NOM-027-STPS-2008, Welding and cutting activities - Safety and health conditions

Whereas on 27 June 2006, in compliance with article 46, paragraph I, of the Federal Law on Metrology and Standardisation, the Ministry of Labour and Social Welfare submitted to the National Advisory Committee for Standardisation on Occupational Safety and Health the preliminary draft Amendment to this Official Mexican Standard, and that Committee found it to be correct and agreed that it should be published as a Draft in the Official Gazette of the Federation; Whereas, so as to comply with articles 69-E and 69-H of the Federal Law on Administrative Procedure, the corresponding preliminary draft was submitted for consideration to the Federal Commission for Regulatory Improvement, which issued a favourable ruling on it; Whereas on 26 February 2008, in compliance with the Agreement establishing the organisation and Rules of Operation of the National Advisory Committee for Standardisation on Occupational Safety and Health, and with article 47, paragraph I, of the Federal Law on Metrology and Standardisation, the Draft Amendment to Official Mexican Standard NOM-027-STPS-2000, Welding and cutting - Safety and health conditions, was published in the Official Gazette of the Federation so as to become PROY-NOM-027-STPS-2006, Welding and cutting activities - Safety and health conditions, so that within the 60 calendar days following that publication interested parties could submit their comments to the Committee; Whereas, having received comments from two submitting parties, that Committee examined them and ruled on them in due course, and this Ministry published the respective replies in the Official Gazette of the Federation on 12 August 2008, in compliance with article 47, paragraph III, of the Federal Law on Metrology and Standardisation; Whereas, following the incorporation of the comments submitted on the Draft Amendment to Official Mexican Standard NOM-027-STPS-2000, Welding and cutting - Safety and health conditions, so as to become PROY-NOM-027-STPS-2006, Welding and cutting activities - Safety and health conditions, and the final review of the draft itself, various amendments were made with the aim of giving clarity, consistency and legal certainty as regards the provisions that apply in workplaces, and Whereas, in view of the foregoing considerations and given that the National Advisory Committee for Standardisation on Occupational Safety and Health granted its approval, the following is hereby issued: OFFICIAL MEXICAN STANDARD NOM-027-STPS-2008, WELDING AND CUTTING ACTIVITIES - SAFETY AND HEALTH CONDITIONS

To establish safety and health conditions in workplaces to prevent occupational risks during welding and cutting activities.

This Standard is in force throughout the national territory and applies in all workplaces where welding and cutting activities are carried out.

For the correct interpretation of this Standard, the following Official Mexican Standards in force, or those replacing them, shall be consulted: NOM-004-STPS-1999, Protection systems and safety devices on machinery and equipment used in workplaces. NOM-022-STPS-1999, Static electricity in workplaces - Safety and health conditions. NOM-026-STPS-1998, Safety and health colours and signs, and identification of hazards from fluids conveyed in pipework.

For the purposes of this Standard the following definitions are laid down:

4.1 Welding and cutting activities: all those processes and procedures carried out on a permanent or temporary basis, or in the course of maintenance, at floor level, at height, in a basement, in a confined space or in vessels that contain or have contained flammable or explosive residues, for the worker to join, separate or pierce metals.

4.2 Analysis of potential risk: the determination of the unsafe conditions in the equipment, base materials, filler materials, fuel gases used for welding or cutting, work areas, exposure time, personal protective equipment and concentration of contaminants, or the lack of training of the welder, that lead to occupational accidents or illnesses during the welding or cutting activity and that entail harm to the health and life of workers, to third parties or to the workplace.

4.3 Work area: the specific place where welding or cutting activities are carried out.

4.4 Explosive atmosphere: the ambient concentration of hazardous chemical substances that lies between the lower and upper flammability limits.

4.6 Non-respirable atmosphere: the working environment with a deficiency or an excess of oxygen, that is, with less than 19.5% or more than 23.5% of oxygen in the atmosphere of the working environment.

4.7 Labour authority; employment authority: the competent administrative units of the Ministry of Labour and Social Welfare that carry out inspection functions in matters of occupational safety and health, and the corresponding units of the federal states and of the Federal District acting in support of them.

4.8 Authorisation: the act by which the employer, or a person designated by the employer, permits in writing that a trained worker carry out welding and cutting work in an area not specifically designated for these activities.

4.9 Protective helmet: the personal protective equipment used in welding or cutting activities, which serves to protect the worker's eyes, face and neck against ultraviolet, infrared and visible radiation and against burns from splashes of any material thrown out when welding or cutting.

4.10 Welding booth: an enclosure intended for carrying out welding and cutting activities, which makes it possible to protect third parties from burns and radiation.

4.11 Cylinder: a portable cylindrical container used to transport and store the compressed gases used in welding and cutting activities.

4.12 Cutting: the activity by which a metallic material is separated by melting a specific area through the heat of the arc established between the electrode and the base material, or through the chemical reaction of oxygen and the fuel gas with the base metal.

4.13 Slag: a solid non-metallic material coming from the electrode coating or from some foreign material, which is trapped in the weld metal or between it and the base metal at the time of welding or cutting by any welding process.

4.14 Confined space: a place large enough, having limited or restricted means of access or exit, which is not designed to be occupied by a person on a continuous basis and in which specific work is carried out occasionally, with deficient natural ventilation, and so configured that a person can perform an assigned task inside it.

4.15 Source of ignition: any spark, slag, hot equipment or pipework, or material with such characteristics that it may, in combination with adequate quantities of oxidiser or fuel, be a risk factor for fire or explosion.

