By

and

Mr. W. E. McConnaughey

AS THE REGULATORY agency responsible for safety in the transportation of hazardous materials on navigable waters of the United States, the Coast Guard has an intense interest in industrial activities relating to the protection of shipboard personnel and the public. Although this paper is concerned primarily with the Shell-Keystone vapor concentration study, the general importance of industry training and cooperative study programs in the development and enforcement of effective regulations is stressed. The Coast Guard has not made a decision with regard to the need for new regulations stemming

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This article is extracted from paper delivered at the May meeting of the Annual Tanker Conference of the American Petroleum Institute.-Ed.

from the court opinion expressed in the Mission San Francisco case and all sources of pertinent information are being utilized to provide a sound basis for determining if action is required. The Shell-Keystone study is one of these sources and this paper discusses its relation to the Secretary of the Treasury's Tanker Hazards Committee and to the overall problem of tanker safety. Some observations on the results of the study are made

with the conclusion that they provide much-needed information, but raise some technical and regulatory questions. A practical aspect of toxicity applying to tankers carrying chemical cargoes is discussed in connection with the growing need for new, separate chemical regulations to supplement and complement the present Tanker Regulations.

The subject of tanker safety is one of great interest to the Coast Guard not only because of our specifically assigned regulatory responsibilities but because of our general concern with all aspects of safety in marine transportation. The hazard of fire

and explosion has long been identified with some of the products transported by water, and rather comprehensive safety regulations were formulated many years ago with the cooperation of the American Petroleum Institute to minimize the risks involved in the bulk shipment of petroleum products. There is no doubt that these regulations have been an important factor in reducing loss of life and property, and they have stood the test of time with respect to effectiveness and practicability very well. However, tanker safety-to be effective-must be progressive. Operating conditions change, cargoes change, and safety standards are raised or lowered as the factors of safety or ignorance become better delineated. As a general rule, the less known about a given subject, the greater will be the factor of safety applied. As a result, the Coast Guardwith the cooperation of industry-is constantly reviewing and revising the existing regulations as new information and needs become apparent. The simplest approach to the general problem of safety is to wait for a casualty, investigate it, and take corrective action so it won't happen again. While this "regulation by disaster" approach is inevitably an important part of most safety programs, it is essential that effort be devoted to anticipating and preventing accidents. This requires an understanding of processes and operations to be able to identify and assess areas of potential hazard. In other words, insofar as practicable, a preventive approach is preferable to a strictly corrective approach.

EXPLOSION HAZARD STUDY

The Shell Oil Co. and the Keystone Shipping Co. are to be congratulated for initiating and conducting a study which does much to define the problem of the explosion hazard of socalled "empty" tanks and suggest possible approaches to a solution. While this problem area has long been recognized as a potential hazard in the bulk water movement of petroleum products, only recently have activities such as the "Cherry Valley Gas Concentration Studies", been directed toward improving the dearth of technical information available in this area. The Coast Guard appreciates the opportunity to participate in this program for several reasons. First, this is a timely effort directed at a problem which needs attention, and we are always happy to be able to assist such worthwhile endeavors. Second, the program is providing us with education in a specialized area which may have an important effect on the safety standards for tankers. Another important benefit we are receiving from participation in this

program is the opportunity for Coast Guard personnel to become better acquainted with tanker operations in general-not only ship cargo handling but practices and problems in merchant vessel navigation, corrosion control, port and terminal operations, merchant marine personnel management, etc. Such knowledge is essential for personnel engaged in the various facets of merchant marine safety, including plan approval, development of regulations, and marine inspection work. To date, about 30 Coast Guard officers and civilians have participated directly in the Shell-Keystone study involving two round trips per man on the coastwise tanker Cherry Valley. I'm sure you'll agree that the acquired understanding of industry problems by Government regulatory personnel is highly desirable for all concerned because, as you know, firsthand knowledge is always important in the assessment of technical information if one is to arrive at realistic conclusions.

Although it is obvious that a careful study of vapor conditions existing in cargo tanks and ways of controlling them have been much needed in connection with the overall problem of tanker safety, the judiciary findings flowing from the Mission San Francisco casualty have given the subject additional impetus and intensified its study. As a direct result of this opinion, the Secretary of the Treasury, at the suggestion of the Commandant of the Coast Guard, established a special committee to investigate the operation of tankers. In the words of the authorizing letter of April 10, 1962, this committee has been asked to "collect, study, and make recommendations with respect to the operation and navigation of tank vessels with one or more of their cargo tanks in an empty condition. It is expected that the study will encompass every possible aspect of gas freeing or inerting of empty cargo tanks; develop additional information relative to the hazards in the navigation of tank vessels with empty tanks which are not gas free or inert; evaluate suggested proposals for assuring safety on such vessels; and to recommend a national policy in conformity with these objectives." It is evident that this undertaking is broad in scope and of great importance.

