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Volume 17, Number 4July/August 1966

In This Issue

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The Central Fact

On a tanker, "the cargo is the point of everything."

Written by Paul F. Hoye
Photographed by Burnett H. Moody

A board the Esso Den Haag, oil is the central fact.

You don't realize it right away. You are too busy gaping at the sheer size of the deck, a vast stretch of steel plating scrubbed and weathered to the color of old brick, and at the high clean white superstructure rising out of the stern like the side of a glacier. Besides, what strikes you is not the presence of oil, but the absence. How could there be oil, you wonder, on a vessel so well-ordered that the officers greet you in pressed plaid sport shirts and creased slacks? Could there possibly be a mistake? Could they be carrying something else this voyage?

It is not until later—after you have adjusted to the fact that to get to the bridge you take a five-story elevator and realized that really was a swimming pool you saw on the funnel deck—it is not until then that you begin to sense the presence of oil. It is not until then that you realize that somewhere beneath your feet, somewhere deep down under the main deck, are stored nearly 27 million gallons of crude oil and that this cargo, sloshing about silently in the dark there, dominates the lives of the men aboard, controls their work and time off and has dictated the size and shape of the ship to which they are assigned. As the First Officer put it, "The cargo is the point of everything."

It comes on you slowly, this realization. One day, by a sighting port, you see a small stain of oil on the deck. The next day you catch a faint sour smell on the wind, a mere whiff gone as quickly as it came. The third day you notice a seaman unreeling a measuring tape and you learn that he is checking the distance between the top of the hatch and the surface of the oil and that the distance is just five feet. And then comes the day when the First Officer hands you a set of limp cotton overalls and slips into another pair himself. "We're going to tour the ship," he tells you, "and learn something about tankers."

Before I boarded the Den Haag, I had no real idea of what a tanker was like. I couldn't have distinguished the manifold from the foremast. But having boarded the ship and having stowed my gear in the alloted space, I almost immediately came across a set of anodized aluminum plates bolted to the bulkhead of a lower deck companionway. On the plates, stamped in sharp black lines, were complete scale drawings of the Den Haag—so clear and detailed that the most obtuse novice could at least grasp the general layout. Thus, when the First Officer led me down the companionway on. the first leg of the inspection, I had in mind a clear if very general idea of the ship's basic plan.

The Den Haag is divided into three sections. Huddled up forward is the forecastle with, above deck, a clutter of winches, stanchions and bollards just forward of a stubby foremast and, below deck, a warren of fuel and ballast tanks, shops, storage lockers and various compartments and spaces in which are crammed such miscellany as an emergency diesel pump, anchor chains piled in awkward heaps of rusted, salt-crusted shackles, the big Suez Canal searchlight, hoses and special nozzles for washing down the tanks, liquid foam for lighting fires, and sacks of sawdust to sop up oil spillage.

Aft, crowded onto the stern, is the superstructure crowned by the radar scanner perpetually circling while the ship is underway, and the twin stacks leaning against the wind. In the aftership superstructure, arranged in descending order, are the bridge, chartroom and wheelhouse, the quarters for the deck officers, engineers and crew, the galley, dining salon, the lounges, the lifeboats, the stern anchor and, eight decks below, the engine room, ablaze with an eerie, bluish light and vibrant with noise.

And in between is the oil.

The division of the Den Haag into these sections gives the ship we were riding her distinctive look. But the engine room, bridge and living spaces are all located in the stern for reasons of safety and economy, not appearance. On tankers the engine room has always been placed aft rather than midships thus eliminating the need for a tunnel running half the length of the ship to house the propeller shaft. This not only saves valuable cargo space but does away with the danger that the cargo might ignite because of an overheated bearing. Concentrating the bridge and the living quarters at the stern also puts 680 feet of steel and all the cargo between the men and what would probably be the point of impact should a collision occur. This design also assures that the greatest number of the ship's company, on duty and off, would be on that part of the vessel most likely to survive and float even in the unlikely event that she should break in two. Furthermore, the designers of the Den Haag eliminated a hazard common to freighters which have the bridge and quarters amidships: the possibility that a rare spark from somewhere would land oh the cargo area; on the stern such sparks are simply blown overboard into the water.

