Context card
Operating modes in technical documentation
Why do operating modes change what the documentation of a machine has to say?
The short answer
Because a machine is not the same machine in every mode. In setup, cleaning, maintenance or fault recovery, safeguards may be open or reduced, other people work at other places, and other hazards and temptations arise. Documentation that only describes normal operation leaves the riskiest moments undocumented; asking the same questions in every mode — who, where, what activity, which residual risks, which misuse, what is prohibited, which site conditions — shows which information each mode needs.
For: Technical writers, commissioning and service engineers and product safety engineers documenting machinery and production lines
Key points
- ISO 12100 asks the risk assessment to cover all phases of the machine’s life, including setting, process changeover, cleaning, fault finding and maintenance.
- EU machinery law requires that a selected operating mode overrides the other modes (except the emergency stop) and, where safeguards are suspended, that other protective measures apply.
- Each mode changes the people, workstations, activities, residual risks and foreseeable misuse the documentation must address.
- The same questions asked for every mode turn the risk assessment into documentation decisions: safety chapter, task warning, qualification note, special mode section.
- Modes with suspended or reduced safeguards usually need their own section, qualification requirements and warnings before the task.
The context
Not the same machine in every mode
An operating mode defines how a machine behaves and which protective measures act. In normal operation, guards are closed and the machine runs automatically. In setup or changeover, an operator may work inside the hazard zone at reduced speed with an enabling device. In cleaning and maintenance, stored energy, heat, pressure or media may remain after the machine has stopped, and lockout/tagout may be required. In fault recovery, people tend to intervene under time pressure.
ISO 12100 therefore asks the risk assessment to consider every phase of the machine's life — among them setting, process changeover, operation, cleaning, fault finding and maintenance. The Machinery Regulation (EU) 2023/1230 (Annex III, section 1.2.5; applicable from January 20, 2027, until then the Machinery Directive 2006/42/EC) requires that a selected mode overrides all other modes except the emergency stop and that, where a mode requires safeguards to be suspended, other protective measures ensure safety.
The same questions in every mode
A practical way to make the modes visible in documentation is to ask the same questions for each of them:
| Question | Example: cleaning |
|---|---|
| Workstation and user role | Machine area, access point; trained operator |
| Intended activity | Clean surfaces, remove residues, prepare restart |
| Residual risks | Residual energy, temperature, movement, pressure or media |
| Reasonably foreseeable misuse | Unsafe cleaning behaviour, e.g. reaching in before standstill |
| Prohibited actions | Forbidden cleaning methods or access actions |
| Site conditions | Chemicals, ventilation, drainage, contamination |
| Documentation decision | Cleaning procedure, safety chapter, PPE note, reference to the operator's instruction |
The answers come from the risk assessment and the people who know the machine; the documentation decision is where the writer's work begins.
What modes usually need
Modes in which safeguards are suspended or reduced usually need a section of their own, a statement of who may use them (qualified person or instructed personnel), the personal protective equipment required, and warnings directly before the tasks — not only a sentence in the safety chapter.
The questions follow the operating-mode analysis grid of the blueprint Thinking models for technical writers. Describing the modes does not make a machine safe or compliant; mode selection and protective measures are design decisions of the manufacturer.
Questions readers ask next
- Is every operating mode a separate chapter?
- Not necessarily. Modes with the same people, safeguards and hazards can share a section. Modes in which safeguards are suspended or other people work at the machine usually need their own section and warnings.
- Where does the information about operating modes come from?
- From the manufacturer’s risk assessment, the control concept and the people who design, commission and service the machine. The writer asks the questions; the answers are not invented in the documentation.
- Does the documentation define the operating modes?
- No. Operating modes and their protective measures are part of the machine’s design. The documentation describes them, says who may use them and how, and warns about the hazards that remain.
Sources
- ISO 12100:2010 Safety of machinery — General principles for design — Risk assessment and risk reduction — ISO, 1 November 2010
- Regulation (EU) 2023/1230 on machinery — Official Journal of the European Union, 29 June 2023
- IEC/IEEE 82079-1:2019 Preparation of information for use (instructions for use) of products — Part 1: Principles and general requirements — IEC, 8 May 2019
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