Special dipping operations requirements

Hardening or tempering tanks must be located as far as practicable from furnaces. Employers should place tanks at the greatest practical distance from heat sources to reduce fire and vapor hazards in accordance with 1910.126(a)(1)(i).

• If layout constraints limit distance, implement other controls (noncombustible floors, vents, alarms) required by the standard.
• Document the rationale for tank placement as part of your hazard assessment.

Yes — hardening or tempering tanks must be on noncombustible flooring. This reduces fire spread and complies with 1910.126(a)(1)(ii).

• Examples include concrete or metal pads designed to resist heat and chemical attack.
• Ensure any seams or penetrations do not compromise the noncombustible surface.

Hardening or tempering tanks must have noncombustible hoods and vents (or equivalent devices) that vent to the outside, and vent ducts must be treated as flues and kept away from combustible materials, especially roofs. See 1910.126(a)(1)(iii).

• Keep ducts clear of combustible construction and route them outside the building.
• Use noncombustible duct materials and provide supports that maintain separation from combustibles.

Each hardening or tempering tank must have an alarm that sounds if the liquid temperature comes within 50 °F (10 °C) of its flashpoint; that temperature is the alarm set point required by 1910.126(a)(2).

• Calibrate and test alarms regularly.
• Keep records of alarm tests and corrective actions taken when alarms trip.

When practicable, each tank must be provided with a limit switch to shut down the conveyor supplying work to the tank. Install a limit switch where it is feasible to automatically stop incoming work to prevent overloading or run-in incidents as stated in 1910.126(a)(3).

• If physical constraints make a limit switch impracticable, document why and apply other engineering or administrative controls to reduce risk.

If the liquid temperature can exceed the alarm set point (within 50 °F of flashpoint), the tank must be equipped with a circulating cooling system. This requirement follows 1910.126(a)(4) together with the alarm requirement in 1910.126(a)(2).

• Design cooling capacity to keep temperature below the alarm set point under foreseeable loads.
• Maintain and test the cooling system per manufacturer guidance and facility procedures.

Yes — when a tank has a bottom drain, that drain may be combined with the oil-circulating system as allowed by 1910.126(a)(5).

• Ensure valves, piping, and controls prevent accidental spills or cross-connections.
• Maintain equipment to prevent leaks and inspect drains regularly.

No — you must not use air under pressure to fill the dip tank or to agitate the liquid in the dip tank, per 1910.126(a)(6).

• Use mechanical pumps or low-pressure circulating systems instead of compressed air to avoid aerosolizing flammable or hazardous liquids.

For flow coating you must use a direct low-pressure pumping system or a gravity tank of 10 gallons (38 L) or smaller to supply paint, and an approved heat-actuated device must shut down the pumping system in case of fire, as required by 1910.126(b)(1).

• Ensure the heat-actuated shutdown device is installed, tested, and maintained.
• Keep documentation of inspections and device testing.

Piping that supplies flow coating must be substantial and rigidly supported to prevent failure and leaks, in line with 1910.126(b)(2).

• Use appropriate materials rated for the coatings and pressures involved.
• Support piping to prevent undue stress at joints and to accommodate thermal expansion.

You must either bond and ground all metallic parts (including rotating parts) and install static collectors, or maintain a conductive atmosphere (for example high relative humidity) in the vapor area for roll coating operations that use flammable liquids with flashpoints below 140 °F (60 °C), as required by 1910.126(c)(1) and 1910.126(c)(2).

• Bonding and grounding should be tested regularly for continuity.
• If using humidity to increase conductivity, confirm the approach is effective for your materials and documented in controls.

You must ensure the condenser or vapor-level thermostat keeps the vapor level at least 36 inches (91 cm) or one-half the tank width, whichever is less, below the top of the vapor degreasing tank, as specified in 1910.126(d)(1).

• Regularly verify the vapor level control and document inspections and calibrations.