All this the First Officer discussed as he led the way along the narrow catwalk bisecting the main deck from bridge to forecastle, the start of what he said was an essential tour. "If you are to write about this ship," he said, "you must see all of it, and right here is a good place to begin."

"Right here" was a dim compartment high up in the forepcak near the bow, with an open manhole in the deck. We slipped through it and began to descend the rungs of a narrow ladder. It was hot and the smell of oil was strong. The rungs were slippery. Except where the First Officer's gastight flashlight threw a dim beam the place was pitch black.

"This is called the 'forepeak tank,' " my guide explained. "It measures 68 feet from top to bottom, and has a capacity of 100,000 cubic feet. There are also four deep tanks in the foreship having a total capacity of 266,567 cubic feet of fuel oil or ballast water."

For a moment there was silence. Then I heard, faintly, the sound of the open sea washing against the sides of the ship. I suddenly realized two things: that we were standing about 48 feet below the surface of the water outside and that right about here was probably the most vulnerable point of the whole vessel. Right here, the structural strength of the curved bulbous bow and the force of the throbbing turbine aft were pitted against the enormous pressures of the deep and the stunning power of angry waves. I was beginning to wonder how any ship could stand up against these conflicting elements when, in the beam of his flashlight, the First Officer showed me the answer: the entire bow was braced with heavy steel I-beams. There were nine layers of them almost seven feet apart and they formed an interlocked structure so rigid and unyielding that it was hard to conceive of even the worst seas damaging the forward section of the ship in the slightest.

Climbing up to the open deck and proceeding to the forecastle we continued the tour, stopping here and there while the First Officer described the workings of the nozzles which can be dropped down into the tanks to hose them off, or explained that tons of sawdust are carried to sop up spilled oil.

He talked with the enthusiasm and clarity of an officer who knows where each bolt in the ship is and what part of the ship it is supposed to hold together. In an hour's time he pointed out every locker, chamber and compartment in the forecastle, explained the functions and capacities of each, and seemed able to go on indefinitely. Finally, though, he stopped. "Now I must go and inspect a pump. We'll talk more later."

Which we certainly did. All that week, as the Den Haag steamed west through the golden sunshine of the Mediterranean, we—as well as Captain Jansen, the Second Officer, the Third Officer and the Fourth Officer—walked around the Den Haag and climbed up, down and through the Den Haag, and, constantly, unendingly, talked about the Den Haag

"See that red instrument there near the catwalk? The one that looks like an antiaircraft gun? It's a foam monitor for fighting fires. We have to handle it manually and there are eight of them working off what we call a foam-preportioning pump that sends a solution of foam and water through foam lines into the nozzles at high pressure. They're positioned so that we can provide a canopy of foam over the whole cargo area when necessary, and also so that we can handle them from behind the shelters on the fore and aft gangways……This, of course is in addition to the diesel pump up forward that supplies sea water and or foam from a separate tank—250 tons an hour, by the way—and a battery of steel CO2, bottles. One simple pull at a handle directs CO2 gas to the engine or boiler room. For extra safety an alarm is first sounded to enable all men present there to leave before the gas is released

"The anchor? It's hauled aboard with a steam winch and a system of gearing that has a special shut-off valve in case anything sticks down below. We don't want to snap the chain, eh?.

"Yes, the bridge, living quarters and lounges are air conditioned. It sounds expensive but the Den Haag is almost always assigned to semitropical regions and there it can get quite uncomfortable, even at sea. Besides, tests have shown that if you air-condition the ship the corrosion is less and the overall maintenance easier. That saves more than the air conditioning costs....

