The safety of lifting systems

The safety of lifting systems: design, check-outs, programmed maintenance and periodic controls, requalification and assessment of residual life.

Alessandro Mazzeranghi, Luca Belgero – MECQ S.r.l.

A manager of one of the major manufacturers of lifting systems in the world, Konecranes, a Finnish company that, due to its place of origin, has strong competence in the field of overhead traveling cranes for paper mills, told us that in many countries of the world lifting devices – because of their simplicity of construction (sometimes only apparent) and the fact that they are not considered process systems - are “underestimated”.

In reality in our field, if we look at all the overhead cranes in a complete production cycle, we find some that are absolutely indispensable to the process itself, whose stoppage can cause the interruption of a part or of the entire production line. In most cases, reel unloading from the PM takes place through an overhead crane, just like loading the reels onto the unwinders of roll machines … if one of these cranes is out of order for a significant amount of time, production can be in trouble.

You may think: but overhead cranes are sturdy machines, why on earth should they stop? Actually, the possibility exists, like in the following cases.

1. Initial errors in dimensions that lead to the installation of an undersized machine for the type of use to be made of it. The result is that the machine quickly deteriorates and starts requiring more maintenance than expected up until its replacement.

2. Lack of programmed maintenance that causes deterioration of mechanical and/or electrical and/or control parts, making operation unpredictable and substantially increasing interventions for failures.

3. Lack of periodic controls and legal verifications that, besides yielding the same effects as lack of maintenance, can also entail machine stoppage by state control bodies in charge of workplace safety.

4. Use of the means beyond the lifespan determined by the manufacturer which at a certain point leads the machine to operate beyond the limits of the structural project. Apart from possible interventions by state bodies, there is an obvious although remote risk of machine collapse due to fatigue.

Clearly, if we privilege the point of view of personnel safety, superficiality in managing lifting devices (and these include not only overhead traveling cranes but also ropes, harnesses, chains, balancers, etc.) is certainly not very prudent given the fact that the loss of the load (of the reel, for example) is one of the events that in a tissue facility can cause the most serious damage, including death, so it is natural that we should call attention to this aspect.

The aim of a correct management of lifting devices (and equipment). Basically, the objective is to put into place all precautions and actions that allow guaranteeing that, at the time of use, a lifting device or lifting equipment is in a perfect state of conservation, at least as far as all relevant aspects to guarantee personnel safety are concerned.

We would like to briefly list some examples of “specific aims”.

1. The device must be structurally integral, i.e., it must be in the same conditions as the initial project. No deterioration such as cracks in the welding must be present, or wear in the construction elements (pins, for example), or permanent deformations, at least for all those elements that participate in supporting the load.

2. Moving elements such as wheels, pulleys, etc. that could cause a problem in guiding the load or the device itself must not be damaged.

3. Safety systems such as lifting or shifting brakes must be integral and properly functioning.

4. Safety advisers (lights, buzzers, etc.) must be pro-perly functioning.

We won’t continue: check-lists on these topics can be easily found on the Internet. Instead, we would like to ask our readers to try and consider what the possible consequences for people if among the examples cited above, there was something that did not work properly: what if the load fell? If the machine did not stop? If the trolley of the overhead crane derails and falls to the ground?

These are serious accidents, and if there are people in that area, the damage can be very serious.

Good practice for a correct management of lifting devices (and equipment) . This article wants to call attention to an aspect that all of us who work in the field of tissue tend to underestimate. So when speaking about good practices, too, we would like to illustrate how keeping the situation under control is not so complex after all. A minimum amount of organization is required, of course, because there are a few actions to be put into place and these are different for logic and target. Only a harmonized set of preventive actions allows guaranteeing that the device used by a colleague “cannot break down or have a dangerous problem”.

So let’s make a reasoned-out list that will perhaps not be exhaustive but that will surely supply a direction to pursue in organizing this aspect:

1. Purchase: when ordering an overhead traveling crane, it is not sufficient to indicate only the maximum load but also the type of use must be given. This is necessary because the cycle rate and the load at which these cycles are performed is an indispensable parameter for the design technician. Unfortunately, some sly manufacturers do not ask for this information and propose devices having the max load requested but undersized for use, thus seeming more competitive. This little scam is still practiced today by some.

2. Check-outs: although the machine is certified by the manufacturer, it is a good idea to participate at check-outs and understand their meaning, especially in relation to load trials during which it is important to measure the overhead crane’s camber (some, however, do not). NB: a device that when handling a load presents an excessive inflection could be stopped by a state body and downgraded to a lower maximum load capacity.

3. Controls: non-destructive controls (visual, magnetoscopic, with penetrating liquids, to assess good operation) must be performed also based on the intensity of use of the device. Common practice is: not less than once a year, not more than six times a year except in very special cases typical of other fields (steel works).

4. Mandatory verifications by law: these, of course, depend on national legislation but must in any case be considered additional activities to those described at the previous point.

5. Multi-year verification (for overhead cranes, technical norms specify every 10 years): it is a very in-depth technical control through non-destructive detailed checks (that also includes taking the width of structure to detect any deterioration), load trial, post recalculation of the device’s operational figures, making it possible to establish what part of the device’s design life is consumed due to wear (when the verification is being performed) and hence permitting to estimate residual life. Basically, it allows extending, legitimately and with an unexceptionable technical support, the device’s life span which – without this verification - would be considered exhausted.

Conclusions. We have spoken about good practice, of actions that – even independently of law obligations – must be performed to guarantee that the lifting devices (you will certainly have noticed the emphasis we have placed on overhead cranes, but do not forget balancers or simpler equipment) used are in perfect state, i.e., to avoid that people are exposed to very grave and absolutely unnecessary risks.

In concluding we would like to add that the organization we were speaking about, besides guaranteeing the technical aspect and correct scheduling, will also have to consider collecting evidence of the checks made. And this, of course, in order to leave a trace of the company’s commitment in the event of objections/criticisms brought forth by any subject who has a right to do so. *

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