2.1 Risk assessments for machine builders

A series of articles addressing the needs for safety in the industry
by Ray Azizian - Lead product Support Specialist Safety Systems and Standards
Phoenix Contact USA

Thank you for commenting, reading and liking my previous article titled Introduction to Functional Safety Standards. I hope you enjoyed it and if you missed it the link is at the bottom of this article. Thank You.

In this article we will address the following:

• Describe risk assessment standards for machine building in the U.S. and E.U.
• Explain the four-step process for performing risk assessment
• Explain its impact on the U.S. machine-building market

Introduction:

In an industry where machine builders need to market their products, a set of rules by a government or non-government organization must be adopted to maintain good engineering practices. The rules are a set of guidelines followed by manufacturers to reduce the risk of any dangerous consequences that could result. The consequences may result in death or injury to an operator, damage to an expensive machine, production interruption, or environmental disaster.

Based on the type of industry, each piece of equipment has an associated set of guidelines. Analysis must be performed to reduce the risks of a hazard. This analysis is called risk assessment. Companies use risk assessment to identify all hazards, how many times each could occur, and the consequence of 

these hazards. Based on this information, they can determine what type of safety measures should be implemented to bring the risk to an acceptable level.

There are two methods of assessing the risk of a hazard: quantitative, which requires calculations, and qualitative, which uses charts and tables. Regardless of which method is implemented, the conclusion should be the same.  

There are standards required by the members of the European Union to market products across the E.U. borders. U.S. manufacturers interested in marketing their products in the E.U. market must comply with these E.U. standards.

Part 1: Risk assessment standards for machine building in the U.S. and E.U.

Here are some standards and their applications:

ANSI B11.19.TR3: Risk assessment and safeguarding of machinery package.

ANSI/RIA R15.06: Industrial robots and machinery safety package.

ANSI/RIA/ISO 10218-1: Robots and robotic devices - Safety requirements for industrial robots - Part 1: robots.

IEC 61508: In the third phase of the safety life cycle in the analyses group, hazard and risk analysis is performed.

EN ISO 13849: This provides specific requirements regarding safety related parts of a control system using programmable electronic system(s).

ISO 14121: Safety of machinery - Risk assessment - Part 1: Principles revised by EN ISO 12100.

EN 1050: This is a European standard which defines the principles and procedures for risk assessment related to machine safety This standard uses data collected throughout the machine’s life cycle — incidents, harms, accidents, and design — to determine and assess risks.

EN ISO 12100: Safety of machinery — General principles for design — Risk assessment and risk reduction

Part 2: Four-step process for performing risk assessment

Risk is assessed using one of the following methods:

? Quantitative: In a quantitative method, data from the product data sheet for every component used in a machine is obtained and inserted into formulas to determine a value. This is sometimes known as PFH.

? Qualitative: The qualitative method involves events and consequences which are converted into numerical values using charts from which a value is calculated. The same outcome should be obtained by both methods! You can develop procedures or guidelines of your own to assess a risk.

The four steps method is one such method, which involves:

Step 1 – Machine capabilities: Identify machine limitations and capabilities. This information can be obtained from the machine’s data specs. For example: From a palletizer’s technical data we can obtain information about the dimension, weight, area of the movement, electrical power usage, air pressure, movement speed, as well as the product’s life.

Step 2 – Hazard identification: Collect information from the data specs and user manuals, as well as from meeting with machine operators in which you question them about what dangers they may encounter when using the machine.

Hazard categories: ? Electrical hazards include electrical shock, burning from sparks, electrical field ? Thermal hazards include burning from heat and freezing from cold ? Mechanical hazards include drawing-in or trapping, crushing, shearing, severing, cutting, entanglement, impact, stabbing or puncture, friction or abrasion, high-pressure fluid injection (ejection hazard) ? Other types of hazards: noise, vibration, emitting rays, working materials, substances, disregard for ergonomics, chemical release, and radiation 

Step 3 – Consequences and analysis: Once you have identified the hazards, the next step is to determine the frequency of the events and how their severity. 

Welding produces sparks so we can ask the following questions: ? How likely is it that sparks are exposed to the operator? ? How dangerous is this event if the operator would have no protective shield?

Step 4 – Mitigation: Mitigate the risk by using some protective measures, which may not require a safety instrumented system. In step 3 we discussed the sparking caused by welding, now we can build a safe zone for an operator to work in, such as creating a barrier shield or requiring protective gear. 

Other measures implemented could include a safety system:

Covers around the complete machine: Mechanical safeguards.

Protective doors permit access when required: Monitoring /inhibited protective doors

Protect material ejection via constructive measures: Avoid access

The following link has good points about Risk Assessment: Safety vs. Security.

Part 3: Its impact on the US machine building market

Under European law, the EC Machine Directive is set by the European Parliament and the Council of the European Union. These apply to the manufacturers of machines in the course of marketing their products in the E.U. market. It addresses the health and safety of the machine operator. In Europe, machine builders are responsible for safety.

European standards set by the organization are for good engineering practices: ? IEC 13849-1 - This standard addresses the machine-safety industry, which is under the IEC61508 umbrella clause 

• IEC 62061 - Similar to the IEC13849-1, however, it does not cover non-electrical parts
• EN 1050 - This European standard defines the principles and procedures for risk assessment related to machine safety

Under U.S. law, OSHA is the government body with set regulations related to machine safety. OSHA has the right to reference the U.S. Consensus Standards, enforce them to the end user, and hold them liable.

For more information about Machine Building Products, click on the Following links.

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