There are pumps everywhere. The most important, of course, are the cargo pumps and each is driven by a 1,300-horsepovvcr turbine and each can handle 11,000 gallons—U.S. gallons—per minute. The stripping pumps—they're to get what the cargo pumps leave—have a capacity of 1,400 gallons per minute. There is also a clean-ballast pump rated at 9,200 gallons per minute. There are steam pumps, a diesel pump, hydraulic pumps, bilge pumps, main and auxiliary circulation pumps, main feed pumps, lubricating oil pumps, fuel oil transfer pumps, wash water pumps, sanitary pumps … well, as I said, all sorts of pumps…. The fore and aft pump rooms have been equipped with explosion proof ventilators that can change the volume of air many times an hour

"Look at it this way. If the tanks are the belly of the ship, the manifold is the mouth. All it is, as you can see, is a battery of large pipelines running almost all the way across the deck in about the middle of the ship. When we are loading or discharging cargo we couple hoses to the manifold on one side or the other and either open up the valves—if we're loading—or turn on the pumps—if we're discharging—and the oil starts moving in or out. The valves are located at the very bottom of the tanks and they are opened or closed hydraulically or by hand via a long rod that extends from the deck, all the way down. In either case, the oil is routed through three systems of pipelines: 20-inch main lines, 16-inch main branch lines for pumping the oil aboard and 18-inch lines for discharging it. You can see those lines there under the fore and aft gangway, the ones going into the deck. That other line there, the one covered with rust, is not a cargo line; that carries steam forward ....

"During the voyage we must keep constant check on what we call 'ullage.' That's the distance between the surface of the oil and the top of the hatch. Oil, you see, is unlike other cargoes. It expands and contracts and you have to keep this in mind while you're loading. One time, the ship's records show, the oil was loaded when the outside temperature was 105 degrees Fahrenheit. When they finished loading, the ullage was four feet. But when the oil was discharged some 10 days later the temperature was 80 degrees and the ullage was four feet nine inches. That's quite a difference.

"Here in the boiler room is where you can see one good example of mechanization. To maneuver a ship—slow down, speed up, back up, turn, and so forth—requires a constant adjustment in the flow of steam. That's because—I'm simplifying, of course—the pressure of the steam is what turns the turbine fans and, in turn, the shaft and the propeller. Now to regulate the steam—reduce it to slow down or increase it to speed up—means that the burners which generate the steam have to be extinguished and relighted at a fairly rapid pace and this in turn requires that the burners be pulled out or pushed into the combustion chamber. This whole process used to be done by hand. Today, one man standing at a control panel in the engine room can regulate the steam flow, extinguish or ignite the burners and pull the burners out of the combustion chamber or push them in. With this kind of an arrangement, the whole ship can actually be run in a pinch by just two men—one on the bridge, one in the engine room.

"After a cargo has been discharged there is always a mixture of gas and air left in the tanks and pumping system which is potentially dangerous and must be removed. We call it 'gas-freeing.' It is done by pumping sea water through the system, then using gas ejectors to force the gas up through special pipes and discharge them into the air and next circulating fresh air throughout the tank. Until a tank has been gas-freed no one can go in without wearing a gas mask and special shoes. There is always a chance that there is gas left or that a nail in a man's shoe strikes a spark if he slips...

"Now about the tanks. First of all, there are tanks everywhere. It's a tanker after all, eh? Aft there are two fuel oil tanks holding 60,575 cubic feet of bunker fuels; four deep tanks forward with a total capacity of 266,567 cubic feet for fuel oil or water ballast, two fuel oil settling tanks with a capacity of 22,891 cubic feet, two after fuel bunker tanks, plus tanks for water. And naturally there are the cargo tanks. But we'll have to talk more about the cargo tanks, much more."

Like most people, I suppose, I had imagined that the interior of a tanker must be some sort of huge bin amidships. I also had assumed that filling this bin would be rather like turning on the faucet in a large bath tub. I couldn't have been more mistaken.

"First of all," the First Officer said, "we must talk about the arrangement of the tanks. The interior looks rather like an ice-cube tray in a refrigerator, the kind with a metal separator. It is divided into compartments, first to prevent surging and second to permit a tanker to carry more than one grade of petroleum.

"Imagine this ice-cube tray without the separator in it. If you fill it full of water and walk with the tray in your hand the water will splash back and forth or across. And each surge will be a bit stronger than the one before, until it spills. That's surging. In a ship the force of the oil splashing back and forth as the ship rolls and pitches might turn her over. Now put the separator in your tray and look at each compartment as you walk. The water does not splash so much, eh? That's because the free surface is limited.

