Accident Prevention Manual for Business & Industry: Engineering & Technology 13th edition

1. Accident Prevention Manual for Business & Industry: Engineering & Technology 13th edition National Safety Council Compiled by Dr. S.D. Allen Iske, Associate Professor University of Central Missouri

2. CHAPTER 25 HOT WORKING OF METALS

3. Hazardous Materials • Dusts, solvents, and other materials present a health hazard in foundries. • Dust is generated in many foundry processes and presents a twofold problem: • Cleaning to remove deposits • Control at the point of origin to prevent further dispersion and accumulation • Vacuum cleaning is the best way to remove dust in foundries. • Once dust has been removed, prevent further accumulation by using local exhaust systems (LEV) that remove it at the point of origin.

4. Hazardous Materials (Cont.) • Solvents: evaluate each solvent on the basis of its chemical ingredients • Proper labeling, substituting less hazardous for more hazardous chemicals, limiting the quantities in use, and using other methods of control can help minimize the toxic and flammable hazards involved in using solvents. • Other materials: many metal resins, and other substances present safety and health hazards

5. Hazardous Materials (Cont.) • Other hazardous materials that are found in various stages and locations of hot metal operations include: • acrolein • beryllium • carbon as sea coal • carbon monoxide (CO) • chromium • fluorides • lead • magnesium dust or chips • manganese • phosphorus • resins and resin dusts • silica • sulfur dioxide

6. Hazardous Materials (Cont.) • Iron-oxide: fumes and dusts are created during melting, burning, pouring, grinding, welding, and machining of ferrous castings • Use LEV to vent these fumes.

7. Medical Program • Baseline physical examinations, including chest x-rays, audiometric tests, and pulmonary function tests • Periodic physical examinations to detect incipient disease and to help reclassify workers as needed • Adequate first aid facilities and employee training in first aid • Observe regulatory requirements if respirators must be worn • Industrial hygiene monitoring where needed

8. Medical Program (Cont.) • Industrial hygiene equipment, such as a hand-held meter that detects minerals in solution, are extremely helpful in identifying metal contaminants of industrial effluents and water quality. • It can measure a wide concentration range, meeting various international and regulatory standards.

9. Medical Program (Cont.) • Ensure employees are aware of specific hazards to which they may be exposed and the proper control or emergency responses to those hazards. • Make Safety Data Sheets (SDSs) available to all employees.

10. Personnel Facilities • Encourage frequent washing with soap and water, and install adequate facilities. • Coreroom workers whose hands and arms may be exposed to sand and core oil mixtures are candidates for dermatitis. • Prolonged contact with oil, grease, acids, alkalis, and dirt can produce dermatitis. • Reference industrial sanitation standards. • Sanitary food preparation and service is especially important in nonferrous foundries. • Prohibit eating in work areas.

11. Work Environment in Foundries • Good housekeeping, ventilation, and light help maintain a safe and healthy work environment. • Proper inspections, maintenance, and fire protection increase workers’ safety in foundries. • Housekeeping • Clean machines and equipment after each shift, and keep them reasonably clean during the shift. • Place all trash in the proper trash bins. • Keep the floors and aisles in the work area unobstructed. • Properly stack and store materials.

12. Work Environment in Foundries (Cont.) • Floor loading • Many buildings are used for purposes for which they were not designed. • Deadweight of platforms and lift trucks introduce floor load problems. • Overhead cranes and hoists from wood ceiling joists severely taxes roof and floor members. • Insurance engineers or local building inspectors can help determine safe floor load limits.

13. Work Environment in Foundries (Cont.) • Ventilation • Control of air contaminants is the primary purpose of ventilation in foundries. • The need for ventilation may be determined by one of more of the following: • Federal, state, and local regulations or standards • Comparison with similar operations in a like environment • Collection and analysis of representative air samples taken by qualified personnel in the breathing zone of workers

14. Work Environment in Foundries (Cont.) • Noise control • Controlling excessive levels of noise, more than 85dBA, may sometimes be difficult. • Engineering is not always possible because of a lack of technology or is impractical. • Develop a hearing conservation program that provides approved hearing protection for each worker. • Minimize exposure to identified high-noise-level hazards.

15. Work Environment in Foundries (Cont.) • Lighting • Good lighting is difficult to achieve. • Where craneways are used, light fixtures must be placed high and at considerable distances from work areas. • Nevertheless provide good lighting for each work area.