4.16 Fuel gases: gases which, generally in combination with oxygen, are used for the welding or cutting process. Some of them are acetylene, natural gas, hydrogen, propane, stabilised methylacetylene-propadiene, and other synthetic fuels and hydrocarbons.

4.17 Screen: a portable partition or shield that serves to protect third parties from radiation, sparks or incandescent material in welding and cutting activities.

4.18 Base material: the material that is to be welded or cut by any welding or cutting process.

4.19 Consumable material; consumable part: all those items that are coupled to welding and cutting equipment and that deteriorate during their use; these may be torches, hoses, connectors, nozzles and wire feed units, among others.

4.20 Fire-resistant material: any material that is non-combustible and that, when subjected to the action of fire, neither burns nor generates smoke or toxic vapours, and does not fail mechanically for a period of at least two hours.

4.21 Ultraviolet radiation: a form of electromagnetic radiation of shorter wavelength than visible light (from 1 nm to 400 nm), produced by welding and cutting activities, whose penetrating power over a prolonged time causes irreversible injury to the retina and stimulates the production of melanin, which protects the layers of the skin.

4.24 Welding: the localised coalescence of metals, produced by heating the metallic materials to an appropriate temperature, with or without the application of pressure and with or without the use of filler material for the joint.

5.1 To show the labour authority, at its request, the documents that this Standard requires it to draw up or hold.

5.2 To have the analysis of potential risks for the welding and cutting activities carried out in the workplace, in accordance with Chapter 7, and to adopt the corresponding safety and health conditions, in accordance with Chapter 8.

5.3 To inform the workers who carry out welding and cutting activities of the risks to which they are exposed, by means of posters, leaflets, guides or verbally; the information shall be given at least twice a year and a record shall be kept containing at least the names and signatures of the workers who received the information, and the date, the subject and the name of the person who provided it.

5.4 To have the programme for welding and cutting activities in accordance with paragraph 9.1 of this Standard. In addition, it shall include the specific procedures and controls laid down in paragraph 9.2, where there are work areas, confined spaces, processes (temporary or in the course of maintenance) or vessels in which flammable or explosive dusts, gases or vapours are present that pose a danger to the workers.

5.5 To have the safety procedures to be applied by the workers who carry out welding and cutting activities, in accordance with Chapter 10 of this Standard.

5.6 To train and instruct, at least once a year, the workers who carry out welding and cutting activities and the supervisor who oversees the application of the safety procedures, taking as a basis the safety and health procedures included in the welding and cutting programme referred to in Chapter 9 of this Standard.

5.7 To establish specific controls for the welding and cutting activities carried out in vessels, confined spaces or underground and where flammable or explosive dusts, gases or vapours are present that pose a danger to the workers, in accordance with paragraph 9.2. (Continued on page 77) (From page 36)

5.8 To authorise in writing the workers who carry out welding and cutting activities in risk areas such as: controlled areas with the presence of flammable or explosive substances, confined spaces, heights, basements, underground areas, and areas not specifically designated for these activities.

5.9 To supervise that welding and cutting activities in dangerous places (heights, confined spaces, basements, underground areas, controlled areas with the presence of flammable or explosive substances, others) are carried out in safe and healthy conditions.

5.10 To have a rescue procedure for heights, basements, underground areas, confined spaces or vessels in which flammable or explosive dusts, gases or vapours are present, in accordance with Chapter 11.

5.11 To train and instruct, at least once a year, the personnel assigned to carry out the rescue of workers injured at height, underground or in confined spaces, on the basis of the procedures laid down in Chapter 11.

5.12 To have materials and equipment to carry out the rescue of workers injured at height, underground or in confined spaces.

5.13 To train, instruct and authorise the workers to carry out preventive and, where appropriate, corrective maintenance on the equipment and machinery used in the welding and cutting activities of the workplace.

5.14 To provide the workers with the personal protective equipment referred to in Chapter 8, subparagraph c), and that determined on the basis of the analysis of potential risks, and to train them in its use, maintenance and replacement.

5.15 To subject the workers who carry out welding and cutting activities to specific medical examinations, as laid down by the Official Mexican Standards issued in this respect by the Ministry of Health. Where no regulation of the Ministry of Health exists, the company physician shall determine the content of the medical examinations, which shall be carried out at least once every twelve months, and the health surveillance to be applied; these shall be recorded in the medical file kept for that purpose on the worker.

5.16 To have the procedures that make it possible to provide care to a person who may be injured during welding and cutting activities. Where the employer assigns personnel to give first aid, it shall train and instruct them in this field at least once a year.

5.17 To have a first-aid kit in the area where welding and cutting activities are carried out, which shall include the materials required in accordance with the analysis of potential risks.

5.18 To ensure that external personnel engaged to carry out welding and cutting activities in the workplace comply with Chapter 5 of this Standard.

6.1 To take part in the training provided by the employer.

6.2 To carry out their activities in accordance with the procedures contained in the specific safety and health programme and with the safety and health conditions laid down in this Standard.

6.3 To use the personal protective equipment in accordance with the instructions for use and maintenance provided by the employer.

6.4 To carry out welding and cutting activities only if they have the training and, where applicable, the corresponding authorisation.

6.5 To undergo the specific medical examinations that the employer indicates so as to assess their state of health, at least every twelve months.

