Check the scope first
NOM-020-STPS-2011 applies to Mexican workplaces with pressure vessels, cryogenic vessels and steam generators or boilers. The official catalogue continues to list it as current. It contains express exclusions, including certain portable containers, extinguishers and equipment under other regimes. Not every object containing gas automatically receives the same treatment.
The pressure equipment entry introduces the hazards. This standard additionally requires each item to be identified and categorised under the relevant criteria. Classification should not be inferred solely from size or an assumption that the fluid is harmless.
Categories and individual equipment files
The standard distinguishes categories I, II and III. Criteria differ between pressure vessels, cryogenic vessels and boilers, using fluid, relief-device calibration pressure, volume or thermal capacity as applicable. Correct technical data and consistent units are essential when determining the category.
An updated list and individual file connect identity, characteristics, location and equipment documentation. For example, a change of service may alter classification or safety conditions even though the vessel retains its serial number. The file must reflect actual service rather than an obsolete description.
Maintenance and verification
Inspection, maintenance, testing and record duties depend on category. Control instruments and pressure relief devices require monitoring of function and calibration where applicable. The presence of a valve does not establish that it adequately protects the system.
Repairs, particularly welding or alterations, require procedures and personnel with the necessary competence. Pressure tests or non-destructive examinations need justification under the applicable regime. An isolated successful test is not an indefinite guarantee of integrity or permission for any future service.
Operation, emergencies and notifications
Personnel need Spanish-language procedures and training appropriate to their duties. Relevant categories require emergency preparation and records of operation and inspections. Category III equipment has specific notification duties to the authority.
The precise procedure must be checked against applicable provisions before filing. This entry does not calculate test pressures, set relief valves or prescribe repairs. It supports the technical and documentary management needed to decide who may intervene and under what conditions, using current equipment information and competent judgement.
