a) Condition monitoring is not always an appropriate tool. According to BS ISO 1
ID: 2083073 • Letter: A
Question
a) Condition monitoring is not always an appropriate tool. According to BS ISO 17359:2011 there are steps that should be completed in order to justify its use. Provide (with explanation) two steps. b) The performance and condition of machines can be measured in a wide variety of ways. List four measurable properties that are commonly monitored in condition monitoring systems. c) Answer the following questions about condition monitoring techniques, according to your experience during the module. Each is worth 2 marks. 1) Name two vibration analysis methods used to analyze vibration signals. 2) Name two common mounting methods used to mount accelerometers. d) An electric motor is driving a large pump supported by two bearings. The system is equipped with three vibration sensors (A, B and C), as shown in Figure Q2 below. The fan is rotating at 2 Hz. i. Draw the expected frequency series waveform you would expect from sensor A if the left bearing was suffering from looseness and the pump had eight blades. ii. Draw the expected time series waveforms (on a different graph from part i) for sensor Band C if the motor shaft was bent. iii. Draw a sketch of the frequency spectrum you might see if there is a defect in the one of the ball bearings rolling elements. Assume the ball spin frequency is 9.5 Hz.Explanation / Answer
a) Condition monitoring is a commonly used prosess for monitoring the parameters of machinery conditions.
Accordig to BS ISO 17359:2011, The two steps required to justify the use of condition monitoring are:
1. Detection of faliure modes: It s often the first step of desiginig a relaible system. it deals with reweing all the components, systems, subsystems and assemblies in order to ideantify the faliures and their causes. An FMEA worksheet is designed and the qualitative analysis is done. It is a full iductive analysis and the faliure is reduced and avoided by faliure mechanism.
2. Root cause analysis: RCA is a method of solving a problem which is used for the identification of root causes and faults of the problem.The root cause should be permanently removed from the system in order to get the unalterated desirable results. The root cause is always present at the bottom that causes the entire problems in cause and effect chains.
b) The four properties that can be measured in conditional monitoring systems are:
1. Line currents and voltages.
2. Temperatures.
3. Vibrational levels.
4. Rotational Speed and leakage fluxes.
c) The two Vibrational analysis methods are time wafeform analysis and high frequenct detection.
The two common mountig methods for mounting accelerometers are installing accelerometers using stud and installing accelerometers using wax. out of which the use of stud is mostly preferred.
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