NOM-020-STPS Compliance for Inspection Service Providers
Every workplace in Mexican national territory operating pressure vessels, cryogenic vessels, steam generators or boilers, with named exclusions including diving bells, hyperbaric chambers, fire extinguishers, portable compressed-gas cylinders, LPG vessels regulated by the energy ministry and rail tank cars. Personnel are qualified under employer-based certification, so a contracted Level III can sign the written practice and administer examinations for the firm.
The commercial market for an inspection provider is Category II and III equipment, which carries mandatory periodic pressure testing or non-destructive examination. The current designation is confirmed: NOM-020-STPS-2011, published in the Diario Oficial de la Federación on 27 December 2011 and in force from 27 June 2012, superseding NOM-020-STPS-2002, with an authorised alternative procedure published 9 December 2014 and continued validity confirmed by systematic review on 15 August 2022. It is the engine of the Mexican NDT inspection market because it makes periodic non-destructive examination or pressure testing mandatory rather than discretionary for Category II and III equipment. The employer classifies each item into Category I, II or III from fluid hazard, relief-device set pressure and volume, maintains a per-equipment file, and either contracts an accredited inspection unit or — for Category III only — constitutes its own Type B unit.
Source: NOM-020-STPS-2011 as published in the Diario Oficial de la Federación, Segunda Sección, Tuesday 27 December 2011, retrieved from the STPS document repository at asinom.stps.gob.mx and extracted; clauses 3.7, 4.19 to 4.21, 4.32, 4.41 to 4.43, 7 and Table 1, 13.1 to 13.6, 16, 17, 19 and 20, and Reference Guide III read directly. Status as vigente, entry into force on 27 June 2012, the authorised alternative procedure of 9 December 2014, and the systematic review confirmation of 15 August 2022 from the Sistema Nacional de Infraestructura de la Calidad catalogue at platiica.economia.gob.mx. NMX-B-482-CANACERO-2016 — full title, vigente status, DOF declaratoria de vigencia of 20 October 2016, CANACERO as issuing Organismo Nacional de Normalización, cancellation of NMX-B-482-1991, and its recorded international grade of 'no equivalente' — from the same catalogue. Limitation: the text of NMX-B-482-CANACERO-2016 itself was not obtained, so its internal qualification model is not characterised here beyond its recorded grade. Verified 21 August 2026.
| Item | What applies | Why it matters |
|---|---|---|
| Authority | Secretaría del Trabajo y Previsión Social (STPS); conformity assessed by unidades de inspección (statutory term until 2020: unidades de verificación) that are accredited by an accreditation entity and approved by STPS | The body that issues, audits and can withdraw |
| Applies to | Every workplace in Mexican national territory operating pressure vessels, cryogenic vessels, steam generators or boilers, with named exclusions including diving bells, hyperbaric. | Whether this binds your firm at all |
| Personnel certification | Employer-based — the firm certifies its own, under a qualified Level III | Decides whether an outsourced Level III can sign for you |
| Renewal | For Category II and III equipment: the first pressure test or NDT is due before ten years from the manufacturing certificate or code stamp for new equipment that has one; equipment without that certificate or stamp, and all used equipment, is tested before entering service. Thereafter at least every five years, performed within the sixty calendar days before the end of each five-year period. The periodicity is determined by the employer's qualified personnel and may in no case exceed five years (clause 13.2 a). Dictámenes issued by a unidad de inspección are valid ten years for new equipment and five years for used equipment (clause 19.7). Boilers additionally require functional testing of safety shutdowns. Category III equipment requires a notice to STPS within sixty days of the dictamen. | Diarise from the certificate date, not from memory |
| Methods in scope | RT — radiografía industrial (volumetric option), UT — ultrasonido industrial (volumetric option), Neutrography (volumetric option), AE — emisión acústica (volumetric option), PT — líquidos penetrantes (surface option), MT — partículas magnéticas (surface option) | Each method needs its own procedure and qualified personnel |
| Industries | Petrochemical, Chemical, Food and beverage, Brewing and distilling, Pharmaceutical | Where this regime shows up in contracts |
Who does NOM-020-STPS apply to?
Every workplace in Mexican national territory operating pressure vessels, cryogenic vessels, steam generators or boilers, with named exclusions including diving bells, hyperbaric chambers, fire extinguishers, portable compressed-gas cylinders, LPG vessels regulated by the energy ministry and rail tank cars. The commercial market for an inspection provider is Category II and III equipment, which carries mandatory periodic pressure testing or non-destructive examination.
Can an outsourced Level III sign for NOM-020-STPS compliance?
Yes. NOM-020-STPS accepts employer-based certification, which places the obligation on the employer and allows a contracted Level III to write and sign the written practice, approve procedures and administer examinations. The Level III must be qualified in each method they sign for, and the employer still owns the records.
What documents does a NOM-020-STPS audit ask for?
Expediente del equipo — the per-equipment file, maintained for each item including Category I equipment, Classification record placing each item in Category I, II or III under clause 7, based on relief-device set pressure, volume and whether the fluid is hazardous, Registro de la última prueba de presión o exámenes no destructivos practicados a los equipos, Resumen cronológico de las pruebas de presión o exámenes no destructivos, Procedimientos for the pressure tests and non-destructive examinations, with the acceptance and rejection criteria applied to results. Auditors open records before they open manuals, because a manual describes intent while records show practice. The most common failure is a documented system that does not match what the technicians actually do.
How often is NOM-020-STPS renewed?