"The other reason for these divisions is that tankers used to carry different grades of oil that shouldn't be mixed. I say 'used to' because this practice is on its way out. While the Den Haag was being built in 1963 it was decided to assign her exclusively to the transport of crude oil. This meant that except to prevent surging, all that compartmentation—there are 39 separate tanks—was unnecessary. And since the ship was almost finished, it meant that for the next 15 or 20 years the Den Haag would carry a substantial tonnage of unnecessary steel around the world with her. So they cut holes through the compartments, making double tanks, and reducing the weight of the bulkheads...

"On the Den Haag, by the way, all steel surfaces in the cargo tanks are protected by an epoxy paint coating, a tremendous job that was carried out during construction and took about 80 tons of high quality paint to cover the total area of over 17 million square feet of steel, and every square foot had to be inspected."

The First Officer then turned to the problem of loading and unloading.

"Loading is the most difficult part of the job. You may think the Den Haag looks very strong, but in port if you make a false move in loading, it is entirely possible to snap her in two, like a match.

"As you know, the Den Haag is a very long ship. She has to be to provide the Aeaiitsd capacity. But precisely because she is long this ship is vulnerable to the stresses we call 'sagging' and 'hogging.'

Holding up a long yellow pencil, the First Officer pressed down with his thumbs on the center. The center bent downward and the eraser and the point bent upward and the pencil broke in two.

"That's sagging," he said.

He picked up another pencil, pressed up with his thumbs and down with his fingers. That pencil broke, too, but in an upward direction.

"And that's hogging.

"The bottom of a ship always sags where the pressure is applied. For example, if the oil we loaded at Sidon were put into all the wing and center tanks at the middle of the ship, the bottom of the ship would sag in the same way the pencil did when I pressed on the middle. Keep putting the pressure there, tank by tank, and the center would go down as the bow and stern came up. Finally the whole ship—beam, hull, deck—would simply break in two. It is unlikely but it could happen.

"Hogging is just the opposite. If we loaded cargo into all the tanks at the bow and the stern, the center would rise and the bow and stern would sink. But the strain would be the same. The ship can break either way.

"In smaller ships," he went on, "sagging and hogging are less serious because the longer the ship, the greater the danger. The sag would be two inches in a fully loaded ship of 25,000 tons, for example, four inches in a ship of 35,000 tons but 12 inches in a 90,000-ton-ship like the Den Haag."

The problem has been solved, of course—is solved each time the Den Haag loads another cargo—by simply filling all the tanks in the center of the ship first, leaving the wing tanks empty. By opening all the valves in the center tanks simultaneously the First Officer keeps an even amount of oil in the bow and stern and amidships all the time and so minimizes sagging. After the center tanks are filled the flow is routed into the wing tanks. Thus the stresses are balanced one against the other and excess sagging and hogging are avoided.

It would seem logical that once this was done, future loading could follow the same pattern. But this ignores an important aspect of oil. Different products have sharply different specific gravities and so, also, have different kinds of crude oil. Since this changes the stress patterns significantly each shipment must be calculated separately—now, fortunately, with the help of an instrument called the "londicator" which indicates the proper sequence to follow once it has been fed the basic information. Furthermore, the First Officer must take into his calculations another factor: the "trim" of the ship, or how she sits in the water with reference to a level horizontal plane.

As the hours went by the First Officer ranged over a seemingly endless number of factors concerning tanks, listing their capacities and limitations and problems, and tossing out statistics and measurements with the speed of a computer.

And then, he smiled and said, "I think we've covered everything—except.."

"Except what?"

"Except that you cannot possibly know a tanker until you have gone into the tanks."

He was right, of course. You may listen to all the explanations and read all the statistics, but the central fact does not strike you until the moment you scramble through a hatch that looks no bigger than a dinner plate, climb carefully down an endless ladder and stand in the blackness and silence. Above, nearly seven stories over your head, is the hatch, now the size of a dime. Below are the bilges. And all around is an enormous empty space—the space, you realize, that they fill with oil, submerging frames, webs, girders, everything around you including the very ladder you climbed down just before.

This article appeared on pages 11-13, 15-16,19 of the July/August 1966 print edition of Saudi Aramco World.


Check the Public Affairs Digital Image Archive for July/August 1966 images.