Dorr cleans up at Alstom AMF

Citation

(2003), "Dorr cleans up at Alstom AMF", Aircraft Engineering and Aerospace Technology, Vol. 75 No. 6. https://doi.org/10.1108/aeat.2003.12775fab.002

Dorr cleans up at Alstom AMF

Dorr cleans up at Alstom AMF

Keywords: Aerospace, Manufacturing, Components, Cleaning

It took leading Aerospace Manufacturing Facility (AMF) of Alstom, Lincoln, UK, over 2 years to investigate an alternative solution to component cleaning in order to move away from traditional, but highly efficient, trichloroethylene-based solvent method. The drive to overcome health and safety, as well as environmental concerns, was seen as important because the company still had to maintain strict specification requirements and especially so on complex components which often involved deep, dirt-trapping cavities.

Ian Williamson, Group Head, explains: "So important was it to make the right decision, that we thoroughly investigated, the market, the processes available and then became involved with in-depth cleaning trials. It was only then that the decision was made to purchase a Dürr Ecoclean 81 W Universal aqueous-based industrial cleaning and drying system".

Supplied by StarragHeckert UK of Brackley, the Dürr Ecoclean was one of the number of machines that Alstom AMF shortlisted. According to Ian: "The Ecoclean was by no means the cheapest. But it was by far the most effective – to such an extent that we now feel its performance is better than we could ever achieve using a solvent-based degreaser".

Alstom's AMF was established in a completely renovated warehouse in the late 1980s following the winning of a major contract to manufacture core components, such as blisks, impellers, impeller shafts and cooling plates, for a CFE738 turbofan engine for the Dassault Falcon 2000 business jet. This project is still live at present, having produced parts for over 600 engines and runs alongside other business jet applications, such as the production of power turbine discs for Honeywell Aerospace in the USA.

It was in the late 1990s that Alstom AMF won an order to supply 1,200 spooled compressor rotors for the Northrop T38 Talon military aircraft over a period of 5 years. More than 40 components make up the final assembly to which a rear spool is prime example which starts off as an 84 kg forging and ends up as a 16 kg machined component – reflecting 81 per cent of the original material ending up in the swarf bin. As a result of winning the contract, Alstom AMF had to expand its premises to accommodate extra capacity which then initiated the cleaning process investigation.

Many of the parts machined at Alstom AMF arrive as forgings before being subjected to a series of complex turning, milling, broaching and grinding operations. It is the complexity of these components and the associated cleaning problems that concerned Ian when the decision was made to select a new industrial cleaning process. He said: "All our parts have to be subjected to non-destructive fluorescent crack detection after manufacture and therefore have to be spotlessly clean and thoroughly dry. Also, some parts have extremely deep cavities and we were very concerned they would be a problem for any aqueous-based washing system".

One of the key factors of Dürr machines is that they can be tailored to suit most applications. This led to a vacuum drying system being added to the Alstom AMF specification to ensure perfectly dry components which even extended to the deep cavities. "This was very important to us. We had to have a cleaning system that allowed us to single operation parts to extremely high process standards and we did not want to have to add any further processes" said Ian.

He then describes how as a company it has always been very conscious of health and safety and knew that washing with detergent and water would be inherently safer than solvent use. This method therefore became one of the main drivers for the cleaning project. As part of process research and trials, Alstom's engineers visited Dürr's headquarters in Germany, where the Ecoclean 81W was put through its paces to clean parts contaminated with coolant, heavy cutting oil and a very difficult abrasive flow medium. This abrasive is used in the automatic polishing of radii and surfaces on component materials which include inconel 718, waspalloy, titanium and high-grade stainless steel.

The trials were successful and as a result the Dürr Ecoclean 81W was installed in mid 2002 (Plate 1). In fact, so successful is the cleaning process that all parts manufactured by the company are automatically passed through the machine.

Plate 1 StarragHeckert UK's Dürr Ecoclean 81W universal cleaning system provides environmental solution to part cleaning at AMF Alstom

Components are loaded into coated mesh baskets of 670 × 480 × 300 mm and restrained using a system of retainer rods which prevent them working loose during the washing cycle. The basket is then slid through the door of the front-loaded single vacuum working chamber in which parts are all sequenced through a three-stage cleaning process involving washing, pre-rinsing, finish rinse using de-ionised water, ultrasonics, hot air and vacuum drying. Programs are selected according to the component type allowing the basket to remain still, be oscillated or continuously rotated. Cycle times vary between 5 and 20 min depending on the type of part.

Within the Alstom specified Ecoclean 81W there are three tanks. One contains an aircraft approved detergent which is heated to 70°C for washing, a second rinsing tank contains just a small addition of detergent and the third contains pure, de-ionised water for rinsing. The use of de-ionised water is critical especially when cleaning titanium parts used on aircraft engines. As the process progresses, the chamber is sequentially filled and evacuated with the contents filtered through a high level system of cartridge and bag filters before being returned to the individual holding tanks.

According to StarragHeckert, an added advantage for the environment is that the Dürr system enables the cleaning media to be fully recycled in another integral aquaclean system that effectively evaporates the media and allows it to trickle back for use within the main system. So effective is this process that it leaves any contaminants behind and ensures that only the minimum of maintenance is required.

Ian concludes: "StarragHeckert are always on hand with the specialist knowledge should we experience any difficulties and we have had good support. If we take everything into consideration, we would still make the same decision. Sometimes this level of technology can be difficult to justify, as no one really wants to pay to wash parts. But for us, it is an absolute necessity and even though a large number of different operators use the machine, we have never had a single complaint over the quality of our cleaning process."

Details available from: StarragHeckert UK Ltd. Tel: +44 (0)1 280 705482; Web site: www.starragheckert.co.uk