3.0
Machine Safety
To simplify access to some of the most important safety standards for machinery the following sections are presenting some key rules contained in them in a more practical way enhanced with clear-cut illustrations.
Basic rules
Risk assessment - Why and how?
When designing machinery, engineers’ primary focus is on function, efficiency and economic concerns. Safety rarely is of much concern, especially not at the early stages of a project.
However, it may be very difficult to integrate safe operation into the overall functional and operating concept later on.
In fact, safety measures added during the final stages of the project often impair accessibility and efficiency of the machinery. Therefore, it is best to think about the hazards generated by a function from the start and to conceive of counteracting measures as early as possible.
Take three steps:
- Eliminate the hazard, if at all possible.
- If you cannot get rid of the hazard or it would be too costly, lock the hazard in (or people out)
- If you cannot keep people’s hands and feet out, monitor the presence of people near the hazard, to stop it in time.
This process of identifying hazards, determining their risk potential and then reducing or eliminating such risks is referred to as “risk assessment.” In the past, engineers did not normally follow a methodical approach to safety issues. But since stricter regulations and standards on product safety have been introduced in the 1990s, “risk assessment” has become the most important step toward safe products and conformity with regulations.
5 Steps how to proceed with risk assessment
Most regulations and standards on the subject require five steps to be taken in risk assessment.
- Determine the limits of the machinery, which include the intended use and any reasonably foreseeable misuse.
- Identify the hazards that can be generated by the machinery and the associated hazardous situation.
- Estimate the risks, taking into account the severity of the possible injury or damage to health and the probability of its occurrence.
- Evaluate the risks, with a view to determining whether risk reduction is required.
- Eliminate the hazards or reduce the risks associated with these hazards by application of protective measures.
Overview of each step in risk assessment
Understanding and implementing a thorough risk assessment process is crucial for ensuring machinery safety and reliability. Below is a detailed breakdown of each step:
Follow a life risk assessment now
Define task to be assessed
Task:
Operator brings pallet into the machine and checks it.
Find the hazards and describe the hazardous event
Hazard
Approach of a moving element to a fixed part:
- Crushing, shearing
- Impact
Hazardous event
Operator may be crushed between moving robot and pallet or machine parts.
Select a safety measure
Type of measure:
Combination of guards and protective devices (llc).
- The hazard zone is enclosed by a guard fence that prevents intentional and unintentional access.
- A door is provided for access, which serves as a movable guard.
- The movable guard is provided with interlocking and guard locking that holds the door closed until robot and machine movements in the hazard zone have stopped.
- The machine cannot start as long as the door is still open or not locked.
- The door switch must be provided with an escape release lock.
Allocate requirements from directives/standards
Machinery directive:
- 1.3.7 – Risk related to moving parts
- 1.4.2.1 – Fixed guards
- 1.4.2.2 – Interlocking movable guards
EN ISO 12100: 2010: sections 6.3.3.2.2 and 6.3.3.2.3
Do a risk estimation to find the PL for the interlocking function
Do a risk estimation to find the PL for the interlocking function
S – Severity of injury: 2
Operator could be seriously injured by the robot, fatal injury possible.
F – Frequency and duration: 1
The pallet must be replaced approximately once per hour.
P – Prevention of harm: 2
The robot moves at speeds of up to 10 m/s, avoidance hardly possible.
O – Probability of occurrence: 2
No evidence available.
PLr: d