From an asset management perspective, it is necessary to understand the root cause of plant failure in order establish effective condition monitoring and asset management strategies. AIG and other organizations have conducted considerable research into the reasons for plant failure. Not surprisingly, many plant failure studies into mechanical and electrical equipment failures reveal similar system failure root causes, which are indicated in Figure 3
and 4.
The data for Figure 3 has been taken from a number of industries of varying ages and capacity factors. In general, the data indicates that human intervention in the machine in the form of lubrication quality and contamination control is the primary factor in the longevity of mechanical plants. The data also indicates that lubrication analysis is the prime control method of determining mechanical plant condition, particularly in rotating mechanical plants.
Figure 4 depicts the systems within electrical plants that have been the principle failure cause for those plants. It is interesting to note that mechanical systems within electrical plants are the prime failure areas. The obvious connotation from this data is that the complete suite of both mechanical and electrical testing and condition determination regimes must be applied to all plant types. The complimentary nature of the condition assessment techniques requires that the systems used to record and report on plant condition need to be fully integrated, and contain data, analysis and prognosis from disparate CM tools to give a complete description of the plant
condition.
With these failure modes in mind, to obtain an excellent rating from insurers the asset management and condition monitoring technologies that are required for a utility include:
Mechanical:
. Online vibration spectral analysis of main plant including turbines, generators, feed pumps.
. Online vibration measurement and trips on auxiliary plant.
. Spectro chemical and Microscopic wear debris analysis of all main lube oil systems.
. Infrared thermography of all main plant including turbine casings, boilers, auxiliary plant bearings.
. Eddy current testing of condensers
. Time of flight ultrasonics (TOFD)
. Eddy current & remote field testing (EC & RFT)
. Remote visual inspection (RVI)
. Replication
. Bore oxide ultrasonics
. Mini creep testing
. X Ray analysis
Electrical:
. Dissolved gas analysis (DGA)
. Dissolved moisture
. Oil quality (acid, interfacial tension, dielectric strength, dielectric dissipation factor)
. Particle count
. Dissolved metals and sulphur
. Furans
. Dielectric loss angle
. Insulation resistance
. Dielectric dissipation factor
. Insulation recovery voltage
. Partial discharge
. Time reflectometry
. Radio frequency emission
. Transfer function
Risk Assessment Tools:
. HAZOPS - Hazard & Operability Studies
. QRA - Quantitative Risk Assessment
. WRAC - Workplace Risk Assessment and Control
. RCM-RA - Reliability Centred Maintenance Risk Assessment
It should be carefully noted however that the existence of these systems at a site is not the determining factor for a risk management engineer. The critical aspect is how these systems are utilized in the asset management planning cycle. All of the above systems require analysis and prognosis development by humans, and the qualifications and experience of the people conducting the testing and performing the analysis are of crucial importance to the insurance industry.
Tip from Ian Barnard, Author, Engineering Asset Management an Insurance Perspective
