1. Intended route 2. Departure time 3. Tank pressure and liq uid temperature e. Harbor control in congested areas or Coast Guard escort. f. Daylight traverse of restricted areas. g. Periodic position reports including tank pressure and changes in ETA. Review of such barges would also include examination of facility piping and transfer apparatus to insure that equipment was capable of handling any increase in vapor pressure during voyage which could cause venting during transfer operations. Generally the problem areas in the provisions for carriage of LNG in ships and barges have now been covered. The other subparts of Part 38 have been applied in vessel design September 1971 with no problems in interpretation. One important reason for this is the fact that our regulations are only directly applicable to U.S.-flag vessels and today no U.S.-flag LNG vessels exist! Part 2.01-13(a) of Title 46 Code of Federal Regulations states: "Foreign vessels registered in mitted sufficiently in advance to The submission of pertinent plans and/or calculations has been referred to as foreign vessel "plan review." Plan review and a subsequent arrival inspection are currently required for 39 chemicals, among which is methane. Completion of plan review and an inspection by U.S. Coast Guard Marine Inspection and Captain of the Port personnel will qualify the vessel for a Letter of Compliance, attesting that the vessel complies with plans approved by the Coast Guard and may carry the cargoes listed on the Letter in U.S. ports. The criteria used in reviewing foreign plans or calculations are those. included in U.S. Regulations for U.S.-flag vessel construction. The use of our regulations established minimum standards and insures no double 167 standards exist for foreign and U.S. construction. Viewing such foreign vessels from an office at U.S. Coast Guard Headquarters, it appears that the construction of gas ships is booming. Unfortunately for some aspects of the U.S. economy, all the now operating liquefied flammable gas ships fly foreign flags. However, if these sophisticated gas ships did not exist, exports of liquefied gas cargoes would not occur. Now we face importation of a liquefied gas to satisfy a recognized demand. This gas presents a greater hazard than those liquefied gas cargoes carried in bulk previously. Let us consider the hazards posed by a 120,000 cubic meter (m3) LNG vessel delivering a cargo in New York. We will assume that this ship contains five membrane type tanks (see figure 4), 24,000 m3 of LNG in each. Figure 1 is a chart of New York harbor and has been marked to indicate the vessel's track to an offloading terminal on Staten Island. In our hypothetical illustration, the following conditions prevail: Time of day: Night time Air temp: 70° F. Water temp: 60° F. Surface wind: 260° T, 8. KTS Visibility: Cloud Coverage 4/8 In Figure 2, the LNG tanker has collided with an outbound vessel in Port Reading Reach, near Smoking Point, Staten Island, and one tank has been breached, releasing 24,000 m3 of liquefied natural gas onto the water. The cross sectional area of the spill has been drawn in, plus the vapor plume. The shaded area in the plume represents the explosive range, 5.314.3% methane in air. Figure 2 represents the vapor plume characteristic which would evolve from vaporization from a quiescent liquidmethane interface as determined ex perimentally. This would be a "minimum" size vapor plume. The plume shown in Figure 2 was based upon a continuous vaporization of the LNG at a rate of 2,000 m3/min or a 12 minute duration. The plume as a result of instantaneous vaporization would appear as indicated in Figure 3. The plume in Figure 3 illustrates the "maximum" plume length. Actually the plume, for the conditions anticipated, would lie between the plumes shown. Vaporization would be accelerated by wave action or chop which would tend to increase heat transfer area and prevent the formation of ice. The Bureau of Mines did a study on the "Hazards of LNG Spillage in Marine Transportation" for the Coast Guard. One hazard which I have not mentioned, but which has been widely publicized is the flameless explosion phenomenon observed by the BUMINES investigators for this study. Current thinking is that this phenomenon is the result of superheating of the liquid natural gas and subsequent violent vaporization. A great deal of effort is being expended by several large companies plus the Government through BUMINES to determine conclusively the cause of the explosion and what methods can be used to prevent it. One way of preventing superheating might be the adulteration of the LNG with an innocuous substance which would provide nucleate boiling sites and thus prevent any possibility of superheating. Another consideration regarding the hypothetical release of LNG from the tanker in New York is the question of brittle fracture of the tanker's inner or outer hull due to contact with the cargo, either within the hull or on the surrounding water. The question to be resolved is how effective a heat sink is the surrounding water in preventing brittle fracture of the tanker's hull. The BUMINES study indicated that LNG does not flash immediately but forms an ice/hydrate layer which then vaporizes. The hazards associated with the marine transportation of liquefied natural gas have been very briefly outlined. Each particular hazard including those of plume characteristic and vapor dispersion increases in magnitude and importance with each new LNG vessel. Considering the quantities of gas aboard one LNG supertanker, no one wants to "learr from experience" what may happen if a casualty occurs. AMVER (Continued from page 161) are participating in the AMVER program. Last year, the center provided more than 1,500 SURPIC's and figured in such prominent cases as the 1970 Atlantic rescue by the S/S President Jackson of seven people from the schooner Tina Marie Doncine, 135 miles northeast of Bermuda and in the saving of some 40 persons from the blazing freighter Don Jose Figueras, 900 miles at sea in the Pacific. In commenting on the effectiveness of AMVER, RADM Engel added that "Casualties at sea among the merchant fleet have persisted at an alarming level. The Coast Guard's activity in this field has consequently remained high, and vessels of many countries cooperating with AMVER have offered much assistance. This luncheon enables us to acknowledge the contribution of vessels from over 60 nations plotted by our computer." Details of AMVER System operations may be obtained from Commander, Eastern Area, U.S. Coast Guard, Governors Island, New York, N.Y. 10004 and from Commander, Western Area, U.S. Coast Guard, 630 Sansome St., San Francisco, Calif. 94126. THE TRAGEDY OF OF THE M/V MARJORIE MCALLISTER Green water pours over the port quarter of the Marjorie McAllister's sister ship, Helen McAllister. Much heavier seas than these 6 footers inundated the stern of the Marjorie McAllister on the night of the casualty. ON 2 NOVEMBER 1969, a motor towing vessel, the M/V Marjorie McAllister, sank off the coast of North Carolina with the loss of all hands. Since there are no witnesses to the casualty, and since the vessel itself has not been located, the piecing together of exactly what happened that day involves a large measure of speculation. What is actually known of the casualty is that the Marjorie McAllister departed New York City shortly before noon on 30 October, bound for Jacksonville, Fla. She was making this voyage without tow. The voyage went routinely until the first of No- present position, and that he intended to put into Morehead City if refuge from the weather became necessary. The Master, both mates, and a deckhand, all lived within 20 miles of Morehead City. Had the Master known what lay ahead for the tug and her crew of six, his decision would undoubtedly have been different. The weather along the Atlantic Coast on the evening of 1 November and in the early morning of 2 November was severe. By 1200, 1 November, gale warnings had been posted for the entire coast from Virginia Beach, Va., to Charleston, S.C. |