16. Work Environment in Foundries (Cont.) • Inspection and maintenance • Follow standard inspection and maintenance procedures in foundries. • Carefully select maintenance personnel. • Train them in safe practices, especially in procedures for locking out controls and isolating other energy sources.

17. Work Environment in Foundries (Cont.) • Fire protection • Make periodic fire inspections. • Perform emergency fire fighting drills. • If a fire brigade is present, it will aid the safety program by keeping its members, as well as other employees in the foundry, safety conscious.

18. Work Environment in Foundries (Cont.) • Facility structures • Entrances and exits—all doors should have an eye-level window opening. • Stairways: provide handrails, standard guardrails, and toeboards for stairs having four or more risers. • Floors and pits: install special types of flooring where explosion hazards exists; keep clean and dry. • Galleries: provide galleries with solid, leak-proof floors. • Gangways and aisles: should be firm enough to withstand daily traffic.

19. Work Environment in Foundries (Cont.) • Compressed air hoses • Do not use air hoses to clean clothes. • Improper use and “horseplay” have caused severe injuries to internal organs and eardrums. • Reduce air to less than 30 psig. • Install whip checks at all joints. • Prohibit blowing and brushing sand from new castings without regard for dust clouds produced. • Substitute vacuum methods when possible. • Train workers on the safe use of air hoses.

20. Materials Handling in Foundries • General safe working recommendations • Instruct workers in the safe methods of manual and mechanical materials handling. • Provide PPE such as eye protection, safety hats, face shields, and gloves. • Plan the sequence and method of handling materials to eliminate unnecessary handling. • Safeguard mechanical devices and set up inspection procedures to ensure proper maintenance. • Keep good order at storage piles and bins, and pile materials properly. • Keep ground and floor surfaces level. • Install side stakes or sideboards on tramway or railroad cars to prevent materials from falling off. • Chock railroad cars and flag tracks.

21. Materials Handling in Foundries (Cont.) • Sand, coal, and coke • Prevent falls through hoppers while unloading bottom-dump railroad cars with fall protection. • Be sure observers are on the scene and prepared to summon help in emergencies. • Use safety ratchet wrenches for hopper doors to keep the doors from swinging and striking workers. • Prevent hand and foot injuries by using safety car movers instead of ordinary pinch bars to spot cars by hand. • To reduce cave-ins of loose material, prohibit the undermining of piles and avoid overhangs. • Prevent electric shock by grounding portable belt-conveyor loaders. • To keep dump cars under repair from being moved, use locking switches and car chocks.

22. Materials Handling in Foundries (Cont.) • Ladles • Provide a manually operated safety lock and suitable covers for portable ladles. • Thoroughly dry out and heat ladles before use. • Provide LEV to control vapors and fumes. • Ensure that the ladle is suited for its intended operation and make necessary adjustments.

23. Materials Handling in Foundries (Cont.) • Hoists and cranes • Require preventive maintenance program. • Gear the program to ensure that the operation is much safer than simply to comply with minimal regulations. • Conduct inspections on a weekly basis by trained specialists. • Nondestructive testing (ultrasonic) may be required to locate cracks and other issues.

24. Materials Handling in Foundries (Cont.) • Conveyors • Conveyors are used to carry sand to and from the mixing room. • An endless conveyor is used to handle molds. • When installing a system, guard shear points, crush points, and moving parts. • Where conveyor systems run over passageways and working areas, protect employees beneath them with screens, grating, or guards. • Guarding should be strong enough to resist the impact of the heaviest piece handled.

25. Materials Handling in Foundries (Cont.) • Storage • Store materials and equipment not in regular use in a safe, orderly manner on level and firm foundations. • When removing equipment and materials from floor level or from storage piles, do not undermine piles and cause cave-ins. • Cover bottom feeding hopper bins. • Use racks and shelves to store patterns and provide keepers. • Store flammable liquids in accordance with NFPA 30. • Ensure good lighting and floor conditions in storage areas.

26. Materials Handling in Foundries (Cont.) • Slag disposal • Design furnaces and pits with removable receptacles into which slag and kish (separated graphite) may flow or be dumped. • Unless disposed of in the molten state, provide enough receptacles so slag can solidify before dumping. • Use slag or cinder pots to decrease slag pit accumulation. • The pots can be set aside for cooling and eliminate explosion dangers. • Dump where there is absolutely no water or dampness. • Water might cause an explosion if some slag is still molten. • Before breaking up slag allow it to stand for several hours.

