Mechanical (Rotary) Common Questions -7

EPC-School 2012

M for Mechanical 

Topic - Condition Monitoring

1. What are the various maintenance approaches for rotating equipment?

2. Define vibration and what are its units?

3. What is the allowed vibration limit for pumps for process plants?

4. What are the online vibration instruments used on a reciprocating compressor?

5. What are the online vibration instruments used on a high speed centrifugal compressor?

6. Which instrument is used to measure vibration on an antifriction bearing/gear box?

7. What is critical speed for a rotary machine?

       8. At natural frequency of a machine, vibration increases suddenly/increases steadily/decreases/steady?

      9. In what units is vibration velocity measured?

10. In what units is vibration acceleration measured?

11. What are the different units for frequency?

12. Centrifugal force created by unbalance is proportional to  

13. What is the purpose of the key phaser?

14. What are the different trip logics used in refinery?        .

      15. What is the principle of operation of a proximity probe?

      16. Of what make is the MCMS system in petro plants generally?

      17. Name some non contact type and contact type transducers?

      18. What are the three parameters that describe a vibration signal?

Answers to Above Questions-

1. Breakdown maintenance, Preventive maintenance, Predictive maintenance, Condition monitoring

2. Vibration is defined as the to and fro motion of a body from its mean position.

    Measured in displacement(mm), velocity(mm/sec) and acceleration (mm/sec2) 

3. 7 mm/sec pk to pk

4. Velocitymeter on shaft bearings, proximity transducers for rod drop

5. Radial position proximity transducers near bearings, axial position transducers on thrust collar

6. Accelerometer

7. It is the speed at which the natural frequency of the rotor assembly matches the rotating shaft frequency

8. Increases suddenly

9. mm/sec

10. mm/sec2, ‘g’ value

11. Hz, cycle per min

12. Mass, radius, square of angular velocity

13. Speed measurement

14. 1out of 1 (1oo1), 2oo2, 2oo3

15. It detects change in relative position of probe and shaft using eddy current generation principle

16. Bentley Nevada, DM 3500

17. Contact: velometer, velocitymeter, accelerometer, RTD, thermowel, mechanical tachometer      

     Non contact: proximity probe, optical tachometer, stroboscope, magnetic pick up

18. Amplitude, frequency, phase