This Tanker Hazards Committee is chaired by Prof. H. L. Seward, professor emeritus at Yale University, and the members represent a wealth of talent drawn from the Bureau of Mines, the Maritime Administration, the National Bureau of Standards, the National Fire Protection Association, the Naval Research Laboratory, the American Bureau of Shipping, the shipping industry, and

the Coast Guard. With such a diversified membership, the question can be approached in an unbiased, scientific manner and the findings and recommendations of this group are expected to be of great value to both industry and the Government.

While it is inappropriate to speak for the Tanker Hazards Committee, it is evident that the Shell-Keystone vapor concentration study and the earlier work on crude oil tankers by Shell Tankers, Ltd., provide very useful data which would not otherwise be available. It is indeed fortunate that these industry-sponsored programs were and are being undertaken in time to contribute to such an important overall investigation.

GENERAL POLICY

Before commenting on the vapor concentration study, the Coast Guard's position should be explained. The Coast Guard is the regulatory agency responsible for all aspects of merchant marine safety including transporting hazardous materials on navigable waters of the United States, and, as such, it has a keen interest in all industrial activities relating to the safety of shipboard personnel and the public. While we are anxious to work closely with industry-and, indeed, to have industry solve its own problems wherever possible it is essential that we remain impartial and unprejudiced. It is also necessary that we be as well informed as possible and seek information from the best available sources. This general policy is being applied to the specific problem of empty cargo tank hazards. However, it would be premature to try to make any decisions before the Tanker Hazards Committee has concluded its investigation and made its recommendations. Therefore, no changes to the tanker regulations on the points in question will be made until the committee completes its deliberations and submits its report for consideration. Such changes as appear necessary will then be proposed for adoption after being considered at a public hearing.

This is not to say that no changes of any kind are envisioned for hazardous material regulations. In addition to a number of detailed changes which were discussed at the March 1963 public hearing, it is presently planned to develop a separate set of regulations pertaining to bulk shipments of chemicals to supplement the present Tanker Regulations. This action is based on the fact that a wide and rapidly increasing variety of chemicals are being carried by tankers, and these often introduce hazards which differ markedly from the familiar fire and

explosion hazards of petroleum products. One of the basic problems in developing chemical regulations is to distinguish between "chemicals" and "petroleum products." This is admittedly difficult-and some arbitrariness will no doubt be required. At least for the present, the following distinction is made. By "petroleum products," we mean complex mixtures of materials obtained from petroleum which are identified primarily by physical properties such as boiling range, vapor pressure, viscosity, etc. By "chemicals" we mean relatively pure materials which are identified by chemical composition. Thus, gasoline is a petroleum product, but ethyl ether is a chemical even though it is commonly produced from petroleum. We recognize that the distinction will not be so simple for many materials, and suggestions for an alternate system would be welcomed. Incidentally, we regard "petrochemicals" as an indication of source rather than characteristics.

CHEMICAL HAZARDS

The assumption of fire as the primary hazard is proper for petroleum products and a gradation of hazard (and classification) by flashpoint and vapor pressure is both logical and practical. However, chemicals have several hazards which must be considered and fire may or may not be the primary one. Many chemicals do not burn, but they may be extremely toxic or unstable or reactive with other cargoes or normal materials of construction. For example, carbon tetrachloride does not burn and hence it cannot be classified under existing Tank Vessel Regulations. However, it is quite toxic in a very subtle manner and may be a real hazard to tanker personnel-and possibly the public as well.

On the

basis of flashpoint and Reid vapor pressure alone, ethylene oxide is classed as a grade A inflammable liquid. However, it is much more hazardous than casinghead gasolineanother grade A inflammable-because of its extreme reactivity, instability, and toxicity.

Thus, changes in regulations may be expected, although they will be evolutionary rather than revolutionary and may or may not involve empty tanks containing explosive

vapors.

The technical details and proposed applications of the vapor concentration study have been discussed very effectively by Captain Laidlaw. Keystone and Shell Oil have approached the study in an intelligent and thorough manner in order to extend the British crude oil tanker investigation to refined or clean cargoes.

