Steam Engine

Dec 29, 2000
Excuse my lack of knowledge, but I am a Newbie in Titanics Story. I am 30 years in age and during my hobbies I work as an beginners firemen for a railroad steam engine, so I got basic knowledge about stoking a boiler and maintaining the engines, as well as how steam engines opperate. During my workers time in a powerplant, I was also involved with typical steam turbines, so I gathered also here a kind of basic knowledge.

So does anybody knew how Titanics steam engines operated? I read everywere, that she's got a triple expansion steam engine with four cylinders and a low pressure steam turbine.
So triple expansion engines are commonly used ship engines: The steam comes from the boiler, will pass the main steam valve into the engine steam gear box. Now it will send by direction, time and amount into the high pressure cylinder. Passing out steam will be entering the compound box, from there into the mid-presure steam gear box and from there into the mid-pressure cylinder. Again the used steam passed out into the compound box, into the low pressure steam gear box into the low pressure cylinder and from there finaly into the condensator units, which will condese the used steam into best boilder feed water!
so as you can see: For a triple expansion only three cylinders are needed, because triple expansion means used the steam three times.
so for what reason Titanic got a four cylinders? Was the mid-pressure cylinder divied into two cylinders?
Well, next point is the low pressure steam turbine which propelled the middle propeller. From my knowledge the turbine was single directional and powered by exaust steam of the starboard and backboard main engines. So the turbine was not available for astern direction and the middle propeller was nut used if Titanic was driving backwards. Also in all brake manouvers, were reverse thrust was given by the propellers the middle propeller was not used. So does anyone knew how the steam was send to the turbine? Turbines are very tender, and if operated with not enough 'dry' stream, the droplets in the steam can easily damage the turbine, making it useless. Was the steam after coming from the main engines send again to the boiler to reheat and 'dry' it?
and if the engines were swithced from ahead to astern, how long did it take to decouple the turbine and send the exaust steam from the engines without turbine into the condensor?

Cal Haines

Dec 2, 2000
Tucson, AZ USA
Hello Steffen and welcome aboard!

Your description of a triple expansion engine is correct. Titanic's reciprocating engines had two low pressure (LP) cylinders each. As I understand it, the primary reason for this was that the size of a single LP cylinder, for the expansions used, would have been too large. The LP stage was designed to exhaust at 9 psi absolute, which is well into the vacuum range, so a large volume was needed. The cylinders diameters, fore to aft, were: 97" LP, 54" HP, 84" IP, 97" LP, all with 75" stroke. If a single LP cylinder had been used, it would have had to be 137" (11.4 feet) in diameter. This large diameter may have exceeded their ability to manufacture and would certainly have produced engines that were very wide. An additional benefit of using two LP cylinders was the ease of balancing the engine.

The exhaust from LP cylinders of each engine was lead through the aft bulkhead of the reciprocating engine room to two massive change valves, one for each engine. The change valves could direct the exhaust steam to the turbine or to the main condensers. The turbine was direct coupled to the center shaft and operated at about 165 RPM. The change valves incorporated strainers that apparently removed water vapor prior to the steam entering the turbine.

There was no astern turbine and the turbine was taken off line when the ship was maneuvering. The change valves operated vertically and were held in the upper position by a Brown's engine (basically just a steam cylinder) to allow steam to the turbine inlets. A lever on the port reciprocating engine controlled the change valve engine, driving the change valves to the lower (condenser) position with the assistance of gravity. I suspect it took a matter of seconds for the change valves to divert steam to the condensers. Sluice valves on the exhausts of the turbine could also be closed to further isolate the turbine from the condensers. It's my understanding that the sluice valves were only used if there was a problem with one of the condensers, so it was not necessary to close them to disable the turbine.

Some ships were fitted with quadruple expansion engines. Carpathia, the ship that rescued Titanic's survivors, was propelled by two four-crank, quadruple-expansion engines. The cylinders of her engines were 26", 37", 53", and 76" diameter by 54" stroke.

Warm Regards,


Erik Wood

Apr 10, 2001
Luckily I have driven Steam powered turbines most of my life and I will have to get my books out to get a better verbal understanding.

But for the most part Cal is right I do believe.

Dec 29, 2000
Thanks for your answer, it will support the Theorie about titanics engines.
Of course: To chnge the steam into the condensor direkt form the engines only chnage valves are needed, but you must have stopped the turbine, before start marching backwarts, of the backwards power will damage the well and still forward truning turbine, so I guess a couple of time was need to realy change Titanics engine power to backwards.
Whats your guess, because here seems to exist some guys realy having knowldge about this!

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