Tire Manufacturing

Before being added to the mixer the, raw rubber may need to be cut into small pieces on a bale cutter or guillotine. Ingredients are mixed together and fed into an enclosed mixing chamber via a feed hopper and mixed by the shearing action of two winged rotors and the walls of the mixing chamber (e.g., Banbury mixers). The final process of Banbury mixers is extrusion that involves forcing uncured rubber through a die under pressure to form a shaped profile or sheet. Rotating knives (or die face cutters) can then convert extruded material into pellets or slugs for further processing. Rubber can be dumped direct from an internal mixer into an extruder below it. The major hazards with Banbury mixers and extrusion are the use of ignitable liquids or powder (e.g., organic peroxides, sulphurs, azodicarbonamide, calcium and zinc stearates), dust explosion hazards in powder handling, hydraulic oil hazards and mechanical breakdown of extruders.

Tire production begins with calender machines that have several horizontal rolls heated or unheated through which rubber is passed under extreme pressure. Rubber sheets are created as per required thickness, and then receive an additional coat layer of liner or ply onto the rubber compounds. The liners or ply are treated with solvents to achieve a good bond with rubber in addition to drying in a hot air oven prior to coating. The major hazards associated with calendaring is the use of flammable solvents, risk of static charges during the rolling states, and heated ovens.v

Carcass assembly and belt assembly occur concurrently. Carcass assembly involves the inner liner (thin airtight rubber sheet) coated in a ply textile rubber compound. Next beads are added via steel wire covered in rubber compound wound into a ring. Ply layers are then turned up around the beads and rubber compounds forming the sidewalls, then sides are turn down. Belt assembly and carcasses are pushed into each other in the last step and are joined together using compressed air. At this point, tire production is completed, and tires are called “green tires.”

Tire assembly involves placing new formed green tires in a mold and vulcanizing them at a temperature of over 340°F. The tire leaves the vulcanized station as a patterned, finished tire. After the mold is closed, a bladder is inflated inside the green tire which presses it against the mould from either high-pressure steam or hot water. Depending on the tire type and size, vulcanization takes approximately 10 min. at temperatures between 340 to 390°F, at a pressure of about 320 psi (22 bar).

Tire composition traditionally includes nine layers, from inside to outside – inner liner, carcass ply, lower bead area, beads, sidewall, casing ply, belts and tread.

The main hazards involved with tire manufacturing includes the use of ignitable liquids in the compounding stage, storage of finished tires and combustible dust (from re-treading operations). Ignitable liquids utilized in tire manufacturing are highly hazardous and industry recommended best practices and guidelines should be followed for the handling, transfer, storage of flammable liquids. For storage areas, storage limitations should be followed as recommended in the standards considering storage type, pile dimensions aisle width and clearance to ceiling. In addition, an effective emergency response plan facilitating early discovery, prompt employee action coupled with adequate sprinkler protection will make it possible to control fires at the early stages.

methods minimize the amount of space needed for storage as well as the amount of surface area exposed in a fire. Tires are also more stable as they are interlocked in one of the three storage patterns.

Automatic fire protection for the tire storage greatly depends on storage height and height of the building. NFPA recognizes tire manufacturing as an Ordinary Hazard Group 2 occupancy (rubber processing). Tire storage is very demanding. Additional factors that should be noted during the installation or inspection of automatic sprinkler protection is the use of permanent or portable racks. Additionally, both NFPA and FM Global require that protection be provided for steel columns within storage areas. NFPA 13, Standard for the Installation of Sprinkler Systems, states that storage between 15 to 20 ft., one sidewall sprinkler directed to one side of the column at the 15 ft. level is required. Likewise, if storage height exceeds 20 ft. that two sidewall sprinklers, one at the top and the other at the 15 ft. level are required.

Overall superior administration of management programs is critical to prevent large losses. Risk Logic can recommend and help develop preventive maintenance and property loss control programs at your facility. Please contact us to schedule a property survey at your facility by one of our engineering specialists.

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