Marad Design C4-S-57a "CHALLENGER-Class" (United States Lines)

General

The Challenger-class vessels, first ships to be built by the United States Lines in its vessel-replacement pro­gram, are big, fast and versatile. The ships have 670,905 cu ft of dry-cargo space, cruise easily at 21 knots, and can handle and stow efficiently a great variety of cargoes. The class comprises 11 vessels, five of which are being built by the New­port News Shipbuilding and Dry Dock Company, Newport News, Va., and six ships by Bethlehem Steel Company, Quincy, Mass. Both groups are the same except that some ma­chinery suppliers differ, as will be seen in the equipment list at the end of this article. First to be delivered is the American Challenger from Newport News SB and DD Co. Most of the technical data and photographs in­cluded in this article refer to this vessel.

Design Concepts

The Challenger-class design was developed by United States Lines in cooperation with Gibbs & Cox Inc., naval architects, New York City, who also acted as owner's plan approval agent. A concerted effort was made to in­corporate the many, varied features necessary to service the complex North Atlantic trade route. There are very few tools available to the industry today to help in mak­ing a thorough, economic forecast of the efficiency of a new design. We are now only in the diaper stage of math­ematical models and computer simu­lations of fleet operations. In the early stages of this design, the only tools available to U. S. Lines were pains­taking pro-forma examinations and experience. Fortunately, U. S. Lines has a wealth of varied experience in a wise spectrum of break-bulk trades. As a result of the careful examination of the new design potential, a few well defined ground rules were developed. Included were: The vessels must be designed to the needs of the shipper, so far as these could be ascertained. The vessel must have a mini­mum first cost without sacrificing the first requirement. The vessel must be strong, safe and possess unusual stability and sea-keeping features and be suitable for use as a naval auxiliary. The vessel should have the lowest maintenance cost consistent with the above. The freight and operating departments then collaborated on developing a tentative table of desirable characteristics. The translation of the information available into a design compatable with the broad policy directives pre­viously mentioned was necessarily complex and time consuming. A brief discussion of a number of design con­siderations may be desirable to illustrate the latitude covered in a ship design and the decisions required.

Sea Speed

So far as the shipper is concerned, he has but one need for the employment of ocean transportation delivery of his goods to market. It is of singular importance to him to get this material from departure point "A" to destination "B" in the shortest elapsed time. To the ship operator this translates into speed becoming a very important selling point in the competition for cargo. The operator realizes that many factors influence elapsed transit time. Such factors as improved cargo gear cutting port time have an obvious effect on transit time. But the shipper sees only speed as equating with shorter transit time. Therefore, any discussion of other time-saving devices is looked upon as sales talk. Thus, a service speed of 21 knots becomes a basic concept for this class.

Hull Characteristics

While speed established the need of a large vessel, the newest para­meters of speed-length numbers estab­lished by various studies permitted some variation of dimensions. How­ever, the operating department of U. S. Lines laid down firm require­ments for intact stability more stren­uous than the usual. This requirement coupled with the physical need for beam to accom­modate the triple hatches at Nos. 3 and No. 4 Holds established for all practical purposes a minimum beam of 75 ft. Appraisal of the St. Law­rence Seaway limitations established a 75-ft beam as the maximum per­missible,  a final clinching argument. With the beam fixed, the waterline length was established and the depth became a function of the in­tact stability requirements set forth by operations. A number of studies were under­taken next to establish the most efficient use of the cubic. Included in this study were various arrangements for engineroom location.

