metal fabrication shops general presentation (andew cutz, cih)

METAL FABRICATION SHOPS

Andrew Cutz, CIH

Wednesday, July 08, 2009

Andrew Cutz, CIH 2

Presentation Outline

Describe the potential exposures to hazardous substances, means of exposure generation and the types of workers who could be exposed (directly or indirectly).

Describe how one would assess the worker's historical exposures.


Andrew Cutz, CIH 3

Fabrication Shops

Fabrication, when used as an industrial term, applies to the building of machines, structures and other equipment, by cutting, shaping and assembling components made from raw materials. Small businesses that specialize in metal fabrication are called ‘fab shops’.

Steel fabrication shops and machine shops have overlapping capabilities, but fabrication shops generally concentrate on the metal preparation, welding and assembly aspect while the machine shop is more concerned with the machining of parts.


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Metal fabrication

Metal fabrication is a value added process that involves the construction of machines and structures from various raw materials. A fabrication shop will bid on a job, usually based on the engineering drawings, and if awarded the contract will build the product.

Fabrication shops are employed by contractors, original equipment manufacturers and value added resellers. Typical projects include loose parts, structural frames for buildings and heavy equipment, and hand railings and stairs for buildings.


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Specialty Processes

Many metal fabrication shops have specialty processes based on their customers needs and their expertise:

* brazing * casting * chipping * drawing * extrusion * forging * heat treatment * punching * shearing * soldering * spinning * welding


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Brazing

Brazing is a joining process whereby a filler metal or alloy is heated to melting temperature above 450 °C (840 °F) by the American Welding Society definition, and distributed between two or more close-fitting parts by capillary action.

At its liquid temperature, the molten filler metal and flux interacts with a thin layer of the base metal, cooling to form a strong, sealed joint.

By definition the melting temperature of the braze alloy is lower (sometimes substantially) than the melting temperature of the materials being joined.

The brazed joint becomes a sandwich of different layers, each metallurgically linked to the adjacent layers.


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Filler materials for brazing

A variety of alloys of metals, including silver, tin, zinc, copper and others (e.g. bronze, brass, gold) are used as filler for brazing processes. There are specific brazing alloys and fluxes recommended, depending on which metals are to be joined.

Brazing filler material is commonly available as flux-coated rods, very similar to stick-welding electrodes. Typical sizes are 3 mm (0.12 in) diameter.


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Flux

In most cases, flux is required to prevent oxides from forming while the metal is heated and also helps to spread out the metal that is used to seal the joint. The most common fluxes for bronze brazing are borax-based.

The flux can be applied in a number of ways. It can be applied as a paste with a brush directly to the parts to be brazed. Brazing rods can also be purchased with a coating of flux, or a flux core. In either case, the flux flows into the joint when the rod is applied to the heated joint.

Many types of brazing flux contain toxic chemicals, sometimes very toxic. Silver brazing flux often contains cadmium, which can cause very fast onset of metal fume fever. Due care must be taken with these materials to protect persons working, and also the environment.


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Soldering

Soldering is a process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, the filler metal having a relatively low melting point. Soft soldering is characterized by the melting point of the filler metal, which is below 400 °C (752 °F). The filler metal used in the process is called solder.

Soldering is distinguished from brazing by use of a lower melting-temperature filler metal; it is distinguished from welding by the base metals not being melted during the joining process.

In a soldering process, heat is applied to the parts to be joined, causing the solder to melt and be drawn into the joint by capillary action and to bond to the materials to be joined by wetting action.

After the metal cools, the resulting joints are not as strong as the base metal, but have adequate strength, electrical conductivity, and water-tightness for many uses.

Soldering is an ancient technique and there is evidence that it was employed up to 5000 years ago in Mesopotamia.


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Soldering


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Solder

Soldering filler materials are available in many different alloys for differing applications. In electronics assembly, the eutectic alloy of 63% tin and 37% lead (60/40) has been the alloy of choice. Other alloys are used for plumbing, mechanical assembly, and other applications.

Lead-free solders are suggested anywhere children may come into contact with the item or for outdoor use where rain and other precipitation may wash the lead into the groundwater.

For environmental reasons, 'no-lead' solders are becoming more widely used. Unfortunately most 'no-lead' solders are not eutectic formulations, making it more difficult to create reliable joints.

Specialty alloys (containing bismuth/silver) are available with properties such as higher strength, better electrical conductivity and higher corrosion resistance.


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Flux

In high-temperature metal joining processes (welding, brazing and soldering), the primary purpose of flux is to prevent oxidation of the base and filler materials. Secondarily, flux acts as a wetting agent in the soldering process, reducing the surface tension of the molten solder and causing it to better wet out the parts to be joined.

Fluxes currently available include water-soluble fluxes and 'no-clean' fluxes which are mild enough to not require removal at all.

