Monitoring: Fan performance can be conducted with a manometer, flow indication, and a motor power meter. By comparing the measured performance with the shop test data, you can determine if performance has degraded.
Inspection frequency: Annual performance evaluations are common.
Monitoring Guidelines for Reciprocating Pumps
Figure 3.6 Typical Reciprocating Pump
Vibration Collection and Analysis: Most reciprocating pump vibration levels are monitored on a periodic basis using “walk around” data collection programs. Assessments are made by placing a vibration sensor, usually an accelerometer, with a magnetic base on to the bearing housings at specified locations. Overall vibration amplitudes are trended to see if any changes are occurring. If a significant change in overall amplitude is observed, a frequency analysis is performed in an attempt to identify the nature of the malady.
Inspection frequency: Monthly and quarterly inspection intervals are common.
Temperature Monitoring: Bearing temperatures can be taken at the same time vibration data is collected. Assessments may be either absolute or relative criteria. For example, you may decide that if a bearing temperature exceeds 200°F (93.3°C) you will shut down (this is an absolute criterion). Or if you see a 20°F (6.7°C) increase in bearing temperature from one inspection to the next, you will investigate. (This is an example of a relative analysis criterion.)
Inspection frequency: At the same time the vibration data is taken.
Oil Analysis: Oil analysis is typically reserved for critical machines with large oil reservoirs. Smaller, less critical pumps like most reciprocating pumps are frequently protected with periodic oil changes.
Inspection frequency: Monthly and quarterly inspection intervals are common.
Pressure Pulsation Analysis: This type of field analysis is usually conducted whenever damaging pump/piping interactions are occurring. It is hoped that if a thorough pulsation study and design analysis was performed before machine installation, pulsation will be controlled to low, healthy levels. However, reciprocating pumps that rely on pulsations with gas-filled bladders are prone to failure that can result in excessive pressure pulsations. Clues as to when to conduct a pressure pulsation analysis will be excessive piping vibration, broken bolts, high pulsations observed on a pressure gauge, etc.
Inspection frequency: Only required when issues arise
Piping Vibration: This type of analysis is normally conducted only if piping failures have occurred or if the piping is deemed to be moving excessively. Piping analysis methods are similar to a vibration analysis performed on rotating machinery except that the assessment criteria are quite different.
Inspection frequency: Only required when issues arise
Performance Monitoring: Performance testing is normally not conducted on reciprocating pumps.
Monitoring Guidelines for Reciprocating Compressors
Figure 3.7 Reciprocating Gas Compressor
Vibration Collection and Analysis: Most reciprocating compressors moving flammable gases are equipped with permanently mounted vibration sensors, usually accelerometers or velocity transducers, on crankcases and crosshead guides. These sensors are then tied to local monitors that can be configured to alarm and/or trip the compressor whenever high vibration levels are encountered.
Overall vibration amplitudes can also be trended to see if any changes are occurring. If a significant change in overall amplitude is observed, a frequency analysis is performed in an attempt to identify the nature of the malady.
Inspection frequency: Monthly and quarterly inspection intervals are common.
Temperature Monitoring: Bearing and stage discharge temperatures are both commonly monitored continuously. High bearing temperatures may be an indication of a failing bearing or lack of lubrication. A high cylinder discharge temperature can either signal a cylinder valve failure, cylinder wear issue, or excessive stage compression ratio.
Inspection frequency: At the same time the vibration data is taken
Oil Analysis: Periodic oil analyses are typically performed on reciprocating compressor. These analyses can help detect oil degradation or contamination or machine wear issues.
Inspection frequency: Monthly and quarterly inspection intervals are common.
Pressure Pulsation Analysis: This type of field analysis is usually conducted whenever damaging compressor/piping interactions are occurring. It is hoped that if a thorough pulsation study and design analysis was performed before machine installation, pulsation will be controlled to low, healthy levels. Clues as to when to conduct a pressure pulsation analysis will be excessive piping vibration, broken bolts, high pulsations observed on a pressure gauge, etc.
Inspection frequency: Only required when issues arise
Piping Vibration: This type of analysis is normally conducted only if piping failures have occurred or if the piping is deemed to be moving excessively. Piping analysis methods are similar to a vibration analysis performed on rotating machinery except that the assessment criteria are quite different.
Inspection frequency: Only required when issues arise
Condition monitoring methods unique to reciprocating compressors
Performance Monitoring: Performance monitoring of reciprocating compressors requires specialized equipment and training. This topic is beyond the scope of this book; however the basic methodology will be presented here. To analyze reciprocating compressor performance, dynamic pressure transducers must be installed in the head-end and crank-end cylinder volumes and a means of determining the crank’s angular position is required. By plotting the in-cylinder pressure versus crank position, a pressure-volume (P-V) diagram can be generated similar to the one shown in Figure 3.8. P-V diagrams help enlighten the analyst as to the condition of critical internal components, such as valves and rings. Additionally, vibration versus crank position is collected to determine the condition of critical bushings.
Inspection frequency: Quarterly performance evaluations are common.
Figure 3.8 Typical Pressure Volume Plot
Impact Monitoring: Simply measuring vibration velocity can be unreliable; the increase in velocity from incipient failures is usually small and will be buried in the larger signal due to machine movement. By the time the fault has been detected, major secondary damage may have already occurred. Impact monitoring overcomes this problem. First it takes raw (i.e., unprocessed) acceleration signals from an accelerometer permanently mounted in the compressor frame. It then counts the number of excursions that exceed an alarm threshold in a set