The analysis of potential risks shall contain at least the following: a) The identification of the processes and work areas where welding or cutting activities are carried out; b) The list of the equipment, base materials, filler materials and fuel gases used for welding or cutting; c) The determination of the dangerous conditions, including the emergencies that may arise in the equipment or machinery used (example: leakage of compressed gases in the welding and cutting procedure); d) The determination of the chemical and physical agents produced that generate contamination of the working environment; e) The type of risk faced by the workers (direct or indirect) and the exposure time; f) A list of the harm to health that includes the cause-and-effect relationship of exposure to fumes, vapours, non-ionising radiation (infrared, ultraviolet and bright light, among others), noise, electric shock, sudden changes of temperature, explosions or non-respirable atmospheres. See the example in reference guide I; g) The identification of the parts of the body that require protection to prevent harm to the health of welders or cutters; h) The means of control to minimise or eliminate the risk in: 1) The worker (personal protective equipment required to control the exposure of welders); 2) The work areas (natural or artificial ventilation, for example air extractors), the protection required to prevent harm to third parties, to control incipient fires that may arise or to control the presence of chemical agents, among others, and 3) In the event of an accident, the list of the minimum contents of the first-aid kit. Where required, the equipment and materials to apply the rescue procedures at height, underground or in confined spaces, in accordance with Chapter 11; i) The welding and cutting equipment; j) The identification of areas with non-respirable atmospheres, and k) The need to apply rescue procedures at height, underground or in confined spaces, in accordance with Chapter 11.

a) To have an ABC-type fire extinguisher of a capacity matching the analysis of potential risks, within a radius of no more than 7 metres, in the area where the welding and cutting activities are carried out; b) To have welding booths or screens to demarcate the areas where welding or cutting activities are carried out; c) To use at least the following personal protective equipment, according to the welding or cutting process employed: welding helmets or goggles with a shade, face protection, welding hoods, a fume respirator, an apron, welding gloves, spats, sleeves and safety footwear; d) To check that the safety equipment and items coupled to the cylinders containing fuel gases are in working condition. The results of the check shall be recorded in a log stating the serial number, batch, make and model of the equipment and coupling items, and their condition as regards tightness and cleanliness (free of grease); e) To prohibit the use of reconditioned pressure regulators; f) To apply the safety procedures, which include the measures needed to prevent harm to the exposed personnel and the actions to be applied before, during and after the work on the equipment or in the areas where the welding and cutting activities will be carried out; g) To place safety signs, notices, padlocks or labels, in accordance with NOM-004-STPS-1999 and NOM-026-STPS-1998, on the electrical installations supplying power to the welding and cutting equipment, and to restrict entry to the areas in which the welding and cutting activities are carried out, and h) To have natural or artificial ventilation before and during the welding and cutting activities in the work areas.

9.1 A welding and cutting activities programme shall be in place that includes at least: a) The welding and cutting activity (permanent or temporary); b) The welding and cutting procedure; c) The type of risk; d) The safety procedure; e) The authorisation procedure and the person(s) who authorise, as the case may be; f) The date of authorisation; g) The duration or period; h) The work area, and i) The name of the person who will supervise the worker carrying out the welding and cutting activities in accordance with the procedures laid down.

9.2 For all those work areas, confined spaces, underground areas, processes (temporary or in the course of maintenance) or vessels in which flammable or explosive dusts, gases or vapours are present that pose a danger to the workers, the welding and cutting activities programme shall in addition include the following specific procedures and controls: a) A procedure for detecting explosive, irritant or non-respirable atmospheres, where applicable; b) Specific controls to prevent explosive or non-respirable atmospheres, and c) A rescue procedure.

The safety procedures shall include:

10.1 In welding and cutting activities, with: a) The description of the activities to be carried out; b) Specific instructions on the work. The content of reference guide II may be taken as a reference for drawing up the instructions; c) The number of workers required to carry out the work; d) The identification of those welding and cutting activities carried out in areas, containers, vessels or confined spaces in which flammable or explosive dusts, liquids, gases or vapours are present that constitute a risk condition for the workers, and e) For cases involving work at height, underground, in basements and in confined spaces, the instruction to apply the rescue procedures in accordance with Chapter 11.

10.2 In the equipment and machinery, as applicable: a) Instructions to verify that: 1) The hose connections do not leak, the connectors are not corroded and are coupled tightly; 2) The electrical connections maintain continuity, show no mechanical damage to their insulation and are in a usable condition; 3) The equipment or machinery is connected to the general earthing system or to an alternative system meeting the specifications of NOM-022-STPS-1999 and is in working condition, and 4) The voltage of the supply line matches that required by the welding machine; b) That the equipment using fuel gases does not leak; c) That instructions are available for the storage, use and transport of cylinders with fuel gases inside and outside the premises of the workplace; d) That instructions are available for checking and replacing the consumable parts of the equipment used in the welding and cutting process; e) That corrective maintenance of the equipment is carried out by personnel trained and authorised by the employer; f) That procedures are established for the handling and operation of cylinders, valves, regulators, hoses and their connections, electrical power supplies and welding and cutting operations or activities in confined spaces; g) That the tools and the personal protective equipment are selected according to the welding process and the machinery to be used, and h) That monthly checks are carried out on the welding and cutting equipment to determine its functionality and the corresponding maintenance.

10.3 In the areas or installations, as applicable: a) That safety signs, notices or protective barriers such as screens, welding booths, padlocks, partitions or any other device are placed when welding and cutting activities are carried out, so as to demarcate or restrict the work area, and b) That it is verified that the work area is ventilated by natural or artificial means and that there are no combustible materials within a radius of less than 10 metres.

10.4 In the event of a leak of fuel gases in the welding and cutting process, the following shall be complied with: a) To have and use the personal protective equipment recommended in the risk analysis for this emergency; b) To have specific instructions to control the leak and to apply the safety procedure to control the risks; c) To have available the equipment and materials to be used to control the leak, and d) To designate a supervisor to watch the damaged or faulty container in the zone until the pressure of the cylinder is released or the situation is brought under control, so as to make sure that no fire occurs or that it does not get out of control; who shall notify the supplier verbally and in writing of the current state and identify the damaged vessel.

