Marad Design C3-S-46a " BANNER-Class" (American Export Lines)

By W.J.Dorman , Vice-President-Technical, American Export Lines

When developing the design of the [Export Banner-Class vessels back in 1958, we were guided by a philosophy which is best described by the slogan "Cargo Is King." We wanted a vessel for our East Coast U.S.A.Mediterranean service. This trade carries every conceivable variety of general cargo, the majority of consignments being in the high-cubic category. This cargo demands spaces which are of maximum volume, clear of obstructions and as rectangular as possible. It needs clear tank top and tween-deck areas to stow on, and hatchways of the greatest possible dimensions. And finally, as in all trades, the cargo must be handled rapidly and efficiently. Our goal was to cater to the above cargo requirements, after accepting the principal dimensions and characteristics which were dictated by port conditions and/or various "ground rules" which the Maritime Administration sets up for subsidized new construction. An over-all length of less than 500 ft was indicated for efficient operation in many of the smaller Mediterranean ports. The beam and depth were greatly influenced by MarAd stability requirements. The speed and the power plant size was established by MarAd. These requirements resulted in comparatively fine hull lines, and it was very obvious that we had to go to a machinery-aft design if we were to make cargo our king and give it the best space in the vessel. It also was evident that the best cargo-cubic totals were obtained by moving the machinery "all-the-way" aft, A modern steam-propulsion plant can be fitted compactly into the extreme stern of the vessel by a split-level arrangement. We could see no good reason for a compromise "part-way-aft" location, or for the small cargo space in 'tween decks abaft the propulsion space that is found frequently in machinery-aft designs. We, of course, recognized the traditional objections to a machinery-aft dry-cargo vessel and made every effort to overcome them. The trim problem was met with adequate tankage forward and aft and in the installation of powerful ballast pumps and large ballast-transfer lines. The possibility of excessive hull vibration was faced and great care was exercised in developing the structure in way of the engine room, particularly the main turbines, reduction gear and shaft-bearing foundations. We are happy to report that we have no vibration problem. She does not shake. The problem of visibility in navigation was answered by placing the navigating bridge, deck-officers' quarters, etc., in a narrow deck house near amidships. This feature is expected to cause considerable discussion. We can only assure all interested that we have weighed all the pros and cons of the present arrangement versus "everything aft/' and still have an open mind on the subject. And so, we proudly present the Export Banner to our customers and the marine fraternity. We hope we can keep her spacious holds and 'tween decks filled with cargo through a long and prosperous career, for here is a ship where "Cargo Is King."