27. Cupolas • Definition: Vertical cylindrical furnaces used to melt iron • Charging • Dangers are principally confined to handling material. • Never unevenly load or overload barrows or buggies. • Break open scrap cylinders, tanks, and drums before charging to prevent an explosion. • Install railings or other safeguards underneath the elevators, machines, hoists, and cranes.

28. Cupolas (Cont.) • Charging floor • Use bolted, heavy steal plates. • Install brick flooring near the furnace to avoid extremely hot steel flooring. • Observe good housekeeping. • Construct railings from angle iron at 42 in. high, and 4-in. toeboards around all floor openings. • Place guardrails across the charging opening.

29. Cupolas (Cont.) • Carbon monoxide (CO) • Is generated during some cycles in the operation. • CO is an explosion hazard if it gets into the wind boxes and blast pipes. • Supply adequate ventilation in the back of the cupola, and open two or more tuyeres after the blowers are shut down. • Locate CO indicators around the cupola that light and give a loud sound. • If CO concentration is continually above 200 ppm, an engineering assessment should be considered. • OSHA 8-hour TWA is 35 ppm and the ceiling limit is 200ppm.

30. Cupolas (Cont.) • Blast gates • Blast Gates and explosion doors are successfully used to prevent damage from gas explosions. • Often placed in front of tuyeres so fresh air can enter when the blowers are down. • Never close them until the blast has entered the wind box and driven out all gas. • Equip positive-pressure blowers with safety valves. • Every cupola should have at least one safety tuyere, with a small channel.

31. Cupolas (Cont.) • Tapping out • Operators should not thrust the bott directly into the stream of metal. • Dropping the cupolas bottom doors • Place temporary supports under the bottom doors. • One of the best methods for doing this is to use a block and tackle with a wire rope and chain leader attached to the props that support the doors. • Carefully inspect beneath the cupola for water. • Have one worker check the danger zone and warn nearby employees with a horn or other signal.

32. Cupola (Cont.) • Suggested method of raising the bottom doors of the cupola by mechanical means. • Only careful and experienced workers should repair a cupola’s lining. • A screen placed over the charging door prevents falling objects from dropping on workers repairing cupola linings.

33. Crucibles • The principal danger in handling refractory clay crucibles is that one may break when full of molten metal. • Have a trained inspector check all new crucibles for cracks, thin spots, and other flaws. • Return to the manufacturer those showing signs of dampness. • Examine the packages and the car in which they were shipped to find out whether or not they were exposed to moisture in transit.

34. Crucibles (Cont.) • Storing • Store in a warm dry place. Generally best in an oven on top of a core oven, or some other point where waste heat can be used • Annealing process • Crucibles are heated over 8–10 hours before use. • Do not allow crucibles to cool before they have a charge. • Moisture in walls of crucibles is quickly converted into steam and could become a crack or pinhole.

35. Crucibles (Cont.) • Charging • Proper care of crucibles is good economy as well as good safety. • To protect the crucibles lining and structure, establish a process for cleaning. • Charge them carefully, do not throw in ingots with such force that they bend the bottom walls of the crucible out of shape. • At white heat, they are soft and easily forced out of shape; handle with great care.

36. Crucibles (Cont.) • Handling • Select tongs of the proper size and shape. • Never drive tong rings down tight with a skimmer. • Avoid ramming the fuel bed around a crucible. • Where possible, use a mechanical device to remove heavy crucibles, those exceeding 100 lbs. • Observe safe operating practices of hoists when using air or electric hoists to move large crucibles.

37. Ovens • Principal hazards in the construction and operation of core ovens and mold-drying ovens are excessive smoke, gas, and fumes. • Other unsafe conditions are unprotected firing pits; unguarded vertical sling doors or their counterweights, which may drop on workers; and flashbacks from fireboxes. • Guard firing pits. • Install safe vertical sliding doors, wire ropes and chains, sturdy fastenings. • Thoroughly inspect all sliding doors at frequent intervals.

38. Oven Ventilation • Where fumes, gases, and smoke are emitted from drying ovens, install ducts and exhaust fans near the ovens door’s hoods and Install the proper size flues to prevent flashbacks. • Equip core ovens with explosion vents. • Lightweight panels may be installed on top of the oven, or the oven may have hinged doors with explosion latches. • Larger ovens should have forced-draft ventilation. • Interlock the ventilation system with the gas supply through a time relay that allows for three changes of air in the oven before burners are lit.