10.5 Welding and cutting activities in confined spaces shall contain the instructions for the following: a) The supervisor is to assess the inside of the confined space before entry, during and at the end of the welding and cutting activity, to verify that the oxygen content in the air is in the range of 19.5% and 23.5%; b) The presence of explosive atmospheres is to be assessed by means of direct-reading equipment; c) The types of chemical substances stored are to be determined and the decontamination procedure for the confined space is to be applied; d) The worker is to have the written authorisation of the employer before entering the area; e) The worker is to place safety tags indicating the isolation of the power supply, machinery and equipment related to the vessel and confined space where the welding or cutting activity will be carried out; f) Ventilation is to be carried out and monitoring performed with direct-reading equipment to confirm the concentration levels of oxygen in the air and the absence of an explosive atmosphere, where the oxygen levels laid down in subparagraph a) are not reached, respiratory protective equipment with a breathable air supply may be used; g) Local extraction equipment is to be used to remove dangerous gases, vapours and fumes; h) The person responsible for maintenance is to confirm that the artificial ventilation system is in working condition and operates under a maintenance programme; i) The cylinders and the power sources are to be placed outside the confined space; j) The time of continuous stay of the worker inside a confined space is to be controlled at a maximum of one hour of continuous work, with minimum breaks of 15 minutes outside the confined space; k) Explosive atmospheres are to be eliminated or reduced to a minimum in confined spaces that have contained flammable liquids or other types of fuel, before proceeding to weld or cut; l) The supervisor is to ensure that the safety procedures laid down are applied, from the entry of the worker until the end of the operation; m) The welder is to use a harness with a lifeline during the operation. The ropes of the lifeline shall be resistant to the chemical substances present and long enough to allow manoeuvring within the area, and to be used to rescue the welder if necessary, and n) Cleaning and inspection are to be carried out to detect and control the possible risks, after every working shift.

10.6 The authorisation procedure for the workers who carry out welding and cutting activities at height, in basements and confined spaces, in controlled areas with the presence of chemical or explosive substances and in areas not specifically designated for these activities shall comply with the following: a) It is to be granted in writing; b) It is to include: 1) The description of the activity, the name and signature of the worker who will carry out the activity, the place where the activity will be carried out, and the time and date scheduled for the start and completion of the activity; 2) The name and signature of the person responsible for the area or the person who authorises, the place where the activity will be carried out, the name and post of the person who will oversee this activity, the name and signature of the maintenance manager acknowledging notice, the type of inspection and the instruction to attach to the authorisation the safety procedure for carrying out the activity; 3) The instruction to give copies of the authorisation to all those who sign it. The worker's copy shall be displayed in a visible place while the work is being carried out and the copy of the person responsible for the authorisation shall be kept by the employer for at least one year, and 4) Verification that the designated personnel supervised that permanent ventilation or extraction of gases and fumes, whether natural or artificial, was in place before and during the performance of the welding and cutting activities; c) The list of the possible dangerous conditions and the protective measures required, and the personal protective equipment to be used, and d) The obligation to carry out monitoring to detect explosive, irritant, toxic or oxygen-deficient atmospheres.

of welding and cutting at height, in basements, underground, in confined spaces or in vessels where flammable or explosive dusts, gases or vapours are present. The procedure for rescuing a worker injured during welding and cutting activities shall contain at least the following: a) A list of the personnel assigned; b) The functions and responsibilities of the personnel assigned; c) Specific instructions on how to carry out the rescue; d) The equipment or apparatus needed to carry out the rescue; e) Techniques for applying cardiopulmonary resuscitation (CPR), and f) A plan for the care and transfer of casualties to places of medical care, stating: 1) The display in a visible place of the specific instructions on what to do in the event of an accident; 2) The immediate actions, which include disconnecting the source of energy, ventilating the work area by natural or artificial means, the instructions for removing the injured worker from immediate danger, placing the casualty in a safe place, applying first aid or the instruction to call the appropriate person and ask for help; 3) The manner in which a secondary response is to be given, describing the information to be provided in relation to the accident, for example whether the casualty came into contact with electrical energy, whether the cause was an electric shock or an explosion of an electrical device, or whether it was oxygen deficiency in confined spaces or another cause; 4) The nearest hospitals or medical units to which the casualty is to be transferred to receive medical care, and 5) The telephone numbers to call in an emergency.

12.1 The employer may choose to engage a verification unit, accredited and approved under the Federal Law on Metrology and Standardisation and its Regulation, to verify the degree of compliance with this Standard.

12.2 Verification units engaged at the request of a party shall verify the degree of compliance in accordance with the conformity assessment procedure.

12.3 The validity of the verification opinion, where it is favourable, shall be two years, provided that the conditions on which it was issued are not altered.

12.4 Verification units shall give the employer the favourable verification opinion where the requirements of this NOM have been met.

13.1 General provisions.

13.1.1 This conformity assessment procedure applies both to inspection visits carried out by the labour authority and to verification visits carried out by verification units.

13.1.2 Conformity assessment against this Standard may be carried out, at the request of an interested party, by the verification units accredited by the accreditation body and approved by the Ministry of Labour and Social Welfare.

13.1.3 To obtain the directory of the verification units approved by the Ministry, the website of the Ministry of Labour and Social Welfare may be consulted, via the Internet, at the address: www.stps.gob.mx.