For Category II and III equipment: the first pressure test or NDT is due before ten years from the manufacturing certificate or code stamp for new equipment that has one; equipment without that certificate or stamp, and all used equipment, is tested before entering service. Thereafter at least every five years, performed within the sixty calendar days before the end of each five-year period. The periodicity is determined by the employer's qualified personnel and may in no case exceed five years (clause 13.2 a). Dictámenes issued by a unidad de inspección are valid ten years for new equipment and five years for used equipment (clause 19.7). Boilers additionally require functional testing of safety shutdowns. Category III equipment requires a notice to STPS within sixty days of the dictamen. Firms that diarise renewal from the certificate date rather than from the last audit avoid the lapse that forces a full reapplication.
What are the most common NOM-020-STPS findings?
Equipment misclassified into Category I or II to escape the Category III duties to have a unidad de inspección present and to notify STPS, Only a volumetric examination performed, with no accompanying surface or flux-loss examination as clause 13.5 requires, NDT results endorsed by a technician whose certification cannot be traced to NMX-B-482, its replacement, or a demonstrably equivalent scheme, Pressure test endorsed by an NDT technician rather than by an engineer with knowledge in the matter, contrary to clause 13.2 f and i. These recur because they are records problems rather than capability problems — the work is being done correctly and the evidence is not being kept.
Which NDT methods does NOM-020-STPS cover?
RT — radiografía industrial (volumetric option), UT — ultrasonido industrial (volumetric option), Neutrography (volumetric option), AE — emisión acústica (volumetric option), PT — líquidos penetrantes (surface option), MT — partículas magnéticas (surface option), ET — electromagnetismo, corrientes de Eddy (surface option), Leak testing by halogen detector, mass spectrometer or bubble chamber (flux-loss option). Each method in scope needs its own approved procedure and personnel qualified in that specific method; a Level III qualified in ultrasonics cannot sign for radiography.
Personnel certification under NOM-020-STPS
Clause 4.21 defines 'personal certificado' as a person with the technical capability and experience to perform, supervise, interpret and evaluate NDT results in accordance with NMX-B-482-1991, or the standards that replace it, or an equivalent. That replacement is NMX-B-482-CANACERO-2016, 'Industria siderúrgica — Capacitación, calificación y certificación de personal en ensayos no destructivos', issued by CANACERO and declared in force in the DOF on 20 October 2016. Crucially, NOM-020 names no accredited certification body for NDT personnel and its 'o equivalente' wording admits other recognised schemes, so an employer-based written practice supported by an outsourced Level III is defensible under the norm itself — unlike Brazil. Client contracts, notably Pemex, routinely override this.
The audit sequence
- Classify each item into Category I, II or III per clause 7 and Table 1, using the set pressure of the relief device, the volume, and whether the fluid is hazardous.
- Build and maintain the per-equipment file, operating and maintenance procedures, and train the workers involved.
- Perform the pressure test or NDT on the statutory cycle — for new Category II and III equipment holding a manufacturing certificate or code stamp, the first before ten years from that certificate or stamp; for equipment without one, and for used equipment, before entering service.
- Select the NDT scope — clause 13.5 requires, following a visual review, at least one volumetric examination combined with one surface or one flux-loss examination; results endorsed by name and signature of personal certificado.
- For Category III equipment, perform the test or examination in the presence of a Type A, B or C unidad de inspección (clause 13.2 j).
- The unidad de inspección issues the dictamen de evaluación de la conformidad, carrying its accreditation number, the dates of accreditation and STPS approval, the equipment data and the dictamen validity.
- For Category III, file the aviso with STPS within sixty days of the dictamen; STPS assigns a número de control to each item and issues the official letter within five working days of receiving the notice.
Documents an auditor asks for
- Expediente del equipo — the per-equipment file, maintained for each item including Category I equipment
- Classification record placing each item in Category I, II or III under clause 7, based on relief-device set pressure, volume and whether the fluid is hazardous
- Registro de la última prueba de presión o exámenes no destructivos practicados a los equipos
- Resumen cronológico de las pruebas de presión o exámenes no destructivos
- Procedimientos for the pressure tests and non-destructive examinations, with the acceptance and rejection criteria applied to results
- Records signed by personal certificado endorsing NDT results, and by an engineer with knowledge in the matter endorsing pressure tests (clause 13.2 f and i)
- Dictamen de evaluación de la conformidad, or dictamen de evaluación de la conformidad con reporte de servicios where a Type C unit provided the services
- Aviso a la Secretaría for Category III equipment, filed within sixty days of the dictamen, together with the STPS-assigned número de control
- Registros de capacitación — theoretical and practical training records for workers who operate, maintain, repair and test the equipment (clause 17)
Findings firms get against NOM-020-STPS
- Equipment misclassified into Category I or II to escape the Category III duties to have a unidad de inspección present and to notify STPS
- Only a volumetric examination performed, with no accompanying surface or flux-loss examination as clause 13.5 requires
- NDT results endorsed by a technician whose certification cannot be traced to NMX-B-482, its replacement, or a demonstrably equivalent scheme
- Pressure test endorsed by an NDT technician rather than by an engineer with knowledge in the matter, contrary to clause 13.2 f and i
- The five-year examination performed outside the sixty-day window before the end of the quinquennium
- Aviso to STPS not filed within sixty days of the dictamen, leaving Category III equipment without a número de control
- Chronological summary of pressure tests and non-destructive examinations missing from the equipment file
- A dictamen relied on beyond its validity — five years for used equipment, not the ten that applies to new
Related: the NOM-020-STPS overview, outsourced ASNT Level III cover, written practice development, NDT procedure development, a programme gap assessment, interim Level III cover.