RN & RCN Y100 steam powerplant

 The following text was written in 2008 and originally appeared on the now-defunct Haze Gray and Underway  / Canadian Navy of Yesterday and Today website, and much is largely paraphrased and/or excerpted from the RCN Publication Machinery Digest for Destroyer Escorts, 205, 206, 257 and Classes. It should be noted, however, that this document does not make mention whatsoever the failure of the automatic clutch and resulting removal of the cruise turbines, and this information has been obtained from other unofficial sources. All photos are the copyright of the author, unless otherwise noted.

 General Layout and Description

Y100 powerplants were installed in a number of ships in the Royal and Royal Canadian Navies in the 1950s and 1960s, including the RN's Type 12 and Type 14 frigates, as well as the Cadillacs (ST. LAURENT, RESTIGOUCHE, MACKENZIE, and ANNAPOLIS class destroyers) of the Royal Canadian Navy. The Y100 plant consisted of two boilers in a single boiler room forward, with two geared turbines in a single engine room aft. The reduction gearboxes were installed right in the engine room, just aft of each turbine. The boiler and engine rooms were separated by a watertight bulkhead. The RN's Type 12 frigates were arranged similarly to the RCN ships, while the Type 14 frigates only had a single propeller shaft, and therefore only had a single turbine and reduction gear set. HMCS ST. LAURENT received an RN type Y100 powerplant with English Electric turbines (as supplied by Yarrows Ltd), while the rest of the Canadian ships received a slightly modified powerplant (manufactured in Canada) with Parsons turbines and a different gearbox.

A cross section of a RESTIGOUCHE class destroyer, showing the location of the Boiler Room and the Engine and Gearing Room. Image courtesy of LCDR Roger Heimpel, CFNES Damage Control Division.

The main propulsion machinery, as designed, consisted of a cruise turbine and a main turbine, of which RCN destroyers had two of each. From between 5% and 30% of full power, the more efficient cruise turbine was connected through the gearbox and provided all forward propulsion. Above 30% of full power, an automatic clutch system disconnected the cruise turbine and engaged the main turbine to provide up to and including 100% of full power. The astern turbine was incorporated at the exhaust end of the main turbine casing.  The two-stage main condenser was slung underneath the main turbine.

Power was transferred from the main gearbox to the propeller shaft by the double reduction gearbox. Power from the cruise turbine was transmitted to the main turbine drive gear via the automatic clutch and an additional reduction gear. Both the cruise and main turbines were controlled by a single ahead throttle wheel, and power was transferred automatically by the clutch. Power was transmitted to the hull by the gearbox, which had its own integral thrust block.

In practice, however, the automatic clutch never worked properly, and eventually the cruise turbines were either disconnected or removed in most or all of the RCN ships and probably the RN ones as well. Fortunately, the astern turbine was integral with the main turbine, and the ships were able to operate without the cruise turbine, although presumably with higher fuel consumption. (The author is interested in hearing more about the cruise turbine and why the clutch didn't work, and whether or not the RN experienced the same problems.)

Looking forward and to starboard over top of the starboard gearbox in Terra Nova. It was the starboard gearbox in KOOTENAY that blew up in October 1969, killing nine crew members and injuring 53 others.

In 1969, HMCS KOOTENAY suffered an explosion in her starboard gearbox while running at full power, an event that killed 9 men. My story on this event appeared in the September and October 2019 issues of Warships IFR magazine.

This is the aft bulkhead immediately behind Terra Nova's port gearbox looking to port. From George Webster: "This photo was taken from the centreline of the platform which runs along the aft bulkhead of the engineroom and is looking to Port.  In the foreground are the main lubricating oil filters for the turbines and main gearing.  The filter covers used to weep oil when the oil was cold as is apparent on the top of a couple of filters."

Machinery Controls

The machinery control panel was located at the forward end of the engine room, ahead of the turbines. 

The throttle control station and control panel, looking aft and to port. The big hand wheels were originally the common throttles for the cruise and main turbines (later just for the main turbines after the cruise turbines were removed), port (right) and starboard (left), while the smaller wheels control the astern turbines. While standing at this control panel, you would be facing aft. Compare this to the same station on PLYMOUTH in Item #'s 42, 44, and 45. To the right of the photograph, in the background, is the monitoring panel for the port side main circulation pump.

From George Webster: "As an aside, to the best of my recollection, the cruise turbine throttle was fitted right on the front end of the engine which made it very difficult for a throttle watch keeper to perform an astern movement as he would have to close the cruise throttle then run back to the main console to open the astern turbine throttle."

The engine room status board, as it appeared on July 11, 1997, the date of TERRA NOVA's final sailpast in Halifax Harbour.

A close-up of the control panel, showing the readouts for the starboard turbine.

The throttle control station looking aft and to starboard.

Looking aft and to starboard at the throttle control station.

The starboard turbine throttle control station looking aft.