13.1.4 The verification opinion shall be available to the labour authority at its request.

13.2 The aspects to be verified during the conformity assessment, which are applicable by means of physical and documentary checks and questioning (interview) of the workers exposed to welding and cutting risks, are:

5.2 Documentary and physical. The employer complies when: 9 It presents the analysis of potential risks for the welding and cutting activities; 9 The analysis complies with Chapter 7, and 9 On carrying out a walkthrough of the workplace, it is verified that the employer adopts the safety and health conditions laid down in Chapter 8. For greater precision on the elements that make up the analysis of potential risks, it is advisable to review Chapter 7. To verify that the safety and health conditions are adopted, it is advisable to review Chapter 8.

5.3 Documentary. The employer complies when: 9 It presents the record of the information provided to the workers, including at least: ○ The names and signatures of the workers who received the information; ○ The date on which the information was provided; ○ The subject on which they were informed, and ○ The person who provided the information. 9 It presents evidence that it informed the workers of the risks to which they are exposed at least twice a year.

5.4 Documentary. The employer complies when: 9 It presents the programme for welding and cutting activities, and 9 The programme includes the specific procedures and controls for welding and cutting activities, where there are work areas, confined spaces, processes (temporary or in the course of maintenance) or vessels in which flammable or explosive dusts, gases or vapours are present that pose a danger to the workers. For greater precision on the elements that make up the programme of welding and cutting activities, it is advisable to review paragraph 9.1. For greater precision on the specific procedures and controls, it is advisable to review paragraph 9.2.

                elements that make up the
   9 It presents the programme for the

        specific procedures and controls
                specific procedures and controls

5.5 Documentary. The employer complies when it presents the safety procedures for carrying out welding and cutting activities. For greater precision on the elements that make up the safety procedures for carrying out welding and cutting activities, it is advisable to review paragraphs 10.1, 10.2, 10.3, 10.4, 10.5 and 10.6.

   carrying out the welding and     safety procedures for
   cutting activities.              carrying out the activities of

5.6 Documentary. The employer complies when: 9 It presents documentary evidence that it trained and instructed the workers who carry out welding and cutting activities and the supervisor who oversees the application of the safety and health procedures, or 9 It presents evidence that it trained and instructed, at least once a year, the workers who carry out welding and cutting activities and the supervisor.

5.7 Physical. The employer complies when it has specific controls for the welding and cutting activities in vessels, confined spaces or underground areas where flammable or explosive dusts, gases or vapours are present that pose a danger to the workers, determined in accordance with paragraph 9.2. Examples of specific controls are: 9 Contaminant extraction or air injection systems; 9 Self-contained equipment or equipment with an air line, and 9 Detection of non-respirable, flammable or explosive atmospheres.

5.8 Documentary. The employer complies when it presents the authorisations that it grants in writing to the workers who carry out welding and cutting activities in controlled areas with the presence of flammable or explosive substances, confined spaces, heights, basements, underground areas, and areas not specifically designated for these activities. For greater precision on the particulars that the authorisation shall contain, it is advisable to review subparagraph 2) of subparagraph b) of paragraph 10.6.

5.9 Physical. The employer complies when, on carrying out a walkthrough of the workplace, where welding and cutting activities are observed to be carried out in dangerous places (heights, confined spaces, basements, underground areas, controlled areas with the presence of flammable or explosive substances, others), it is verified that there is a person in charge of supervising those activities.

5.10 Documentary. The employer complies when: 9 It presents the procedure for rescuing workers who carry out welding and cutting activities at height, in basements, underground, in confined spaces or in vessels in which flammable or explosive dusts, gases or vapours are present, and 9 The procedure has the elements laid down in Chapter 11. For greater precision on the elements of the rescue procedure, it is advisable to review Chapter 11.

5.11 Documentary. The employer complies when: 9 It presents documentary evidence that it trained and instructed the personnel assigned to rescue, on the basis of the procedure for rescuing workers who carry out welding and cutting activities laid down in Chapter 11, and 9 It presents evidence that it provided training and instruction to the personnel assigned to rescue at least once a year. Documents such as training programmes, certificates, awards or diplomas for courses received by the personnel in this field are considered to be evidence of compliance. It is also valid to take into account the workers who, at the time of the inspection or verification, as the case may be, are included in the training process.

5.12 Physical. The employer complies when it is verified that it has materials and equipment to carry out the rescue of workers injured at height, underground or in confined spaces. Examples of materials and equipment are ropes, stretchers and self-contained breathing equipment.

5.13 Documentary. The employer complies when: 9 It presents documentary evidence of the training and instruction provided to the workers who carry out preventive and, where appropriate, corrective maintenance on the equipment and machinery used in welding and cutting activities, and 9 It presents evidence that it authorises the workers who carry out maintenance activities. Documents such as training programmes, certificates, awards or diplomas for courses received by the personnel in this field are valid. It is also valid to take into account the workers who, at the time of the inspection or verification, as the case may be, are included in the training process.

   of the training and              certificates, awards or
   instruction that is               diplomas for courses received by the

5.14 Documentary or physical. The employer complies when: 9 It provides the personal protective equipment described in subparagraph c) of Chapter 8; 9 It provides the additional personal protective equipment determined in accordance with the analysis of potential risks; 9 It presents evidence that it provided the workers with training in the use, maintenance and replacement of the personal protective equipment. Documents such as training programmes, certificates, awards or diplomas for courses received by the personnel in this field are valid. It is also valid to take into account the workers who, at the time of the inspection or verification, as the case may be, are included in the training process.

5.15 Documentary. The employer complies when: 9 It presents evidence that the specific medical examinations have been carried out on the workers who carry out welding and cutting activities; 9 The medical examinations are carried out at least every twelve months and are recorded in the medical file kept for that purpose on the worker.