General Description

The first of American Export Lines high-cubic engine-aft ships, the Export Banner, entered service in October, 1961. It immediately proved its high-cubic capabilities and its ability to serve the military needs by loading a full cargo of vehicles in Seattle for Northern Europe. A quick check of Export's records indicates that this cargo may be the largest! cubic load ever carried by an Export I freighter. This cargo lift substantiated] the usefulness of the side ports, bulkhead doors and other features of the vessel specially installed for carriage of vehicles. The Export B a n n e r is the I first of four freighters, Design No. C3-S-46a, being constructed by National Steel and Shipbuilding Company, San Diego, Calif., for American Export Lines. It also is the third vessel built by NASSCO for Export, having been preceded by two engine-amidship vessels. The BANNER-class of ships was designed by the J.J. Henry Co., Inc., of New York and Philadelphia, the owner's naval architect. The construction also was supervised by the  J.J. Henry Co. National Steel retained Sun Shipbuilding and Dry Dock Company to prepare the detailed working plans. This combination brought into the construction picture three firms with wide experience and undoubtedly contributed to the apparent success of these ships. As explained in "The Philosophy of the Design," every effort was expended to increase cubic. While American Export's trade is based generally on cubic requirements, there are times when cargo deadweight is important. For this reason, the 493-ft ship has a scantling draft of 30-ftj 6 in, while its predecessor class only had a 28-ft scantling draft. The Export Banner, with a 19,350-ton-displacement, is a single-screw, steam turbine-driven vessel with a raked stem and a cruiser stern. It is subdivided by eight transverse bulkheads. The hull is constructed with a combination of transverse and longitudinal framing. The bottom shell, tank top, Second Deck and Main Deck are longitudinally framed while the side shell and Third Deck have transverse frames. The shipbuilder found that this design proved to be more easily constructed than with full transverse framing. Some of the design features incorporated in this vessel to make for better cargo stowage are: No bilge brackets, the scantling of the frames was increased slightly; piping that usually is run along the frames has been installed in a shallow pipe tunnel which is recessed into the tank top and plated over; air escapes, sounding tubes, etc., are run up between the stiffeners of bulkheads -there is no piping on the smooth side of bulkheads; wireways, CO2 piping, etc., are run between the longitudinal frames, and box construction has been used for hatch side girders to reduce their depth. The extended forecastle provides space over No. 1 Hold for special cargo. Each side of this space is sepa-rated from the hatchway by screen Bulkheads with 18-ft-wide sliding doors. Deep tanks are provided in No. 1 Hold for cargo oil or salt-rater ballast. In Hold No. 2, an Mop Deck is provided so that the lower hold is subdivided for easier general cargo stowage and segregation. Large sideport doors are provided at the Second Deck level in Holds Nos. 3 and 5 for loading vehicles or other cargo by means of fork-lift trucks. These holds are connected (No. 3 with No. 2 and No. 5 with No. 4) by sliding watertight doors in the transverse bulkheads. This pro-vides an open deck area extending from Frame 31 to Frame 131, 250-ft long on the Upper 'Tween Deck.The Poop Deck is extended forward over Hold No. 6. This provides special-cargo stowage similar to that over No. 1 Hold. On the two 'tween decks in this hold are the refrigerated cargo compartments. The lower hold is divided into six deep tanks, four of which are onvertible for dry cargo. These deep tanks are stainless steel clad with smooth interiors. It is possible to heat the cargo in these tanks by heating grids of angles welded to the outside of the tanks in the cofferdam spaces. Fitted between the hatches of Nos. 3 and 4 Holds is the Bridge House. The dimensions are such that it does not take up any more deck space than would be used by the normal winch house. This erection is four decks high with the wheel house, chart room, sea cabin and gyro room on the Navigation Deck. The Captain's office and stateroom, the Second Officer's and Radio Operator's staterooms and the radio room are on the Lower Bridge Deck. The First, Third and Fouth Officers' staterooms and a pantry are on the Cabin Deck. On the Main-Deck level of the house are the hydraulic pump room, motor-generator sets, CO2 room, fan room, user's office and deck office. All other personnel staterooms, gal-ley, mess rooms, lounges, etc., are located in the after house. There are no accommodations for passengers. All accommodations, both aft and amidships, are air conditioned by Carrier 45.8-ton and 11.2-ton, respectively, units.

The hatches to Holds Nos. 2, 3, 4 and 5 are extra large, 31-ft wide by 40-ft long. The hatches to Nos. 1 and 6 Holds are made smaller due to the hull shape and types of cargo carried. While the hatch openings could have been wider, the owner's operation requires ample wing spaces on all decks for segregation of cargo for the many ports of call involved in the Mediteranean run. All hatch covers are hydraulically operated with the hydraulic machinery located in the 'midship house. The Greer Marine covers are specially designed so that the center leaves can be opened vertically without raising the other leaves. Fittings are provided to insert boards between these two raised sections, thus forming a grain feeder. Special openings are lovided in the hatch girders so that grain can be fed into the wing spaces. The cargo spaces are dehumidified by two 7,000-cfm Cargocaire units. Individual hold controls allow for use of these units as required by the various cargoes being carried. The ducting for these units are fitted under the longitudinal deck beams but do not extend below the hatch side girders. All hatches, except No. 1, are double rigged. Ebel-type gear with square kingposts is used throughout, except for the after end of No. 3 Hold and forward end of No. 4 Hold which have conventional rigging, and the after end of No. 6 Hold where two Lake Shore level-luffing 5-ton cranes are installed. The square king-posts for the conventional-type gear midships form part of the house structure. Holds Nos. 2, 3, 4, and 5 are each served by a pair of 10-ton booms and a pair of 7-ton booms. Holds Nos. 1 and 6 are fitted with 7-ton booms. A 60-ton boom serves Hold No. 4.