Operational Characteristics

Trade route experience indicated that the vessel should have unusual sea keeping characteristics. Accord­ingly, a vessel with full scantlings, a high freeboard forward, satisfactory powering for all expected conditions of operation, and special tankage to reduce stiffness when running light westbound, was designed. Many of the design features coin­cided with the established general concepts of MARAD. In this category could be placed such items as speed, high capacity cargo gear, full scant­lings and cruising radius. The greatest possible cruising radius is U. S. Lines' aim. At casual glance this would appear easy to attain with a vessel as large as the Challenger. Operating ex­perience dictated a design obviating the need for ballasting any fuel tanks in any but emergency conditions. Ob­taining a large cruising radius re­quired some compromises and some considerable ingenuity. A cruising radius in excess of 11,000 miles for average conditions of sea state and bottom cleanliness was obtained. In the requirement for one-com­partment subdivision, the desires of MARAD, U. S. Lines and the design agent coincided. In the detail design, scrupulous attention to strength, loca­tion of penetrations and openings, use of superior materials, etc., insure the maximum retention of positive GM in the event of damage. In this respect the design exceeds conven­tional requirements. It was decided to make at least two of the best cargo holds at least 75 ft in length to accommodate the long cargo which is offered today for shipment with increasing frequency. The long holds were to be further subdivided longitudinally to take ad­vantage of other features desirable to the shipper, including safer stowage and freedom from shifting of cargo, permanent grain fittings and absence of pillars. The engine room was put as far aft as practical to permit maximum employment of the fullest portion of the vessel as possible, yet not so far aft as to make the vessel difficult to trim.

