Leather manufacturing uses chrome tanning (Cr(III)), surface dyeing and finish coating with flammable solvents (toluene, MIBK, ethyl acetate). Cr(VI) fumes are carcinogenic. NFPA 34 (Dipping, Coating and Printing Processes) defines dip tank separation, 12 ach ventilation and fire protection.
Chrome Bath Risks
- Cr(VI) toxicity: carcinogen (IARC Group 1)
- pH 2-3: corrosive - 316L stainless tank required
- Temperature: 40-50 C - overheating can release H2
- Electrostatic: large agitator surfaces - bonded ground
NFPA 34 Dip Tank
- Tank separation: 1.5 m from other equipment, 3 m from building exterior
- Cover: auto-closes on fire detection
- Overflow: 24 h accumulation capacity
- Drainage: fuel oil and solvent separator
- Floor slope: 1 percent to a containment trench
12 ach Ventilation
- Chemical storage: NFPA 30 12 ach explosion-proof fan
- Paint room: spray booth Class I Div 1 - solvent vapor
- Local exhaust: lip exhaust above chrome tank
- Make-up air: tempered, 90 percent of exhaust
Fire Protection
- Dip tank: cover + CO2 total flooding
- Spray booth: NFPA 33 dry chemical pre-engineered
- Solvent storage: NFPA 13 OH2 0.20 gpm/ft2 sprinkler
- Paint room: NFPA 30 Class III-A flammable liquid
- Portable extinguisher: ABC 6 kg every 15 m
Tannery ventilation with MEP Calc
MEP Calc sizes NFPA 34 12 ach ventilation, local exhaust and make-up air for tannery chrome and solvent areas.
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Sources & Further Reading
NFPA 34, NFPA 33, NFPA 30, OSHA 29 CFR 1910.1026, IARC Monographs Cr(VI). NFPA 34 Dipping and Coating.