Condition Monitoring Techniques and Structural Health Monitoring | Qualitative Systems Reliability A

Main steps in implementing a condition monitoring program

What are the main steps in the generic procedure for implementing a condition monitoring programme which are outlined in BS ISO 17359:2011?

Answer the following about condition monitoring techniques, according to your experience during the module:

1- With the aid of a block diagram, outline the main elements of a vibration analysis system

2- Name two vibration analysis methods used to analysis vibration signals.

3- For the given accelerometer response (shown in the figure Q1.1):

i. At what approximate frequency does attenuation occur?

ii. What approximate frequency does resonance occur?

4- Name two sources of Acoustic Emission signal in machinery condition monitoring, and the corresponding AE signal types.

5- Name two approaches used in oil debris analysis.

c) For the gearbox, use the BS ISO 13373-3 standard (Equations provided in Appendix A) to calculate the expected defect frequencies of bearings no. 6, if the input shaft speed is 6000rpm.

d) For Gear A in the helical gearbox shown in Figure Q1.2, calculate the expected gear fundamental frequencies, if the input shaft speed is 6000 rpm. (5 marks)

a) Identify the three main elements of a structural health monitoring system architecture for an aircraft application. Provide examples of the typical systems or components to be found in each element

b) Describe three of the key benefits of structural health monitoring over current methods used for inspecting and maintaining safety critical structures such as aircraft.

c) Fibre optic sensors provide an alternative to electrical strain gauges for the measurement of strain at multiple points on structures. One form of fibre optic sensor systems uses Fibre Bragg Gratings (FBGs) as the strain sensing elements I. Draw a diagram of a fibre optic sensor system that uses FBG as strain sensors.

Label each of the main components and describe briefly what function they fulfil.

II. List the main advantages of fibre optic strain sensors when compared with electrical strain gauges.

d) An aircraft monitoring application requires strain measurements in the range -3,500 microstrain (µε) to + 3,500 microstrain (µε) . The temperature range over which they must operate is between -500 C and +1050 C An FBG sensor system has the following characteristics for each FBG sensor:Strain sensitivity, Δλ / ε = 1.2 pm / µε Temperature sensitivity,  To achieve the full strain measurement range of +/- 3,500 µε, at a constant temperature calculate the wavelength bandwidth needed for each sensor (in units of

II. At a constant strain level, calculate the change in wavelength (in units of pm) experienced by each FBG when subject to the full temperature range for the aircraft application

III. Using the answers from I and II, If 5 FBG sensors are required in a single fibre system calculate the minimum overall wavelength bandwidth of the system to accommodate all 5 sensors ensuring there is no overlap between each sensor channel.

Principle of a Fibre Bragg Grating (FBG) strain sensor. Each FBG sensor reflects at a nominal peak wavelength. When the FBG experiences tensile strain and/or temperature increase, the peak shifts to longer wavelengths. When subject to compressive strain and/or decrease in temperature, the peak shifts to shorter wavelengths.

a) FMEA and FTA are two key concepts to perform system reliability analysis. (i) What do the letters stand for in the acronyms FMEA and FTA? (ii) State the advantages of an FMEA process.

b) A water turbine is a rotary machine that converts kinetic energy and potential energy of water into mechanical work. It is mostly found in dams to generate electric power from water  kinetic energy, which is clean and renewable.Below shows the cut-away view of a  water turbine and electrical generator. Figure Q3. Water turbine and electrical generator cut-away view State two design for reliability principles according to British Standard and how they could be applied to the wind turbine design.

c) Perform an indicative 3-level system break down describing the water turbine and generator  system, identify ONLY 4 failure modes (at least two different modes for one component) and perform FMEA to prioritise risks.