DOW Caustic Soda Solution

General Storage System Guidelines

Caustic soda solution users are responsible for building and maintaining a properly designed storage and handling system, which meets applicable safety and regulatory requirements. Each caustic soda solution user is responsible for design and implementation of a storage and handling system that is suitable for its individual facility.

In designing a storage and handling system for caustic soda solution, caustic soda solution users should be mindful of the following:
  • Caustic soda solution is highly corrosive and can be hazardous to personnel.
  • The viscosity of 50% caustic soda solution increases rapidly when its temperature falls below 65°F (16°C).
  • The weight of 50% caustic soda solution is 1.5 times that of an equal volume of water.

Eyewash fountains and safety showers should be conveniently located and readily accessible to personnel in the unloading area and in other areas where maintenance or processing could expose workers to caustic soda solution. Safety showers should be located directly above the eyewash fountains. It is recommended that a horn or other such alarm device be installed at the safety shower so that it can be activated to summon help if use of the safety shower and/or eyewash fountain becomes necessary. Self-draining and heated safety showers and eyewash stations may be required in freezing conditions. Safety showers and eyewash fountains should be tested frequently and especially before each unloading operation.

Users should follow all Federal, State, Provincial and/or local laws, regulations and rules for handling and storage of caustic soda solution.

Tank areas and pumps should be marked with warning signs at all entry points stating "Danger! Caustic Soda — Authorized Personnel Only." Governmental regulations may require additional labeling.

General Storage Guidelines for 50% Caustic Soda Solution

  • Product should be stored between 85° to 100°F (29° to 38°C).
  • Over time, precipitation of calcium and magnesium hydroxide, carbonates and oxalates will occur. A 2 to 4 year out-of-service tank cleaning schedule is recommended.
  • Tank discharge should be elevated at least 1-foot (30-cm) above the tank bottom to minimize entrainment of sediment.
  • A second tank discharge and a manway at the bottom of the tank for cleaning is recommended.
  • Tank inlet should be above the highest anticipated tank level with an inlet dip pipe, which extends below the lowest anticipated tank level to prevent splashing of the caustic soda solution.
  • Splashing or freefalling liquid, leaking pump suction gaskets, etc. will enhance additional carbon dioxide absorption resulting in the formation of insoluble sodium carbonate. These situations should be avoided.
  • Tank inlet should have a syphon break and be opposite the discharge line.
  • A 100% containment dike should be built around the storage tank.
  • It is recommended that an all Alloy-20 material of construction plug valve be used as the first valve on the tank.
  • A continuous tank level measurement device should be installed. High level and overflow alarms should be installed on each storage tank.
  • Mild steel, butt-welded tanks are suitable for caustic storage below 120°F (49°C).
  • If the application is iron sensitive, tank and pipes should be lined.
  • For an internal tank heating system, a nickel bayonet-type heat exchanger is recommended.
  • For an external heating system, a heat exchanger with circulating pump is recommended.
  • Redundant temperature sensors should be installed for temperature control.
  • High temperature alarms should be included.
  • Tanks should be vented to atmosphere and the vent line routed to within 3-feet (0.9 meter) of grade. The vent line should include a syphon break.
  • Tanks and pipes should be insulated and traced to prevent the caustic soda solution from freezing.
  • The entire piping system should be free draining.
  • Pipe and fittings should be seamless carbon steel, butt-welded schedule 40.
  • Electric heat tracing is recommended and preferred over steam tracing.
  • Centrifugal pumps with wetted parts made of Alloy 20 are recommended.
  • Pumps should be equipped with mechanical seals. If dilution of caustic is a concern, a double mechanical seal or repeller equipped seal-less pump should be considered.
  • Aluminum, magnesium, zinc, tin, chromium, bronze, brass, copper, and tantalum are incompatible with caustic soda solution and must not be used for wetted parts used in equipment such as tanks, pumps, piping, instrumentation, etc.
  • Galvanized (zinc coated) materials should not be used in caustic soda solution storage and process areas.

For additional information on caustic soda solution storage, review The Chlorine Institute, Inc. Pamphlet 094 "Sodium Hydroxide Solution and Potassium Hydroxide Solution (Caustic): Storage Equipment and Piping Systems." This pamphlet and additional resource materials can be purchased through the Chlorine Institute web site or send your request via fax to (703) 741-6068.

The information contained above is supplemental to the Internet Disclaimer and is not intended to be all-inclusive as it relates to use, handling, storage, disposal and all other described activities. Recipients must make their own determination of suitability and are responsible for compliance with all applicable federal, state, provincial, municipal laws and/or other regulations. This information is offered solely for your consideration and verification and in no event will The Dow Chemical Company be responsible for damages of any nature whatsoever resulting from the use or reliance upon this information or the product to which this information pertains.