The risk of ‘unsafe’ CE certifications for category C standard equipment

The complexity of regulations, the strength of habit, the cost of technical and safety standards — both in the acquisition and understanding of documents, and their application within business — all like behind the major risks associated with ‘unsafe’ CE certifications, writes expert Marc des Rieux of C3-expert.com. This is especially true of machinery that comes under category C standards (a standard dealing with detailed safety requirements for a particular machine or group of machines).

In certain markets, such as continuous conveyor belt bulk handling, which falls under EN 620 (category C), I have observed that a very large number of conveyors that bear the CE mark, do not precisely meet the safety requirements of the Machinery Directive 2006/42/EC and repeated by the category A standard, reference EN ISO 12100v2010.

In my observations, I was able to deduce that all of these statements were, in my opinion, ‘non-compliant’, and the reasons for this included:

HABITUAL PRACTICE

The problem, resulting from the use, can be defined thus: the study of a project is carried out first of all according to a mechanical approach. When one study is complete, this adds a layer of ‘security’ to a project, which becomes almost ‘frozen’ mechanically. This is common practice, although it is contrary to the principles of the ‘New Approach’ described in EN ISO 12100.

FIRST REASON

As markets are very competitive, manufacturers have to spend as little time as possible on the development of their technical offer. The best way to achieve this is to rely on copy-paste of previous business and/or files that have been established for a long time. Unfortunately, this way of doing things, for which the economic reason is understandable, ‘freezes’ the conceptions for the future, especially when the contract is signed.

This first reason, falling under the breach in terms of safety compliance, comes from a multitude of poorly understood technical standards that are supposed to represent the state of the art. As a result, these standards are poorly enforced. This fact is reinforced by the certainty of a well- established knowledge that prevents any questioning (see # usage).

To illustrate this severe statement and among many other poorly understood

standards, ISO 5048 (technical standard) — which defines the method of calculating a conveyor — includes in its article 5.3.3 a formula for calculating the chain profile (so of parabola, of loop). This loop forms the belt between two supports and gives the admissible upper and lower limits of sag (lowest point of the loop). In its 1973 version, this article was completed by two examples and in its 1987 version, these were rightly deleted, since the example values were erroneous. Unfortunately, in 2018, it is still the ‘wrong’ example values that are applied in the designs. Later in this article, I present the relation with EN ISO 12100.

SECOND REASON

It is necessary to get back into the context of the hierarchy of laws to understand where the drift is leading, in good faith or otherwise, for unfortunately ‘unsafe’ CE certifications.

The Machinery Directive 2006/42 / EC specifies, in its articles 173 and 174 (note: use the Guide for the application of the Machinery directive 2006/42 / CE 2nd edition), a hierarchy of “the most adequate solutions and in the sequence indicated”.

These articles of the Directive are superseded over by EN ISO 12100v2010 in Articles 4e and 6.1, Step 1, Note 1. Indeed, if Article 4e is subject to interpretation because of a comma instead of a new paragraph (4 e: remove the dangerous phenomenon, or reduce the hazard ...), Article 6.1, Step 1, Note 1 is particularly clear, without discussion or possible interpretation, specifying that everything that exposes to at least one hazard should be removed if it is possible and if it is not possible, then and only then, will it be used as a way to reduce the hazard (example: safety hood, grid, etc.).

So why is this prescription not applied or too infrequently?

As stated in the preamble, the complexity of the standards is such that when you are told that the safety standard that covers your type of machine is No. xxx, it is a rare individual that bears in mind that this standard can only be applied once the general standards — such as Category A — have already been applied. QED!

This complexity can be seen, for example, in the EN 620 standard which follows 29 standards as a reference, and 17 other standards that are noted in the bibliography. That means, a first set of 46 standards must first be applied in order to master the application of EN 620; to this we must add the normative references and library standards mentioned in each of the first level standards, and so on. It’s a lot !!

PROPOSAL

In order to put everything in good order to meet the standards of Category C, I recommend that this warning is added: “This EN xxx standard, like all Category C standards, applies only after the exhaustion of the solutions prescribed in the general category A standards, notably EN ISO 12100v2010 # 4 e and 6.1, Step 1, Note 1.”

Readers of this article can express their support for my wording, above in italics, by writing to Dry Cargo International — or to me via the magazine which will pass on all correspondence — in order to obtain the introduction of this additional wording to the C standards.

REPRESENTATIVE EXAMPLES

Below are four examples of belt conveyor designs — because this is my area of expertise — whose certification is unsafe; this affirmation is proven by calculation.

EXTRA RADICAL CASE, N°1

Here, the entire machine should be removed.

I believe 100% of ‘speeding up’ conveyors should be removed because they are ‘unsuitable for their destination’ (mechanical aspect) and they involve at one risk (safety aspect). The proof lies in the calculation of the fall parabola of the product, projected on the unloading pulley, which must be considered as the angle of travel of the aggregates at the time of contact on the downstream belt.

Indeed, moving the product on the downstream belt at speed is not carried out according to the expected functions, and this is the cause of several problems with the machine.

GENERAL CASE N°2

In this case, a conveyor has a centre -to- centre distance of 425m. In its original form, it was equipped with nine pulleys and 144 return idlers. After calculation, the new design had only two pulleys and 27 return idlers — i.e. a reduction in the number of potentially hazardous components — [100- (100/9 * 2)] = 78% for the pulleys and [100- (100/144 * 27)] = 81% for the return idlers. These changes were motivated by recurrent disturbances on the original version and that the optimized design solved to ensure a very high level of reliability and security.