Printing Operations can be divided into four production processes: Letterpress Printing, Silk Screen Printing, Gravure Printing and Lithographic Printing. All types of printing production pose similar fire and property damage hazards, mainly separation and ventilation, flammable liquids, and management practices revolving around ignition source controls.
Regardless of the printing operation, proper construction, physical separation, and ventilation are recommended. Presses should be located in separate buildings or separated by a 2 hr. fire rated wall or in a room where at least one outside wall has explosion relief (NFPA 68, Standard on Explosion Protection by Deflagration Venting). Floors should be comprised of conductive (non-sparking) concrete and with adequate pitch for liquid draining. Floors above the pressrooms should be liquid tight. Separate ignitable liquid operations (storage, mixing, parts washers, solvent recovery, etc.) from other production areas of the site (press hall, storage, etc.) as per FM Global Property Loss Prevention Data Sheet (FMDS) 7-32, Ignitable Liquid Operations. Provide a 1 hr. fire rated separation between the motor control rooms, electrical/mechanical rooms and other support areas. Continuous ventilation is required throughout.
Letterpress Printing operations fall under three main types: Flat-Bed Printing, Platen Printing and Rotary Printing. Letterpress Printing is typically used for the production of business cards, letterheads, proofs, billheads, forms, posters, announcements, imprinting, embossing and hot-leaf stamping. The working principle of Letterpress Printing includes polymer plates with specific designs that can be printed on negative film. Ink is mixed and supplied into the press via rollers or impression cylinders. Pressure is applied to the surface of the paper substrates; ink generally dries quickly and is then cut into required sizes. Letterpress Printing normally utilizes low-viscosity, fast-drying inks that are based on alcohols, water, hydrocarbon solvents or UV monomers. Typically, water and solvent based inks are more common and contain up to 50% alcohol by volume.
Silk Screen Printing is the least common type of printing compared to the other printing methods. Silk Screen Printing substrates include all types of plastics, fabrics, metals, papers, leather and textiles, Masonite, glass, ceramics, wood and electronic circuit boards. The working principle of Silk Screen Printing operations uses porous mesh screens with an ink-resistance image on the substrate’s surface. The non-imaged areas are blocked by hardened emulsion while images areas are open, allowing the ink to pass through. Silk Printing normally utilizes Plastisol inks, that are high density inks. Water-based discharge inks are also utilized that help removed the color of the fabric on the areas where it is applied and replaced it with its pigments.
Gravure Printing is predominantly used for large batch printing at high speeds. Gravure Printing is commonly used for art, greeting cards, advertising, currency, stamps and wrapping paper. The working principle of Gravure Printing operations revolves around large cylinders with recessed grooves that rotates in an ink bath while a smaller roller (typically rubber) is used to applied pressure as the paper medium passes through. Images are transferred directly onto the paper substrate. Gravure Printing normally utilizes solvent based inks (Class 1A Flammable Liquids, NFPA 30, Flammable and Combustible Liquids Code and NFPA 34, Standard for Dipping, Coating, and Printing Processes Using Flammable or Combustible Liquids). More recently, water-based and vegetable oil based inks have been made available for Gravure Printing operations.
Lithography Printing was originally developed in the late 18th Century and has been updated throughout the years. Modern Lithography Printing is called Offset Lithographic Printing (OLP). Lithographic Printing is primarily used for books, magazine and newspaper. The working principle of Lithography Printing operations are similar to Gravure Printing, where cylinder plates with images or words are wetted first by water, then by the desired ink color. The ink only adheres to the image areas, while the water is attracted to the non-image areas and washes off any ink in these areas. The substrate then passes onto a second cylinder “off-set” called the blanket cylinder. Next, the substrate is inked again as it is sent in between the blanket cylinder and the third cylinder called the impression cylinder. Finally, the substrate is dried in either UV, IR, or ovens. Some modern facilities have introduced an Anti-set-off (ASOS) powder on the blanket cylinder to aid in a quicker drying period. Lithography Printing normally utilizes the highest viscosity inks compared the other printing operations. Ink is oil based and may contain other chemicals to improve temperature stability of pigment molecules in the ink and are highly ignitable.
For all printing operations if the inks used are flammable then all FM Global and NFPA guidelines should be followed and would require extensive risk assessments. If water-based inks are employed, it would result in minimal time for risk assessments. If solvent based inks are used then industry recommended practices and guidelines must be followed for the handling, transfer, storage of flammable liquids and fire protection. Additionally, solvent based inks would involve separating high frequency risk/hazard areas (e.g., printing presses) from areas containing large amounts of combustibles (e.g., storage), adequately designed ventilation and exhaust systems and control of ignition sources.
The major hazards for all printing operations revolve around pre-press operations, printing press operations, ignitable liquids, drying, storage and waste. Pre-press operations may contain the use of photographic chemicals, paper or film to make negatives for the printing plates. Plates are generally made from plastic or rubber and coated with solutions (that can be ignitable) to make certain areas of the plates insoluble in water. Printing press hazardous operations includes vapor emission from volatile organic chemicals, high combustible loading, the use of hydraulic systems and several ignition sources from either static or unrated electrical equipment. Ignitable liquids are used throughout the printing process in inks and dyes, as well as in platemaking (generally a Ferric Chloride solution) and in adhesives and glues. Drying hazards include the use of Heat Transfer Fluids (HTF), high temperatures, vapor release and residue build-up in the dryer exhaust ducts. Depending on the scale of the printing operations, storage can be very hazardous containing large volumes of inks, solvents, printing substrates, finished goods, negative films, polymer plates, roll paper adhesives and more.