On December 17, 1976, a crude oil tanker, the S.S. Sansinena, which was moored at Berth 46 in the Port of Los Angeles (Port), exploded and burned while ballasting and fueling. Six crew members were killed. Additionally, two crew members and the security guard were missing and presumed dead. There were approximately 36 personal injuries suffered by the general public. There was reported damage as far away as 6 miles, but the most severe damage occurred around the terminal. The surrounding residential area suffered some severe structure damage, including broken windows and doors.
Description of S.S. Sansinena
The S.S. Sansinena was built in 1958 at the Newport News Shipbuilding and Drydock Co., in Newport News, VA. (LOA 810’; beam 104.4’; draft 47’; 70,630 DWT). She was carrying the Liberian flag and her crew was Italian. She was single hull, powered by steam and all cargo tanks carried crude. The S.S. Sansinena was not equipped with inert gas and did not have segregated ballast tanks. This tanker was built with her engine room aft and a midship deck house navigation bridge. The engineering officers and crew had accommodation in the aft house and the deck officer’s quarters were in the midship deck house. The S.S. Sansinena was very typical in design, construction and crewing for a tanker operating in 1976.
Cargo Operations in 1976
In 1976 cargo operations, both loading and discharging, were conducted with an open system (i.e., cargo vapors were allowed to mix with oxygen and reach the explosive range). During loading operation, cargo vapors in the cargo tanks were displaced by the liquid cargo. The displaced vapor was emitting from the tanks through the ullage hatches and the cargo vents. Upon reaching the deck, these vapors would mix with the air and become explosive. This same emitting process occurred when the tanker was ballasting into the cargo tanks. If the mixture found a source of ignition, an explosion would occur. As the S.S. Sansinena was ballasting into the cargo tanks, the vapor in the tanks emitted to the deck became an explosive mixture; a source of ignition was found and the explosion occurred.
Current Cargo Operations
Today, cargo operations (both loading and discharging) are conducted with a closed system (i.e., cargo vapors are not allowed to mix with oxygen). This change occurred with the installation of tanker cargo inert systems and all access to the cargo tanks are kept closed during all operations. During loading operation, the inert vapor being displaced is vented high above the tanker’s decks. During the discharging operation, the inert gas system manufactures inert gas used to displace the liquid cargo. The inert gas does not allow an explosive mixture to occur in the cargo tanks. During the manufacture of the inert gas, the oxygen content of the inert gas is controlled to below 5 percent oxygen. Since the requirement of inert gas on all tankers, there have been virtually no tanker explosions from cargo operations. If the S.S. Sansinena had an inert gas system, the accident would likely not have occurred.
