Technical Diagnostics and NDT

Sometimes, smallest of the defects can be hardly visible for human eyes. That is when engineers use the Liquid Penetrant (PT) or Dye Penetrant test. Liquid Penetrant Examination is a Non-Destructive Testing method used to detect surface breaking defects, such as cracks, laps, porosity etc., which are unperceivable with the bare eye. The method is rest upon the ability of a fluid to be drawn into a "clean" surface-breaking flaw by smooth action. After a certain time period, unnecessary surface penetrant is displaced and a developer is applied that functions as a "blotter". Color contrast penetrants demand adequate white light whereas fluorescent penetrants are suggested to be used in dark environment and require ultraviolet "black light" where penetrant glows with a luminous color which can be easily seen from our eyes.

Some days ago I heard that Sri Lanka's ministry of tourism is going to develop a village called Kalpitiya in the western cost of the island, as a new tourist destination. I tried to find more information. It is quite a nice place with many small islands, white sandy beaches and yea! dolphins. Looking forward to travel there and see how it looks like.

Pre-flight Walk Around Inspection of a Light Sport Aircraft Walk around inspection of a MD-83

Figure: Boeing 777 aircraft Commercial aircrafts are frequently inspected visually. There is a primary inspection called "walk around check" both in the line and the base, transit checks, daily check, weekly check, A check, B check etc… Line is the more about the quick checks while aircraft is in the park or in between flights. Base is mostly the hanger, where hard checks, repairs take place. A qualified engineer walk around the aircraft and inspect structural items visually. Engine is also checked during the walk around checks. There engineer watches for oil leaks, structural damages in the engine, inlet of the engine for composite parts fixtures to the structure, fan/first stages of the compressor, last stages of the turbine for deterioration or damages , or any unusual changes of the engine. In this example shows how, engineer/Pilot carry on a walk around inspection of a Boeing 777 aircraft. Figure: Walk around inspection of a Boeing 777 1. Left Mid Fuselage...

Gas turbine engines are widely used in different fields for generate energy. They are commonly used in aircrafts. If you watch a huge passenger aircraft, you can see the gas turbine engines are either hanging on the wing section or tail section. Those power plants gives enough energy to generate thrust which finally result the aircraft fly. Figure: An Airbus A340's 4 engines are situated on the wing, 2 in each side. Figure: A Tupolev 154 Aircraft where engines situated on the empennage  How does a gas turbine engine work? There are several sections inside of an engine. First one is the air intake and fan which direct the air to inside of the engine, then the compressor, which compress the air to a very high pressure while reducing its speed. Then air meets the combustion chamber, where kerosene (fuel) is spread as small particles and burned in a high temperature.  

Visual Inspection is one of the most common NDT methods used to evaluate the condition and provide a better quality of an item. Visual method is easily carried out, inexpensive and usually does not require special equipment. It entails reflected or transmitted light from a test object being imaged with a light-sensitive device, such as the human eye. Such a testing method requires proper vision, good lighting conditions and the knowledge of what exactly to look for.

As we saw in the beginning, 2nd Section of technical diagnostics is about functional methods. They consist of: • Evaluation of long term and short term statistical data such as, the temperature of the part/machine, Pressure of the hydraulic systems, fuel/air consumption etc… By analyzing such parameters, engineer can predict the economical use of the part/machine and prognosis future failures, so that it will be possible to remove it and put a new part/ or totally stop using the machine before a catastrophe. • By analyzing the physical and chemical parameters such as the spectral analysis of oil in order to detect foreign particles (for example, small particles of metals can be found in oil system when a ball bearing is destroyed, and that can lead to a failure of the whole machine) • Vibration diagnostics: where engineer analyses the vibration of machine and evaluate faults and trends. An experienced engineer watches the frequency spectrum of the vibration without even touching the ma...