Treatment For Aero Engines

Modern jet engines are incredibly reliable, and many precautions are taken to ensure that they remain in prime condition. Every engine is regularly overhauled and subjected to stringent tests and examinations by trained specialists. Even very small flaws in engine casings are repaired and expertly stress relieved by heat treatment before being allowed back into service. In an industry, which demands the highest technical standards, this stress relieving process must be carried out under carefully controlled and monitored conditions.

For this reason GE Aircraft Engine Services Ltd of Nantgarw, Cardiff have installed a purpose build electric heat treatment centre which can stress relieve several very small areas of metal components simultaneously at high temperatures. The unit incorporates the latest technology to meet their demanding quality requirements. Jonathan Powell, Repairs Development Engineer for GE Aircraft Engine Services Ltd said, "the advantage of the purpose built facility is that we now have the flexibility which we require as well as the assurance that heat treatments are geared to our particular needs".

Heat treatment is used to reduce internal stresses, which can be induced during weld repairs, and it can also improve elasticity, ductility and strength. The process involves heating the affected area and maintaining a predetermined temperature for a fixed period before cooling at a controlled rate.

The new unit is capable of stress relieving small areas of castings in confined spaces, even if these are in difficult to reach positions or are of thin material. The maximum temperature, which can be achieved, is 1000 degrees centigrade and the heated zone can be kept to a minimum size. As an added safeguard, over temperature protection has been incorporated to avoid the possibility of expensive accidental damage.

The heat treatment centre was designed and manufactured by Mannings Thermal & Environmental Engineers of Southport. Before being awarded the contract, Mannings carried out a study of the technical requirements and prepared a report of their recommendations. Manager of Industrial Heating, Les Oliver said, "heat treatment of aircraft components is one of our many specialist areas and we have gained valuable experience by working closely with some of the worlds best known aerospace companies over many years.

The heat treatment unit is housed in a portable, skid mounted, steel cabinet. It has a separate programmer for each of twelve independent heating zones and is fitted with all the necessary monitoring instruments, indicators and alarms. Two chart recorders with selectable channels allow a permanent record of up to 48 separate temperatures to be obtained from sensing elements fixed to the workpiece. A feature of the new system is the array of heating elements provided with the unit. These are critical to the stress relieving process since they provide the energy at the location where it is required. The elements are marked with the engine repair type so that similar heat treatments can be easily replicated.

More advanced equipment is being continually developed in response to the high standard demanded by the aerospace industry and this 'state of the art' facility has reached new heights in modern heat treatment technology.