For the first time, we have a definitive picture, for the major refined petroleum products, of vapor conditions in a cargo tank during typical tanker operations. This type of information is important for several reasons. First, to be able to assess the hazards in any situation, it is axiomatic that you must know what conditions exist. For a tanker, it is not sufficient to know that the cargo can produce inflammable or explosive vapors on mixture with air. A real understanding requires that internal vapor concentrations and gradients be known as a function of time and the various operations aboard a tanker such as loading, ballasting, ventilating, and the various tank-cleaning procedures. From this, it can be determined what hazards to operating personnel and the public exist and when. A second reason for the importance of vapor concentration information obtained in this study is that it provides a basis for designing efficient and effective control equipment. Empirical and intuitive approaches are no longer satisfactory, nor are they consistent with modern technological advances in the industry. A third reason for these data's importance is that it was obtained from full-scale tanks on an operational tanker. Although the relative merits of scale model studies in the laboratory versus full scale field studies are always a subject for lively discussion, it appears that the latter is especially desirable in this

case.

SCALING

The problem of scaling up from carefully controlled model work is difficult at best and it becomes much more so when there are many poorly defined variables. A few of the variables which may affect tank atmospheres are ship motion; vapor densities; tank temperature gradients and differentials with respect to the air, piping, and tanks; tank geometry; the human factor, etc. While such factors cannot all be controlled in the field, by means of repetitious measurements, some insight as to their significance can be obtained. The realism of shipboard full-scale data coupled with the results of precision model testing under controlled but arbitrary conditions seems to offer the most reasonable opportunity of achieving the desired end result.

DATA RELIABILITY

What about the quality of the results? The happy combination of elaborate instrumentation and a convenient ship operating schedule has permitted the collection of a great deal of diversified and confirmatory data. In spite of early problems with instrument calibrations, the wide and

unpredictable ranges of vapor concentrations, and the sometimes difficult working conditions, reliable data on vapor concentration gradients and behavior patterns have been obtained for gasoline and related petroleum products. These clearly show the stratification or almost liquid behavior of the vapors and their relatively slow diffusion rates. They also show the effectiveness of vapor removal equipment when used to take advantage of these properties.

EXPLOSIVE LIMITS

In spite of its general excellence and potential for practical application, this work raises a question as to the value of the lower explosive limit (L.E.L.) which would be applicable if vapor removal should become a required tanker operation. In the Shell Oil-Keystone study, 0.5 L.E.L. was used as the maximum safe concentration for a cargo tank and in the Shell Tankers' crude oil study, 0.25 L.E.L. was used.

From an economic standpoint, a high value is desirable to conserve time and money, but there are some uncertainties which make selection of a proper safety factor difficult. For one thing, there is lack of agreement among published values for L.E.L. For example, two reputable organizations, National Fire Protection Association and Factory Mutual, give 1.9 and 1.6 percent, respectively, for butane which is a major component of gasoline and crude oil vapors. In addition, tank geometry may alter values obtained under laboratory conditions, and variations within a large tank may make single readings obtained during normal tanker operations unreliable. And finally, vapor compositions are subject to variations with source of cargo and time. When these uncertainties are considered along with those resulting from unavoidable instrument errors, the question of what reasonable maximum vapor concentration will assure nonexplosive conditions in an empty cargo tank become difficult. The question is raised because it appears to warrant discussion. It is certainly not intended as a criticism of the vapor removal approach to tanker safety.

DEGASSING PROBLEMS

Another question raised by this work is the possibility of difficulty with air pollution and port regulations if degassing became a regular dockside practice. Even though vapors are now regularly released into the atmosphere during loading operations, there is a steady increase in the number of regulations applying to operations of

this nature. Also there is a wide variation in port regulations which might prevent any uniform degassing procedure. The possible problem arises from the fact that these regulations are established and administered by many different agencies other than the Coast Guard, and coordination would be difficult. Even though the Shell Oil-Keystone data indicate that vapors discharged by a steam exhauster are more diffused and apparently less dangerous than those from normal loading operations, the degassing operation is a change which would have to be carefully studied.

The findings regarding methods of degassing tanks should prove interesting to industry, since they are evaluated in terms of key industrial factors-time and money. Results obtained so far in the study appear to indicate that quite acceptable amounts for both can be achieved by very simple equipment which should require little, if any, maintenance. In theory, at least, it is hard to dispute the merits of exhausting high concentration vapors instead of continuously diluted vapors. For perfect stratification in a tank containing 20 L.E.L. vapors initially, one air change by the use of a bottom exhaust completely degasses, whereas, with complete mixing, one air change by blowing air into the tank leaves a uniform concentration of 7.3 L.E.L. Of course, in practice, the difference is less, and only actual measurements, such as are being reported at this meeting, can determine the relative economic merits. From the safety standpoint, stratification exhaustion is attractive because it confines internal explosive concentrations to only part of the tank and away from the hatches.

