September 16, 2014
If non-repeatability is an issue and it is not due to setup of the laser or ambient vibration, then it may be of interest to check the bearing clearances. This can be accomplished very easily with a laser. A little bit of information is necessary to accomplish this. We will need the following:
a) Acceptable bearing clearance and tolerances.
b) Distance between bearings.
c) Distance from receiver of laser system to first bearing.
d) Rotalign Ultra laser system.
For instance, suppose that the distance between bearings is 10 inches, and the distance from the receiver to the first bearing is 5 inches, and that the acceptable clearance is 4 mils. This means that with the shaft bottomed out in the bearing, there is a total of 4 mils of clearance available, or lift. With the receiver at the 12:00 o’clock position in XY-View, press the SET ZERO button. This will give you a zero-reference for the values displayed on the sensor. Simply lift the shaft until it contacts the top of the bearing and record the Y value of the movement. With the above distances, we are allowed 4 mils/10 inches, (or 0.4 mils/1 inch), 10 inches being the distance between the bearings. From the receiver to the front bearing is 5 inches, so with a good bearing we would expect to see another 2 mils/5 inches, (or 0.4 mils/ 1 inch). Add the two together and we get a total of 6 mils/15 inches. This means that if the lift of the shaft shows 6 mils of change at the receiver, the clearance is acceptable. If greater than 6 mils, clearances may be excessive.
September 9, 2014
Tips for visually identifying loose components on a machine:
- Make sure that the machine has reached normal operational temperature, because loose components may not appear until this temperature has been reached.
- Squirt water or soapy water on components. This may create small bubbles and allow identification of the loose component.
- Use a strobe light
- Utilize technologies such as vibration and phase analysis.
September 4, 2014
When moving machines for alignment, always use jackscrews. If you don’t have them, beating on the machine frame with a steel-face hammer is a lousy idea.
First, you run the risk of damaging the bearings, seals and other delicate components in your machines. Secondly, you have little control over the magnitude of your moves. Thirdly, it’s unprofessional. If you don’t have time to weld or screw on jackscrew assemblies, consider using a couple of carpenter’s pipe clamps, tensed against each-other. This makes for a handy portable jackscrew arrangement that is safe, inexpensive and offers you plenty of control. If this is not possible either, and you must hit the machine with a hammer, then at least do so with a plastic-face, shot-loaded deadblow hammer.
September 2, 2014
One of the first rules of good engineering practice is the KISS principle. KISS is an acronym for “Keep it simple stupid”. Basically, this means that most things function best if they are kept simple. It is often believed that expensive complex activities/functions are required to improve equipment reliability. Improving equipment reliability can be complicated and expensive in certain situations. Thankfully, this can be the exception and not the rule within your facility. Don’t focus excessively on the complex and expensive reliability functions you cannot complete and thereby overlook the fundamental things that are required to keep your equipment reliable.
What reliability improvements can you make in your facility that do not require expensive or complicated actions? Start with the “basics” such as:
- Align (shaft, coupling, etc.)
- Balance (rotating components: fan blades, impellers, rotors.)
- Tight (eliminate looseness and excessive vibration.)
- Lubricate (correctly—not too much or too little!)
- Apply condition monitoring
- Understand where your efforts should be focused
Don’t wait until the equipment has been installed and is operating. The basic functions listed above must be included in the specification, design, purchase and routine operation of your equipment. Failure to address these vital aspects from the beginning through operation of your equipment will result in higher maintenance costs and reduced equipment reliability.
Often fundamental reliability functions are not completed due to a lack resources, understanding, time, funding, etc. Ensure that your engineering, maintenance, production, purchasing and management teams understand and routinely employ these fundamental maintenance practices to keep your equipment reliable from the beginning.
Watch video tutorial about Reliability Basics
August 28, 2014
A customer in Florida needed to do an alignment between a gas turbine and a generator. Their main issue was that the gas turbine shaft could not be rotated by hand and engineering was reluctant at that time to turn on the lift oil pumps. This customer owns and uses the ROTALIGN ULTRA iS. We suggested using the Multipoint measurement mode in the ROTALIGN ULTRA iS in conjunction with one ALI 2.230 Magnetic Sliding Bracket for the turbine shaft and one ALI 2.112set Compact Magnetic Bracket. With the shafts uncoupled, the generator shaft could be rotated to any position, and the sensor could be positioned at any rotational position on the turbine shaft with the magnetic sliding bracket. A very big advantage of using the ROTALIGN ULTRA iS in the Multipoint mode is that thanks to the quality factor value obtained from the readings a very clear picture emerges of the quality of the data obtained while taking the readings. Any rogue measurements caused by surface imperfections in the turbine coupling can be eliminated without compromising otherwise good data. The ROTALIGN ULTRA’s Technical Note # 12 – for Non- Rotating Shafts was provided to the customer to better guide the process.
Accurate readings were obtained quickly and efficiently, resulting in many man-hours saved on this critical alignment job.
August 26, 2014
There are two primary types of accelerometers: one is the ICP (integrated circuit piezoelectric) having voltage output, and the other is known as a CLD (current line drive) type, with a current output. The standard ICP accelerometer has a nominal output of 100 mv/g and the output of a standard CLD accelerometer is 9.81µA/g.
Cable movement during low frequency measurements with ICP accelerometers can induce triboelectric noise. Triboelectric noise results when two materials are rubbed together creating an electrical charge between them. Triboelectric noise can be generated by flexing or vibrating the accelerometer cable during data acquisition. Such movement can result in friction between the cable’s various conductors, insulation, and fillers. This friction can generate a surface charge resulting in triboelectric noise. Vibration data collectors will measure the voltage generated by this effect. This can cause data integrity issues with acquired data. CLD sensors output current rather than voltage and are therefore not subject to the triboelectric effect from cable movement.