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Engine Room Terms


The coupler-flange is the flanged end of the crankshaft where it bolts to the thrust bearing. The Spindle Guide is a component of the one-way valve through which steam flows from the boiler to the main steam line which supplies the engine throttle valve. Some engines incorporated a valve arrangement that used guides above and below the cylinder steam valves. The upper "spindle guide" on these engines was the highest part of the engine.


Also MID WATCH or THE MIDS - The time period between midnight and 4 A.M., and noon and 4 P.M. Common usage refers to the period beginning at midnight. Ships operate 24 hours-a-day, and some of the tasks, such as steering, navigating, or tending the engine requires constant attendance. Most merchant ships use a system of watches which divides the day into 4-hour blocks; 12X4, 4X8, and 8X12 (spoken as 8-to-12) A watchstander normally works 4 hours "on" followd by 8 hours "off." Any work "off Watch" is normally counted as overtime.


Speed of the propeller shaft, in revolutions per minute. Engineers count "turns" of the shaft to help determine engine horsepower and efficiency. Deck officers use the number of turns to measure the ship's speed and distance travelled.


Flax fibers, woven into loose rope. Tow was often used as a packing or gasket material in low-pressure applications.


Electrical generators.


Until recently, nearly all ships were built with a "midships house." The engine and boilers were located beneath the house. The propeller shaft ran through the after holds and was enclosed in a "tunnel" to maintain watertight integrity and allow access by engineers. Modern ships, with the house and engine-room near the stern, have much shorter shafts and the space is referred to as the shaft "alley."


Loco boilers are very much like a large drum, about 12 feet in diameter and nearly as long. On the front of each boiler (looking aft, towards the stern of the ship) were two furnace doors, side-by-side. The furnaces were each about 4 feet in diameter and looked like nothing more than lengths of corrugated steel culvert extending nearly to the rear of the boiler. The front portion of each furnace held an area of cast-iron grating. This is where the coal (carbons) was burned. The grate-bars, or fire-bars were individually removeable and when burned from long use caused the fireman no end of grief by falling to the bottom of the furnace as he trimmed the fires.


Boiler feed-pump valves, and the one-way valves leading to the boilers (checks or clacks) made a peculiar click-clack noise when the flow of water through them was pulsating or irregular. This was sometimes caused by a sticking feed-pump suction valve.

CUNARD (Lines)

Operator of the Queen Mary, Queen Elizabeth, and more recently, the Queen Elizabeth II. Cunard was synonymous with luxury and excellence in all matters maritime.


The pump which forces water into the boiler(s). As steam is taken from a boiler, water must be replaced. The source of this "feed" water may be tanks in the bottom of the ship, "feed bottoms," or a "feed-heater" tank which is replenished with condensed exhaust collected in a "hotwell" at the bottom of the main condenser.


Early steam engines could be difficult to start, at least without having to admit large quantities of high-pressure steam. To facilitate slow, smooth, starts a "blow-through" valve was fitted to the engine. This valve allowed steam to pass directly to the condenser and clear it of any air and water that may have collected. Once steam entered the condenser, the resulting vacuum helped to start the engine. A SNIFTER valve was mounted at the lowest point of the condenser to allow air and excess water to escape. Operation of the snifter valve was automatic, once vacuum was established the valve remained closed.


A ship's propeller


Moving parts of the engine had to be oiled by hand. An engine room worker called, appropriately, an Oiler, made regular rounds with an oil can. It is a matter of pride to minimize the quantity of oil used each watch. Too much oil wastes money and also adds to the haze of steam, smoke, and fumes which permeates the atmosphere of engine room. The term "cap" where an Oiler would have said "cup." The upper part of a bearing is called a cap, mounted on each cap of engine was a "cup." The Oiler - swilled the cup - with oil, overfilling it and wasting expensive lubricant.


A ship riding at anchor in fog must ring a bell forward and sound a gong from the stern at regular intervals to warn other vessels of its presence.


Strictly speaking, a differential valve-gear is used to equalize power and speed in both directions of the small steam engine which powers the rudder. Valves on most propulsion steam engines are designed to allow adjustment of opening and closing points to "fine-tune" the engine for economy or power.


Crawling in the crank-pits, below the crankshaft, in the sump of the engine, to inspect lower bearings. A dirty, cramped and thoroughly unpleasant job.


Until recently, most merchant ships were built with the engine and boiler rooms midship, about half-way between bow and stern. The propeller shaft extended from the engine room to the stern frame within a "tunnel" which allowed engineers access to the line bearings and separated the shaft from the cargo holds above. See the drawing at the top of this page.


These refers to the enemies of efficiency, those inescapable elements of a propulsion plant that consume precious fuel while slowing the ship's passage.

KNOCK is the sound made by loose components or the slap of reciprocating parts against worn bearings. It is a sign of impending damage, and the engine (so too, the ship) must be stopped to correct the problem. A stopped ship generates no revenue and may be seen to reflect on the skills of the Chief Engineer.

SCALE is an insulating layer of minerals formed when sea-water is heated in the ship's machinery. Sea-water is used to cool much of the engine room equipment and because scale retards heat transfer machinery may overheat and be damaged, or forced to operate at lower speed. Scale may also develop in the boilers and cause steam generating tubes to fail, putting the boiler out of service and slow or stop the ship.

FRICTION is the enemy of any machine. An engine's (and an engineer's) efficiency is measured by the amount of energy (horsepower) delivered to the output shaft compared to the amount of energy (heating value of the fuel) supplied to it. Poor lubrication, under or overheating, misalignment, can all lead to increased friction which absorbs power that should go instead to the propeller shaft.

WASTE, in this case, is probably a reference to waste heat. Each lump of coal contains within it a certain quantity of energy and is, theoretically, capable of moving the ship a certain distance along its voyage. It is a matter of pride among the ship's engineers to maximize the distance travelled for each unit of fuel consumed.

When coal is burned in the ship's boiler a fraction of the energy (heat) released produces steam, another fraction warms the incoming feed water. The remainder is wasted, it warms the engine room or passes out the stack with the smoke and non-combustible gases. There are practical limits to boiler efficiency, modern oil-fired boilers extract narly 90 percent of the heat released by combustion.

High-pressure steam from the boilers was the life-blood of the ship. Energy contained within the steam was released in the engine to drive the propeller, in the dynamoes to generate electricity; in the evaporators to produce fresh-water from sea-water; and on deck to operate the winches that lifted cargo to and from the holds. Leaking steam produced no useful work, and wayward heat was the owner's cash, pumped overboard with cooling water or carried up the stack with smoke.

Waste, or cotton waste, is also the English marine engineer's term for the trimmings and discarded threads produced by textile mills. Around the turn of the century this material was plentiful and inexpensive and was widely used instead of rags.

SLIP The "pitch" or twist of a ship's propeller is measured in feet. A cargo ship might have a propeller with a pitch of 20 feet. If that propeller acted like a screw (to which it is often compared and usually called), in a solid medium each revolution of the shaft would move the ship forward 20 feet.

Water is fluid, however, and the flow around the propeller is altered by the shape of the hull. Some of the water in a ship's wake is actually moving forward, and the ship may move more or less than 20 feet for each revolution of the propeller. The difference between the distance the ship might have advanced, calculated by multiplying the number of turns by the propeller pitch, compared to the actual distance the ship advanced is "apparent slip." Slip is normally stated as a percentage of distance advanced. Depending on weather and load, slip usually falls between 5 and 10 percent on modern vessels.