39. Oven Inspection • Before core ovens are lit, they must be thoroughly inspected. • Only trained and qualified personnel should do this work. • Establish an inspection and preventive maintenance program for core ovens. • The first step of an inspection should always be to shut off the main valve that controls the fuel supply and check the pilot lights before entering to make sure they are off.

40. Foundry Production Equipment • On production-line equipment, fully guard moving parts and other common machine hazards in accordance with standard practices. • Ground electrical equipment to eliminate shock hazards. • Allow repairs only on equipment that is locked in the OFF position and after all other sources of energy have been eliminated. • Observe LOTO procedures for operations that require an employee to enter for cleaning or repairs.

41. Foundry Production Equipment (Cont.) • Sand mills and dough mixers • Principal danger exists when operators reach in for samples of sand or attempt to shovel out sand while the mill is running. • In doing so, they may be caught and pulled into the mill. • Guard them so that entry into either device is limited. • Train employees in safe operation of both machines.

42. Foundry Production Equipment (Cont.) • Sand cutters • Throw sand and pieces of metal with bullet-like force. • Guard so that efficiency of the operation is not reduced or give operators proper PPE if guarding is not feasible. • Sifters • Guard with enclosures or angle iron pipe railings. • Place controls within reach of operators. • Anchor portable sifters.

43. Foundry Production Equipment (Cont.) • Molds and cores • The principal hazards in hand molding and core making include letting flasks down on feet, pinching fingers between flasks, dropping heavy core boxes on feet, cutting hands on nails and other sharp pieces of metal in the sand, and stepping on nails. • Minimize hand and foot injuries by training workers to handle flasks and core boxes properly and to wear foot protection with stout soles. • Screening or magnetic separation to remove nails and other sharp metal from the sand is also essential.

44. Foundry Production Equipment (Cont.) • Molds and cores • In general molding and core making, gagger rods and core wires are cut, straightened, and bent using hammers and cutting sets, which can create flying pieces of metal and dirt. • Brace heavy cores in large molds to keep the core from toppling over. • Prohibit work underneath molds suspended from cranes. • Vent molds properly to avoid explosions during pouring.

45. Foundry Production Equipment (Cont.) • Molding machines • Three types of molding machines are used in foundries: straight, semi-auto, and auto. • Equip all molding machines with two-hand controls for each operator. • On automatic molding machines, install shields or apron-type metal guards. • The carry-out person should stand clear of the squeeze at the back of the machine. • Operators should never touch the frame while it is moving.

46. Foundry Production Equipment (Cont.) • Core-blowing machines • Straight, semiautomatic, and automatic core-blowing machines are used in foundries • On semi-auto and auto machines, guard core-box push cylinders, counterweight cable pulleys, wheel guide, and table-adjusting footpads. • Install an automatic barrier guard between the operator and machine. • Equip auto and semi-auto machines with double-solenoid valves, and maintain the slide valve well.

47. Core-Blowing Machines • To prevent sand blows, maintain parting lines in good condition. • Figure 25–7 of a core box shows a rubber dike seal, which prevents sand blows and abrasion of the box.

48. Flasks • Iron or steel are preferable to wood. • Discard defective flasks immediately. • Have competent inspectors inspect flasks at frequent intervals. • Flask trunnions should have end flanges at least twice the diameter of the trunnions to minimize the danger of hooks slipping or jumping. • Large flasks should have loop handles. • Design trunnions and handles with a safety factor of at least 10.

49. Foundry Production Equipment • Sandblast rooms: Should be dust-tight and workers should wear air supplied respirators when working in them. • Tumbling barrels: Need frequent care to be kept dust-tight. • Shake-out machines: Present the danger of hands and feet being crushed or arms and legs being broken. Steel-toed boots are recommended.

50. Cleaning and Finishing Foundry Products • Have qualified personnel mount and change abrasive grinding wheels. • Keep required wheel guarding intact. • Speed-test new wheels before allowing them to be used on the job. • Require operators to wear full PPE for eyes, face, hands, and feet. • Dust generated by abrasive wheels is a potential health hazard. • Keep the space around the machines dry, clean, and as free as possible of castings and other obstructions.