The carriage of chemical cargoes by tankers is relatively new-at least compared to the movement of petroleum products-but it is rapidly increasing in volume. Therefore, it is pleasing to hear that chemicals are to be investigated as part of the future vapor characteristics study program. Not only will the resulting information eliminate the necessity for attempting to apply petroleum product data to materials with quite different properties but it may lead to a method of predicting the vapor characteristics of new cargoes under tanker operating conditions. If data can be obtained for a sufficient number and variety of materials, it should be possible to establish the significant parameters. Although factors such as vapor density, vapor pressure, diffusivity, temperature, and convection suggest themselves, only actual experimental work will determine the complete list and which are of practical importance. It is interesting to note

that many common chemicals carried by tankers such as the Cherry Valley have vapor pressures which maintain void space over the liquid cargo in the explosive range whenever equilibrium conditions prevail.

PERSONNEL SAFETY

As a side observation during these studies, it has been interesting to see a practical aspect of chemical toxicity in tanker operations. It is commonly necessary for personnel to enter empty tanks while underway and the question arises, "When is it safe to enter?" For gasoline and related petroleum products, this is relatively easy to determine. The safe vapor concentration is taken as 0.1 percent, and this can be determined, at least approximately, with the usually available portable explosive gas detector. But what about a material like acrylonitrile which at present is carried as a grade C flammable liquid? At least one major chemical company uses the industrial threshold limit values as the limiting concentration for people to enter cargo tanks on barges and tank ships. The limit in the case of acrylonitrile is 20 parts per million (0.0020 percent), and even on a combustible gas detector calibrated for acrylonitrile the lowest measurable concentration is around 1500 p.p.m. (0.05 L.E.L.). This is unquestionably a dangerous concentration in terms of permanent, serious body damage whether there are immediate symptoms or not. Admittedly, the nose is much more sensitive than the instrument and is much more likely to be used. However, in the absence of specific toxicity information and appropriate instrumentation, a negligible L.E.L. reading and no immediate toxic symptoms will undoubtedly be taken as justification for entering the tank, with possible serious after effects. Although some companies are now providing toxicity literature to masters of their ships, this is by no means universal or uniform. As was mentioned earlier, toxicity is one of the new hazards which is leading to the development by the Coast Guard of separate regulations for the riage of bulk chemicals. In addition, a Navigation and Vessel Inspection Circular No. 4-63 has been published which includes relative toxicity ratings for a large number of chemicals which have been proposed or approved for bulk shipment by water. These ratings were developed for the Coast Guard by the National Academy of Sciences and it is hoped that they will be useful in alerting people to potential toxicity problems.

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OVERALL PROBLEMS

At this point, I'd like to make a few comments on the overall problem of tanker safety. This paper and others presented this morning have been concerned primarily with methods of eliminating the hazard of empty cargo tank explosions. Important as this subject is, the Coast Guard views it as only one approach to the ultimate solution. Another important approach is the prevention of collisions-which, incidentally, would eliminate most of the hazard from empty cargo tanks. Certainly the present widespread use of radar and the increasing use of single frequency bridge-to-bridge radiotelephone are major steps forward.

However, collision remains the major cause of tanker casualties and continued progress is required. Therefore, I'd like to suggest that the tanker industry undertake two operations research projects.

The first is to determine the maximum safe speeds for large tankships operating in channels having reIstricted widths and depths.

The second is to develop a code of recommended practices for the operation and navigation of tankships. Such a code, if adopted and published by the tanker industry and used by the seagoing personnel of the tanker fleets, should result in reasonable tanker speeds in restricted waters. There is no doubt that such efforts would contribute much to reducing the incidence of collision.

Another area for further work is the training and education of tanker personnel. It has been repeatedly shown that the major underlying cause of casualties is personnel error rather than equipment failure. Oftentimes this results from a lack of information or misinformation rather than carelessness. Tankermen need up-to-date information on cargo properties, their handling and their hazards. The training of new personnel on tankers and the updating and further education of experienced personnel to keep them abreast of changing cargoes and advancing marine technology is a necessity. Certainly there is much room for improvement in this area and many rewards to be gained from fewer casualties.

In conclusion, I'd like to say that it has been a most-rewarding experience for the Coast Guard to participate in the Shell Oil-Keystone vapor concentration study and we hope that continued good use is made of the unique facilities on the Cherry Valley to obtain additional much-needed technical information-especially in the area of chemical cargoes.