Triple-expansion steam engine.

Joe Whelan
28th May 2009, 14:18
Has anyone knowledge or experience of a triple expansion steam engine having the three cylinders arranged with the H P.forward, L.P. in the centre and the M.P. aft.

28th May 2009, 15:22
Don't know if this will help. but a link from the SS JOHN W BROWN's website -

I've been in the engine room many times whilst underway.. very impressive sight.

28th May 2009, 15:39
Never seen a LP as center piston, but have seen quad cylinder engines (double expansion), where the two middle pots are LP, on some vessels(not many) these exhaust to a low pressure turbine.

The USS Texas has four legged double expansion engines two of each on each shaft, I'm afraid that I cannot remember the coupling system. I also visited the ER of a 1916/18 German built tanker that had a four legged; can't remember the name, she had been laid up in Barry, for years, after the war.

david freeman
28th May 2009, 19:53
I do not regonise the layout? HP IP and two LP Legs being of one design, or three legs HP Ip and Lp with Bauwer Wach Exhaust turbines. You might be better putting this in the Fishing vessel section as the old side winders out of HULL and Grimsby where single boilers coal/Oil fired and operating in the 'Cod wars' of the Late 60' 70. And any class surveyor, company superintendent or other engineer from the repair drydocks, or from the builders at Hessle and Beverley may be able to give you a more difinitive answer.

29th May 2009, 04:07
Served my apprenticeship on building and repairing steam recip engines on Clydeside. The only time I seen a LP cylinder in the center of a trple expansion engine was on a 4 cylinder triple expansion with the two LP cylinders in the center of the engine. If I remember correctly it had been built by North Eastern Marine on Tyneside.

Joe Whelan
29th May 2009, 14:34
Thanks to members who replied to my query. To date I have only discovered one vessel with L.P.cylinder fitted betwwen the H.P. and I.P. The twin screw Canadian Pacific T.S.S. Metagama of 1915. The propulsion units were quadruple expansion with cylinders placed as follows,H.P forward followed by L.P and Nos 1 & 2 I.Ps.

29th May 2009, 19:42
Some North East Marine "reheat" engines had the L.P. in the middle of their "three legged" Triple's expansion's.

31st May 2009, 08:07
Triple expansion engines.

During my apprenticeship I spent 2 ˝ years in the ship fitters work shop which entailed mostly ship board work in engine and boiler rooms of the Naval vessels such as the Dido class cruisers, Loch class frigates and the Bird Class minesweepers, the latter two with triple expansion steam engines and while I can recall the single screw sweeper’s engine layout of HP, IP, LP in a row and a three crank shaft I am not sure of my memory of the arrangement of the bigger twin screw frigate engines.
To the best of my recall these were four cylinder but triple expansion whereby the steam expanded from the HP to the IP and then to two LP cylinders via a manifold. This arrangement was used on bigger engines to provide a smoother running engine with four cranks rather than three and the twin LP cylinders’ total piston area was the same as a single cylinder would have been but was more compact than having to use a very large diameter.
When we talk of Quadruple expansion I imagine that it would be a HP, first IP, second IP (slightly bigger diameter than the first) then the LP cylinder?
I have been trying to clarify this on the net as I do not remember any manifold from the IP to the two LP cylinders but most web sites describe the Loch class frigates as having four cylinder triple expansion engines.
It is interesting to read that the RN ordered no less than 110 of these ships but 54 were cancelled at the war’s end. They were originally intended to have steam turbines but an over loaded Parsons Works were unable to supply after the first two and the balance were fitted with reciprocating engines. The Naval Command also decided that the latter engine was more familiar with the many RNR and Merchant Navy engine room crews that they could recruit.
After the war NZ took over six of these frigates and re named then as Lake Class and after NZ lakes. and each of them went through the process of complete engine rebuilds and refits to rectify their wartime wear and tear in the years that I was there.


31st May 2009, 11:22
I have found a drawing of a North East Marine Engine in a basic layout drawing of a Collier called the "Arundel" with the LP on the "middle leg" but unfortunatly it is subject to copyright so I cannot put it in the engine photo section.

31st May 2009, 13:02
Has anyone knowledge or experience of a triple expansion steam engine having the three cylinders arranged with the H P.forward, L.P. in the centre and the M.P. aft.

Hello Joe
There is a rather interesting website
which has a sub-heading, "Various Cylinder Arrangements"
This reproduced book page shows a six cylinder steeple engine! among many different set-ups.

Joe Whelan
1st June 2009, 13:46
Hello Geordie Chief, I think we are reading from the same book regarding the"Arundle" page 44. Joe.

1st June 2009, 18:17
i made two trips on ocean weather ships in 1969. these were converted castle class built in war time for convoy duties. there was a one triple expansion main engine which had HP IP and two LP cyls. not sure who made the main eng but the recip generator was a bellis and morcombe triple expansion and there was a turbine generator. boilers were yarrow in two pressurised stockholds.

Peter Short
2nd June 2009, 02:25
As has been mentioned, North Eastern Marine Engineering Company built many three cylinder triple expansion engines with the LP in the middle. According to the excellent Steam at Sea by Denis Griffiths, these engines were the most popular, and longest produced, of the "reheat" engines adopted prior to, during and after WW2.

He gives the reason for this layout. Because of the high temperature of steam to both cylinders, these engines used poppet valves on both HP and IP cylinders. The LP generally used a balanced slide valve.

The poppet valves were cam driven, and to give easy access to both HP and IP cylinders and their valve gear, they were placed at either end of the engine. A photo shows the poppet valves and operating mechanism right on the ends of the engine, very accessible.

These reheat engines interest me because the principle is clever and simple. On NEM engine with the full reheat system, the boiler steam going to the HP is used to re-heat steam leaving the HP (via a tubular heater). This means the steam temperature can be higher than would otherwise be possible on a reciprocating engine because the boiler steam is de-superheated by the reheat system, yet at no loss because the heat 'lost' is added to the IP steam. I believe the same principle is applied to the last of the Skinner marine engines, the compound uniflows (one still running commerically I believe).

There is a drawing of one of these NEM reheat engines in a 1945 article by George Watkins which has recently been reprinted by ISSES in their Journal No,13.

A couple of examples: S.S. Conakernian, 2,210 ihp at 85 rpm, steam at 225lb and 630deg F. at HP chest. Temperature at superheater not given but another example says 760 deg. F at the superheater and 630 deg F at the stop valve.

Lancaster Castle, 1,790 ihp, 1.02lbs/ihp/hr on coal, steam at 220 psi and 750 deg. F, steam temperature at HP inlet 635 deg F after reheating the HP exhaust which entered the IP at 560 deg F.

Joe Whelan
2nd June 2009, 14:16
Seeking confirmation that the following vessels built by Greys Of West Hartlepool had the cylinders of their triple expansion engines with H.P. forward L.P. in the centre and M.P.aft. s/s Lancastrian,s/s Castledore,s/s Lucy, all built in 1956. Thanks, Joe.