by James Barlow
The wiring system of the ship led up from the generating plant in the engine room and spread with infinite ramifications through the ship. No one really knew its exact travels unless it was the chief electrician, and he was a very harassed man on the Areopagus. Electric wires had been armoured in lead and were lasting almost as well as the wire in the equivalent hotel on land – which was hardly looked at in twenty-five years. But there were many areas where wire couldn’t be protected, and in any case it could never be buried or carried between floor boards. Inevitably, although armoured, the wire had to be led through cargo spaces, areas of dampness and corrosion, up the sides of bulkheads and along many alleyways. How easy it was for someone fixing a bathroom cabinet, a bunk, a mirror or a wardrobe to drive a screw through a wiring conduit on the other side. How easy for a piece of cargo or even baggage to chafe against a circuit in a heavy sea. Fire was the greatest risk at sea, and the most dreadful had been due to electrical short circuits.
The number of things which had to be borne in mind in regard to the motion of the vessel was formidable. In this respect the Areopagus was old-fashioned and sensible. She had handrails in corridors and foyers, lee-rails on the tables, deck clamps to chairs and pianos. For nothing could really withstand the massive inertia of a big wave, or rolling and pitching, and the dimensions of the Areopagus would have otherwise allowed alarming movement of those objects farthest removed from the centre.
Like all ships, the Areopagus was essentially a large box girder divided into watertight sections. The sides and bottom of the girder were in effect the sides and bottom of the ship and the top was the main (Metaxas) deck although this was not obvious to passengers, for there were other decks and much superstructure above it. The ‘girder’ had to withstand the stresses of pitching rolling and corkscrewing, and had to be strong enough to stand poised amidships on the crest of a big wave with its two ends so little supported that they were virtually hanging.
The number of watertight compartments into which the Areopagus had been divided had been determined by a set of compulsory flooding regulations, designed so that she would float after a collision or heavy stranding had fractured the hull. The subdivision of the Areopagus was related to her skeleton of inner construction and it was into this that the cabins had to be fitted. The hull was of steel and its skeleton was a series of ribs about three feet apart which formed the sides and were called frames. These were joined transversely by similar ribs known as floors at the bottom and beams at the top. Outside, the skeleton was covered with flesh of steel plates tacked together by millions of rivets. Inside there were two bottoms, one secured to the underside of the floor framing – this being the real bottom of the vessel – and the second the false bottom laid along the top. The space between the two was divided into sections and used for housing fuel oil, drinking water or water ballast. The tapered ends of the Areopagus, like every modern liner or merchant ship, were cut short inside with strengthened watertight partitions, being collision bulkheads, which gave the ship a good chance of surviving a collision with something ahead or astern without serious flooding.
All the bulkheads and cabins had been permissibly pierced by pipes and wiring, and lower down the bulkheads were pierced by the propulsion shafting, but in the former case they could be protected by the closing of watertight doors at intervals along those decks likely to be flooded. The propulsion shafting was protected as it passed through watertight bulkheads by a surrounding of stuffing boxes and glands, so that there would be no leakage around the shaft from a flooded compartment to its adjacent compartment, nor any interference with the work of the propulsion shafting itself.
It all seemed easy enough to the passengers. They rarely considered these aspects of the Areopagus. They were more concerned with bars and swimming pools and the ports of call.
The Areopagus had in her lifetime steamed something like 4,300,000 miles. It was not surprising, then, that as she set sail the more than two thousand miles from Fremantle to Bali and Singapore on an Indian Ocean calm and warm, she had a formidable collection of minor faults caused by her age.
It was hardly surprising that she no longer made the twenty knots she had thirty years earlier. She had to strain to make seventeen. The high temperatures of steam passing year after year through the rows of high-speed rotor blades had resulted in the first rows in a very slight distortion, lack of strength and rigidity and minute misalignments. There was windage loss caused by fluid friction as the turbine wheel and rotor blades turned in the surrounding steam and diaphragm packing loss caused by leakage of steam from one stage to another through the diaphragm packing.
She was a very old liner, but like the steam-driven railway engines of yesteryear there was no theory no reason why she should not steam on forever. Perhaps the fundamental difference between the two was that a railway engine didn’t need to use its pure water over and over again. It could fill up with new. A ship did and, in addition to this returned ‘condensate,’ used desalinated seawater. Only corrosion and breakages and the increasing cost of repairing them should ever make her uneconomical to operate. But where the entire ship floated in a corrosive fluid and the very air was so salt laden that a razor left on the cabin dresser turned brown in a day, all the care taken with water passing through tubes and boilers couldn’t keep it entirely pure all the time. The Areopagus’ boilers were over thirty years old and of an outdated design, and many of the scores of tubes – most of them two inches in diameter – reached ‘end point’ and cracked from excess pressure or from age and corrosion on each voyage. They were, however, easily replaceable.
The boilers were secured in position in the ship by means of saddles and supports. Each enormous boiler steam drum was supported by the tubes which in turn were supported by the water drums and the water headers. The boiler casings were supported by steel framework built up from the water drums and water headers. The webbed beam construction, riveted to its various members, rested upon huge rigid beam structures built up from and a part of the rigid longitudinal structural members of the ship’s framework. These rigid boiler supports were braced both fore and aft and athwartships.
