Dip Tank Standard, 29 CFR 1910
When you coat metals, strip furniture, repair vehicles, service aircraft or tan leather, dip tanks are a necessary part of the process. The liquid chemicals used in dip tanks are often dangerous, posing both a safety and health risk. These liquids include flammables, corrosives and chronic toxins. OSHA estimates that the majority of facilities that operate dip tanks are small companies with 20 or fewer employees.
In May 1995, President Clinton asked all federal regulatory agencies to review their regulations to determine if they were inconsistent, duplicative, outdated or in need of being rewritten in plain language. In that review, OSHAs dip tank standards 29 CFR 1910.108 and 29 CFR 1910.94 (d) were identified as standards in need of clarification.
The 2 standards became 29 CFR 1910.122 through 29 CFR 1910.126, which did not change the technical substance of the former standards, nor did it modify the regulatory obligations subjected to employers. The updated performance-oriented standard, written in plain language, was designed to facilitate better compliance because it gives employers more compliance options than the previous standards.
29 CFR 1910.122 is the table of contents for sections in 1910.123 through 1910.126. It also contains a summary of the applicable questions and answers asked in each section which are used to qualify compliance.
Note: This document is not the complete dip tank standard, but highlights what is covered in the standard. For the complete standard with all requirements, please see OSHAs 29 CFR 1910 subpart H, sections 122–126. Section 123 of the dip tank standard clarifies who is covered and what operations are covered by this standard.
(a) Does this rule apply to me? (1) This rule (1910.123 through 1910.126) applies when you use a dip tank containing a liquid other than water. It applies when you use the liquid in the tank or its vapor to:
(a)(1)(i) Clean an object;
(a)(1)(ii) Coat an object;
(a)(1)(iii) Alter the surface of an object; or
(a)(1)(iv) Change the character of an object.
(b) What operations are covered?
Examples of covered operations are paint dipping, electroplating, pickling, quenching, tanning, degreasing, stripping, cleaning, roll coating, flow coating and curtain coating.
(c) What operations are NOT covered?
You are not covered by this rule if your dip-tank operation only uses a molten material (e.g., molten metal, alloy, or salt).
Section 124 focuses on the general requirements for dip tank construction and ventilation of dip tanks.
(a) What construction requirements apply to dip tanks?
Any container used as a dip tank must be strong enough to withstand any expected load.
(b) What ventilation requirements apply to vapor areas?
(1) The ventilation that you provide to a vapor area must keep the airborne concentration of any substance below 25% of its lower explosion limit (LEL).
(b)(4) When you use mechanical ventilation, it must conform to the following standards incorporated by reference as specified in 1910.6:
(b)(4)(i) ANSI Z9.2-1979, Fundamentals Governing the Design and Operation of Local Exhaust Systems
(b)(4)(ii) NFPA 34-1995, Standard for Dip Tanks Containing Flammable or Combustible Liquids
(b)(4)(iii) ACGIHs Industrial Ventilation: A Manual of Recommended Practice (22nd ed., 1995); or
(b)(4)(iv) ANSI Z9.1-1971, Practices for Ventilation and Operation of Open-Surface Tanks, and NFPA 34-1966, Standard for Dip Tanks Containing Flammable or Combustible Liquids
(b)(5) When you use mechanical ventilation, it must draw the flow of air into a hood or exhaust duct.
(b)(6) When you use mechanical ventilation, each dip tank must have an independent exhaust system unless the combination of substances being removed will not cause a:
(b)(6)(ii) Explosion; or
(b)(6)(iii) Chemical reaction.
(c)(2) You must ensure that any exhaust air recirculated from a dipping or coating operation using flammable or combustible liquids is:
(c)(2)(i) Free of any solid particulate that poses a health or safety hazard for employees; and (c)(2)(ii) Monitored by approved equipment.
(c)(3) You must have a system that sounds an alarm and automatically shuts down the operation when the vapor concentration for any substance in the exhaust airstream exceeds 25% of its LEL.
(e) What requirements must I follow when an employee enters a dip tank?
When an employee enters a dip tank, you must meet the entry requirements of 1910.146, OSHAs standard for Permit-Required Confined Spaces, as applicable.
(f) What first-aid procedures must my employees know?
Your employees must know the first-aid procedures that are appropriate to the dipping coating hazards to which they are exposed.
(g) What hygiene facilities must I provide?
When your employees work with liquids that may burn, irritate, or otherwise harm their skin, you must provide:
(g)(1) Locker space or other storage space to prevent contamination of the employees street clothes;
(g)(2) An emergency shower and eye-wash station close to the dipping or coating operation. In place of this equipment, you may use a water hose that is at least 4 feet (1.22m) long and at least 3 /4" (18 mm) thick with a quick-opening valve and carrying a pressure of 25 lbs. per square inch (1.62 k/cm) or less; and
(g)(3) At least one basin with a hot-water faucet for every 10 employees who work with such liquids. (See paragraph (d) of 1910.141.)