Traditional rosin fluxes are available in non-activated (R), mildly activated (RMA) and activated (RA) formulations. RA and RMA fluxes contain rosin combined with an activating agent, typically an acid.


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Welding

Welding is a fabrication process that joins materials, usually metals or thermoplastics. This is often done by melting the work pieces and adding a filler material to form a pool of molten material that cools to become a strong joint to produce the weld.

This is in contrast with soldering and brazing, which involve melting a lower-melting-point material between the work pieces to form a bond between them, without melting the work pieces.

Many different energy sources can be used for welding including gas flame, electric arc, laser, electron beam, friction and ultrasound. While often an industrial process, welding can be done in many different environments, including open air, under water and even in outer space.

Regardless of location, welding remains dangerous and precautions must be taken to avoid burns, electric shock, eye damage, poisonous fumes and overexposure to ultraviolet light.


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Gas metal arc welding


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Shielded metal arc welding


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Arc welding with PPE


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Gas welding using the oxy-acetylene process


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Arc welding with industrial robots


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Six Degrees of ‘Occupational Disease’ Causation by Douglas R. Mah, Q.C.2008 Meredith Presentation (June 18, 2008)


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The Gig Saw Puzzle: Looking for that needle


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CCOHS Web Information Service


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CCOHS: Occupational Diseases and Welding


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Health Effects of Welding and Cutting Fume - An Update by Gary Liss, MD


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AWCBCAssociation of Workers’ Compensation Board of Canada


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About Haz-Map


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About Haz-Map

Haz-Map is an occupational toxicology database designed to link jobs to hazardous job tasks which are linked to occupational diseases and their symptoms. It is a relational database of chemicals, jobs and diseases.

The Haz-Map Jobs table is based on the 1997 Standard

Occupational Classification (SOC) system. The Industries table is based on the North American Industry Classification System (NAICS). The Diseases table is based on the International Classification of Diseases (ICD-9). Information from textbooks, journal articles and electronic databases was classified and summarized to create the database.

The 2,800 chemical and biological agents in the database are linked to industrial processes and non-occupational activities. Linkage indicates the potential for exposure to the agent.


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Haz-Map: occupational diseases

The 225 occupational diseases in the database are linked to findings (signs and symptoms of the disease) and hazardous job tasks. Linkage to a hazardous job task indicates an increased risk for significant exposure and subsequent disease.

Linkage between job tasks and jobs or industries indicates an increased likelihood for workers in these jobs or industries to engage in the hazardous job tasks.

In this database, chronic occupational diseases are linked to both jobs and industries, while acute diseases and infectious diseases are linked only to jobs. Cancers are not linked to jobs, industries or findings.


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Haz-Map: Welding, Soldering & Brazing


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Browse Haz-Map

Job Name: Welders, Cutters, Solderers & Brazers

Description: Use hand-welding, flame-cutting, hand soldering or brazing equipment to weld or join metal components or to fill holes, indentations or seams of fabricated metal products. Causes of allergic contact dermatitis include colophony flux, chromates and nickel.

Category: Welding, Soldering & Brazing SOC Code: 51-4121


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High risk job tasks associated with SOC Code: 51-4121

• Arc weld aluminum• Arc weld stainless steel Braze using cadmium-based solder Clean, repair or dismantle oil-fired furnaces or boilers Decompose polymers by welding, burning, brazing or soldering Degrease metal Gas or arc weld on galvanized metal Gas weld or cut in a confined space Machine or weld on cadmium-alloyed or cadmium-plated steel Remove chromate-containing paints by abrasive blasting Remove lead coatings Use manganese-containing welding rods Use solder containing colophony, zinc chloride or ammonium chloride

flux Weld mild steel Weld or machine on beryllium-containing alloys


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HAZ-MAP: Chronic Obstructive Pulmonary Disease (COPD)


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High risk job tasks associated with COPD:

Arc weld aluminum Arc weld stainless steel Grind or cut tiles, stones, concrete, bricks or terrazzo Produced rubber with long-term exposure to curing fumes Remove insulation installed before 1975 Weld mild steel Work in potroom at aluminum smelter Work in tunnel construction with exposure to blasting & diesel

exhaust Worked in foundry with exposure to gases/fumes and mineral

dust Worked in pulp and paper mill with exposures to irritating gases Worked in smelter with exposures to sulfur dioxide and metal

fumes


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The Gig Saw Puzzle: An industrial hygiene solution


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The Gig Saw Puzzle: Prevention


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Chronic Obstructive Pulmonary Disease

in Great Britain (HSE UK)


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NIOSH Occupational Respiratory Disease Surveillance


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NIOSH Occupational Respiratory Disease Surveillance – ICD-10 Codes (1999-Present)


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Pneumoconiosis due to other inorganic dust: Siderosis


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Canadian Institute for Health Information ICD-10-CA Codes


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ICD-10-CA Codes


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THE END


metal fabrication shops general presentation (andew cutz, cih)

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