Introduction Welding Brazing Cutting

Transcription

1 Welding Safety

2 Introduction There are over 500,000 workers involved in some form of welding, cutting or brazing work. These are hazardous activities which pose a combination of both safety and health risks for employees. Welding, cutting and brazing are all very dangerous and proper work practices must be followed to avoid injuries, fires and even explosions.

3 Introduction Welding is the process of joining two different objects by melting their surfaces together. This is done by heating the metals until a molten puddle is formed. Usually, more metal is added to the mix by means of a welding rod or filler rod. Welds are most commonly done on like metals. If done properly, the weld will be as strong as the metal being joined. Brazing is the process of joining two different metal objects with the use of a third dissimilar filler metal. The two objects are bonded together by completely wetting the surfaces with molten filler metal and held together until the bond solidifies. The bond is only as strong as the filler metal but, can still be very strong. Cutting means just what the term implies: cutting metal. Instead of bonding two separate metal objects together, the welder removes or severs a piece of metal in to different pieces.

4 Types of Welding There are many different methods of welding which use a variety of energy sources. Two of the more common types are Gas Welding and Shielded Metal Arc Welding. OxyFuel Welding, a form of gas welding, is one of the oldest and still more popular methods of welding. It involves the use of a fuel combined with oxygen to produce a very hot flame. The most common fuel used is acetylene. Other gases used are propylene, MAPP gas, natural gas, hydrogen, liquefied petroleum and propane.

5 Types of Welding Shielded Metal Arc Welding joins two metals together by producing an electric arc between the base metals to be joined and a flux coated consumable electrode rod. A flux is a chemical cleaning agent, flowing agent or purifying agent. As the weld is laid, the flux coating disintegrates, giving off vapors which serves as a shielding gas and also provides a layer of slag, protecting the weld area from atmospheric contamination.

6 Types of Cutting Two common cutting processes are Oxygen and Arc. With Oxygen Cutting the metal is heated to its kindling temperature by gas flame and then cut with a high-pressure stream of oxygen focused on the area to be cut. Arc Cutting is the process of melting or cutting metal using the intense heat generated from the electric arc. In this training program Welding will mean any electric or gas welding, cutting and brazing activity and Welder will mean any operator of electric or gas welding and cutting equipment.

7 Hazards of Welding Welding is performed in many different environments including confined spaces, open air, underwater, underground and even in space. Welding can be dangerous and includes such hazards as fires, confined spaces, eye damage, inhalation of poisonous gases and fumes, shock, cuts and exposure to intense ultraviolet radiation. Many of these hazards can be greatly reduced with proper work practices and personal protective equipment.

8 Fire Prevention and Protection Welding activities produce sparks, slag, molten metal and hot work surfaces. Sparks are the main cause of fires and explosions. They can travel great lengths and even more so when they fall from upper levels. If the object being welded can t be moved, then all movable fire hazards in the vicinity should be taken to a safe place. Fire hazards include such combustible materials as wood, clothing, paper, chemicals, liquids and fuels. Guards must be utilized if the object being welded and all fire hazards can t be moved, to confine the heat, sparks and slag and to protect the immoveable fire hazards. If the object being welded can t be moved and all fire hazards can t be moved AND guards are not feasible, then welding should not be performed.

9 Special Precautions When the nature of the work to be performed requires guards as stated above, then certain additional precautions may be necessary. Whenever there are floor openings or cracks which cannot be closed, precautions must be taken to protect readily combustible materials from sparks which might drop through the floor. The same precautions must be taken for holes and cracks in walls, open doorways and open or broken windows. Appropriate fire extinguishing equipment must be maintained and ready for instant use. A fire watch must be maintained for at least 30 minutes after the welding job is complete where other than a minor fire is possible. The firewatcher must be trained and qualified and know the location of fire alarms.

10 Special Precautions The person responsible for welding operations must inspect the area and determine the necessary precautions to be followed, preferably in a written permit. Floors should be swept clean of combustible materials for a radius of 35 feet away from the work area. Combustible floors must be kept wet, covered with damp sand or protected by fire-resistant shields. When floors have been wet down, personnel operating arc welding equipment must be protected from electrical shock. Welding is prohibited in the following situations: - In areas not authorized by management; - When sprinkler protection is impaired; - In the presence of explosive atmospheres; and - In areas near the storage of large quantities of exposed, readily ignitable material. (examples: bulk sulfur, baled paper or cotton).

11 Special Precautions Other safety measures include: - Moving combustible items 35 feet from the work site when practical. Otherwise they must be properly protected or shielded. - Shut down ducts and conveyers which might carry sparks. - When welding in close proximity, protect combustible walls with fire-resistant shields or guards. - When welding on non-combustible walls, protect items on opposite side of the wall from igniting, preferably by relocating. Otherwise, a fire watch is required. - If welding on a platform, scaffold or runway, welders and helpers must be protected from falling. - Keep welding cable and other equipment clear of passageways, ladders and stairways.

12 Special Precautions Management has obligations to the employees to keep them safe. Always follow company rules and regulations. Welding Containers Welding should not be performed on used drums, barrels, tanks or other containers until they have been thoroughly cleaned and it is absolutely certain there are no flammable substances still present. Any pipe lines or connections to the container must be disconnected or blanked also. All hollow spaces, cavities or containers must be vented to permit the escape of air or gasses before welding. Purging with inert gas is recommended.

13 Protection of Personnel Employees must be protected from various hazards when welding or working in the vicinity of welding work. The proper Personal Protective Equipment can protect welders and others from burns, electric shock, eye damage, sparks and other hazards and is required in all welding situations. Proper eye and face protection must be provided, based on the type of welding being performed. Not only should the welder be protected but also any other employee working nearby. Such protection may include welding helmets, safety glasses, goggles, face shields, curtains or combinations thereof. All face protection must meet certain safety requirements and standards as required by OSHA. Lenses should bear a permanent marking indicating the manufacturer and the shade number.

14 Protection of Personnel Some standard safety guidelines include: - Clean and inspect welding helmets and eyewear regularly and keep in good condition. -Wear safety glasses with side and top protection under welding helmets. - Make sure the goggles or helmets have the correct shade of filter for the task. - Keep face and eye protection on whenever hazards are present. - When possible, isolate welding areas from others with partitions or curtains designed to absorb harmful welding rays. - Follow manufactures guidelines and procedures to ensure proper eye protection.

15 Protection of Personnel Appropriate protective clothing must be worn when welding. The size, nature and location of the work will determine the type of clothing protection needed. Some general guidelines include: - Wear a fire-resistant cap under the welding helmet. - The use of earplugs or muffs might be appropriate to keep hot sparks or other material from entering your ears and to protect against loud noise. - Wear leather high-topped boots to protect your feet and ankles. The use of fire-resistant boot protectors might be required also. Never wear cuffed pants which can collect flying sparks or hot metal. Keep your pants pulled over the tops of your boots.

16 Protection of Personnel - Always wear fire-resistant insulated welding gloves which are free of holes or other damage. - Clothing made of wool or heavy cotton is best to wear. Wear long sleeve shirts with buttoned cuffs and collars and long heavy duty pants. Keep all protective clothing dry, clean and without any holes. This helps prevent clothing from catching fire. - Remove all objects from your pockets before welding. - Use leather aprons, sleeves and leggings as needed.

17 Ventilation Ventilation is necessary to keep hazardous fumes, gases and dust away from the welder in general and more specifically their breathing area. Proper ventilation can be obtained through natural means or mechanical. Natural ventilation utilizes the natural flow of air through open doors and windows. Mechanical ventilation manipulates the air flow with devices like a fan, exhaust hood, or booth to keep contaminates below Permissible Exposure Limits. If welding is performed and screens are used on all four sides, they must be arranged in such a way as to not restrict ventilation. It is best to mount the screens about 2 ft. above the ground unless this would create a glare hazard for nearby workers.

18 Ventilation Toxic fumes, gases and dust must be kept below the maximum Permissible Exposure Limits (PELs) through local exhaust or general ventilation systems. Natural ventilation is sufficient when the following criteria are met: - The welding area contains at least 10,000 cubic feet per welder; - The ceiling height is at least 16 feet high; - There are no barriers to blocking cross ventilation; and - The welding space is not a confined space. If any of these requirements are not met then mechanical ventilation is required and must exhaust at least 2,000 cubic feet of air per minute per welder unless: - Airline respirator is used. - Local exhaust hoods or booths are used. Local exhaust hoods or booths must provide airflow of at least 100 linear feet per minute.

19 Ventilation Specific materials which require mechanical ventilation measures include: - Fluorine Compounds - Zinc - Lead - Beryllium - Cadmium - Mercury - Cleaning Compounds - Stainless Steel

20 Work in Confined Spaces When welding is performed in confined spaces, specific OSHA requirements regarding the confined space must also be considered and followed before work can be performed. Some of the things which must be considered include: Ventilation - Confined spaces must be adequately ventilated to prevent the accumulation of toxic materials or possible oxygen deficiency. This applies to the welder as well as helpers and other personnel in the immediate vicinity. If adequate ventilation is not possible, airline respirators must be used. In areas Immediately Dangerous to Life, a self-contained breathing apparatus must be used. Oxygen should never be used for ventilation. Gas cylinders and welding machines must be left outside of the confined space.

21 Work in Confined Spaces Where a welder must enter a confined space through a manhole or other small opening, a lifeline must be provided for quickly removing the welder in case of emergency. When arc welding is to be suspended for any substantial period of time, such as during lunch or overnight, all electrodes must be removed from the holders and the holders located to prevent accidental contact. Additionally, the machine must be disconnected from the power source.

22 Work in Confined Spaces In order to eliminate the possibility of gas escaping though leaks or improperly closed valves, torch valves must be closed and the gas supply to the torch positively shut off at some point outside of the confined space when not being used for a substantial period of time, such as during lunch or overnight. Where practical, the torch and hose should also be removed from the confined space. After the work is complete, the welder should mark the hot metal or provide some means of warning other workers. If welding in a confined space, make sure you are adequately trained. OSHA has specific training requirements regarding confined spaces.

23 Conclusion Some basic safety guidelines to follow when welding: Always inspect equipment prior to welding. Needed repairs should only be performed by qualified people. Only weld in areas approved by management. Move combustible items 35 feet from the work site or provide protection from the welding work. Wear the appropriate protective clothing and PPE. Inspect the PPE before using. Do not use worn or defective PPE. Do not breathe in the fumes or gases. Position yourself such that you keep your head out of the danger zone. Use the correct ventilation methods. If the use of a respirator is necessary make sure the correct type is used and you are properly trained on its use. If welding in a confined space, additional training is necessary to ensure your safety.