the machine safety lifecycle

The ability to operate the machines and have the confidence of being safe opens the door for better operational metrics and control of your equipment. These benefits are measured in terms of increased efficiencies, less downtime, and reductions in safety-related incidents, all resulting in cost savings.

Machine Safety

The Lifecycle of Machine Safety

Machines can function and be safe at the same time. This is called functional safety. In the past, ‘safe’ used to only mean ‘off’ or not functioning. Now, machines can function while maintaining a degree of safety.

Anyone can do what they think is best for safety, but how long will a machine be safe? Will it tolerate faults and still maintain a required level of safety? Will it alert you when it detects a fault in a safety component while it maintains safety?

Having a certified functional safety engineer build safety into your machines raises confidence levels and ensures you meet the OSHA requirements that require employers to provide a workplace free from serious recognized hazards.

We understand the need to protect your personnel. Our Team of TÜV Rheinland Functional Safety Engineers has the experience to help you mitigate risk and comply with OSHA standards to provide a safer working environment.

Machine Safety Lifecycle
Machine Safety

What’s the Standard?

Create a clear execution path for machine safety compliance. Use this guide to know and understand the standards for machine safety.

Machine Safety

Lifecycle

Including machine safety during the concept stage can greatly reduce complexity, retrofits, overall costs, and time to production. Overlooking this has oftentimes been detrimental to the success of a project. Tacking on machinery safety as an afterthought will nearly always be complex and costly. Bring certified machinery safety engineers in during the concept and ideation phase to give guidance in the design directions.

A Safety Risk Assessment (SRA) begins just after the ideation phase and before anything is designed. It will need to be updated during the design iteration phase as changes are fleshed out, but it should be completed before the design is complete.

This step involves identifying all of the human/machine interfaces or tasks that would be related to a piece of equipment, including any reasonably foreseeable misuse. This step also identifies every hazard that is associated with this machine. These hazards could include mechanical, electrical, controls, ergonomic, thermal, noise, vibration, radiation, material, and environmental.

Every task is evaluated based on the hazards that were identified while performing the task. These task/hazard combinations are evaluated based on their severity, frequency, and probability of occurrence to get a hazard score. This is called Risk Estimation.

A risk reduction measure must be selected to reduce the hazard using the hierarchy of hazard controls from most effective to least effective. The task/hazard combination must be reevaluated to determine the new hazard level. This new level must be assessed to determine if the hazard is properly mitigated. The SRA is complete when all of the hazards have been identified and properly reduced to an acceptable level.

SRAs should never be completed by one person to ensure all the information is captured and evaluated. Include people from all aspects of the machine interaction including engineering, operations, and maintenance. Any changes must follow the defined change management protocols.

A Safety Requirements Specification (SRS) is a crucial document to explain to the designers the details on how to build the machine to meet the requirements of the SRA. The SRS captures all the details necessary and provides the required design and operational criteria for each safety function. This critical document must never be skipped and should be completed prior to designing the machinery.

A good SRS should contain a Risk Assessment Summary, a Cause & Effect Matrix (Safety I/O Matrix) and identification and description of every Safety Function (SF).

This step includes all activities prior to building the machinery. Functional Safety engineers should be involved with design iterations to provide guidance. Design reviews should always include the safety team to ensure the design is following the SRS and to monitor any design changes.

Once the design is complete or near complete, it’s time for the Safety Verification which goes through the mechanical and electrical design to ensure the combination of the Input, Logic, Output (I-L-O) components for each safety function meets the SRS. It will look at each Safety Related Parts of the Control System (SRP/CS), how they are laid out in the architecture, and how they are used to determine if their overall performance level meets or exceeds the SRS. This should be the design approval gate before moving forward to building the machine. SISTEMA is a software tool to evaluate the SRP/CS. The required documentation includes the Electrical Schematics with BOM.

There should be a change management plan that informs the safety team of any changes during the construction phase.

The Safety Validation is a process by which examines the machine, as built, to validate that it was designed exactly as it was verified and meets the SRS. This is usually completed at the Factory Acceptance Testing (FAT) and Site Acceptance Testing (SAT) of the machine. The preference is always at the FAT as much as possible as it is much easier to rectify issues before the machine is shipped.

As an option (and a requirement in some regions), 3rd party Nationally Recognized Testing Laboratory (NRTL) inspections can serve as further certified validation as to the performance of the safeties of the machine.

The operational management of the machine must adhere to the operational and maintenance specifications as defined by the safety risk assessment and the safety requirements specification. These requirements are usually documented in the operations and maintenance manual of the machine from the data in the safety verification To be operations ready, you must ensure test intervals and a maintenance plan are set in place.

In each safety function, there may be some SRP/CS that are designed for a specific reliability life-span. For example, there may be a component that its safety integrity is only designed to last for 100,000 cycles and its life-span is calculated to only last for five years before it needs to be replaced. At that 5-year mark, the component must be replaced by an identical component in order to maintain the safety integrity of the safety function even if the component is still technically operational. It is extremely important that an identical component is selected for any replacement of an SRP/CS. If an identical component cannot be found or another component is requested, the new component must be officially verified again and documented before it can be replaced. This will ensure the safety integrity meets or exceeds the original design safety requirements.

Machine Safety Lifecycle

Stay Informed

Learn more about the different stages of the Machine Safety Lifecycle

Hierarchy of Hazard Controls

Every task/hazard must be evaluated in relation to the Hierarchy of Hazard Controls.

  • Eliminate by Design

  • Control by Safeguarding

  • Control by Administration

Hierarchy of Hazard Controls

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