What are machinery risk assessments?

In the context of CE marking machines, machinery risk assessments should be done prior to build and during the design phase. For this reason, it is often referred to as a design risk assessment (DRA).

When are machinery risk assessments required?

Machine risk assessment or design risk assessment (DRA) is required during the CE conformity assessment procedure to provide evidence in the technical construction file (TCF) that suitable protective measures have been applied after a proper analysis of the risks specific to that machine.

Is there a machine risk assessment template?

There is no fixed format for a machine risk assessment but there is guidance from the HSE and in the harmonised standards on the methods than can be used and the characteristics of those methods that make them suitable.

In the end, so long as the method demonstrates that the appropriate steps have been taken in a systematic manner, then any machine risk assessment format is acceptable including:

  • Technical Explanations
  • Start with a Checklist (top down)
  • Start with Hazard and Task Analysis (bottom up)
  • Minutes from meetings
  • Comparisons against other machines

Equally, the format of the risk estimation may vary widely depending upon the preference of the CE auditor/assessor, the nature and level of the inherent risks and the quantity or number of occurrences of that risk. These may include methods such as:

  • Risk Matrix (e.g. 5x5)
  • Risk Graph
  • Numerical Scoring (e.g. Preliminary Hazard Analysis – PHA, using the Hazard Rating Number (HRN system)
  • Quantified Risk Estimation

What are the 4 most important stages in machine risk assessment?

The most important stage in machinery risk assessments is getting started…. and at the right time!

It should begin during the design phase of any substantial modification or new machine build and continue in a systematic manner through the build and commissioning phase. So, in order to get a good start, remember the following basic steps:

1)     Determination of the Limits of the Machine

This means that the characteristics and performances of the machine(s) in an integrated process, the related people, environment and products should be identified first of all. This may be done in the form of a specification taking account of the space, use and time limits. This specification will be repeated in the information for use upon completion and delivery of the machine dictating the intended use limits to the user or customer.

2)     Machine Hazard Identification and Task Analysis

This requires a systematic identification of reasonably foreseeable hazards (permanent hazards and those which can appear unexpectedly), hazardous situations and/or hazardous events. This will take account of all:

  • Tasks / interventions
  • Possible states of the machine
  • Unintended behaviour of the operator including reasonably foreseeable misuse.

3)     Machine Risk Estimation

This shall be done for each hazardous situation identified in the previous step. I.e.; where a hazard may result in harm during a task or intervention, including reasonably foreseeable misuse. There are many methods for estimating risk but all methods shall consider the following:

  1. the severity of harm;
  2. the probability of occurrence of that harm, which is a function of
    1. the exposure of person(s) to the hazard,
    2. the occurrence of a hazardous event, and
    3. the technical and human possibilities to avoid or limit the harm.

The type, frequency, and duration of exposure to any given hazard shall be considered, as should the relationship between the exposure and its effects. Accident data may be used for this purpose; however, where accident history shows zero accidents this in itself cannot be taken to show a low probability of risk.

Human factors will affect risk estimation and are normally closely related to the task in hand at the time. For example, an interaction between two operators may increase the risk of injury at start-up  as one operator may not see the other operator in the danger zone. Fatigue and stress will drive the identification and estimation of risks associated with ergonomic design issues.

 

There are many standards applicable to ergonomic design of machinery but the starting point should be the following:

EN 614-1:2006+A1:2009 Safety of machinery - Ergonomic design principles - Part 1: Terminology and general principles

http://shop.bsigroup.com/ProductDetail/?pid=000000000030179195

 

EN 614-2:2000+A1:2008 Safety of machinery - Ergonomic design principles - Part 2: Interactions between the design of machinery and work tasks

http://shop.bsigroup.com/ProductDetail?pid=000000000030179199

 

How to account for the competence of the operators (and engineers)

Training, experience, and ability can reduce the likelihood of an occurrence. However, none of these factors can be used in place of the correct application of the three-step method. See Risk Evaluation.

 

4)    Risk Evaluation

During this step in machine risk assessment, you have to determine if risk reduction is required. If not then this is recorded in the DRA.  If risk reduction is required, then you must consider the appropriate protective measures in order to reduce the risk to an acceptable level.

This is where the use of Harmonised standards really comes to fore. You don’t have to use them but using them gives you a presumption of conformity, i.e. an acceptable level of risk. Even if you choose to do something different to what the harmonised standard requires, you can estimate the risk difference between the two options and hopefully show that your alternative proposal introduces the same or less risk than that required by the harmonised standard.

What is the three-step method?

The three step method is a hierarchical approach to the selection of appropriate protective measures. In other words, when faced with a risk on a machine, you will first apply step 1, then 2 then 3. At no time will you select a measure in a step without showing that the previous steps have been applied, to the extent that is effective, where feasible.

Here are the three steps used in this method:

Step 1: Inherently safe design measures

All risks identified on the machine shall be designed out where feasible. This may be done by changing the features and layout of the machine that may, in turn, remove the need for a certain task or reasonably foreseeable misuse.   

Step 2: Safeguarding and/or complementary protective measures

All risks that remain after the application of step 1 should be addressed using appropriately selected safeguarding and complementary protective measures.

Step 3: Information for use

Any risks that remain after the application of step 1 and step 2 are residual risks that the operator (or engineer) will be exposed to. In order that safe operating procedures can be developed you must provide them with suitable information for use that may include but not be limited to the following:

  • operating procedures
  • recommended safe working practices
  • warnings on the machine and in the instruction handbook
  • description of any recommended personal protective equipment (PPE)

Everything you need to know about machine risk assessment can be found in BS EN 12100 2010. This standard can be purchased from the following link:

http://shop.bsigroup.com/ProductDetail?pid=000000000030240710

Further reading could include Technical Report 14121-2. This provides detailed explanations of the theory behind machine risk assessment:

http://shop.bsigroup.com/ProductDetail?pid=000000000030239222

Or, if you prefer the personal touch, why not book on to one of our Machine Safety workshops for a one day intensive Q&A: