Magnetic Rope Testing (MRT)

MRT is a non destructive, magnetic and contactless procedure that allows us to detect broken wires, distortions and corrosion on steel wire ropes.

The Magnetic Rope Testing method was introduced in the cableways sector to inspect the haulage and carriage and to entify external and internal defects. In the 80s this technique broadened the offshore heavy lifting market due to the increasing needs in terms of efficiency and safety.  ISO4309 includes MRT as an assessment method for the inspection of generic heavy lifting steel wire ropes.

Innovative concepts in the MRT, improving both magnetic development and user-interface facilitating a full wire rope inspection thanks to an automatic setting included in the software.

MRT devices are equipped with two different signals (on two separate electric circuits) that can be useful for the operator to identify and estimate damages such as internal and external broken wires, corrosion, wear, etc.

The LF signal is the main technique in this field and it is completely regulated by international standards. It consists in the measurement of the leakage flux that appears when a defective portion of rope is introduced into the device.

Industries

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Heavy lifting, cableways and the elevator market use wire ropes in different ways, but the general aspects about safety and service continuity are very similar. Cableways carry people from one place to another and the condition of wire ropes is really important to avoid accidents. This applies also for elevators and heavy lifting, in which a failure of the rope could cause huge issues in terms of responsibility, human life and finance.

 

1.  Heavy lifting

MRT made its first appearance in this sector in the ’80s, especially for some specific applications. Although heavy lifting ropes don’t lift humans but loads, safety is really important because a failure can cause a disaster (imagine a steel mill, or a mine).

A strong progress in technology in the early 2000 led to the availability of heavy lifting devices, compliant with cableways standards, in order to improve the final user experience and simplify the use of MRT systems in this environment. The updated version of ISO4309 (2017) indicates MRT as stateof-the-art method for internal damages.

Non rotational wire ropes are actually used in many applications. Non rotational wire ropes behave differently according to each layer ropes. The degradation often starts from the inner part of the rope, and a standard visual inspection cannot be enough to ensure a correct evaluation. In these cases an MRT inspection is strongly suggested to avoid failures and damages.

 

2.  Cableways

In this sector MRT is usually requested and, in some Countries, mandatory. Safety is the main concern and being aware of the actual conditions of the ropes is really important.

The MRT application is not limited to internal damages, but also for external wires. Furthermore, the cableway sector is the first environment in which specific standards for the MRT inspection have been developed. These standards, such as the EN12927, now applies to different fields.

 

3.  Eleavator market

The application of MRT to elevators is quite new. Since the early 2000s such devices and the technology is no longer just a ‘testing application’, but a recognized inspection system.

In this industry the safety is really important because an elevator machine moves people from one floor to another and millions of runs are  performed every day. A failure in one or more ropes can cause injuries and other issues (stop of the plant, damages, etc.). Visual inspection is extremely difficult due to the tight spaces and to the time required. Maintenance process can benefit a lot from MRT in terms of time saving.

The elevator market is characterized by different types of suspension elements, such as steel wire ropes, coated ropes and belts. An elevator plant is not always the appropriate place to perform a visual inspection, it is usually too dark and tight.

AMC Instruments, together with Mennens Netherlands developed special tools to perform an accurate magnetoinductive inspection on all the mentioned suspension elements, also on belts and coated ropes where visual inspection is practically impossible.

These solutions allow to save time as well. Wire ropes on a fifth floors elevator can be inspected in less than 2 minutes (test setting included)
increasing tenfold the accuracy of a visual inspection performed in a dark and small environment.