The cargo-handling equipment is of the all-electric type furnished by General Electric Company and the Western Gear Corporation. It includes besides the cargo winches, topping and vanging winches which are kingpost mounted. The winch-control platforms are raised above the winch-house top and project over the hatch covers when in the opened position. This provides for a clear view of the cargo sling by the operator even when loading directly on the tank top. The C. H. Wheeler two-cylinder electro-hydraulic type steering gear is classed as one of the features of the vessel. The unit is equipped with dual pumping units, either one is capable of handling the steering requirements. These two pumping units are so connected electrically that if one unit fails, the other cuts in automatically. In addition, the arrangement provides convenient, positive control of the transfer valves in any emergency requiring fast rudder response. This flexibility is provided by a power synchro transmission system. If both pumping units are used simultaneously, the rudder responds twice as fast. This feature is most useful in close quarters and canals. The Hyde anchor windlass is of the horizontal, spur-geared, electro-hydraulic type with two wildcats. The pumping unit is located below deck. The four two-speed electric-driven capstans can provide a 20,000-lb line pull at 35 fpm. These units are standard Western Gear design with the drive units located below deck. The plastic lifeboats together with the davits and winches were furnished by Marine Safety Equipment Corporation and are installed on the after Boat Deck. Life rafts are provided for the amidship house.

The wheelhouse is wider than on the predecessor vessels but is not as deep. The 15 Kearfott windows across the front of the house provide for excellent visibility without the need to use the bridge wings except during docking. Navigating equipment is located on the after bulkhead where it is not congested but yet puts the instruments within easy view of the view of the officer on watch. Aft of the wheelhouse is the chart room. The standard magnetic compass is located on the flying bridge. The helmsman can view it through a periscope. This not only eliminates the need for a magnetic compass at the wheel but removes a piece of equipment that takes up room. Other wheel-house equipment includes a Sperry automatic-steering control, gyro compass and course recorder; Henschel rudder-angle indicator and engine-order telegraph; Raytheon echo depth sounder and both relative and true-motion radar, and a Mackay Radio Loran. The radio room is outfitted with Mackay Radio equipment. A docking announcing system provides for instant communication between the bridge and docking stations forward and aft. The indicators and control for the Cargocaire dehumidification system are located in the chart room. A Walter Kidde fire-detection system also has indicators on the bridge.

Power Plant Design of Export Banner'

It is a well-known fact that to design a marine power plant to operate efficiently and one that will have a large degree of habitability, meet with all the requirements of the Regulatory and Governmental authorities and still satisfy the Owner's Operating Department, is a very difficult task. The only way to accomplish this is by the combined effort of the designers and the owner's operating department. On this design, American Export set up a New Construction Committee which included not only their own personnel but also that of the J.J. Henry Co. Since an engine-aft ship was new to the American Export people, and the J.J. Henry personnel had had experience only on tankers and ore carriers where machinery is aft but not so restricted in space, many conferences were held. George J. Mortensen, Superintending Engineer, American Export Lines, and his assistants John E. Bone and John Fenton, and the J.J. Henry Co. people spent every effort possible to eliminate unnecessary equipment; rearrange machinery to fit in the minimum space, yet be easy to maintain, and to provide a workable arrangement. By the use of large-scale sectional plans, studies, mock-ups, etc. they were able to develop a design of a machinery space within the confines of the after hull lines which has been highly praised. The unique feature of the arrangement is the use of a "split-lever' design which does not give the operating personnel a feeling of claustrophobia. Without sacrificing fuel economy or safety and reliability, certain usually fitted units such as oil and water separator, a third turbo-generator set, the low-pressure steam generator and the drain cooler with its associated steam trap were eliminated. This not only saved space but reduced the cost of equipment and piping as well as future maintenance expenses. Another innovation was to provide a pipe tunnel to serve the after cargo-oil tanks which contains the necessary suction and filling piping as well as manhole openings. These latter items permit butterworthing and cleaning of the cargo tanks while cargo is still contained in the 'tween-deck spaces above them. Thus, the four convertible and two fixed deep tanks can be readied for their next liquid or dry cargo with a minimum, if any, delay once the liquid cargo is discharged. The cargo-oil pumps are located in a recessed pump room between the engine room and the pipe tunnel. The fuel-oil transfer pump and oily-ballast pump and all cargo-oil, fuel-oil and double-bottom tank manifolds also are located in this recess.