When gas is used as a fuel to heat the tank liquid, you must prevent solvent vapors from entering the air-fuel mixture by making the combustion chamber airtight except for the flue opening, per 1910.126(d)(2).

• Seal combustion chambers and inspect seals periodically to avoid explosive mixtures.
• Consider using indirect heating or segregated burners to reduce vapor ingress risk.

The flue must be corrosion-resistant and extend to the outside, and a draft diverter is required if mechanical exhaust is used; additionally, you must not allow the heating element temperature to decompose the solvent or generate excessive vapor, as required by 1910.126(d)(3) and 1910.126(d)(4).

• Use corrosion-resistant materials (e.g., stainless steel) for flues exposed to solvent vapors.
• Monitor heating elements to ensure they operate within safe temperature ranges and have over-temperature protection.

Cyanide tanks must have a dike or other safeguard to prevent cyanide from mixing with an acid if a dip tank fails, in order to avoid releasing toxic hydrogen cyanide, per 1910.126(e).

• Design dikes to contain the maximum foreseeable spill volume and prevent cross-contamination.
• Keep acid storage and cyanide tanks physically separated and labeled to reduce the risk of accidental mixing.

If you spray a liquid over an open-surface cleaning or degreasing tank, you must, to the extent feasible, enclose the spraying operation and use mechanical ventilation that provides enough inward air velocity to prevent the spray from leaving the vapor area, as required by 1910.126(f)(1) and 1910.126(f)(2).

• Use spray enclosures, local exhaust ventilation, and face/respiratory protection as needed.
• Verify inward airflow rates regularly and document performance checks.

Only approved electrostatic equipment may be used, electrodes must be substantial, rigidly supported, and insulated from ground with nonporous, noncombustible, clean, dry insulators; conveyors must support goods being deteared; and goods must not be manually handled during electrostatic detearing, as required by 1910.126(g)(1), 1910.126(g)(2), and 1910.126(g)(3).

• Inspect insulators and electrodes for damage and contamination.
• Use conveyors and automation to eliminate manual handling in the high-voltage area.

Maintain a minimum distance equal to twice the sparking distance between goods being electrostatically deteared and the electrodes or conductors, and display that minimum distance conspicuously on a sign near the equipment as required by 1910.126(g)(4).

• Measure the sparking distance specific to your equipment and double it to set the minimum clearance.
• Keep the sign legible and placed where operators can readily see it.

Electrostatic equipment must have automatic controls that immediately disconnect high-voltage power and signal the operator if ventilation or conveyors fail, a ground or imminent ground occurs in the high-voltage system, or goods come within twice the sparking distance of the electrodes, as required by 1910.126(g)(5) and its subparagraphs 1910.126(g)(5)(i), 1910.126(g)(5)(ii), and 1910.126(g)(5)(iii).

• Test interlocks and automatic shutdowns at intervals recommended by the manufacturer.
• Maintain alarms and document any trips and investigations.

You must use fences, rails, or guards made of conducting material and adequately grounded to separate paint-detearing operations from storage areas and personnel, as required by 1910.126(g)(6).

• Ground these conductive barriers to prevent stray charges.
• Keep access restricted to authorized personnel and post warnings where appropriate.

To protect paint-detearing operations from fire, you must have either automatic sprinklers or an automatic fire-extinguishing system that meets the requirements of subpart L of part 1910, as stated in 1910.126(g)(7)(i) and 1910.126(g)(7)(ii).

• Coordinate fire protection design with local fire codes and the facility fire protection engineer.
• Maintain and test sprinklers or extinguishing systems per applicable standards.

You must provide drip plates and screens to collect paint deposits and clean those plates and screens in a safe location, as required by 1910.126(g)(8)(i) and 1910.126(g)(8)(ii).

• Perform cleaning away from the high-voltage area and flammable material zones.
• Dispose of collected paint in accordance with environmental and hazardous-waste rules.