Cargo Operations

Until worldwide port facilities are revolutionized, the only practical method of improving safe cargo out­turn is to improve those vessel design features which play any part in cargo efficiency. The results of the many pro-forma studies indicated a need for a vessel of cargo deadweight capacity in the 8,500- to 11,000-ton range. The ves­sel was to have capacity for 1,000 tons of liquid cargo with a wide range of small lot potential and was to have approximately 30,000 cu ft of fixed refrigerated space with as much con­vertible space as possible. Provision was to be made for heavy-lift gear at two holds. All other special features of practical value were to be in­cluded. September, 1962 Liquid-cargo space was fixed at 1,000 tons in a minimum of eight tanks to give a variety of lot sizes. Nowhere has there been more change and transition than in the re­quirement for liquid cargo. Since the chemical industry is expanding rapid­ly, every day brings new products into the fore. Shippers are inquiring about space for products for which there is no operating experience. Two requirements are common to all these products: (1) The tank must be as nearly surgically clean as possible; (2) the temperature of the cargo must be minutely controlled. Having eight tanks, the possibility of carrying eight distinctly separate temperatures is obtained. To satisfy operations, the tanks were divided four forward and four aft. To insure facility cleanliness, smooth and flush inside surfaces were dictated. Experience had indicated that the only truly consistent and safe heating method was to press up a tank under the cargo tank and heat the liquid in this lower tank until the cargo reached the desired temperature. It was possible to provide both these features and insure complete separa­tion of temperature boundaries by providing peripheral cofferdams. Thus all stiffeners could be kept inside the cofferdam. Air space above the bottom would provide tempera­ture separation and heating coils in the bottom cofferdam would provide an effective, nonscorching method of heating the cargo (the cofferdam be­ing filled with water for this pur­pose). The tank cleaning system uses heated sea water, fresh water, chemi­cal solution, or any combination of the three. The system has three 400-gpm Worthington pumps and a Davis Engineering heater and drain cooler. The tank cleaning machines are Sellers. Experience indicated that the ship­per was reluctant to use ordinary steel tanks except for a relatively few com­modities. It was decided to coat the tanks in No. 2 Lower Hold with a modified epoxy which had proved to be a better than average coating. In order to increase the ship's ability to carry the wide range of liquid cargoes now moving, it was decided that an additional four tanks in No. 5 Hold were to be constructed with stainless steel clad interiors. Both fixed and container-type re­frigerated capacity was provided to take advantage of the benefits offered by each of the two systems. This makes provision for the small-lot ship­per as well as for the shipper of van-load lots of reefer cargo. Approximately 26,000 cu ft of fixed space and 22,000 cu ft of additional convertible space are fitted in the upper 'tween decks of Nos. 5 and 6 Holds. Each wing compartment is fitted with a Mario Coil air cooler. The vessel also can handle up to 28 refrigerated containers on the Main Deck at Hatches 3, 4 and 5 where electric outlets have been provided. Up to 28,000 cu ft of space in refrigerated vans thus is available. To improve the efficiency in the fixed reefer, two sets of large double doors were provided in each box and one hold is double rigged. The reefer cargo spaces are serviced by a Freon-12, direct expansion system designed for complete auto­matic operation. There are four air-cooled, single-acting York compressors. A basic general cargo concept was the provision for maximum opening to cargo spaces. The triple-hatch-abreast concept at Holds No. 3 and 4 was employed to the maximum to provide the many shipper advantages inherent in this system: These include direct spotting of cargo, reduction in shoring time, increase space for hatch-square stowage and bulk cargo flexi­bility. The remainder of the holds were provided with as large size openings as could be fitted. To  further  improve  the  handling of general cargo, full sheer was limited to the Main Deck. The Third Deck has no sheer at all. Furthermore, the decks were designed ab­solutely flush and this feature has been maintained at great sacrifice. This feature supplemented by the improved ventilation will permit maximum use of fork-lift trucks within the holds. The decks have been strengthend to accommodate fork lifts of 6-ton capacity. Deckhead clearances have been specially dealt with and permit the loading of wheeled vehicles and vans throughout the 'tween decks. Provision of the longitudinal divi­sional bulkheads in No. 3 and 4 Lower 'Tween Deck and Hold made these spaces available for grain or bulk at any time without further fit­ting. These six spaces plus the eight deep tanks give an unusual flexibility in lot sizes of bulk cargo without taking time for fitting shifting boards. Being sensitive to general transition of the type cargo available, unusually heavy capacity cargo gear was provided. In addition to providing boom capacities for 10 and 15 tons at every hatch, two hatches were to have 70-ton capacity, fully rigged, thus giving an everyday service where pre­viously an advanced scheduled crane barge was required. Advantage was taken of a Euro­pean development in heavy lift gear, the Stulcken boom supplied in this country by MacGregor - Comarain, Inc., which permits use of the gear at two hatches alternatively without rerigging. This simplified ship design somewhat by reducing topside weight and improved flexibility. Having designed a vessel with ex­cellent characteristics for spotting, U. S. Lines studied the use of cranes to complement this feature. This study led to many innovations, including cooperating with a deck gear company in developing a new type of traveling crane gear. However, the crane gear was found not to be suitable for the service requirements in United States Lines' trade. The result was to revert to the boom-gear system. The result was to turn back to boom-gear systems. Investigating the several systems available, it was de­cided that the schooner-guy type of­fered the most flexibility. Powered vangs, topping and guy lines, it was felt, should provide both the crane advantages and the boom advantages. These winches were sup­plied by Western Gear Corporation. Burtoning was a simple design sit­uation. Synchronizing vang and schooner-guy functions provided ton loads for either No. 3 or 4 Hatch without rerigging gear swinging boom function as well. A master control incorporating safety under all conditions was devised and the system, as tested, provides a swinging boom that is, for all events and purposes, a crane. Additional to the functions of the system, the design stressed safety. The very latest in electric gear, de­veloped by General Electric Corpora­tion, provides instant control and positive braking. The controls are so devised that any accidental overload­ing of the vangs and guy breaks the circuitry and sets the brake. The only functions which then are operative are those which tend only to elimin­ate the overload. The winch operator is always high up overlooking the hatch that he is working and he is protected. The blocks have been sized to carry the loading and yet be light enough to service. This is no small feat when one considers that the first working drawings included blocks of three and four times the final weight. Greer Marine folding hatch covers have been provided for the Chal­lenger-class vessels. In the interests of economy it was first decided to make the folding hatch covers all mechanically operated. This type of cover had proved its reliability in the Mariner. A study of hydraulic hatch covers already in use, however, in­dicated that the faults could be corrected, and the improvement in working time plus the safety factor adequately supported a shift to hy­draulic operation on the weather deck. The covers in all 'tween decks are flush to the deck and are all ade­quately strengthened to provide for the fork-lift operation. No attempt was made to design a container ship. U. S. Lines trade is such that, while more and more con­tainers are being used, a cellular ves­sel would be disadvantageous to the great majority of shippers whose cargo is not containerable. The approach to the container traffic was to design a vessel for break bulk, but to pay the strictest atten­tion to those details which would permit maximum container lift wthin the conventional confines. Thus in checking deck heights, pillar obstructions, vent ducts, etc., care was taken to permit clearances to accommodate the present trend of container dimensions. Although the fore-and-aft divisional bulkheads may limit the container lift, the large hatches and swinging booms permit spotting containers without lateral movement. In addition to the usual double row of padeyes located in the cargo spaces, a net shoring system developed by Peck & Hale Incorporated is provided. This system is expected to substantially reduce shoring time and cost, as well as minimize cargo damage. The shoring system has been provided in No. 2 Hold, the upper 'tween decks of Nos. 3 and 4 Holds and the lower 'tween decks of Nos. 5 and 6 Holds. When the net shoring is not in use, the wire-rope net rolls to a stowed position at the overhead. All deck fittings are recessed and flush with the surrounding plating. Lashings have been provided for the ondeck containers and for the lashing of underdeck wheeled vehicles.

