In machine safety, there are stop categories, emergency stop categories, and safety control categories. Each of them categorizes different safety elements, and before exploring emergency stop categories, it is important to make a clear distinction with the other categories.

Safety Control Categories

These categories classify the various parts of safety-related control systems based on their resistance to faults and their behavior following a problem. This is achieved through the structural arrangement of the control system, its level of fault detection, and its reliability (ISO 13849-1:2015).

Stop Categories and Emergency Stop Categories

These two categories are the stop categories that are well defined by standards (emergency stop and normal stop). The emergency stop category is small and is often considered a sub-category of general stops, despite its special characteristics. Emergency stops must comply with different standards, especially regarding the power system and maintenance.

According to the safety norm EN 60204-1 "Safety of machinery – Electrical equipment of machines Part 1: General requirements", there are three categories of stop functions:

• Stop Category 0 : Uncontrolled stop resulting in immediate termination of system power. Sometimes, additional measures, such as braking, need to be employed to make the stop smoother.
• Stop Category 1 : arrêt contrôlé par le maintien d’alimentation aux actionneurs jusqu’à l’arrêt de la machine, suivi de la coupure de la puissance quand l’arrêt est obtenu. Le système continue donc d’être alimenté jusqu’à l’arrêt complet du mouvement.
  Controlled stop by maintaining power to the actuators until the machine comes to a stop, followed by power cutoff when the stop is achieved. The system, therefore, remains powered until the complete cessation of movement.
• Stop Category 2 : Category 2 stops are also controlled, but unlike category 1 stops, the system remains powered even after the complete cessation of movement.

These three categories are taken from specific standards such as ISO 13850 and IEC 61800-5-2. According to the ISO 13850 standard regarding the emergency stop function, only a stop category 0 or 1 can be used for an emergency stop. Category 2 is therefore excluded and is a standard stop category. This same standard also allows for defining color codes for buttons, indicators, and wiring markers.

Some Stop Examples

The EN 61800-5-2 standard "Adjustable Speed Electric power drive systems Part 5-2: Safety Requirements – Functional" defines some examples of Safe Stop functions including:

• Safe Torque Off (STO) : Cette fonction est un arrêt de catégorie 0, et donc un arrêt non contrôlé. L’alimentation du moteur est coupée en toute sécurité, de sorte qu’aucun mouvement n’est possible. This safety function corresponds to a category 0 stop (uncontrolled stop). The power to the motor is safely removed, so that no further movement is possible.
• Safe Stop 1 (SS1) : Safety function which corresponds to a category 1 stop (controlled stop). It initiates and controls the motor deceleration rate to stop the motor and initiates the STO function when the motor speed is too low or after a specific time delay.
• Safe Stop 2 (SS2) : Safety function which corresponds to a category 2 stop (controlled stop). It initiates and controls the motor deceleration rate to stop the motor and initiates the safe operating stop function when the motor speed is too low or after an application specific time delay.

L’arrêt sécurisé 2 diffère de l’arrêt sécurisé 1 en ce sens qu’au lieu d’entrer en STO lorsque le mouvement s’arrête, le système entre en arrêt de fonctionnement sécurisé (SOS). Cela implique que le moteur est amené à une position spécifique et y est maintenu et surveillé par le variateur.
Safe Stop 2 differs from Safe Stop 1 in that, instead of entering into STO when motion stops, the system enters Safe Operating Stop (SOS). During a safe operating stop, the motor is brought to a specific position and held there by the drive. Full torque is available to keep the tooling in position. The stop is monitored safely by the drive.

How to Choose the Correct Industrial Stop Category?

The choice of stop category for your industrial machine should not be taken lightly and will depend on several criteria. In general, machines with moving parts without inertia and whose stop does not pose additional risks will require a category 0 stop. Machines with hazardous parts with inertia or requiring other safety systems typically require a category 1 stop. However, this generalization is not 100% reliable, and it is necessary to consider several pieces of information to make an informed choice.

First and foremost, it is imperative to verify which laws or safety standards govern the use of your machine and the types of stops available. Industrial safety norms and laws vary from one country to another, and it is important to comply with the applicable standards.

