There are many uses for infrared thermography other than inspecting electrical switchgear and mechanical components. Inspecting buildings for heat loss was one of the first commercial uses for infrared thermography.
As with many condition monitoring techniques, infrared thermography is a skilled art form that requires technician and engineeers to be educated in infrared physics, have a thorough understanding of applications and be able to develop their knowledge with continual field experience.
Mirant Mid-Atlantic’s condition-monitoring team consists of a central group of four technicians and one team leader. The team’s primary responsibilities are the company’s four coal-fired power plants; as resources and priorities permit, the team also provides support to other assets.
For Condition Monitoring (CM) purposes a range of technologies are available, each having its own strengths and weaknesses, and it is usual to consider each of them as a tool in the CM toolkit. The Acoustic Emission (AE) technique has a 40 year history of use for machinery condition monitoring and although it got off to a slow start, in recent years it has gained very widespread acceptance across industry.
Many power generation steam turbine generators today are required in service well beyond their intended lifetimes. Dismantling for inspection is expensive, and owners need to consider all relevant information in making the decision. Application of condition monitoring in all the applicable methods is justified, with each showing different degradation modes. Performance analysis is less well publicised, yet unlike vibration analysis and oil debris analysis, it will show conditions which reduce machine efficiency and output, such as deposits on blades and erosion of internal clearances. The paper outlines, with examples, some condition monitoring techniques that have contributed to retaining some large fossil machines in service for up to 17 years without opening high-pressure sections.
A common approach to looking at vibration spectra is to display the graphs and then ask “What is wrong with this machine?” Another common approach to analyzing vibration spectra is to display the graphs and then ask “What is this peak?” and “what is that peak” A better approach to analyzing data is to first ask “What faults can this machine have?”, “Which of these are most common for this machine?” and finally…
A vibration test and analysis guide is a simple book or electronic document that contains a variety of information about the machine. Information should include: A simple schematic of the machine with test points identified, instructions for testing the machine (especially if loads and speeds must be manipulated or verified), name plate information and a simple schematic of internal components. This information is invaluable for conducting a proper diagnosis of the machine.
When troubleshooting or using vibration in a Predictive Maintenance program comparing identical machines to each other is often the best method to diagnose a problem – especially if you suspect a problem exists in one or more of the machines. When vibration data is collected on a bearing housing using an accelerometer, one is not only measuring vibration forces, but also the effect of the structure on these forces.