Hot Work: what it is, risks, and requirements of NR-34

Hot work is one of the most critical activities in industry and requires strict control according to NR-34. Activities such as welding, cutting, and grinding can only be carried out with a Work Permit (PT), JHA (Job Hazard Analysis), and well-defined preventive measures.

To ensure the safety of employees and property, compliance with NR-34 is essential.

In this article, we have gathered everything you need to know to perform these activities safely and in compliance.

What is Hot Work according to NR-34?

According to NR-34 (item 34.5), hot work is defined as any activity involving welding, gouging, grinding, cutting, or other operations that can generate ignition sources, such as heat, sparks, or flame.

In practical terms, if the tool or process releases enough heat to start combustion or generates flying sparks, the activity is classified as hot work and requires a specific Work Permit (PT).

Examples of Hot Work in the Industry

Although welding is the most classic example, several routine maintenance activities fall into this category. The main examples include:

• Welding: Processes for joining parts.
• Hot Cutting (Oxy-fuel cutting): Use of torches and combustible gases for cutting metals.
• Grinding: Use of sanders and angle grinders that project incandescent particles over long distances.
• Gouging: Removal of metal using an electric arc and compressed air.
• Brazing: Joining metals using heat and a filler metal, very common in copper piping.
• Heat Treatment: Localized application of heat for stress relief in welds.

What are the risks of Hot Work?

The risks of hot work go far beyond the visible fire. The hazard analysis must cover:

1. Fire and Explosion:

The most critical risk. It occurs when sparks or hot slag come into contact with combustible materials, flammable gases, or oil/grease residues in the vicinity. 2. ##### Physical Burns:

Skin injuries caused by direct contact with the heated piece, molten metal splashes, or thermal radiation. 3. ##### Toxic Gases:

Inhalation of toxic fumes from metal fusion and electrode coating can cause severe long-term respiratory diseases. 4. ##### Non-Ionizing Radiation:

Exposure to ultraviolet (UV) and infrared (IR) rays generated by the electric arc can cause eye injuries (such as "welder's flash") and skin injuries.

Safety and Control Measures required by NR-34

To mitigate the risks mentioned, NR-34 establishes a strict hierarchy of controls. The main mandatory measures are:

1. Preliminary Inspection and Cleaning (Item 34.5.2)

Before starting, the area must be inspected. It is mandatory to remove all combustible and flammable materials from the surroundings. If removal is not possible, they must be protected with fire-retardant blankets.

2. Fire Protection (Item 34.5.3)

The employer must install physical protection (such as screens or fire-retardant blankets) to prevent sparks, splashes, or heat from reaching combustible materials.

The standard requires (Item 34.5.3.1.d) inspection of the site upon completion of the work to prevent reignition or delayed fire outbreaks.

3. Control of Fumes and Contaminants (Item 34.5.4)

Smoke inhalation is a serious hazard. The standard requires: cleaning the surface before welding (removes oil/grease); Air renewal (exhaust/ventilation) to eliminate gases and vapors. And, if the coating of the piece is unknown, the use of respiratory protection is mandatory (Item 34.5.4.3).

4. Gas and Cylinder Safety (Item 34.5.5)

This is a critical point where many accidents occur. The rules are clear:

• Flashback arrestor valve: Mandatory on the hose and torch feed in oxy-acetylene equipment (Item 34.5.5.3).
• Prohibited in confined spaces: Never install gas cylinders inside confined spaces (Item 34.5.5.7).
• Storage: Cylinders always in an upright position, secured, and away from flames.
• End of service: Hoses must be disconnected and cylinders closed.

Hot Work Watcher: when is it mandatory?

A fundamental point of NR-34 (Item 34.5.10) is the figure of the Fire Watch. When defined in the JHA, this professional must remain at the site in permanent contact with the work front, focused exclusively on preventing and fighting initial stages of fire.

JHA and Work Permit (PT) for Hot Work

To formalize safety, two documents are indispensable according to items 34.5.7 and 34.5.8:

1. JHA (Job Hazard Analysis):

Defines the control measures, isolation radius, and the need for a fire watch. 2. ### PT (Work Permit):

The result of the preliminary inspection must be recorded in the PT before starting activities. Without a signed PT, work does not begin.

Regulatory Standards (NRs) Related to Hot Work

Although NR-34 is the most detailed technical reference on the subject, other standards also apply depending on the scenario:

• NR-18 (Construction Industry):

  Has a specific chapter on welding and hot cutting operations on construction sites.

• NR-33 (Confined Spaces):

  Essential when hot work is performed inside tanks, silos, or piping.

• NR-35 (Work at Height):

  Frequently, welding and cutting are performed at height, requiring the integration of fall prevention measures with fire protection (use of blankets to prevent sparks from falling to lower levels).

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