Bottom Unloading by Pumping

Unloading by this procedure is recommended for 50% caustic soda solutions.

Personal protective clothing and equipment must be worn throughout the preparation steps, as well as during unloading. For specific information, see the Personal Protective Equipment section.

A typical layout for unloading caustic soda solution through the bottom outlet valve using a pump is illustrated here:

Safety showers and eyewash fountains should be conveniently located, clearly marked and readily accessible to personnel in areas where normal operations or maintenance could expose personnel to caustic soda solution. Safety showers should be located directly above the eyewash fountains. Self-draining and heated safety showers and eyewash stations may be required in freezing conditions. Safety showers and eyewash fountains should be tested frequently for proper operation and especially before work begins in the vicinity. 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.

1. Be sure the storage tank vent is clear and the tank has enough volume to hold the contents of the car while leaving at least 10% of the storage tank unfilled (freeboard).
2. Slowly and carefully, open the valve on the 1" air inlet connection to relieve and equalize the pressure in the car.
3. Open the manway cover and assure that the cover remains slightly open during the unloading operation. If not done, a vacuum with develop in the tank car and it will implode.
4. If necessary, heat the bottom outlet valve and the 50% caustic soda solution. See additional directions in the Thawing Frozen Caustic Soda Solution in Tank Cars section.
5. Cautiously remove the plug from the external bottom outlet valve. It may be necessary to use a second backup wrench to prevent the external bottom outlet valve from turning while removing the plug from the valve.
6. Connect the unloading line to the external bottom outlet valve.
7. Open the external bottom outlet valve.
8. Open the internal bottom outlet valve by turning the valve rod handle on the top of the tank car and allow the 50% caustic soda solution to flow. NOTE: If the outlet valve handle does not turn with moderate pressure, it indicates that some frozen caustic soda solution remains in the bottom of the car and further steam is necessary. Do not attempt to force the handle.
9. Check for leaks.
10. Shutdown as needed to correct leaks before proceeding to the next step.
11. Start the pump.
12. Recheck for leaks. Shutdown as needed to correct leaks during the offloading process.
13. When the tank car is empty, stop the pump and close the external bottom outlet valve and then the internal bottom outlet valve.
14. Visually inspect the car to confirm it is empty. See Empty Tank Car Confirmation for more information.
15. Clear and disconnect loading hose.
16. Clean out the unloading hose with steam or water inside the containment area.
17. Prepare the car for return to Dow. See Empty Tank Car Return for more information.

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.