Underneath the tubes and brick and metal baffles was the furnace. The steel casing was lined with insulating blocks, high-temperature insulation bricks, and refractory firebricks. The insulating blocks were made of uncalcined diatomaceous earth, which in its best form was pure silica, whit, light in weight and insulated up to 1,500 degrees F. The refractory (or ‘dense’) firebricks, a compound of silica, alumina and calcined flint clay, could withstand temperatures of 3,000 degrees F and had excellent flame resistance.
It could hardly be expected that with over thirty years at sea the Areopagus would not show her age. The very nature of the sea had a compressive strength about which little was known. The buckling load of stiffened panels and the effects of residual stress and temperature factors were still theoretical considerations, papers read to learned societies, as were the lateral load and in-plane axial movement of the edges of the panels, which were free to slide inward but clamped against rotation. Loading might have a bearing as well as external forces. Price had a relevance, merchant-ship designers had to use simple and sturdy construction, seven times cheaper than the elaborate structures of warships. Isolated extreme loading could cause local cracks or hasten the metal fatigue caused by years at sea. The pressure of the sea in the storms encountered over thirty years caused the Areopagus to creak at the joints and make odd noises in the night. The vibratory stresses and very high transient local pressures in longitudinal bending caused by slamming and riding the crests of huge waves with the enormous weight of the bows and stern in mid-air had loosened very slightly many parts of or within the main hull of the entire ship.
In a liner so old seawater leaks, corrosion, lubrication leaks, dissolved oxygen all took their toll. The Areopagus had desalinating apparatus and Dimitrios had at times cleaned this, breaking lumps
of salt as hard and big as rocks. But salt-water leaks were inescapable, to be fought continuously. The Areopagus creaked and groaned; things wee loosened, and impurities found their way into the boilers if the struggle was neglected for a moment.
Boiler compounds were used on the Areopagus to defeat these corrosive processes and the dissolved oxygen in the boiler feed water was controlled by heating and mechanical de-aeration. But the old piping of the ship had to be cared for like the stomach of a duodenal ulcer patient. Any impurities, such as oil, in boiler water promoted foaming and priming which caused carry-over of moisture in the steam from the saturated steam drums to the superheater or even the machinery. Baked sludge still reduced heat transfer so much that blistering occurred and this sludge was not disintegrated by boiler compound. The exact condition of the boiler feed water was checked very occasionally for alkalinity, salinity, soap hardness and dissolved oxygen, but there was an understandable, possibly Greek tendency to let something happen and then repair it.
The whole purpose of the boilers, superheaters and other equipment was to generate steam – dry superheated steam of a temperature of 900 degrees F at the superheat outlet and a working pressure of 600 psi – which would convey thermal or heat energy to the turbines, the exhaust steam being converted into water and returned to the boiler for repetition of the cycle.
The Areopagus had two old-fashioned large boilers – one placed athwartship in each engine room – of the type called sectional header boilers because the front and rear headers (square-sectioned tubes) were built up on sections.
The normal water level in these boilers was near the middle of the steam drum – a huge construction high above the furnace and tubes – at the lower lip of the return circulating tubes. Feed water entered through the feed stop-and-check valves and was distributed throughout the steam drum by means of the internal feed pipe, which was a large pipe having holes along its sides and extending the length of the drum near the bottom. The relatively cool and heavier water descended from the drum through the downtake nipples and front headers to the front end of the scores of two-inch tubes, that is, at the lower end of their eighteen-degree incline, via the cross-box, and then went into the tubes and to the rear headers and up them. The hot gases of the furnace, passing over the tubes, transferred heat to and through them to the water, which, when heated, became lighter and therefore rose up the incline of the scores of tubes and vertically up the rear headers. As steam bubbles formed in the heated water they rose also and tended to accelerate the circulation. The hot water and steam flowed to the tops of the rear headers and through circulating tubes to the steam drum.
The hot water flowing from the circulating tubes mixed with the relatively cooler water in the drum and recirculated, but the steam was directed downward by a baffle over the ends of the circulating tubes, rose through the water to the top of the drum and into the dry pipe (still inside the massive boiler). From there it went through external piping to the superheater.
Steam passing through the tubes of the superheater element had its temperature raised to 900 degrees. The superheated steam now passed to the main steam line and operated the turbines. At this temperature it was not only dangerous but difficult to handle, and did not give up its heat as readily as steam, which was just at the saturation temperature.
It was desirable to use steam for the general services of the Areopagus – running anchor capstans, windlasses, heating accommodation and galley stoves and improving the viscosity of the heavy-grade fuel oil to make it pumpable – but it was so dangerous and unchangeable that for these purposes it had to be desuperheated. It was necessary to reduce the heat of the steam supply, where it was diverted, to a point just above the saturation temperature and at the pressure for which the auxiliary equipment was designed to operate. This was done by injecting relatively cold water into the steam so that by diminishing the temperature a larger quantity of steam at a lower temperature was obtained. The control had to be sensitive or cracking noises would come from the pipes. In fact it was done by a device which sensed the steam temperature and then introduced water by means of the desuperheater. The water was at once reduced to a fine mist so that it mixed readily with the steam and took the excess heat out of it.
