The importance of the interpretation
(Reading time: 5 min)
Today data are everything. Their analysis and extrapolation allow us to interpret past and contemporary events and under certain hypothesis to forecast the future.
In magnetic rope tests inspectors need to manage and interpret data to understand the rope behaviour.
During this process many different questions could rise: which is the difference in terms of signal between a broken wire and a deep corrosion? Do they weight the same? Is that a broken wire or a distortion? Is that a fake signal or an internal broken wire?
Training is the best answer.
In this article we will evaluate the importance of a good training in magneto-inductive device inspections.
The best device with the worst technician is less accurate than the best technician with the worst device, because the system is only an interface between the technician and the rope.
This is true also for visual analysis, a not-trained technician can easily fall in misunderstandings and errors. Trivially, the eyes (interface) are not enough to perform an inspection without knowledge.
It is fundamental that each technician attend a well-structured MRT training course before operating.
In the next paragraphs we will specify and explain the minimum topics of an MRT training.
THE OPERATIVE TRAINING
This preparation must teach the inspector to use the device correctly both in laboratory and on the field, to read and interpret the data on the software and to prepare a report in full compliance with the regulation.
The training represents the first step on a path for becoming MRT expert technicians. Later, practice and good after-sales services will help keep them updated. This path must help them to know how an MRT inspection works..
- Minimum required knowledge, Regulation, and Report
Technicians must know what characterizes ropes and the inspection environment. Ropes terminology, characteristics and construction are the minimum required knowledge for operating.
Mastering ISO4309 for the heavy lifting sector is half the journey.
The standard establishes general principles for care, maintenance, inspection and discard of steel wire ropes used on cranes and hoists. Furthermore, it provides realistic discard criteria covering maximum number of broken wires, reductions in rope diameter and corrosion and it gives a method for assessing the combined effect of deterioration at any position in the rope.
A compliant report shows if the inspection procedure has been respected and legally protects the technicians in case of claims. These features are mandatory also for visual inspection, which is usually underestimated. It is always necessary for an operator to know the difference among defects and their relative severity rating. A valley break has 100% of severity rating (the rope must be discarded), whilst the severity rating of an external/internal broken wire depends on rope construction.
- MRT signals and their interpretations
This part is the core of Magnetic Rope Tests. Inspectors must learn the correspondence between signals and defects, how and why signals vary, how to recognize fake signals and most importantly to choose the best signal (LM vs LMA)
- Software Training
It could seem easier to have defects numbers or damages percentage instead of diagrams, but these numbers are a quantitative representation performed by a machine. Reading a number defined on different rope behaviour conditions could be tricky when you have the responsibility of the result. This topic regards also the unappropriated use of filters. We do think that a training starting from raw data leads technicians to safer interpretations. In this part of the training the user must learn how to apply filters and their meaning and how to set the diagram for a real time and post-processing evaluation.
- Technical Practice
MRT systems are experience goods, users usually start to evaluate these products only after several technical approaches. This part of the preparation allows the customer to be confident with the equipment and to perform several tests before the first inspection on the field.
This training is mandatory in the cableway sector and allows the technician to be considered as MRT expert in heavy lifting sector.
This course is held by qualified companies under the supervision of third-party organism, usually a notified body.
This training is technically deeper than the operative one, providing all the necessary knowledge to operate in accordance with International Standards. The candidate will learn the basics of electromagnetism, the system working, the signal creation and the different regulations.
After the course, the technician will be able to understand the physic concepts behind the device designing.
Trainings are necessary tools to become an MRT inspector. Furthermore, we think that a constant support from teacher/MRT supplier could be very useful to bring technicians to a full understanding of each phenomenon.
Professional inspectors interpret diagrams and provide a rope status report, ordinary inspectors read numbers.