5.16 Documentary. The employer complies when: 9 It presents the procedures for providing care to a person who may be injured during welding and cutting activities; 9 Where it has assigned personnel to give first aid, it presents evidence that it provided them with training and instruction at least once a year, or where, on interviewing at least one of them, it is confirmed that the person has been trained to give first aid. Documents such as training programmes, certificates, awards or diplomas for courses received by the personnel in this field are valid. It is also valid to take into account the workers who, at the time of the inspection or verification, as the case may be, are included in the training process.

5.17 Physical. The employer complies when it has the first-aid kit in the area where welding and cutting activities are carried out, including the materials determined in the analysis of potential risks. It is also valid for the first-aid kit to be located in the areas intended for the medical service, provided that it is available while the welding and cutting activities are being carried out.

5.18 Documentary or physical. The employer complies when it ensures, where there is external personnel carrying out welding and cutting activities, that they comply with this Standard. Note: Documentary evidence may be presented in printed form or as an electronic file.

13.3 Opinions.

13.3.1 The opinions issued by the approved verification units shall be recognised by the Ministry of Labour and Social Welfare.

13.3.2 The opinions issued by verification units shall include compliance with this Standard and shall be in accordance with the Procedure for the conformity assessment of Official Mexican Standards issued by the Ministry of Labour and Social Welfare, published in the Official Gazette of the Federation on 20 October 2006.

RISK        PLASMA   SMAW  GTAW  SUBMERGED  OXY-FUEL
            (PAW/PAC)      (TIG)  ARC        WELDING
            CARBON ARC     GMAW   (SAW)
                           (MIG) FCAW
Ergonomic        9     9     9     9
Electric shock   9     9     9     ×
Intense light    9     9    (9)    9
Non-ionising radiation 9 9  (9)    ×

Enforcement of compliance with this Official Mexican Standard is the responsibility of the Ministry of Labour and Social Welfare.

a) ANSI/ASC Z49.1-1988. Safety in Welding and Cutting American National Standard. United States of America. b) Criteria for Recomended Standard Welding Brazing and Termal Cutting. US Departament of Healt and Human Services. National Institute for Occupational Safety and Health. April 1988. United States of America. c) Treatise on Occupational Health and Safety. Ministry of Labour of Spain. National Institute of Prevention. d) Federal Regulation on Occupational Safety, Health and Working Environment. Published in the Official Gazette of the Federation on 21 January 1997. e) Federal Law on Metrology and Standardisation. f) Federal Regulation on Metrology and Standardisation. g) Technology of welding processes; P.T. Houldcroft; Ediciones CEAC. h) Manual of flame welding; J. González Vázquez; Ediciones CEAC. i) Gas-shielded metal arc welding; Mássimo. Piredda-Carai; Editorial LIMUSA. j) Welding; James A. Pender; Ediciones McGraw-Hill. k) Welding; Ediciones Instituto Politécnico Nacional. l) Procedure for the conformity assessment of Official Mexican Standards issued by the Ministry of Labour and Social Welfare, published in the Official Gazette of the Federation on 20 October 2006.

This Standard does not correspond to any international standard, as no such reference existed at the time of its drafting.

FIRST. This Official Mexican Standard shall enter into force sixty calendar days after its publication in the Official Gazette of the Federation. SECOND. During the period indicated in the preceding article, employers shall comply with Official Mexican Standard NOM-027-STPS-2000, Welding and cutting activities - Safety and health conditions, or shall carry out the adaptations needed to observe the provisions of this Official Mexican Standard and, in the latter case, the labour authorities shall provide, at the request of the interested employers, advice and guidance for putting compliance into effect, without the employers becoming liable to penalties for non-compliance with the standard in force. THIRD. From the date on which this Standard enters into force, Official Mexican Standard NOM-027-STPS-2000, Welding and cutting activities - Safety and health conditions, published in the Official Gazette of the Federation on 8 March 2001, shall cease to have effect. Done in Mexico City, Federal District, on the eighth day of the month of October of two thousand and eight.- The Minister of Labour and Social Welfare, Javier Lozano Alarcón.- Signed.

Identification of the risk according to the welding process used. The content of this guide is a supplement for a better understanding of this Standard and is not mandatory. It is presented so as to show the different risks that may arise during the welding process selected. WELDING PROCESS (infrared, ultraviolet, etc.) (9) = Indicates that there is a risk if no flux is used. × = Indicates that there is no risk. Abbreviation Concept PAW (PAW) Plasma arc welding PAC (PAC) Plasma arc-carbon SMAW SMAW (SHIELDED METAL ARC WELDING) Shielded metal arc welding. GTAW (TIG) GTAW (GAS TUGNSTEN ARC WELDING) Gas tungsten arc welding. GMAW (MIG) GMAW (GAS METAL ARC WELDING) Gas metal arc welding. FCAW FCAW (FLUX CORED ARC WELDING) Flux cored arc welding. (SAW) SAW (SUBMERGED ARC WELDING) Submerged arc welding

