marine steam engines

hi, looking at pictures of marine steam engines I notice that few of them has fly ball governors fitted. why is this and how is the speed governed. gary

By an engineer who opened or closed the main steam valve in accordance with the rev counter and the relevant signal on the engine room telegraph.

Governors are used to provide a constant or near constant RPM. A marine engine has to be able to use various speeds whilst manoeuvring hence no governor.

When a ship is running in heavy seas the propellor will come out of the sea enough for the engine to over rev if not governed even the motor ships had a govenor not that you see it.

As above, once set at the required RPM the load on the engine remains constant as the propshaft and propeller are permanently attached to the engine. The engineer on watch keeps an eye on the dial just in case.

This is the engine from the T.S. Glen Strathallan, I must have been one of the last cadets to "keep an eye" on this engine whilst steaming around the Thames Estuary. The engine is now part of the Science Museum collection and the ship lies at the bottom of the English Channel near Plymouth Sound. Plenty of info online from a name search.

John

I have read accounts of the main propulsion engine beginning to race up to governor run out speed when the prop came out of the water in heavy weather.

On motor vessels the injection pump (on small vessels) has an integral governor. On larger engines with an individual pump for each cylinder, there would be an external governor connected to the control rod for each pump.

If you have been close to an engine when it is running away, you have not missed anything! It is a frightening experience, if if you expect something dramatic to happen.

Ditto for crankcase explosions. The lucky folk are the ones who live to tell the tale.

Howard

Too true. I was on the flybridge of my motor cruiser slowly coming in to Shotley Point Marina when the tacho of the starboard engine went off the scale. The big 7 litre engine wouldn't shut down even when the fuel cock was closed. We were blanketed in white smoke. I dashed below pulled the covers off the engine and managed to find a block of wood to hold over the air inlet to choke it into submission.

When I came back on deck there was the harbour pilot boat on one side of me and the RNLI on the other asking if I needed help.

I have since heard of a similar case where the flywheel broke free, smashed through the housing and made a large hole in the hull. In these circumstances a governor wouldn't help as it was using the engine oil as a fuel following a bearing fail in the turbocharger.

Russell

thanks for all the replys very interesting, gary

Many years ago I was standing on the dock at the Moorings Marina in Tortola BVI where a couple of local mechanics were working on a small Perkins diesel in a 43.foot sailboat. Suddenly the engine revs rose really quickly with lots of white smoke, Got to a point where it let go and the flywheel exited through the side of the boat about 3" above the water line, went under the dock and into the side of the 43 next door where it embedded itself on the waterline. Only the fact that the flywheel kind of plugged the hole saved the boat from sinking at the dock.

I have never seen two face so scared when the guys came out!

Martin

You have to remember those old steam engines ran at little more than 100 rpm in many cases, so not so much chance of runaway flywheels etc. as with the Perkins!

I was on motor ships in the 70s 6 cylinder opposed piston Doxford Diesel engines 130 rpm flat out they didn't half shake the ship when the prop came out the water. No flywheel direct drive to the prop.

With huge engines, whether steam or diesel, the inertia forces are immense, so any overspeed will really shake things. The Emma Maersk and her sister ship are powered by a 108 rpm 102,000 hp turbo charged two stroke, so components are BIG. Cylinder Head studs 14 feet long, and the Crankshaft weighs 300 tons.

Even when you deliberately induce run away, when it happens, you scarcely feel in control.

Throttling the air intake should reduce the compression ratio to the point where the cylinder contents can no longer reach the temperature of the flash, or ignition point, of whatever it happens to be using as fuel at that time.

In the cold chamber at C A V, there was always someone with a rubber faced bat, ready to block the air inlet, should an engine start to run away.

Other than that, about the only steps that you can take are long and quick ones, to somewhere else!

The Governor boys at Acton, told me that the engines they found most difficult were the Commer TS3 and the Rolls Royce C Range. Both, apparently were capable of acceleration rates of 5,000 rpm/second! (i e reaching treble their rated speed in a second. And to think that I regularly used to stand alongside them, until then.

My colleague who went to the Tilling Stevens factory in Maidstone (Where the TS3 and TS4 were made ) was told that if he was alongside a TS3 when it took off, he had 5 seconds to either grab the stop control or to run! After that he would have hot metal flying about as company! I wouldn't wait that long!

Howard

A friend was in the National Guard over here. A self propelled Artillery piece had a runaway. The guy was working around it and had nothing to stuff the intake with, so He used His chest. Don't remember if He made it or not.

There was an attempted attack on Norwegian convoys by the German Imperial Navy late in WW1. They'd actually got the date wrong. The battlecruiser SMS Moltke lost a propellor on the run-in. The resulting racing of the turbine engine burst a ring-gear and sent big chunks through condensers and feedwater tanks. Her top speed ultimately dropped to 4 knots, but British intelligence failures meant she still got home despite a damaging torpedo hit from an RN submarine.

It could have - should have - been a disaster for them, all because there was no quick way to govern a marine engine speed if the load (literally) dropped away.

There you are look, worse things do happen at sea !

)

Martin

Governing a marine auxiliary generator is easier than a main propulsion unit.

For many years, the practice has been to sense the frequency and operate off that. The flickering digital readouts can be worrying, until you realise that the final digit is tenths of a rpm! The speed of a geared down turbine can vary by several rpm with little effect on the frequency produced by the three phase alternator. that it drives

The fun begins when trying to parallel several sets together, so that there are no circulating currents from the master set trying to speed up, or slow down one of the slave sets.. Electronic governors have made things so much easier and more precise.

Howard

Under Classification Society rules it has been a requirement for many years now to fit over speed trips to main propulsion machinery many were "miniature" centrifugal governors that only had a maximum speed rating, when they reach that they trip the fuel racks to zero and shut the engine down, they then have to be reset before restart. A real PITA! Modern engines usually have this function fulfilled electronically. I have spent a few "happy" hours in the past setting these trips up driving them from a drilling machine at the correct speed to get them to trip. I have a vague recollection in the past of seeing a trip operated stop valve in the steam supply to a steam engine, probably in a book, never worked on a steam ship apart from a triple expansion engine powered vessel for 2 days 40 odd years ago.

Paul.