform shaker motor tests.

12. For large, special machines with heavy foundations, recheck after several days when the large masses of concrete have reached steady temperatures.

13. Have proper authorities "accept" the machine, and file copies of the "accepted" vibration readings in the proper departments, such as Engineering, Maintenance and possibly the vendor's Service Department.

Textbook Index


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