Predictive maintenance is also known as condition monitoring. It involves monitoring the condition of equipment and detecting defects as they develop. There are a number of technologies that can be used such as: vibration analysis, thermal imaging, ultrasound, lubrication analysis, motion amplification and motor testing. The applications used in these technologies to defect faults are called techniques.
TECHNOLOGY: Vibration Analysis
TECHNIQUE: Vibration analysis, this is trending a piece of equipment over a period of time and then through its vibration patterns detecting defects as they develop. Vibration analysis can be used on rotating equipment where the vibration is reciprocating or it can be used on pipework where the vibration is a little more sporadic.
Technology: Motion Amplification
TECHNIQUE: Motion Amplification: This is a relatively new version of an old technology. It’s where the number of frames per second (FPS) are altered from the normal 24 FPS (like a movie) and changed to the speed of a machine under inspection. This will amplify the movement of the unit at the relevant speed. Why this technology is so effective is because the software added can use each pixel in the image as a vibration sensors and detect the amount of vibration at that point. This will give you the exact RPM and quantifies the vibration. An excellent tool for diagnosis imbalances, misalignments, looseness and other low frequency defects on a machine.
Technology: Thermal Imaging
TECHNIQUE: Motion Amplification: This is a relatively new version of an old technology. It’s where the number of frames per second (FPS) are altered from the normal 24 FPS (like a movie) and changed to the speed of a machine under inspection. This will amplify the movement of the unit at the relevant speed. Why this technology is so effective is because the software added can use each pixel in the image as a vibration sensors and detected the amount of vibration at that point. This give you the exact RPM and quantifies the vibration. An excellent tool for diagnosis imbalances, misalignments, looseness and other low frequency defects on a machine.
Technology: Ultrasonic
UltraSonic is sometimes used on its own and also as a combination with other technologies.
TECHNIQUE: Ultrasonic Greasing: This is route based and data collection of ultrasonic levels of the machines. Once a rise in the Ultrasonic levels has been detected, the first action would be to lubricate the machine if possible. It can then be used when lubricating a unit. The problem with the old method of just pump in a set amount of grease into a bearing is that you don’t know when is enough, too much or not enough. If you listen to the ultrasonic probe as you lubricate the unit you can keep on pumping the unit until you hear the noise level drop. Once the level bottoms out this is the adequate level of lubrication needed for each bearing.
TECHNIQUE: Ultrasonic of Electrical Panels: Tracking, arcing and the presents of coronas can be detected using ultrasonic equipment. This is where ultrasonic can be initially used and then other technologies like thermal imaging could then be used for detecting exactly where the fault is. Ultrasonic of Electrical panels is can be used when panels can’t be opened or can only be opened a small amount.
TECHNIQUE: Compressed Air leak Detection: some compressed air leaks can be heard when you walk into a room but other types of leaks can’t be heard with your own ear. This is an easy way of detecting all compress air leaks throughout a plant. Why fix an air leak? There are 2 reasons. (1) air leaks are wasteful expenses because the compressor has to generate the extra air for these leaks and this results in wasted electricity. (2) air leaks can get progressively worse over time. This could lead to process equipment not performing due to pneumatics not operating e.g. actuator valves not opening and closing.
TECHNIQUE: Steam Traps (moving parts): detected defects with steam traps is one technique where it’s best to use a few technologies. With the ultrasonic probe you can hear the steam traps operating (opening and closing) or if the strainer is blocked but this can be confirmed using a thermal imaging camera to see the temperature differentials across the trap. Like air leaks there are two advantages to detecting faults with steam traps. One is cost savings and the other is if condensate is getting into you steam system it will affect its performance.
Technology: Lubrication Analysis
TECHNIQUE: Oil Analysis: this involves taking a sample of oil from a unit and analyzing it for degrading the oil itself and also looking for any impurities such as foreign metal objects or water. Only taking a sample will save on replacing all the oil when there would be no need to, hence resulting in a cost saving but more importantly if foreign objects were detected in the sample this would indicate that there are signs of deterioration of the unit itself. This is especially effective in slower moving parts such as gearboxes. The samples will tell you what’s in the oil but the diagnosis of the unit will lies with the analyzer who knows how the unit operates.
Technology: Electric Motor Testing
TECHNIQUE: Static Motor Testing: this primarily tests the electrical properties of the stator of an AC induction motor and are carried out by a specialist test unit which connects to the motor. Each test increases in magnitude and it is advised for safety reasons to always start at the lowest voltage test and then advance in line with the voltage tests. The first number of tests will indicate if there is a present fault in the motor, however, the last tests check the condition of the unit and can indicate if weaknesses are developing.
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