October 05, 2006
Planning and Scheduling Maintenance Tips
Timeliness of Actual Information
Scheduling is only as good as the underlying information it is based on. During execution of maintenance work, actual information is sometimes only fed back into the system after the job is finished completely.
For example: A facility shutdown in the petrochemical industry is scheduled for 30 days. Work is executed and the results are written down on paper. The results are only entered back into the system for cost purposes after the shutdown is finished.
If the information is entered as soon as it was executed (or at the end of every shift) it allows:
• rescheduling of the project plan based on actual information
• the project manager to identify early discrepancies between plan and actual
• the execution team to be proactive rather than reactive
Tip provided by Martin Stenzig, Vesta Partners, LLC
October 05, 2006
Infrared Thermal Imaging Tip
Making accurate measurements
A lot of engineering effort is expended to ensure thermography cameras are very accurate but the techniques used in the field to accurately measure temperatures are somewhat more complex than pointing a camera at an object and placing a cross hair on a point and reading the display. There are many factors:
What is the material’s emissivity? Emissivity is the ratio of energy (heat) emitted verses reflected off an object. For example, if you were to approach a piece of slab steel during processing the emitted heat would not allow you to get very close while if you were visit an aluminum mill you could likely get quite close to the hot metal. Of course the steel temperature is much hotter but there is an order of magnitude in the difference of emitted energy from a non reflective surface like steel verses and reflective surface like aluminum.
How small a spot are you trying to measure? Thermal cameras require between a 1x1 to a 5x5 pixel cluster to make an accurate measurement. This is primarily a lens performance issue. Check with your manufacturer about the number of lens elements in the camera lens. More is typically better.
If a target is too close that you cannot focus on it or the object is too far away and the lens/system resolution is inadequate you should consider buying a wide angle and or telephoto lens. Make sure the additional lenses are calibrated with the system if you intend to make accurate measurements
What is the background temperature? In most situations the objects typically looked at are oxidized or have other conditions that cause the emissivity to be fairly high. Some instruments have built in material lists with emissivity values so train your inspectors to use this feature and you’ll see more consistent thermography program results.
To determine the background temperature simply turn opposite to the object being imaged and using an area function (if your camera features one) and enter the average temperature for the area.
Follow these few suggestions and your measurement results will be consistent and more accurate.
Tip provided by Electrophysics
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