Boiler Room

The boiler room was situated athwartships and contained two Babcock and Wilcox natural circulation, single furnace boilers (integral furnace, with superheat control) located side-by-side and each with its own uptake merged into a single funnel; the nine ships that received the DDH conversion received twin funnels to allow for the installation of a hangar. Each boiler was of the two-drum, bent-tube type, fitted with double casings, and worked in an open boiler room. The double air-tight casings were of stainless steel, between which the combustion air was led to the burner registers.

A piece of artwork painted during the 1991 Gulf War deployment, based on the equipment shown.

Looking between the two boilers.

Each boiler operated at 550 lb/sq.in. and 850 deg.F, and heat from fuel combustion was transferred to the feed water in four ways:

·         The heat of combustion of fuel in the furnace was transferred by radiation and conduction to the waterwalls of the furnace and the three rows of firerow tubes;

·         By convection and conduction to the generator tubes known as the convection bank;

·         By conduction and radiation to the steam in the five pass superheater;

·         By conduction from the furnace gases that passed the regulating dampers, to heat the feed water in the economizer.

Each boiler was totally enclosed with its own forced draught and ducting, and the boiler room itself was kept largely at atmospheric pressure. There was a cross-over connection between the forced draught blowers, in the form of a hand-operated damper fitted between the boiler casings of the two boilers, such that either blower could provide air to both boilers (in case of failure of one blower) under cruise and emergency conditions.

Boiler control was automatic to control steam temperatures and drum level, with remote or manual control also provided. All other aspects of boiler operation were manually controlled. A console was fitted just aft of the boilers that incorporated the automatic and manual controls and all indicators required for operation of the boilers.

Looking forward and to port at the main boiler room control panel. The red and green on the left and right of this panel indicated, respectively, the port and starboard boilers. The rows of red and green lights on the nearly horizontal part of the panel (bottom left) are the port and starboard boiler oil gun controls, respectively.

From Dave Holmes: "The boiler room had two stokers, one on each boiler, two at the control panel and one manning the evaporators. One of the guys on the control panel, usually an LS would control the amount of oil guns that the stoker would insert and light off. He would manually flick a toggle switch, and the light would come on. The stoker would then insert and light off. You always had to keep an eye open to see the lights going off and on, all done manually. If we needed more steam, he would flick a couple of toggle switches and the stoker would put the oil guns in service corresponding to the lights. The guy who flicked the switches controlled the number of oil burners and the oil pressure. The guy who sat behind him, controlled the FD fans, and air flow to the boilers."

A periscope type fitting was installed near the boiler room panel so that smoke conditions could be observed.

Engines

Each engine originally consisted of main and cruise turbines (with the cruise turbine mounted separately outboard of the main turbine) and a set of single helical, double reduction gearing (i.e. the gearbox). Each engine was installed side-by-side in a single engine room. As noted above, the cruise turbines were later removed or not installed in most ships. According to George Webster and Ron Monette, HMCS ST. LAURENT retained the cruise turbines.

Looking forward and to port at the top of HMCS Terra Nova's port turbine.

From George Webster: "To start with, the cruise turbines were fitted to one ship that I have personally seen and that was HMCS St. Laurent.  Apparently the clutch arrangement was poorly designed and the cruise engine was rarely used.  The cruise turbines were indeed fitted outboard of the main engines and in the remaining ships of this type (Y-100 machinery), there is a wider than normal platform out board of the ahead main turbine where the cruise turbine was originally supposed to have been fitted.  I can't recall how many cruise turbines were actually fitted but they were all removed shortly after their introduction."

One of HMS Plymouth's turbines with an inspection plate removed, exposing the turbine blades.

The main turbine drive was transmitted through a flexible coupling to the gearing, and thence through a thrust block to the propeller shaft. Power from the cruise turbine was transmitted via the automatic clutch and a single reduction gear to a pinion driving the outboard main primary train gearwheel and then to the propeller shaft, with a total triple speed reduction.

Each main engine set was designed to produce 15,000 shp (30,000 shp combined) at 220 rpm when steaming ahead in the deep draught condition, and 227 rpm in the light draught condition, with a seawater temperature of 85 deg.F. and the ship 6 months out of dock. Each astern turbine generated 5,000 shp.

Turbine	Cruise Turbine	Main Turbine	Astern Turbine
No. of Stages	Curtis wheel + 8 impulse	8 impulse (by-pass into Stage 5 when cruising)	Single Curtis Wheel
Mean Diameter	22"	34"	26"
Weight between centres	1,800 lbs	4,650 lbs	--
Speed at Maximum Power	8,510 rpm (light draught)	5,750 rpm (light draught)	4,000 rpm (5,000 shp)
Critical Speed	11,760 rpm	7,320 rpm	--

 

The greater part of the machinery life is typically spent at cruising speeds, and therefore the cruise turbine was designed to be lightweight and highly efficient, to give good overall performance from 5% to 100% full power, and maximum efficiency between 5% and 30% full power. Maximum efficiency was intended at 5% full power, which would have produced approximately 12 knots.

