Last August I posted an incident where a 3rd party carrier unloading his/her NH3 truck to an LPG storage tank (SAFTENG Membership content). The contents of the LPG tank had to be burned/flared off which took around 60 hours. There were no injuries in that incident, but the consequences of such an error could be catastrophic. And unfortunately, this exact scenario occurs more than most know; partly because the two chemicals are hauled in the same DOT trailer at different times of the year. Of course, when the business has not considered “human error” in their design, we will only see these incident continue. Case in point, check out the unloading station at a “distributor” in MN:
Source: Minnesota Department of Agriculture (MDA)
I will give the credit for an excellent job of labeling and color coding (however both vent lines are yellow), but placing these stations in such proximity increases the odds that a driver inadvertently would hook up to the wrong connection. And I understand the argument that even if the connections were on opposite sides of their respective tanks, a driver could still pull up to, hook up and unload to the wrong tank. So much so, that the State of MN has issued an alert regarding mixing up LPG and NH3… “Anhydrous Ammonia in Propane Tanks – Hazards and Response.” This alert is a MUST READ for those who have both NH3 and LPG on site as it explains what happens when NH3 comes into contact with materials rated for LPG, but NOT NH3 (such as hoses, piping, fittings, etc.). What occurs inside the storage tank is a more significant issue as the two chemicals in the same tank will cause the tank to exceed its MAWP and lift the RVs when it is only 70º-80ºF outside! And folks, there is NO WAY to stop this without cooling the tank in some serious fashion!