Section 215.TABLE D  Repair Welding

a)         All containers, piping and appurtenances which have contained or have been in direct contact with nitrogen fertilizer solutions containing ammonium nitrate must be thoroughly cleaned and washed with water (or steam) to eliminate all solid ammonium nitrate before welding or torch cutting may be attemped. Extreme caution should be taken before attempting to weld or torch cut any container when ammonium nitrate could be trapped, for example, in the area between tank shell and a reinforcing plate.

b)         All containers, piping, and appurtenances which have contained aqua ammonia (ammonium hydroxide) must be thoroughly vented and thoroughly washed with large quantities of water.  After washing, they shall be filled with water to a level higher than area to be welded or repaired.

c)         All containers shall be welded in accordance with the Code.