Saga Sapphire Technical Department: Show Us Your Engines!


Saga Sapphire is one of my favourite cruise ships, I love virtually everything about her and I’m sure there are plenty of other people out there that also have a soft spot in their heart for her. When I enjoy something or I am passionate about something, I like to learn as much about whatever it may be that I can, so my blog today is a look behind the scenes of Saga Sapphire and what goes on below decks to enable her to sail us to the incredible places that she does. We all love a bit of technical information every now and then!

Saga Sapphire’s Propulsion Plant

Saga Sapphire has two main engines and each one is connected to its own shaft and propeller. The propellers are 5 bladed fixed pitch, so this means the propulsion of the vessel is directly linked to the loading of the engines.

What Are The Main Engine’s?

Sapphire has large Slow Speed Two Stroke Reversible Engines: MAN Bremer Vulkan, KZ SZ 70/125B. Each of her main engines are bigger than a traditional London double decker bus. Each one consists of 7 cylinders and each cylinder has a bore of 700mm diameter. Each piston has a stroke of 1250mm; this is the travel of the piston from top dead centre to bottom dead centre. The maximum operating speed of Saga Sapphire’s engines is 125 rev/min. This provides a ship speed pf up to 17 knots.

Each engine has two turbo chargers and one common scavenge air belt, which is known as a constant pressure turbocharging system. The engine has no inlet or exhaust valves, instead there are scavenge ports and exhaust ports in the liner to allow for the exchange of air change which is required for combustion. The ports are closed to the cylinder depending on the position of the piston.

How Is Saga Sapphire’s Engine Started?

To start the engines, they use a compressed air system, which is known as the start air system. This consists of 4 reciprocating air compressors which fill two start air receivers. Each of which has a volume of 9500 litres at a pressure of 30 bar.

From here, the air is supplied to the engine main start air valve. A signal from the Engine Telegraph system opens the start air valve which supplies air to each unit’s start air valve. Depending on the position of the engine, the air distributor will ensure that the air goes to the correct unit to open the relevant start air valve on the cylinder head, hence forcing the piston on a downward stroke causing the engine to rotate.

A sensor fitted on the engine flywheel detects the speed of the engine. Once the engine has reached a predetermined speed, the electronic governor admits fuel to the engine and closes the start air valve. The engine now accelerates to 45 rev/min which is dead slow ahead or stern.

How Big Are Her Propellers?

Each of Saga Sapphire’s 2 propellers is 4.75 metres in diameter and weighs 11.4 tonnes. Each propeller has 5 blades and can be compared with the size of an average person.


What Is The Bunker Capacity and Fuel Consumption Of Saga Sapphire?

Saga Sapphire operates on two types of fuel: IFO 380 and MGO.

Total Capacity: IF 380 – 338,000 gallons – 1460 tonnes | MGO – 325,000 gallons – 1250 tonnes

At a service speed of 16 knots, Saga Sapphire has a fuel consumption of approx. 150 feet to the gallon, or 184 litres per knot mile.

Did You Know…

Engineer Officers wear gold stripes with purple because when Titanic sank, all engineers went down with the ship. King George V decreed that the Royal Purple will be worn in their memory from that date on.

The information contained in my blog today comes to us courtesy of 2nd Engineer Officer Luke Doyle.

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