Thermal Arrangement

The plant's thermal arrangement employs a two feed-heater, steam air-heater cycle with turbine-driven feed pumps and two condensing turbogenerators. Throttle steam is at 600 psi and 850 F with 28.5-in Hg condenser vacuum when steaming in 75 F sea water. Feed water enters the boilers at 285 F. Except for the feed pumps, all auxiliaries are motor driven. The low-pressure feed heater located high in the engine room drains to the atmospheric drain tank through a barometric drain which makes possible the elimination of a drain cooler and its associated piping and equipment. The high static head on the 1-p heater drain overcomes the shell vacuum and drains the heater without the use of a trap. The drain tank is then pumped into the condensate line before the deaerator. This avoids condenser flash losses. Combined with elevated feed temperature, cast-iron finned economizers were fitted in the boilers to avoid all possibility of sulfuric-acid condensation and corrosion. The cycle is carefully arranged to assure that under no condition of steaming would the feed temperature fall below 275 F. These vessels are to be used on runs where part of the time they will operate at powers as low as 60 percent of normal. It is therefore desirable that the high feed temperature be economically maintained by bleeder feed heating down to this power, instead of the usual live-steam feed-heating make-up. On the preceeding C3-S-38a Class vessels, this was accomplished by the use of a small topping feed heater, thermostatically controlled and using high-pressure steam. On the Export Banner group of vessels, the turbine manufacturer modified the turbine design, making available an intermediate-pressure bleed point at 80 psi, This bleeder then supplies the necessary steam through a regulating valve to supplement auxiliary-exhaust steam for feed heating in the deaerator. The resulting system is simpler and more reliable with only a very slight sacrifice in efficiency at normal power.

Propulsion Machinery

The main propelling unit is a 12,-50O-shp, normal rating, General Electric cross-compound steam tur-bine and double-reduction gear set driving a single propeller shaft. The main unit is similar to that on the previous class of Export vessels except for a 10 deg F increase in steam temperature. j A service speed of 18V2 knots will be attained while the propeller is turning at 107 rpm. The main unit is designed so that it can operate continuously at 13,750 shp, and also at a Navy defense rating of 17,500 shp by reducing main-turbine bleed-ing and sacrificing plant efficiency. This maximum rating, of course, utilizes gear loading, furnace heat-release rates, etc. higher than norml merchant-marine practice. All piping, heat exchangers, pumps, etc. are sized to permit operation at this emergency defense power. The two Babcock & Wilcox two-drum marine-type steam generators are designed for 750 psi supply steam at 615 psi and 855 F at the superheater outlets. These double-cavity boilers have a normal steam flow of 48,400 lb/hr each, and are fitted with two-element feed-water control and a feed-water level indicator. As stated previously, the boilers have cast-iron finned economizers and steam air heaters and retractable soot blowers for superheater banks. The condensing equipment consists of a 9,000 sq ft, all copper-nickle Ingersoll-Rand condenser and two Worthington 1170 sq ft copper-nickle auxiliary condensers. The main condenser supports the L-P turbine while the auxiliary condensers are suspended under the turbo-generator sets. These are on either side of the propeller shaft. The main circulator and other centrifugal pumps were furnished by Fairbanks Morse while the rotary pumps were manufactured by Warren Pump. Other equipment includes a 16,000 gpd Griscom Russell distilling plant, DeLaval lube-oil purifier, Griscom Russell fuel-oil heaters, American Standard lube-oil coolers and Green Fuel Economy forced-draft blowers. The suppliers list at the end of this article gives all the major engineroom equipment, all of which added to the success of this plant.