Machinery Design

While the machinery plant reflects many advances in the state of the art, it is by and large a very conservative design. Reliability was the keynote here-on the basis that a vessel as costly as present vessels are, cannot afford any downtime for debugging. Also, economy was a major factor. The Mariner cycle, with modification, was used. Conditions of 600 psig-850 F at the superheater outlet were set. Based on past experience and cog­nizant of the changes occurring in the crewing situation, U. S. Lines insisted on a steam air-heater cycle, with economizer. Although aware of other types of air heaters which would ostensibly improve the fuel rate, it was felt that the broad con­cepts of the design would not be satisfied by any disruption of arrange­ments. By the same token, a conservative approach to the propulsion units, generators and boilers was maintained, insisting on design departures only where experience required change. One of these areas included the boilers where floor tubes were not permitted in the insulation and where a double cavity design in way of the superheater become a requirement. Still in keeping with the extreme desire for reliability, the concept of two feed pumps and a port feed pump was altered to three equally sized main feed pumps. A conventional approach to power­ing was maintained using a model test and applying the MARAD formula which since has been changed. The normal of 16,500 shp and the continuous maximum of 18,150 shp provide adequate margin for maintaining the scheduled speed. The main propelling unit consists of a Westinghouse high-speed, cross-compound, double-reduction geared turbine, driving a single propeller. Superheated steam is supplied from two Foster Wheeler oil-fired, two-drum, bent-tube, marine boilers. The guaranteed fuel rate is 0.54 Ib/shp/hr with the plant operating at normal power and using one gen­erator loaded to 575 kw. Paramount in the arrangement was the desire to maintain both engine and boiler controls on one level. This gives the engineer maximum control and maintains reliability. An automatic combustion-control board was supplied by General Reg­ulator Company. Forced draft blow­ers are Buffalo Forge, each of two with a capacity of 20,500 cfm. Space has been designed to provide for future installation of St. Lawrence  Seaway requirements. The three main Coffin feed pumps are of the single-stage, centrifugal type capable of delivering 435 gpm at a total head of 760 psi. Copes-Vulcan feed water regulators are the two-element control, air-operated type. Two complete Griscom-Russell, 10,000-gpd, salt-water distilling plants are installed. Ships service refrigeration is handled by two air-cooled, multi-cylindered, single-acting York com­pressors using Freon-12 refrigerant. Two Bailey Refrigeration ice-cube makers are provided. Electrical power is supplied by two Westinghouses 1250-kw, 450-volt, 1362.5-kva, 3-phase, 60-cycle a-c turbogenerators. While continuing the trend for use of 440 volt ac, special effort was made to provide the safest transmission and transformer system. The lighting sys­tem, for example, is the Delta-Wye type which provides the ultimate in safety by reducing the voltage from any  one  leg  to  ground  to  69  volts. Emergency power is supplied by a General Motors lOOkw, 125-kva, 450-volt, 2-phase, 60-cycle a-c diesel gen­erator set. The capacity was increased to pro­vide for the deck container load in the future, but special effort was made to insure maximum efficiency at normal, not at maximum load. A vessel's design is dynamic. From its first inception to the final stages of construction, a con­tinuing process of alteration and re­vision incoiporates the latest think­ing of the shipper, the designer, the shipowner and MARAD. This design philosophy is epito­mized in the remarks of Mr. William B. Rand, president of United States Lines Company, at the launching of the American Challenger. "Real success comes from shipper support, and I believe shipper sup­port comes with superior service. "That is what we offer you".".