(i) What must I do before an employee cleans a dip tank?
Before permitting an employee to clean the interior of a dip tank, you must:
(i)(1) Drain the contents of the tank and open the cleanout doors; and
(i)(2) Ventilate and clear any pockets where hazardous vapors may have accumulated.
(j) What must I do to inspect and maintain my dipping or coating operation? You must:
(j)(1) Inspect the hoods and ductwork of the ventilation system for corrosion or damage:
(j)(1)(i) At least quarterly during operation; and
(j)(1)(ii) Prior to operation after a prolonged shutdown.
(j)(2) Ensure that the airflow is adequate;
(j)(2)(i) At least quarterly during operation; and
(j)(2)(ii) Prior to operation after a prolonged shutdown.
(j)(3) Periodically inspect all dipping and coating equipment, including covers, drains, overflow piping and electrical and fire-extinguishing systems and promptly correct any deficiencies;
(j)(4) Provide mechanical ventilation or respirators (selected and used as specified in 1910.134, OSHAs Respiratory Protection standard) to protect employees in the vapor area from exposure to toxic substances released during welding, burning or open-flame work.
(j)(5) Have dip tanks thoroughly cleaned of solvents and vapors before permitting welding, burning or open-flame work on them.
Section 125 explains additional requirements when using flammable or combustible liquids regarding piping and draining.
(a) What type of construction material must be used in making my dip tank?
Your dip tank must be made of noncombustible material.
(b) When must I provide overflow piping?
(1) You must provide properly trapped overflow piping that discharges to a safe location for any dip tank having:
(b)(1)(i) A capacity greater than 150 gallons (568L); or
(b)(1)(ii) A liquid surface area greater than 10 feet (0.95m).
(b)(2) You must also ensure that:
(b)(2)(i) Any overflow piping is at least 3" (7.6cm) in diameter and has sufficient capacity to prevent the dip tank from overflowing;
(b)(2)(iii) The bottom of the overflow connection is at least 6" (15.2cm) from the top of the dip tank.
(c) When must I provide a bottom drain?
(1) You must provide a bottom drain for dip tanks that contain more than 500 gallons (1893L) of liquid, unless:
(c)(1)(i) The dip tank is equipped with an automatic closing cover meeting the requirements of paragraph (f)(3) of this section; or
(c)(1)(ii) The viscosity of the liquid at normal atmospheric temperature does not allow the liquid to flow or be pumped easily.
(c)(2) You must ensure that the bottom drain required by this section:
(c)(2)(i) Will empty the dip tank during a fire;
(c)(2)(ii) Is properly trapped;
(c)(2)(iii) Has pipes that permit the dip tanks contents to be removed within five minutes after a fire begins; and
(c)(2)(iii)(iv) Discharges to a safe location.
(c)(3) Any bottom drain you provide must be capable of manual and automatic operation, and manual operation must be from a safe and accessible location.
(c)(4) You must ensure that automatic pumps are used when gravity flow from the bottom drain is impractical.
Section 126 covers specialty applications for dipping and coating.
In addition to the requirements in 1910.123 through 1910.125, you must also comply with any requirement in this section that applies to your operation.
(a) What additional requirements apply to hardening or tempering tanks?
(a)(1) You must ensure that hardening or tempering tanks:
(a)(1)(i) Are located as far as possible from furnaces;
(a)(1)(ii) Are on noncombustible flooring; and
(a)(1)(iii) Have noncombustible hoods and vents (or equivalent devices) for venting to the outside. For this purpose, vent ducts must be treated as flues and kept away from combustible materials, particularly roofs.
(a)(2) You must equip each tank with an alarm that will sound if the temperature of the liquid comes within 50F (10C) of its flashpoint (the alarm set point).
(a)(3) When practicable, you must also provide each tank with a limit switch to shut down the conveyor supplying work to the tank.
(a)(4) If the temperature of the liquid can exceed the alarm set point, you must equip the tank with a circulating cooling system.
(a)(5) If the tank has a bottom drain, the bottom drain may be combined with the oil-circulating system.
(a)(6) You must not use air under pressure when you fill the dip tank or agitate the liquid in the dip tank.
When these operations use a flammable or combustible liquid that has a flashpoint below 140F (60C), you must prevent sparking of static electricity by:
(c)(1) Bonding and grounding all metallic parts (including rotating parts) and installing static collectors; or
(c)(2) Maintaining a conductive atmosphere (for example, one with a high relative humidity) in the vapor area.
This document is not the complete dip tank standard, but highlights what is covered in the standard. For the complete standard with all requirements, please see OSHAs 29 CFR 1910 subpart H, sections 122-126.
Find even more information you can use to help make informed decisions about the regulatory issues you face in your workplace every day. View all Quick Tips Technical Resources at www.grainger.com/quicktips.
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