Oil and gas production handbook An introduction to oil and gas production

Figure 34. Computerized maintenance management system 
 
Condition monitoring includes both structural monitoring and condition 
monitoring for process equipment such as valves and rotating machinery. 
For structural monitoring, the devices are corrosion meters (essentially 
plates that corrode, so that corrosion may be metered), tension force meters 
and free swinging strings. These statistics are logged to a central structure 
condition monitoring system, to show what forces are acting against the 
installation, and the effect those forces are having. 
 
Condition monitoring of machinery is generally used for large rotating 
apparatus, such as turbines, compressors, generators and large pumps. 
Input devices are vibration meters, temperature (bearing, exhaust gases, 
etc.), as well as the number of start/stops, running time, lubrication intervals 
and over-current trip-outs. For other process equipment, such as valves, the 
system can register closing times, flow and torque. A valve that exhibits a 
negative trend in closing time or torque ("stiction") can be diagnosed. The 
maintenance trigger is the mechanism whereby field device or equipment 
monitor resident information, in the form of digital status signals or other