Dangers of process openings and bleeding off NH3 (RV Change out)

At 3:10 p.m. on February 7, 2017, an employee was making preparations to replace the relief valve of a 1,000 gallon ammonia (NH3) nurse tank. The incident investigation reported that the tank was empty of liquid NH3. However, it contained approximately 80 psi of vapor pressure. The employee set up a 30 gallon drum that contained water and affixed it to the nurse tank by way of a hose. He then turned the relief valve of the tank to bleed the vapor pressure into the drum. The vent of the drum was not completely clear, causing the bottom of the drum to burst and become airborne. The drum became separated from the hose and was ejected over the top of the ammonia storage tank, spraying the employee’s lower portion of his body with ammonia. The employee sustained chemical burns and showed signs of toxic vapor inhalation, which he was hospitalized and received treatment.