The result of the above was improved thermal efficiency, due to advanced steam conditions and overall improvement in turbine, condenser, and reduction gearing design. Higher turbine speeds in concert with the double reduction gearing permitted reduced blading diameters to obtain suitable peripheral speeds, and the use of all-impulse blading reduced the number of stages required, thus shortening the turbine rotor length. The incorporation of the condenser into the main turbine casing saved space and weight.

Both the main and cruise turbines were controlled by a single throttle hand-wheel throughout the entire power range, and power was transferred between the two turbines by an automatic clutch and a manually operated nozzle control valve mechanism. According to George Webster and Ron Monette, engaging the astern turbine in ships with the cruise turbine fitted was apparently a challenge, as the throttle watch keeper would have to close the cruise turbine throttle then run back to the astern throttle to engage the astern turbine. Presumably this became easier after the removal of the cruise turbine in most ships.

When the cruise turbine was disengaged, a rolling steam supply (incorporated into the first nozzle control valve) maintained the cruise turbine at 500 rpm to prevent cylinder distortion and rotor hogging.

Power Transmission, Shafting, and Propellers

Power from the turbines was transmitted to the propeller shafts via a MAAG type hardened and ground double reduction gearbox; the cruise turbine experienced triple reduction. As noted above, the automatic clutch designed to transfer power between the cruise and main turbines did not work properly, and the cruise turbines were removed on most or all of the ships. The opening on the gearbox originally intended to accept the shaft from the cruise turbine was plated over after the cruise turbine was removed.

Looking aft and to port at the top of HMCS Terra Nova's port gearbox. The shaft in the background comes from the main turbine, while the flat plate cover just visible behind the main turbine shaft covers the opening intended for the cruise turbine shaft. The rounded cover in the foreground (under the "D") is over the quill shaft. Compare with the port gearbox in PLYMOUTH below.

From George Webster: "This photo shows the rounded cover is over the end of one of the quill shafts in the main gearbox and the original cruise turbine entry point is the flat cover which you can just see outboard over the very top of the main shaft from the main engine turbines (ahead and astern)."

The hollow-bored propeller shaft passed through a watertight bulkhead gland at the aft end of the engine compartment and again in the Plummer Block compartment. Shaft bearings were located immediately forward of the glands. The tailshaft left the hull through a stern tube containing oil-lubricated bearings, and oil seals were fitted at both end of the stern tube to prevent oil and seawater leakage. The hollow bore of the shaft was plugged at both ends to prevent leakage in case the shaft broke. The propeller shaft could be locked by engaging the turning gear in the main gearing (as opposed to engaging a brake on the shaft itself in the Tribal Class). The turning gear was designed to withstand a shaft torque of 1/3 full power to permit a speed of approximately 17 knots. The application of full power on one engine with the other shaft locked was not recommended, but in emergency situations could be used to raise the ship's speed to 19 knots. Alternatively, the shaft could be trailed (allowed to freewheel) by uncoupling the shaft forward of the plummer and trailing block.

The port gearbox in HMS Plymouth, presumably also with a cover over the quill shaft .

The shafting and propellers were interchangeable with the RN's Type 12 frigates. The propellers were a conventional type of 12' diameter constructed of high tensile manganese bronze, and were contra-rotating such that each shaft rotated outboard when moving forward.

Survivability

Each boiler was designed as a single unit supported by the boiler feet. The boiler feet hold-down bolts were designed to fracture before the feet themselves if they were subjected to large underwater explosions. Either forced-draught blower could be used to provide combustion air for both boilers.

Most machinery mountings were of the rigid-resilient type, where under severe shock the mountings would collapse thus preventing damage to castings or bolts, and the weight of the machinery would then be carried by resilient pads until repairs could be made.

The main engines were designed to stay in operation even when submerged up to the bottom of the lowest main turbine bearing.

Ship's Power

The first ships were fitted with two 400 kW turbo-generators (i.e. steam generators), one each in the boiler (port after end) and engine (starboard forward end) rooms; and three 200 kW diesel generators - one in the boiler room, the other two on No.3 deck aft and No.4 deck forward.

A diesel genset on TERRA NOVA, looking aft into the compartment on the starboard side of the ship.

The turbo generators were the main source of power at sea, and were entirely self contained units with their own condensers and pumps, all driven off the turbine shaft.

 

Sources:

Barrie, Ron and Macpherson, Ken. (1996). Cadillac of Destroyers: HMCS ST. LAURENT and Her Successors. Vanwell Publishing Ltd. St. Catherines, Ont.

Steed, Roger G. (1999). Canadian Warships Since 1956. Vanwell Publishing Ltd. St. Catherines, ON.

RCN Publication. (1968). Machinery Digest for Destroyer Escorts, 205, 206, 257 and Classes. Queen's Printer and Controller of Stationary, Ottawa.

Conversation and correspondence with Jim Brewer, June 2006 to February 2007.

Conversations with Ron Monette, February and August 1999.

Correspondence with Dave Holmes, December 2006.

Correspondence with Dave Holmes, June 2007.

Correspondence with George Webster, December 2006 to February 2007.