Specific actions in welding and cutting activities. The content of this guide is a supplement for a better understanding of this Standard and is not mandatory. It is presented so as to provide information related to this Standard. When welding and cutting work is carried out, the area and work equipment must be inspected to achieve a safe working environment. Keep the cables (without joints and of heavy-duty type), the safety plug, the electrode holder and the shoes of the welding machines in good condition. When welding and cutting work is carried out, it is important to inspect that the work area is free of combustible materials (paper, cardboard, oils, chemicals, etc.) and free of explosive atmospheres. Where the combustible material cannot be removed, fire-protection blankets must be used to cover and isolate those products. Whenever welding and cutting work has to be carried out, a permit is required in which the conditions of the area, of the equipment and of its use are assessed, so as to achieve a safe working environment. Handle gas cylinders (acetylene, oxygen, argon, etc.) with extreme care, since these are gases bottled at high pressure, which means that if the cylinders are damaged they can behave like a projectile. Do not expose oxyacetylene equipment to contact with greases or oils, as this may cause fire and/or explosion. When gas is used, it is important to verify that the connections (regulators, hoses and torch) are the correct ones for the type of gas to be used and that they are in good condition. Use a flame arrester (flashback arrester) on both cylinders (oxygen and acetylene) to prevent the flame from reaching the tanks should it be drawn back into the hoses; the arrester shall have the following: a) A one-way (check) valve; b) A flame-cutting filter; c) A thermosensitive automatic shut-off valve, and d) A pressure-sensitive automatic shut-off valve. It is used to cut off the gas supply if there is a flashback or an overpressure in the hose, with a closing pressure equal to 0.7 Bar (10 PSI). The specific instructions for welding machines are as follows: 1.- Preparation of the weld in accordance with the specific welding procedure to be carried out; some examples are: a) Clean the pieces to be welded; b) Clamp the pieces to prevent them from moving; c) Protect yourself properly with gloves, working clothes and a protective screen, and d) Insert the electrode into the holder; 2.- Attach the earth clamp to one of the two pieces to be welded. a) Connect the equipment to a socket with an earth connection, making sure that the electrode is not in contact with the earth; b) Adjust the current of the equipment; c) Rub the tip of the electrode at the point where the weld is to be made (striking the arc). This rubbing strikes the arc; it is easy to tell when this happens because sparks appear. Next, move the electrode away by about 4 or 5 mm to establish the electric arc. Then bring the electrode to within 2 or 3 mm of the workpiece and begin welding. The distance between the electrode and the piece to be welded is equal to the diameter of the electrode and shall be kept constant throughout the process. Continue welding, keeping the electrode inclined at 60 degrees; d) Advance at a steady speed, keeping the gap between the electrode and the piece. To achieve this, the electrode holder must be moved progressively towards the piece to compensate for the loss of material caused by the melting of the electrode; e) Adapt the travel speed to obtain a bead width equal to 1.5 times the diameter of the electrode, and f) Let the weld cool by natural process. Do not use water, as it could crystallise. Welding equipment: depending on the type of current of the circuit used for welding, the equipment can be said to consist of different parts. In alternating-current equipment, a transformer and a frequency converter; in direct-current equipment, a rectifier and a converter. Auxiliary items: the main ones are the electrodes, the electrode holder and the earth clamp. The electrode is a rod with a core of carbon, iron or base metal for welding and a coating surrounding it. It forms one of the poles of the arc that generates the heat of fusion and, where it is metallic, supplies filler material. There are various types, but the most used are thick-coated electrodes in which the ratio between the outer diameter of the coating and that of the core is greater than 1:3. The coating is composed of various products such as iron or manganese oxides, ferromanganese, rutile, etc. Soluble alkaline silicates are commonly used as binders. The electrode holder serves to fix the electrode to the current-carrying cable. The earth clamp is used to attach the earth cable to the piece to be welded, providing good contact between the two. Risks: exposure to ultraviolet radiation, to light radiation, to fumes and gases, to phosgene poisoning and to noise may be mentioned. Exposure to ultraviolet and light radiation is produced by the electric arc. The inhalation of toxic fumes and gases produced by the electric arc varies greatly according to the type of electrode coating or shielding gas and the base and filler materials, and may consist of exposure to fumes (oxides of iron, chromium, manganese, copper, etc.) and gases (oxides of carbon, of nitrogen, etc.). Finally, phosgene poisoning may occur where welding work is carried out near degreasing tanks containing chlorinated products, or on pieces wetted with such products. Specific instructions for oxyacetylene welding: compressed gases are today practically indispensable for carrying out most welding processes. Because of its great flammability and quality, the most used gas is acetylene which, combined with oxygen, is the basis of oxyacetylene welding and oxygen cutting. In non-fixed oxyacetylene welding installations, both the oxygen and the fuel gas (acetylene, hydrogen, etc.) that feed the torch come from the cylinders that contain them at high pressure. It is worth stressing that the flame of an acetylene-oxygen torch can reach a temperature above 3100oC, thereby increasing the danger of this type of welding. In addition to the 2 mobile cylinders containing the fuel and the oxidiser, the main items involved in the oxyacetylene welding process are the pressure regulators, the torch, the non-return valves and the hoses. Torch: this is the item of the system that mixes the gases. Torches may be of the high-pressure type, in which the pressure of both gases is the same, or of the low-pressure type, in which the oxygen (oxidiser) has a higher pressure than the acetylene (fuel). The main parts of the torch are two connections with the hoses, two regulating taps, the injector, the mixing chamber and the nozzle. The following instructions are recommended for its operation: 1) The torch shall be handled with care and shall in no case be used to strike anything; 2) In the lighting operation (of a mixer-type torch) follow this sequence of operation: a) Slowly open the torch valve for the oxygen; b) Open the torch valve for the acetylene by about 3/4 of a turn; c) Light the mixture with a friction lighter (spark) or a pilot flame; d) Increase the fuel intake until the flame gives off no smoke; e) Finish opening the oxygen as required, and f) Verify that the pressure regulator is at the correct pressure. 