Dipping and coating requirements

Your dip tank must be made of noncombustible material. See 1910.125(a) for the requirement.

You must provide properly trapped overflow piping that discharges to a safe location for any dip tank with a capacity greater than 150 gallons or a liquid surface area greater than 10 square feet. See 1910.125(b)(1)(i) and 1910.125(b)(1)(ii).

Overflow piping must be at least 3 inches (7.6 cm) in diameter and have sufficient capacity to prevent the dip tank from overflowing. This is required by 1910.125(b)(2)(i).

Piping connections on drains and overflow pipes must allow ready access to the interior of the pipe for inspection and cleaning. See 1910.125(b)(2)(ii).

The bottom of the overflow connection must be at least 6 inches (15.2 cm) below the top of the dip tank. See 1910.125(b)(2)(iii).

A bottom drain is required for dip tanks that contain more than 500 gallons of liquid unless the tank has an automatic closing cover meeting paragraph (f)(3) or the liquid's viscosity prevents it from flowing or being pumped easily. See 1910.125(c)(1), including 1910.125(c)(1)(i) and 1910.125(c)(1)(ii).

The bottom drain must empty the dip tank during a fire, be properly trapped, allow removal of the tank's contents within five minutes after a fire begins, and discharge to a safe location. See 1910.125(c)(2)(i)–(iv).

Any bottom drain provided must be capable of manual and automatic operation, and the manual operation must be from a safe and accessible location. See 1910.125(c)(3).

Automatic pumps must be used when gravity flow from the bottom drain is impractical. See 1910.125(c)(4).

A conveyor system used with a dip tank must shut down automatically if there is a fire or if the ventilation rate drops below what is required by paragraph (b) of 1910.124. See 1910.125(d)(1) and 1910.125(d)(2).

All electrical wiring and equipment in each vapor area and any adjacent area must conform to the applicable hazardous (classified)-area requirements of subpart S of 29 CFR 1910. See 1910.125(e)(1)(i) and the general 1910 listing for subpart references.

You must ensure there are no flames, spark-producing devices, or surfaces hot enough to ignite vapors in each vapor area and any adjacent area. See 1910.125(e)(1)(ii).

Any portable container used to add liquid to the tank must be electrically bonded to the dip tank and positively grounded to prevent static electrical sparks or arcs. See 1910.125(e)(2).

A heating system used in a drying operation that could cause ignition must be installed in accordance with NFPA 86A-1969, have adequate mechanical ventilation that operates before and during drying, and shut down automatically if any ventilating fan fails to maintain adequate ventilation. See 1910.125(e)(3)(i)–(iii) and note NFPA reference via 1910.6.

Rags and other material contaminated with dipping or coating liquids must be placed in approved waste cans immediately after use, kept out of vapor areas as practicable, and waste can contents must be properly disposed of at the end of each shift. See 1910.125(e)(4)(i)–(iii).

Smoking is prohibited in a vapor area and a readily visible "No Smoking" sign must be posted near each dip tank. See 1910.125(e)(5).

You must provide the fire protection in paragraph (f) for any dip tank with a capacity of at least 150 gallons or a liquid surface area of at least 4 square feet, and for any hardening or tempering tank with a capacity of at least 500 gallons or a surface area of at least 25 square feet. See 1910.125(f)(1)(i)–(ii).

For every vapor area you must provide manual fire extinguishers suitable for flammable and combustible liquid fires that conform to 1910.157 and an automatic fire-extinguishing system that conforms to subpart L of 29 CFR 1910. See 1910.125(f)(2)(i)–(ii).

Yes — you may substitute a cover closed by an approved automatic device if the cover can also be activated manually, is noncombustible or tin-clad with locked joints, and is kept closed when the dip tank is not in use. See 1910.125(f)(3)(i)–(iii).

You must maintain the liquid temperature below the liquid's boiling point and at least 100 °F (37.8 °C) below the liquid's autoignition temperature. See 1910.125(g)(1)–(2).

A "safe location" is a place where the discharged liquid will not create a fire, explosion, environmental, or worker exposure hazard and will not flow back into the dip area; the standard requires overflow and bottom drains to discharge to a safe location. See 1910.125(b)(1) and 1910.125(c)(2)(iv).

You must provide piping that permits the dip tank's contents to be removed within five minutes after a fire begins; that means designing drains/pumps and valves so the required flow and access are available to meet the five-minute removal requirement. See 1910.125(c)(2)(iii) and related ventilation and fire-control requirements in 1910.125(e).

You must provide adequate mechanical ventilation that operates before and during the drying operation, and the heating system must shut down automatically if any ventilating fan fails to maintain adequate ventilation. See 1910.125(e)(3)(ii)–(iii).

Bonding and grounding a portable container to the dip tank is required to prevent static electricity sparks or arcs that could ignite vapors; this is specified in 1910.125(e)(2) and complements the ignition-source controls in 1910.125(e)(1).