The very hot dry steam entering the Areopagus’ high-pressure turbine passed through eighteen wheels and turned 5,132 blades, and the rotor shaft revolved at a maximum of 5,746 turns a minute.
Turbines should operate at high speeds. Propellers, on the other hand, have their highest efficiency at relatively low speeds. If they rotated too rapidly – and the two propellers of the Areopagus each weighed ten tons eighteen hundredweight – they churned the water and cavitation followed. Cavitation was the forming of cavities in the water around the low-pressure sides of the blades as a result of the propeller trying to discharge the water faster than it could flow into the propeller. It was capable of buckling the blades.
Therefore the high rotational speed of the turbine had to e reduced by reduction gears which themselves weighed tons. The Areopagus had double-reduction gears to reduce the 5,000 revolutions a minute of the rotor shaft of the turbine to the 30 of the propeller in the water. These great big main-reduction gear wheels – eight feet in diameter – and the smaller pinions were of the double helical or herringbone type. In theory they were long-pitch screw threads which ran very smoothly with little noise and with even distribution of pressure along the entire length of the tooth. The whole gear assembly was installed in a housing of welded cast steel and boiler-plate construction.
The design of flexible couplings permitted a small amount of misalignment to the hubs. Rigidity would have affected the meshing of pinion and gear and resulted in the breakage of teeth. In the Areopagus this condition was still fulfilled adequately, considering her age. But the radial alignment between the port pinion and gears was not exact and was causing uneven wear due to the driving force being concentrated on a small portion of each tooth rather than over the entire tooth contact surface.
The two engine and fire rooms of the Areopagus were arranged one behind the other, the port being forward of the starboard by as much as seventy feet. Thus the port propulsion shafting was also seventy feet longer than the starboard. The main propulsion shafting transmitted the torque from the main engine and reduction gears and in turn transmitted the axial thrust of the propeller to the ship’s structure. It was not a single piece of steel but several pieces, of which the actual propeller shaft had a diameter of 20 inches and the intermediate shafting one of 17 and one-half inches. The port propulsion shafting of the Areopagus was 140 feet long and it consisted of several sections of single steel forgings with a smooth bored axial hole from end to end.
Due to the weight and length of the propulsion shafting it had to have bearings to support it as well as hold it in alignment.
Over the years these shafts had worn minutely but sufficiently for them to be fractionally out of alignment. This caused a variation in the wake stream (in the sea) of the propellers, and in turn aggravated the propeller blade angle section of incidence which occurred twice per revolution with reduced or misdirected thrust and torque through the 360 degree rotation of each propeller, particularly the Areopagus’ port propeller. Because of this wake variation and the asymmetrical nature of the flow, the centre of thrust was markedly off the original shaft axis and was as much as twelve inches away from the shaft centreline as it now was. The severe cyclic forces induced in the propellers were causing fatigue, although the bronze propellers could be expected to last the life of the vessel. The propellers were, even in normal alignment, a source of shafting vibration, and more so after thirty years of wear with the gradual shifting of position.
Propeller blades are approximately helicoidal surfaces. When rotated about their axes they shove aside the seawater in which they are immersed in a general fore-and-aft direction, providing the alignment of shafting is normal. The sligh
t misalignment in the Areopagus was only noticeable in wasted effort, reduced performance and increased vibration. The solid-built propellers – each made in a single casting and then finished to final dimensions by hand-turned ‘inwards,’ that is, the port propeller revolved clockwise when viewed looking forward, and the starboard rotated anti-clockwise.
The owners of the Areopagus used the cheapest possible fuel and lubrication oils. The selection of oil for a turbine lubricating system was always a compromise, for it had to lubricate under several conditions. In theory, selection should have been based on the most arduous conditions likely to be met. In fact price was the main factor, and the turbine reduction gears, high-speed bearings and gears having heavy tooth pressures were all lubricated from the same system and the viscosity of the oil used was lower than desirable for the bearings.
The oil line to the reduction gears of the port side was part of the main engine lubrication system. The oil was sprayed through nozzles upon the meshing teeth and it fell to the bottom of the casing. The oil level there was neglected. It was still below the lower level of the teeth of the main gear. No oil excluding pan was fitted. If the oil rose any higher the main gears would be immersed in it and would churn the oil into foam or emulsion, which would cause the lubricating oil pumps to lose suction. Further, the oil would have become oxidized and cause harm to metals.
Much of the lubricating oil had to be used over and over again and it had to be clean ad at a proper temperature. This was very nearly hopeless on the Areopagus, for it was impossible to eliminate the scale and sand from various castings or prevent dirt entering during overhauls. These substances were picked up by the oil and, despite strainers and centrifugal oil purifiers, and even magnets within the strainers, they scratched the bearings and gears minutely . . .