Best Practices of Condition Monitoring of Centrifugal Compressors

High equipment availability can be obtained cost-effective by the implementation of a

Predictive Maintenance strategy .Therefore a well-balanced monitoring program

should be implemented related to the criticality classification of the equipment. It

should combine periodic inspection (Off-stream) of easily accessible parts of major

equipment with the day to day on-line inspection and monitoring results.

The basis of the condition-monitoring program is comparing the current performance

with a reference (past) performance. This comparison is done for equipment on a

selective basis on a number of typical selected parameters:

Typical Condition Monitoring Parameters:

• Vibrations , frequency , phase and transient analysis such as bode and polar plots

• Thermodynamic performance (pressures, temperatures, efficiency, flow etc.)

• Oil analysis

• Wear Particle analysis

• Seal oil consumption/ leakage over the seals/ lube oil leakage's/ excessive venting

• Seal gas system i.e. flows and pressures in the supply and leak off lines

• Balance line leak offs

• Radial and axial shaft positions

• Bearing temperatures

• Motor winding temperatures

• Foundations NDT

• Inspection results of previous overhauls

The trends need to be analyzed to determine the 'health' status of the equipment.

Deviations beyond set limits of the parameters should be reported to management and

appropriate action taken.

Do not operate the plant at conditions (feed stock quality, flow rates, process

temperatures/ pressures) beyond the approved operating envelope. Any changes and

deviations in upper and lower design limits shall be thoroughly discussed and

evaluated for machine integrity. Based on this, approved window should be

established.

Ensure that the agreed/ approved operating envelope is clearly known and properly

documented. Make operating staff responsible and accountable for maintaining the

operating conditions of the plant systems and equipment within their respective

envelopes

Regularly measure and evaluate the performance in critical areas by comparing the

results with the Performance Indicator target values and analyze the differences.

Determine the reasons for the variances and identify and apply corrective action, as

and when required and report via monthly and/or quarterly site management reports.

Widely publicize the current performance indicators against the agreed target values

and the results.

In all cases, any foreseen operating deviation must be reported to allow for proper

monitoring of the equipment. Any operation outside the operating envelop of the

plant/equipment must be subjected to a complete review including the safeguarding

system, start-up and shutdown procedures.

After each overhaul it is necessary to log a new base-line reading of operating data to

verify mechanical and thermodynamic performance and to establish whether the

maintenance job has been executed successfully.