A standard for machinery in use
NOM-004-STPS-1999 addresses machinery and equipment used in Mexican workplaces. The official catalogue lists it as current; an update proposal does not by itself replace the standard. Its practical purpose is to connect actual machinery hazards with protective measures and safe working conditions.
The potential risk study must identify factors including moving parts, heat, static electricity, sharp surfaces, ejected materials and tools. Identified risks are considered in terms of harm, severity and likelihood. This connects with machinery safety, but the study needs to reflect the equipment actually present at the workplace.
From the study to a specific programme
The operation and maintenance safety programme must follow from the risk study. It covers procedures, housekeeping, material feeding and removal, tool changes and connections. A generic manual does not demonstrate that the particular way of working has been assessed.
For example, adding manual feeding to an initially automatic machine can create access to a hazardous area. The assessment should examine that task and the protection needed before the change is accepted as a straightforward productivity improvement.
Safeguards that work in practice
The standard distinguishes guards from safety devices. They must prevent access or the development of the hazardous phase according to their function, without creating additional hazards or encouraging unintended operation. An emergency stop does not, on its own, make accessible dangerous machinery safe.
Workers must report damaged, bypassed or non-functioning protections. Observing real work can reveal safeguards that exist on the inventory but are avoided during operation because of usability or maintenance difficulties.
Maintenance and traceability
The programme addresses trained personnel, preventive and corrective maintenance and control of energy during interventions. Protections must be restored to working condition afterwards. The regulatory text requires maintenance records to be kept for at least twelve months.
Modifying or rebuilding equipment requires preservation of its safety conditions. This entry does not provide an isolation sequence or instructions for altering control circuits. Such interventions require equipment-specific procedures, technical knowledge and defined responsibilities. Training records should correspond to the machines and tasks actually assigned, rather than being treated as evidence that every operator can perform every intervention.