Secondly, a risk assessment of the machine and all possible situations must be conducted. The results of this analysis will allow you to choose the perfect stop category that will maximize the protection of your workers without hindering the smooth operation of your business.

A Custom Turnkey Industrial Safety and Machine Safeguarding Service

Our sales and design team can work with you to determine the appropriate type of stop for your application, taking into account factors such as the application and type of machine, your budget, and applicable laws and standards. Contact us today to start creating a safer workplace.

References

L'écho de Laval

Comment différencier les catégories d’arrêts en matière de sécurité machine?

Intervention prévention

Sécurité machine: Les catégories d’arrêts

Protecting their workers should be a leading priority for every industrial company. Unfortunately, most employers tend to believe that investing in workplace safety will negatively impact productivity, which couldn’t be further from the truth! Safe working conditions often go hand in hand with ideal operational conditions. Employees can focus on their work and be more productive, instead of trying to avoid dangers in their workplace.

Machinery safety guards and shields are an effective and essential means of protecting your workers, but they should not be the only security solution used. After all, the best way to stay safe is to be able to identify potential hazards and avoid them altogether. This is where the safety signs come in.

How to Use Safety Signs Effectively

Any potential hazards in a workplace should be accompanied by a safety sign to identify it and keep workers from harm. A simple slippery floor can be just as dangerous as a rotating machine part. Safety signs should be placed near the potential source of dangers and be clearly visible. If possible, place them at eye level in a well-lit area. If the place is poorly lit, use phosphorescent colors, reflective materials and / or artificial lighting. Avoid placing an excessive ammount of safety signs near each other to avoid confusion. They must be big enough to be seen and read from afar. It is recommended to use short, clear and concise text on the panels, since the operators tend not to read or only skim the signs with too long instructions. The use of symbols associated with hazards and actions to follow is recommended.

Safety signs must always include:

• A signal word expressing the seriousness of the risk, such as "Danger" or "Warning"
• The hazard associated with the hazardous area or machine, such as "rotating part"
• The consequence associated with the danger, such as "Danger of death"
• Security measures to avoid danger, such as "Do not approach"

The 4 Colors of Safety Signs

• Red: Hazard signs identifying immediate hazards, prohibitions and safety measures to be applied
• Yellow or orange: Warning signs used to warn of potential hazards or unsafe practices
• Blue : Obligation signs
• Green : Rescue and emergency measures or general safety measures signs

Train your Workers to Read and Understand Safety Signs

Simply putting safety signs everywhere in the workplace is not enough. For these safety signs to be efficient, your workers need to be trained to read and understand them. Each sign has a special color and its own symbols. Therefore, your employees must be able to understand which one is which and which security measures are appropriate. Here are some of the things a worker need to learn during safety signage training:

• The color code of each sign and the meaning of the symbols
• The location where a sign should be placed
• When and how to remove a sign

PRISMONT’s Industrial Turnkey Service and Personalized Safety Solutions

Of course, a safety sign should not replace complete industrial security solutions that comply with the standards. With all the support of the Prismont team, you will benefit from a complete safety solution including a custom design and installation service which comply with all the requirements of the most important conformity and standards
regulations (CSA / OSHA / ANSI / ISO / etc.). We offer a turnkey approach for all services needed including experienced personnel, complete tooling, project planning and scheduling your safety projects large or small.

With an in-depth machine guarding analysis, we can help you identify risks and design a custom safety plan for you to help you deliver optimal Return on Investment (ROI). Contact us today and protect what is most important in your company. votre entreprise.

Reférences

INRS
Signalisation de santé et de sécurité au travail
http://www.inrs.fr/dms/inrs/CataloguePapier/ED/TI-ED-6293/ed6293.pdf

IRSST
Sécurité des machines-outils
http://www.irsst.qc.ca/media/documents/pubirsst/Securite-Machines-outils.pdf

RÉSEAU ICIMÉDIAS
L’importance des panneaux pour la sécurité des machines
https://www.canadafrancais.com/publireportage/limportance-des-panneaux-pour-la-securite-des-machines/