The Importance of Correct Firing Order to a Marine Diesel Engine
A ships diesel engine such as MAN, B & W, and Sulzer are all designed to have a firing order to meet the following requirements;
1. Engine Vibration
Torsional Vibration – caused by the reciprocating components, this is a highly undesirable condition in a marine engine. Not only for the comfort of passenger and crew, but also for the durability of the engine through undue fatigue.
2. Engine Balance
Imbalance of components is once again the cause of fatigue of the rotating components, especially the crankshaft. It is imperative that the firing order compliments not only the balancing of the components, but balances the power output from the cylinders spreading the load over the length of the crankshaft.
3. Gas Forces
Enormous gas forces are produced in the cylinders on the compression/firing stroke. These create individual cylinder torque characteristics that are transmitted downwards into the engine block, and bedplate via the main crankshaft bearings.
So these are the main reasons for the correct firing order in a marine diesel engine. Going back to the 6 cylinder Sulzer diesel engine I sailed on for a few years, I recollect the firing order to be 1,5,3,6,2,4.
Looking at some of the marine diesels on the web, the main engine manufacturers use various different firing orders that, as noted above, are crucial to the design of the ships marine diesel engines.
I have noted some marine engine firing orders below.
- MAN-B&W 6S60MC 6 cylinder, 2 stroke, reversible, slow speed marine diesel engine - firing order 1,5,3,4,2,6.
- Sulzer 6AL20/24 6 cylinder marine diesel engine – firing order 1, 4, 2, 6, 3, 5.
- MITSUI MAN B&W 8K98MC (MARK VI) 8 cylinder marine diesel engine- firing order 1, 8, 3, 4,7, 2, 5,6.
The marine diesel engine design and power output has changed with the new technology since I was an engineer at sea. However, one thing has remained unaltered: the firing order of the engine is paramount to the design of the engine, ensuring a long vibration and fatigue-free service.
1. Wartsila: Technical Papers
2. Ime: Firing Order and Torsional Vibration
3. Scribd: Marine Diesel Working Principles