Method and system for monitoring a piston rod

1. A method for monitoring a condition of a piston rod of a reciprocating compressor, said piston rod having a length defined between a piston end and a crosshead end, said method comprising:

positioning a first probe with respect to the piston rod along a x-axis and positioning a second probe with respect to the piston rod along a y-axis coplanar with and substantially perpendicular to the x-axis;

detecting a current ringing vibration amplitude greater than ten times a maximum of a one-hour average and a noise floor at a ringing frequency; and

diagnosing a bent rod condition.

2. A method in accordance with claim 1 further comprising verifying that a machine speed is within a design limit for at least two minutes.

3. A method in accordance with claim 2 further comprising determining whether at least one of a current ringing vibration amplitude is greater than 10 times a maximum of a one-hour average and a noise floor at a ringing frequency, and a previous ringing vibration amplitude is greater than 10 times a maximum of a one-hour average and a noise floor at a ringing frequency.

4. A method in accordance with claim 3 further comprising increasing a ringing vibration count variable by one, if at least one of the current ringing vibration amplitude is greater than 10 times a maximum of a one-hour average and a noise floor at a ringing frequency, and the previous ringing vibration amplitude is greater than 10 times a maximum of a one-hour average and a noise floor at a ringing frequency.

5. A method in accordance with claim 1 further comprising:

confirming that each of a machine speed, a suction pressure and a discharge pressure is within a design variation limit for an hour;

eliminating a possibility of a process change influence; and

updating a bent rod anomaly result.

6. A method in accordance with claim 1 further comprising comparing a 6-second buffer gap average against a one-hour buffer average for each of the first probe and the second probe.

7. A method in accordance with claim 6 further comprising generating a possible bent rod condition indication if a difference between the 6-second buffer gap average and the one-hour buffer average for at least one of the first probe and the second probe is greater than a defined value for 6 consequent rule processing cycles.

8. A method in accordance with claim 7 further comprising generating the possible bent rod condition indication if a current 6-second buffer average gap step is within +/−10% of a detected step-change gap.

9. A method in accordance with claim 7 further comprising generating a SEVERITY 3 BENT ROD indication if a possible bent rod condition is detected for at least one probe and a ringing vibration count is greater than zero.

10. A method in accordance with claim 7 further comprising generating a SEVERITY 1 BENT ROD indication if the possible bent rod condition is detected for at least one probe and a ringing vibration count is equal to zero.

11. A method for monitoring a condition of a piston rod of a reciprocating compressor, said piston rod having a length defined between a piston end and a crosshead end, said method comprising:

positioning a first probe with respect to the piston rod along a x-axis and positioning a second probe with respect to the piston rod along a y-axis coplanar with and substantially perpendicular to the x-axis;

checking a compressor operation mode;

generating an indication if the machine speed has been within design limitations for at least two minutes;

determine a ringing vibration state;

analyzing each of the first probe and the second probe to determine whether at least one of first probe and the second probe detects a current ringing vibration amplitude greater than ten times a maximum one-hour average and a noise floor at a ringing frequency;

comparing a 6-second buffer gap average against a one-hour buffer average for each probe independently; and

generating an indication that a possible bent rod condition exists if a difference between the 6-second buffer average and the one-hour buffer average for at least one probe is greater than a defined value for 6 consequent rule processing cycles.

12. A method in accordance with claim 11 further comprising generating a SEVERITY 3 BENT ROD indication if a possible bent rod condition is detected for at least one probe and a ringing vibration count is greater than zero.

13. A method in accordance with claim 11 further comprising generating a SEVERITY 1 BENT ROD indication if the possible bent rod condition is detected for at least one probe and the ringing vibration count is equal to zero.

14. A method in accordance with claim 11 further comprising resolving the detected piston rod problem.

15. A method in accordance with claim 14 further comprising:

restarting the machine;

resetting the ringing vibration count to zero; and

setting the buffers used for calculating average values.

16. A method in accordance with claim 11 increasing a ringing vibration count variable by one if the previous ringing vibration amplitude did not meet the above condition for any of two channels.

17. A method in accordance with claim 11 further comprising:

confirming that the machine speed, the suction pressure and the discharge pressure are within the design variation limits for one hour indicates that the machine is working properly;

eliminating the possibility of a process change influence; and

updating a bent rod anomaly result.

18. A computer program embodied on a computer readable medium for monitoring a condition of a piston rod positioned with respect to at least one of a first chamber and a second chamber of a reciprocating compressor, said computer program comprising a code segment configured to:

detect a current ringing vibration amplitude greater than ten times a maximum of a one-hour average and a noise floor at a ringing frequency utilizing at least one of a first probe positioned with respect to the piston rod along a x-axis and a second probe positioned with respect to the piston rod along a y-axis coplanar with and substantially perpendicular to the x-axis; and

diagnosing a bent rod condition.

19. A computer program in accordance with claim 18 further configured to:

confirm that each of a machine speed, a suction pressure and a discharge pressure is within a design variation limit for an hour;

eliminate a possibility of a process change influence; and

update a bent rod anomaly result.

20. A computer program in accordance with claim 18 further configured to:

compare a 6-second buffer gap average against a one-hour buffer average for each of a first probe positioned with respect to the piston rod along a x-axis and a second probe with respect to the piston rod along a y-axis coplanar with and substantially perpendicular to the x-axis;

generate a possible bent rod condition indication if a difference between the 6-second buffer gap average and the one-hour buffer average for at least one of the first probe and the second probe is greater than a defined value for 6 consequent rule processing cycles;

generate the possible bent rod condition indication if a current 6-second buffer average gap step is within +/−10% of a detected step-change gap;

generate a SEVERITY 3 BENT ROD indication if a possible bent rod condition is detected for at least one probe and a ringing vibration count is greater than zero; and

generate a SEVERITY 1 BENT ROD indication if the possible bent rod condition is detected for at least one probe and a ringing vibration count is equal to zero.