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:
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.
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.
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 !!
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.
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.
GENERAL CASE N°3
This is certainly the most common case, which concerns conveyors with a centre- to-centre distance of 42m and above. For these conveyors, the common practice is a design comprising one snub pulley in head, three pulleys for the pre-tensioning device (GTU) and, sometimes, one snub pulley associated with the tail pulley and with, for the pitch between return idlers, a standard pitch of 3m.
Here, the ISO 5048 and ISO 3870 technical standards, well understood and well applied, make it possible to reduce the number of pulleys from six or seven pieces to two pieces and to increase the pitch between 3m and 12–15m return idlers, for a very high level of reliability and security.
GENERAL CASE N°4
These are conveyors with a centre-to- centre distance of up to 30m, for which in most cases, there should be zero return idlers, instead of a number of unnecessary idlers. For these conveyors, it goes without saying that the number of pulleys is limited to two, except and subject to calculation, extractors (+1).
To ensure the relevance of these four examples, there is a conveyor that has been in service since 2002, with a flow rate of 700tph (tonnes per hour), with a centre distance of 1,100 m of center distance, 28m of elevation, with one head pulley and one tail pulley. The return idlers have a step of 12m. This suggests that all smaller conveyors can have such a simple mechanical design for perfect safety compliance. Yes! It’s ok!
As can be seen from the examples above, machine calculation notes are essential to a true statement of conformity for certification purposes; it is still necessary that these calculations are carried out properly.
WHAT ARE THE RISKS OF AN UNSAFE CERTIFICATION? ?
Given the estimated number of machines (conveyors) in service, whose certification is probably insincere, we can consider, according to the adage ‘not seen, not taken’, that the subject is unimportant.
The risks, in case of control or audit following an accident or near-accident, are a withdrawal, a revocation, a termination of the conformity statement (EN ISO 17000). Such a situation leads to the immediate cessation of the operation of the machine and the obligation to carry out the safety modifications for compliance to be able to operate the machine again. For example, a CRAM (* CRAM : Regional sickness and work accident insurance fund) in France had to order modifications to a conveyor in a cast iron foundry, to be carried out within three months, under penalty of shutdown.
In case of an accident on a machine, which is shown by experts to have an unsafe certification, the owner is then vulnerable to a court conviction (Case M ... 1996) with serious consequences for the company.
MANAGE COMPLIANCE AS A GOOD FAMILY MAN
To achieve a high safety level (rules of good governance), you have to start with the removal of machines, machine parts and components that are hazardous and have no functional utility and replace these with machines that offer better reliability, with a very high level of safety.
There are organizations that can assist the machine owner to obtain, at least, an opinion on the quality of the safety compliance of his machine. First and foremost, CRAM engineers and insurers in general can provide advice or direct the request to an expert.
The habitual practice today is to call on a control body. Nevertheless, the report issued can be a false guarantee of conformity if the competence and the mission of the organization are limited to note that this or that exposure to a hazard is protected or unprotected. In this context, it will be difficult to say that this or that component, exposing him to a hazard, has no use, an affirmation demonstrated by a calculation for which, in general, he is not authorized.
C3 Expert has created the labels ‘C3 Label’ and ‘C3M Label’ in order to guarantee, after the audit, a safe CE certification of the machines and with an easy and safe maintenance.
IN A WORD!
This article should encourage the reader to consider the design of the machines under his responsibility and to ask the question for each component posing a risk, according to the list of hazards established from the standards EN ISO 14121, 14121- 1, 14121 -2 ‘Machine Safety – Hazard Assessment’. It will sometimes be necessary to recalculate the machine according to an optimized design, that is to say a design whose components not justified by the calculation have been removed.
Your remarks and comments on this text are welcome to change practices to the benefit of all.