Unknown Ship Board Chemical Reaction; Houston, TX

Source report excerpt: “Sector Houston has requested that NOAA assist in a post-incident investigation of possible chemical reaction aboard. The vessel, currently off-shore, who while completing discharge of 2-Ethyl Hexyl Nitrate (PSN Alkyl C7-C9 Nitrates) at a facility experienced a venting of cargo vapor from the vessels high velocity pressure relief valve. Background Provided by USCG: The Ships initial report indicated that at the time of the incident the high pressure and High temp alarms activated, the PV activated releasing the pressure. Cargo tank temperature was noted at 250 degrees Celsius (that’s hot), the PV mast was found very hot causing discoloration of epoxy coating on PV vent pipe. Deck was cooled […]”

Source report excerpt: “More Information and request for support: Upon further information gathered from Vessel representatives lets change the focus slightly. I am attaching a diagram of the cargo block. The Tank (1 C ) is uncoated stainless. The Tank ( 1 C ) Contained 2-Ethyl Hexyl Nitrate (Alkyl (C7-C9) Nitrates. The Cargo Tank Adjacent (2 C ) was empty. Ballast tank B1C was partially full. Tanks 3P/S & 4 P/S were empty, but had residual LPG cooling/conditioning. Temperature in Houston was over 100 degrees F. (hot, sunny day). The Deck Temperature is estimated at over 63 degrees C. based on a temperature collected by leaving a thermometer on the deck for an hour the following day while the vessel was underway […]”

Source report excerpt: “You're quite right I see to focus on the 2-ethyl hexyl nitrate with a tank temperature @200 deg. C. That's pretty hot, I don't know what kind of an autoignition temperature may be for this compound, but at this temperature I could see where you may start getting an oxidation-reduction reaction, The oxidizer being the nitrate and the reducing end of the compound being the hydrocarbon. So you could conceivably get a "charring" of the hydrocarbon end due to the fact that there is insufficient oxygen/oxidizer to fully oxidize the hydrocarbon. This charring phenomenon is well known to occurr where you have such conditions, as in mixing an oxidizing acid like sulfuric or nitric acid with organic […]”

Source report excerpt: “I concur that the ethyl-hexyl nitrate underwent a self-generating exothermic reaction thereby increasing the temperature the vessel above 200C. Before this run away exothermic reaction, the vessel was almost empty and due to the fact that the outside temperature was hot, the metal vessel now mostly absorbs the ambient heat and thereby increasing its temperature to the critical level. The remaining chemical in the vessel, as it approaches the critical temperature which is 212F underwent a self-generating exothermic reaction increasing the vessel's temperature past 200C and also increasing the internal pressure. One course of action which was already done is to cool off the vessel using […]”

Source report excerpt: “Thank you for all your assistance with this incident on such short notice, I continue to be in awe of the fast, accurate and timely information you (NOAA) provide, again thank you! Jamie Wilson found a "best practice" guide on the internet for this product, I have not had a chance to peruse it yet, but from what he indicates, in addition to what you all have provided, it does appear that we were lucky not to have something "worse" occur and require your assistance in a different fashion. As Mr. Wilson indicated, the owner/operator has sent samples off to the lab to see if they can "ground truth" the information contained in the MSDS. In the short term, they are putting out a fleet wide […]”

Source report excerpt: “At the request of the USCG, NOAA ERD chemist provided insight and assessment of a chemical transfer that could have gone terrible wrong. Fortunately, the release was small but the accident indicated a clear need for safety when handling such chemicals under extreme heat conditions, which are not uncommon in the Gulf of Mexico during summer months. It is likely that the extreme heat resulted in a self-generating exothermic reaction increasing the vessel's temperature past 200C and also increasing the internal pressure. Soot was well as vapor was released. Fortunately, the transfer was essentially completed when the reaction occurred or this might have been much worse. As the NOAA Scientific […]”