Exhausting Welding Fumes

Following topics to be discussed in this article are 

  1. SCOPE
  2. REFERENCES
  3. GENERAL
  4. SAFETY
  5. LOCAL MECHANICAL EXHAUST SYSTEMS

Exhausting Welding Fumes Figures

  1. Typical Fixed Single Station Exhaust System
  2. Typical Fixed, Multiple Station Exhaust System
  3. Various Types of Pickup Hoods and Nozzles

3A. Rectangular Movable Pickup Hood

3B. Round Movable Pickup Hood

3C. High Velocity, Low Volume Exhaust Nozzle

3D. High Volume, Gun Mounted Nozzle

4. Typical Portable, Single Station Exhaust System with Electronic Air Cleaner

5. Typical Fixed Enclosure for Exhausting Fumes from Welding Bench

TABLE

I – Hazardous Materials Protection Requirements

Exhausting Welding Fumes

1. Scope

This article is about guidelines for ventilation to protect workers from welding and cutting fumes.

2. References

Reference is made in this article to the following document.

Code of Federal Regulations (OSHA)

Chapter XVII, Section 1910.252

3. General

3.1  Natural ventilation is satisfactory if the welding or cutting operation uses nonhazardous materials and the following conditions exist:

a. A space more than 283 m3 (10,000 ft3) per welder. b. A room with a ceiling higher than 4.88 m (16 ft).

c. The welding location is not in a confined space where barriers, for example partitions, balconies, or other structures, significantly obstruct cross ventilation.

d. The welding can be done in a position that keeps the fume plume away from the breathing zone of the welder.

3.2 General mechanical ventilation can be used for nonhazardous materials where the space requirements listed in 3.1 cannot be met. The minimum ventilation rate shall be 57 m3/min (2000 cfm) per welder and 3.1.c and 3.1.d shall be met.

3.3 Local exhaust mechanical ventilation can be used for nonhazardous materials where natural or general mechanical ventilation cannot be used. Local exhaust mechanical ventilation consists of movable pickup hoods or nozzles placed near the source of fumes or fixed exhaust hoods or enclosures surrounding the source of fumes. The hoods, nozzles, or enclosures are to provide 30.5 m (100 ft) per minute velocity at the fume source to capture the fumes and carry them away from the welder.

3.4 Exercise care to be sure that the exhaust from general and local mechanical ventilation systems is kept away from fresh air intakes and areas where personnel could breathe the exhaust fumes.

3.5 Hazardous materials are defined as those having very low permissible exposure limits (1.0 mg/m2 or less). Some of these materials likely to be found in welding and cutting are listed below. Refer to Material Safety Data Sheets provided by the manufacturer for hazardous materials before using the materials in welding or cutting.

Antimony                                          Lead

Arsenic                                           Manganese

Barium                                              Mercury

Beryllium                                          Selenium

Cadmium                                          Silver

Cobalt                                               Vanadium Copper

3.6 Hazardous materials may require the use of respirators as well as exhaust hoods to assure protection of the welder. See Table I for materials specifically listed in OSHA, Chapter XVII, and Section 1910.252.

3.7 Confined areas require breathing air to be supplied to the worker, also ventilation to remove the welding or cutting fumes. See plant procedure.

4. Safety

Follow safe practices prescribed in SES W02-F01 on plant sites.

5. Local Mechanical Exhaust Systems

5.1 Local mechanical exhaust systems with movable pickup hoods or nozzles can be purchased from manufacturers. These systems are available as (1) fixed, single station; (2) fixed, multiple station, and (3) portable, single station.

5.1.1 Fixed, single station exhaust systems usually consist of an exhaust fan, exhaust duct from the fan, articulated hose assembly, and a pickup hood. A typical unit is shown in Figure 1.

5.1.2  Fixed, multiple station exhaust systems usually consist of a fixed exhaust fan with optional cyclone separator or filter (or both) on the inlet side, an exhaust duct or stack from the fan, a duct manifold with multiple takeoff points, flexible hoses or articulated hoses attached to each takeoff and pickup hoods or nozzles attached to each hose. A typical system is shown in Figure 2. Types of pickup hoods (or nozzles) are shown in Figure 3.

5.1.3 Portable, single station exhaust systems consist of a portable, wheeled cart on which is installed an exhaust fan with an optional filter, an articulated hose, a pickup hood or nozzle, and an optional exhaust hose. A typical unit with an electronic air filter is shown in Figure 4.

5.1.4 Commercial exhaust system fans tend to be noisy, so give consideration to mounting them outside the work area.

5.2 Local mechanical exhaust hoods, systems, and enclosures can be designed and fabricated on site.

5.2.1 Two types of movable pickup hoods that can be locally fabricated are shown in Figure 3 with the formulas for determining air quantities needed to give 30.5 m/min (100 fpm) velocity at the fume source noted in the figure.

5.2.2 Round spiral duct will provide the most economical duct work for manifolds in multiple station exhausts and for exhaust duct and stacks from the fan.

5.2.3 Give consideration to minimizing the noise in the work place.

5.2.4 A fixed enclosure that can be designed and fabricated locally is shown in Figure 5. This type of enclosure is ideal for a shop where many small items are welded on a bench top.

TABLE I – Hazardous Materials Protection Requirements

TABLE I - Hazardous Materials Protection Requirements
* Respiratory protection approved by Mine Safety and Health Administration (MSHA) or National Institute of Occupational Safety and Health (NIOSH). ** Check Manufacturer’s Safety Data Sheet and material data from S22-G01 to determine what kind of protection is needed for the compound being used. Note: Respirator refers to supplied air respirator (air line). Hazardous confined spaces may require self contained, supplied air respirator.

FIGURE 1 – Typical Fixed Single Station Exhaust System

Typical Fixed Single Station Exhaust System

FIGURE 2 – Typical Fixed, Multiple Station Exhaust System

Typical Fixed, Multiple Station Exhaust System
Typical Fixed, Multiple Station Exhaust System

FIGURE 3 – Various Types of Pickup Hoods and Nozzles

FIGURE 3 - Various Types of Pickup Hoods and Nozzles
FIGURE 3 – Various Types of Pickup Hoods and Nozzles

FIGURE 3C – High Velocity, Low Volume Exhaust Nozzle

FIGURE 3C - High Velocity, Low Volume Exhaust Nozzle
FIGURE 3C – High Velocity, Low Volume Exhaust Nozzle

FIGURE 3D – High Volume, Gun Mounted Nozzle

FIGURE 3D - High Volume, Gun Mounted Nozzle
FIGURE 3D – High Volume, Gun Mounted Nozzle

FIGURE 4 – Typical Portable, Single Station Exhaust System with Electronic Air Cleaner

FIGURE 4 - Typical Portable, Single Station Exhaust System with Electronic Air Cleaner
FIGURE 4 – Typical Portable, Single Station Exhaust System with Electronic Air Cleaner

FIGURE 5 – Typical Fixed Enclosure for Exhausting Fumes from Welding Bench

FIGURE 5 - Typical Fixed Enclosure for Exhausting Fumes from Welding Bench
FIGURE 5 – Typical Fixed Enclosure for Exhausting Fumes from Welding Bench

 

Leave a Comment

error: Content is Protected.