3) In the shutdown operation, the acetylene valve shall be closed first and then the oxygen valve; 4) Never hang the torch on the cylinders, not even when it is out; 5) Do not place torches connected to the cylinders in closed containers; 6) Torches shall be repaired by specialist technicians; 7) Clean the torch nozzles periodically, as accumulated dirt makes flashback easier. Nozzle cleaners may be used to clean the nozzles, and 8) If the torch leaks, stop using it immediately and have it repaired. It must be borne in mind that oxygen leaks in enclosed premises can be very dangerous. Check valves; one-way or non-return valves are safety devices installed at the gas inlets to the torch, whose function is to block any backflow of gases, preventing them from mixing inside the hoses and creating conditions conducive to flashback. These valves are not flashback arresters. Flashback arrester valves; flashback arrester: these are safety devices installed in the gas supply system that allow gas to pass in one direction only, thereby preventing the flame from travelling back. They consist of a casing, a metal body, a non-return valve and a safety valve against overpressures. Flashback: in the event of a flashback the following steps shall be taken: a) Close the oxygen stopcock, interrupting the supply to the internal flame; b) Close the acetylene stopcock and then the supply valves of both cylinders; c) Avoid bending the hoses to interrupt the flow of gas, and d) Carry out the relevant checks to find the causes and proceed to remedy them. Hoses: a) Keep the hoses in perfect condition for use and firmly fixed to the coupling nuts; b) Prevent the hoses from coming into contact with hot surfaces, sharp edges or sharp angles, or from having sparks fall on them, ensuring that they do not form loops; c) Prevent the hoses from crossing vehicle or pedestrian routes without being protected by crossing supports of sufficient compressive strength; d) Before starting the welding process, check that there are no losses at the hose connections, using a soapy solution for example; never use a flame to carry out the check; e) Do not work with the hoses placed over the shoulders or between the legs; f) Avoid leaving the hoses coiled on the cylinder shoulders, and g) After an accidental flashback, dismantle the hoses and check that they have not been damaged. If they have, replace them with new ones and discard the damaged ones. General safety rules: a) It is recommended that welding and cutting work in premises where flammable or combustible materials are stored and where there is a risk of explosion be ventilated, and that safety conditions be established; b) Before working with vessels that have contained explosive or flammable substances, clean them with hot water and degas them with steam. Also check, with the help of a hazardous-atmosphere meter (explosimeter), the total absence of gases; c) Prevent the sparks produced by the torch from reaching or falling on the cylinders, hoses or flammable liquids; d) Do not use oxygen to clean or blow out pieces or pipework, etc., or to ventilate a room, since excess oxygen increases the risk of fire; e) Keep the valves and pressure regulators of the oxygen cylinders free of greases, oils or fuel of any kind. Greases can ignite spontaneously through the action of oxygen; f) If the valve of an acetylene cylinder catches fire, an attempt shall be made to close it and, if that is not possible, it shall be put out with a carbon dioxide or dry chemical powder extinguisher, and g) After a flashback or a fire at the valve of an acetylene cylinder, check that the cylinder is not heating up by itself. Specific safety rules. Use of cylinders: a) Keep the cylinders perfectly identified at all times; otherwise they shall be taken out of service and returned to the supplier; b) All equipment, pipework, hoses and accessories shall be suitable for the gas pressure to be used; c) Position the valves of the oxygen and acetylene cylinders so that their outlets point in opposite directions; d) Keep the cylinders in service free of objects that cover them wholly or partly; e) Keep the cylinders at a distance of between 5 and 10 m from the work zone; f) Before using the contents of a cylinder, check that the gauge reads zero with the valve closed; g) If the handwheel of a cylinder valve jams and prevents further turning, do not force it. Return the cylinder to the supplier, marking the defect detected; h) Purge the oxygen cylinder valve before fitting the pressure regulator, opening it a quarter of a turn and closing it as quickly as possible; i) Fit the pressure regulator with the adjusting screw fully open; after fitting it, check that there are no leaks using a soapy solution, but never with a flame. If leaks are detected, have them repaired immediately; j) Open the oxygen cylinder valve slowly; otherwise the body of the pressure regulator could burn; k) Do not use up the cylinders completely, as air could enter; always keep a slight overpressure inside them; l) Close the cylinder valves after each working session and purge the pressure regulator, the hoses and the torch; m) Attach the shut-off key for the acetylene cylinder valve to each cylinder in service, so that it can be closed in an emergency or at the end of the welding and cutting process. A good arrangement is to tie it to the pressure regulator; n) The supplier shall remedy faults in the cylinder valves; do not attempt to repair them; o) Do not replace fibre gaskets with rubber or leather ones, and p) If, as a result of being subjected to low temperatures, the pressure regulator of a cylinder shows ice, water from a hose shall be used to thaw it. Risk factors: a) Fire, explosion; b) Exposure to radiation in the ultraviolet, visible and infrared bands; c) Splashes of incandescent metal and contact with the hot objects being welded; d) Projection of particles, and e) Exposure to welding fumes and gases. To prevent accidents: a) Use only welders trained in welding, cutting, heating or straightening operations; b) Make sure that they are aware of the risks and that they are always prepared to act in emergency situations; c) Set aside dedicated areas for welding, cutting and similar processes; d) Define authorisation procedures for work in areas that present fire risks (flammable products or heat transfer) and in enclosed or confined spaces; e) Supply personal protective equipment and supervise its use, and f) Do not exceed the oxygen pressures laid down in the safety procedures for carrying out cutting activities with autogenous welding (too much oxygen pressure can throw an oxygen spark twice the normal distance). For greater precision on the content of the items referred to in subparagraphs a) to h), it is advisable to review this section of the standard. __________________________