Friday, 5 June 2015

HMCS PRESERVER: Tour of electical power generation and the bow thruster

Where the power generating equipment is located across multiple spaces, some of which I have already covered, I decided to break out my summary of power generation onboard PRESERVER into a separate blog posting. As a result, a few photos and descriptions from previous postings may get repeated here. This should be read in coordination with those earlier postings covering the engine room, boiler room, and machinery control room

I will also cover the bow thruster, as it is powered by a rather large diesel engine that isn't in the engine room. As always, I will note that I am by no means an expert on these systems, and am relying on information gleaned from my guides during my tour as well as my own assumptions. Mistakes are my own!

Electrical power generation onboard a warship is a particularly critical capability, required to start propulsions engines, run hotel loads and combat systems, and is therefore designed for redundancy. In PRESERVER, this means that three types of generators (2 steam turbines, 2 diesels, and 1 gas turbine) are distributed across three different spaces (engine room, boiler room, and forward of the bridge respectively).  

Port turbo-alternator (steam turbine generator).
While at sea, the two 1000 kW turbo-alternators (installed port and starboard in the engine room) would normally provide the majority, if not all, of the ship's power requirements. Being steam driven, these generators require steam from the boilers, so these generators would not be used while the ship is alongside with cold boilers. Therefore, in order to provide power to start up the boilers, power is required from other sources.

Poor quality video capture of the two diesel generators, looking forward and to starboard.
The two 500 kW diesel generators are located port and starboard in the boiler room, between the two boilers - this should put them on the ship's centreline. The diesel generators are more or less self contained, and can begin generating power fairly soon after a cold start. The diesels would provide power to the boilers to get steam up, after which power generation would be transferred to the turbo-alternators, and the diesels would be shut down to save fuel. Not only are the diesel generators separated from the turbo-alternators by being located in separate spaces within the ship, they also rely on a separate fuel source, providing additional redundancy. 

Gas turbine generator.
Located forward on No.1 deck on the starboard side of the deckhouse forward of the bridge is the emergency generator compartment, home to a single gas turbine generator. I believe this is the same model as used in the IROQUOIS class destroyers, albeit in a different type of enclosure. If so, this is a Solar Saturn unit rated for 750 kW. Gas turbine generators have the advantage of being able to run up to full power from a cold start almost instantaneously, and therefore they have great value as emergency generators that can come online very quickly when other sources of electricity unexpectedly fail. In addition to being able to be started using local controls, this generator could be fired up remotely from the Machinery Control Room (MCR).

In the photo above, we are looking at the generator enclosure, with the generator itself being installed inside. As I recall, the exhaust pipe for this generator exits the ship not quite six feet above deck level on the starboard side, and is therefore a bit of a head knocker for those not paying attention.

Another angle on the Solar Saturn gas turbine generator.
It is my assumption that the gas turbine generator would not typically be used either alongside or at sea, apart from occasionally being exercised, and that it would be reserved for emergency use. I could be wrong.

Gas turbine local switchboard.
There is a local switchboard installed in the same compartment as the gas turbine generator.

For lack of a better spot, I will also cover the bow thruster here. 

Bow thruster diesel engine.
Being rather large, and driven by a single shaft, these ships are not the most maneuverable. During a refit at some point, during the 1990s I believe, both PRESERVER and PROTECTEUR received bow thrusters to reduce their reliance on tugboat assistance when leaving port or coming back alongside. The bow thruster is effective at speeds of up to 5 knots, and is driven by its own direct drive diesel engine. This diesel does not generate electrical power, but rather is connected mechanically to the bow thruster by a vertical shaft.

Bow thruster diesel engine
I  believe the vertical cylinder on the end of the diesel engine in the photo above is the top of the direct drive shaft leading down to the bow thruster. I am assuming that either the diesel would have to reverse direction in order to allow the bow thruster to direct thrust from port to starboard, or the impeller would need to have adjustable pitch blades. I didn't think to ask at the time, so I don't know how this is done. 

Bow thruster impeller tunnel.
The bow thruster impeller itself is necessarily installed very low in the ship's hull, and we descended several ladders to reach this compartment. I believe this photo is taken looking to port. The impeller for the bow thruster is installed in a water-tight tunnel, as seen here, which allows it to throw water out either side of the ship. The tunnel is roughly as tall as a man, and the direct drive shaft enters the tunnel at top-centre in this photo.

In the compartment above the bow thruster are the guts of the blackwater (sewage) treatment system onboard PRESERVER. The blackwater tanks are in close proximity, and no space on a warship goes unused.

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