X-ray inspection assures helicopter integrity

X-ray inspection equipment from Viscom reliably detects faults in welds and materials for helicopter manufacturer Eurocopter.

Helicopter manufacturer Eurocopter is one of the world's three leading suppliers in the aerospace sector.

The company was established in 1992 on the basis of a merger between Aerospatiale-Matra (France) and DaimlerChrysler Aerospace (Germany) and is now a 100% EADS affiliate.

With more than 1100 employees at 16 international locations, the company earned a consolidated turnover of Eur 2.61 billion in 2003 - 30% of the world market.

More than 9000 Eurocopters are currently in use in 134 countries.

The line of products includes civil as well as military aerospace engineering and ranges from lightweight single-engine helicopters to medium-heavy transport helicopters.

Viscom develops and manufactured high-speed, high-precision industrial vision systems.

Its world headquarters are based in Hanover, Germany, with facilities and representatives worldwide.

Under the broad banner term "automated optical and X-ray inspection (AOI and AXI)", Viscom is involved in an extremely wide range of applications and markets, from customised systems, PCB inspection systems to X-ray and combined AOI/AXI inspection systems Inseto is the UK and Irish technical representative for Viscom's X-ray equipment.

The quality requirements in the field of aerospace engineering are extremely high.

Material weakness or faults can have fatal consequences for the final consumers and economic consequences for the manufacturers.

For this reason, entirely reliable material inspection is required, which allows nondestructive testing on the one hand, while simultaneously providing complete documentation of the test results.

Usually, a 100% test is required when each individual part is inspected.

An inspection procedure, which fulfils these high requirements while also reliably recognising concealed faults, is X-ray inspection.

One of the most important safety relevant components in a helicopter is the rotor gear.

"The material, as well as all connections such as welds, must be in a perfect state in prior to further processing".

"For this reason, all of these critical steel parts together with all welds must be tested for any possible material or production faults using a nondestructive method", explained Frederic Cance, Chef de Projets at Groupe SNEF, co-operation partner at Eurocopter.

If a fault occurs on the shaft or another transmission component, a crash would be inevitable.

The test results are documented individually, checked and kept on file for 30 years.

For 10 years, Eurocopter has used microfocus X-ray technology for inspection.

The company recently decided to purchase a new high power Viscom system for up to 225kV.

It was required to fulfil the following requirements: reliable X-ray inspection of extremely thick-walled metal and synthetic cast parts; extremely good image quality providing exact images and thereby ensuring recognition of the smallest details; archiving of the images for 30 years in the form of individual printouts; and short exposure time suitable for larger production lots.

Together with SNEF, which is a competent and recognised co-operation partner of Eurocopter, all major worldwide suppliers of X-ray equipment were reviewed and evaluated.

The excellent co-operation between all three companies, Eurocopter, SNEF and Viscom as well as the high standard engineering and build was finally the decisive factor for purchasing a Viscom system.

"The aerospace sector places high demands on inspection equipment".

"In the area of X-ray technology, we were also looking for a technically first-class solution capable of meeting the high demands of the company in terms of the safety and quality of the products".

"On the other hand, it was just as important to ensure that the supplier is a competent partner in the area of inspection technology in order to allow flexible reaction and implementation of customer specific adaptations at any time".

"In other words, Eurocopter was not only looking for good equipment but also for a good partner", according to Bernard Peltereau from Viscom France.

Jean-Marc Mercadal, Quality Laboratory - NDT, Eurocopter added: "We were in contact with all important X-ray suppliers and performed many tests and evaluations to study the technical specifications and ensure that we found the best solution".

"The co-operation with Viscom and SNEF fulfils all our requirements".

"After 6 months use, the excellent co-operation with SNEF and Viscom has shown that this decision was correct".

Eurocopter uses a Viscom microfocus X-ray system up to 225kV.

This high tube voltage is required to ensure full X-ray penetration of the thick walled metal parts.

Additionally the high tube power is necessary for short film exposure times required in mass production.

The powerful and even high resolving Viscom microfocus X-ray tubes discern the smallest details.

A special requirement at Eurocopter: X-ray inspection with rod anodes is used, for single wall penetration of nearly closed hollow parts at high energies.

In order to inspect the thick walled steel parts, which are closed all the way around at extremely high radiation energy levels, direct beam as well as the panoramic beam characteristics are used.

For this application the rod anodes are inserted, eg into a gear shaft, in order to X-ray the part from the inside to the outside.

Using a panoramic technique, the X-ray beam radiates the part through 360 degrees to provide an image of the entire object to be tested.

The X-ray image is projected onto an X-ray film, positioned around the part thus the complete inspected area can be evaluated in one single panoramic image.

X-ray film is still used as the detector because the flexible material allows it to bend over 360 degrees.

Another reason for using X-ray film is the extremely high contrast resolution, which allows even the smallest details to be shown precisely.

Finally, the individual images meet the high demands for documentation.

All critical gear parts and their welds are checked 100% for rod fusion, air inclusions, cracks and other material faults.

On that basis it is possible to decide whether the part is to be rejected or repaired.

"Presently, there are no alternatives to X-ray inspection", according to Jean-Marc Beninca, responsible for the NDT section at Eurocopter.

"For the future, we are considering whether we can replace X-ray film with a digital image detector in order to save space for archiving".

"At the moment, we are still using the old procedure, because it guarantees extremely good image quality".

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