Electrical Installation

The design of all electrical equipment for this class of vessels reflects the desire of the naval architect and Owner to effect savings wherever possible. Ease and reduction of equipment maintenance, avoidance of unnecessary refinements, simplification of the electrical plant and its operation, and still providing the proper degree of dependability of the plant and all its parts were factors considered in this design. To accomplish the above, the following steps were taken: 1. All motor connections were made on terminal blocks in the connection boxes, thus avoiding taped connections. 2. High interrupting-capacity circuit breakers were used, rather than fused breakers. 3. Specifically designed lighting fixtures were used to make ground tracing in quarters fast and easy. 4. Since the basic design places the main and emergency switchboards aft, a forward switchboard was installed, incorporating 450-v and 120-v ship-service buses, 120-v and 24-v emergency buses and a 24-v battery charging unit. 5 Special designs were used in cargo holds to keep all cables on the stiffener side of bulkheads and all horizontal cables above the line of the deck-longitudinal angles. 6. Both relative motion and true-motion radar displays were provided for an improved aid to navigation. 7. No antennas are located over cargo holds. 8. The engineer's signal and alarm panel, embodied in the main gage board has been restricted to only the most vital services, and the alarms grouped for easy recognition. Other alarms, which will be active under special circumstances, are located at the operating station concerned with the protected function. Auxiliary electric power is supplied by two 700-kw General Electric turbo-generator sets. Power Is 450-v, 3-phase, 60-cycle a-c at 0.8 power factor. The General Electric Company also supplied all motors and controllers for the vessel on deck and in the engine room. Pacific Electric Company manufactured the main and emergency switchboards.

Machinery Arrangement

The "split-level" type arrangement resulted in an economical use of the space available. The dispositon of the main units is conventional with the boilers over the line shafting and aft of the turbine-operating flat. However, the boiler flat is half a deck higher than the operating flat. Good visibility is provided to the boiler flat and also to the turbo-generator and feed-pump flat immediately be- low the boiler flat. Access to the machinery space is pmvided on the part and starboard sides on three deck levels. Doors from passageways on each level open on gratings which run around the periphery of the engine casing. This leaves a clear opening extending from the removable skylight down to the reduction-gear casing and boiler-firing aisle. The inclined ladders are along the casing sides. This arrangement permits easy removal and replacement of equipment. The upper casing contains the usual d-c heater, lube-oil storage, settling and gravity tanks and the ventilation blowers. The boiler steam drums are at Main Deck level along with the principal steam-reducing-valve station. On the next deck down are the air-conditioning plant, Cargocaire unit, forced-draft blowers and the machine and electrical shops. Below the Second-Deck level, which is at 35 ft 9 in above the keel, are located stepped flats. The flats generally are stepped at the mid-length of the machinery space. The flats located in the after part of the space include the boiler flat at 28 ft, the turbo-generator and feedpump flat at 18 ft and the lower engine-room floor at 8 ft 6 in above the keel. Forward are the distilling plant, to starboard, and the main switchboard and main operating flat, to port, 21 ft 9 in above the keel. Below are the main condenser and main circulator with the lower floor plates located at 10 ft and 6 ft 6 in above the keel. The pump room recess opens off the engine room just forward of the main condenser. Access to the cargo-reefer diffusers is through a watertight door forward of the reefer machinery. The main steam and turbo-generator steam stop valves are located right at the superheater outlets on the after sides of the boilers. The main switchboard is to port of the main turbine operating station and faces inboard. The two electrical group controls are just aft of this location on flats stepped up and down from the main switchboard flat. The auxiliary condensers * are located to port and starboard of the two short line-shaft sections. The tailshaft can be drawn inward and passed out the ship side to port without interference with other machinery. Two unusual features are the "re-mo te" emergency fire pump located in a compartment recessed in the after peak tank and entered through a trunk leading from the steering-gear room, and a high-capacity clean-ballast pump located in the lower forward engine room which is provided to quickly ballast the bow for vessel trimming. The vibration characteristics of this class of vessel were investigated and the recently completed trial trip of the Banner verified the earlier conclusions that the hull and torsonial vibrations would be well within acceptable limits. Mar Ad's Trial Board reported that "The majority of over-all ship vibrations that were recorded compared very favorably with measurements made on previous ships by this office." It is to be noted that the General Electric Company also made their usual torsonial vibration analysis of the machinery plant during the manufacturing stage. Their investigation showed that the first critical speed would occur at 44.9 rpm of the propeller. This condition was overcome by tuning the h-p and 1-p turbine branches to the same frequency, resulting in vibrations 180 deg out of phase, thus eliminating propeller induced vibration. The next critical speed was calculated to be at 126.1 rpm, which speed is safely above the maximum propeller operating speed.