Dipping and Coating Operations (Diptanks)Chapter 296-835, WAC |
Effective Date: 10/01/02 |
Additional requirements for dip tanks using flammable or combustible liquids |
 For
printing |
Important:
This section applies to:
- Flammable and combustible liquids (flashpoint below 200°F)
- Liquids that have a flashpoint of 200°F (93.3°C) or
higher if you:
- - Heat the liquid
- - Dip a heated object in the tank
|
|
Reference: Store flammable and combustible liquids as required by Flammable and Combustible Liquids, WAC 296-24-330, in the General Safety and Health Standards. |
Your responsibility:
Safeguard employees working with dip tanks containing flammable or combustible liquids
You must
CONSTRUCTION
|
FIRE PROTECTION
|
ELECTRICAL WIRING AND EQUIPMENT AND SOURCES OF IGNITION
|
HOUSEKEEPING
|
HEATING LIQUID
|
HEAT DRYING
|
CONVEYORS
|
CONSTRUCTION
Include additional safeguards when constructing dip tanks.
You must
(1) Make sure the dip tank, drain boards (if provided), and supports, are made of noncombustible material.
(2) Make sure piping connections on drains and overflow pipes allow easy access to the inside of the pipe for inspection and cleaning.
Provide overflow pipes.
You must
- Provide an overflow pipe on dip tanks that:
- - Hold more than 150 gallons of liquid
- OR
- - Have more than 10 square feet of liquid surface area
- Make sure the overflow pipe is:
- - Properly trapped
- - Able to prevent the dip tank from overflowing
- 3 inches or more (7.6 cm) in diameter
- Discharged to a safe location.
|
|
Note: Discharged to a safe location could be a:
|
You must
- Make sure the bottom of the overflow pipe is at least 6 inches (15.2 cm) below the top of the tank.
|
|
Note: The overflow pipe should be large enough to remove water applied to the liquid surface of the dip tank from automatic sprinklers or other sources in the event of fire. Smaller dip tanks should be equipped with overflow pipes, if practical. |
Provide bottom drains.
|
|
Exemption A bottom drain isn't required if:
|
You must
- Provide a bottom drain on all dip tanks that hold more than 500 gallons of liquid.
- Make sure the bottom drain:
- - Is properly trapped
- - Will empty the dip tank during a fire
- - Has pipes large enough to empty the tank within 5 minutes
- - Uses automatic pumps if gravity draining isn't practical
- - Is capable of both manual and automatic operation
- - Discharges to a safe location
|
|
Note Discharges to a safe location could be a:
|
You must
- Make sure manual operation of the bottom drain is performed from a safe and easily accessible location.
FIRE PROTECTION
Provide fire protection in the vapor area.
You must
- Provide a manual fire extinguisher near the tank that is suitable for putting out flammable and combustible liquid fires.
Provide additional fire protection for large dip tanks.
You must
- Provide at least one automatic fire extinguishing system or an automatic dip tank cover if the tank:
- - Holds 150 gallons or more of liquid
OR - - Has 4 square feet or more of liquid surface area.
- Make sure automatic fire extinguishing systems or automatic dip tank covers meet the requirements of Table 1.
|
|
Exemption An automatic fire extinguishing system or an automatic dip tank cover isn't required for a hardening or tempering tank that:
|
Table 1: Automatic Fire Protection System Requirements
| IF YOU PROVIDE... |
THEN YOU MUST... |
| An automatic fire extinguishing system |
|
| A dip tank cover |
|
|
|
Reference Automatic fire extinguishing systems have specific requirements. See:
|
ELECTRICAL WIRING AND EQUIPMENT AND SOURCES OF IGNITION
Prevent static electricity sparks or arcs when adding liquids to a dip tank.
You must
- Make sure any portable container used to add liquid to the tank is:
- - Electrically bonded to the dip tank
- - Positively grounded.
Control ignition sources.
You must
(1) Make sure the vapor areas and adjacent areas don't have any:
- Open flames.
- Spark producing devices.
- Heated surfaces hot enough to ignite vapors.
(2) Use explosion-proof wiring and equipment in the vapor area.
|
|
Reference: Electrical wiring and equipment has to meet the requirements of the applicable hazardous (classified) location. See Hazardous (classified) Locations, WAC 296-24-95613. Electrostatic equipment has specific electrical requirements. See WAC 296-835-13010. |
You must
(3) Prohibit smoking in any vapor area:
- Post an easily seen "no smoking" sign near each dip tank.
Provide safe electrical wiring and equipment where the liquid can drip or splash.
You must
- Make sure all electrical wiring and equipment in the
vapor area is approved for areas that have:
- Deposits of easily ignited residue
- Explosive vapor
|
|
Exemption This doesn't apply to wiring that is:
|
HOUSEKEEPING
Keep the area around dip tanks clear of combustible material and properly dispose of waste.
You must
(1) Make sure the area surrounding dip tanks is:
- Completely free of combustible debris
- As free of combustible stock as possible.
(2) Provide approved metal waste cans that are:
- Used for immediate disposal of rags and other material contaminated with liquids from dipping or coating operations
- Emptied and the contents properly disposed of at the end of each shift.
HEATING LIQUID
Make sure heating the liquid in your dip tanks doesn't cause a fire.
You must
- Keep the temperature of the liquid in the dip tank:
- - Below the liquid's boiling point
- - At least 100°F below the liquid's autoignition temperature.
HEAT DRYING
Make sure a heating system used for drying objects doesn't cause a fire.
You must
- Make sure the heating system used in a drying operation that could cause ignition:
- - Has adequate mechanical ventilation that operates before and during the drying operation
- - Shuts down automatically if a ventilating fan fails to maintain adequate ventilation
- - Is installed as required by NFPA 86-1999, Standard for Ovens and Furnaces.
|
|
Note Some, or all, of the consensus standards (such as ANSI and NFPA) may have been revised. If you comply with a later version of a consensus standard, you will be considered to have complied with any previous version of the same consensus standard. |
CONVEYORS
Make sure conveyor systems are safe.
You must
- Make sure the conveyor system shuts down automatically if:
- - The ventilation system fails to maintain adequate
ventilation
OR - - There is a fire.
