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[Bunkerbarge]

We set our current injectors at 410 bar, which is 6150 psi.

They lift in response to the fuel pressure generated by the pumps, as Boatmadman rightly says, which are operated by the fuel cams on the camshaft.

There are new common rail, constant pressure systems (like the old Doxford setup) that use pressures of 2000 bar or 30,000 psi.

[boatmadman]

A slight detour.....

We sailed into a USA port many moons ago. US coastguard required that the sewage treatment system be fully operational, so we got 3E (who doubled as Lecky) to wire up the unit to show the lights on, despite not operating.

US Coastgaurd came to inspect - no worries, proceed to berth!

[Bob]

Talking of Doxfords. What about the serries that didnt have flexible water cooling pipes but "swinging arms" each with special packing (regular feild days), and mechanical fuel valves fitted with a cage and operated from a long camshaft running along the middles. Crosshead driven scavenge pumps. You were like a one armed paperhanger with an itch when maneovouring (cant spell that even now) two levers and a booster pump button. Spherical bottom ends, 3 in each crankpit. a regular pantomine.
Bob

[Ghost in the shell]

by the way, would I be right, or wrong as the case may be, those big marine diesel engines, would they be 2-stroke units?

[boatmadman]

The ones I worked on were 2 stroke, think all the slow speed diesels were.

I suspect the medium speed jobs would be 4 stroke.

(in this case speed = engine rpm)

Ian

[penfold]

 great stories
  bukerbarge,commen rail on marine engines ,are the injecters solenoid operated, would have to be a big magnet, most bm and mini diesels have 2000 bar in the rail,  soenoid makes sense, as an aprentice i remember testing injecters( spray patterns etc) how  do you do it on a huge marine engine??
 cheers penfold

[a3nige]

We had a rig for testing injectors, I seem to remember the Sulzers were about 6000 psi. We used jewelers rouge to finish lapping the mating surfaces. We used to get the pressure up to just before spraying then lean with all your might on the leaver to fire the injector, checking pressure and spray pattern and DO NOT get in front of spray, it will go right through your skin!

Never worked on a 'Desmond DC Doxford' but heard lot of tales.

Nige

[Bunkerbarge]

Penfold, yes the injectors are fired by solenoid valves.  The new systems that are being put together to meet all the new and upcoming emission regs are computer controlled but when they throw a wobbler they can do a lot of damage to an engine.

We test injectors in exactly the same way as you do with the car type.  The fancy ones record the pressures electronically and give you a screen shot of the performance.  Oirs is a handamatic with a big lever and a piece of kitchen roll to see the spray pattern!!

[a3nige]

Just found this site. It looks very interesting especially the 'horror stories'.

http://www.marinediesels.co.uk/

Nige

[Shipmate60]

BB,
Wil your super-duper newer engines meet the incoming NOx limits.
None of our engines have a hope in doing so, so glad it isnt retrospective!!

Bob

[Bunkerbarge]

Our engines won't but they don't have to as they were built before 2000.

Any ship being built now though will have to.

[Ghost in the shell]

having seen the plume off a ferry firing up at liverpool i can see why they are bringing the regs in

[penfold]

nice one bunkerbarge!
    next question!  i believe most large marine engines start on compressed air, HOW?,
  do they use turbos ,slow reving not sure it would be worth it, smaller cats (lifeboats maybe!)
 might be worth it,and lastly do they have a closed fresh warter cooling system or open salt water
if so what problems occured>
 cheers penfold, very inquisitive mechanic(secretly longing top work ships)

[boatmadman]

Air start systems- there is a compressed air system, compressors receivers drains etc. To start the engine, comp air is admitted to the cylinders through an air start valve, one per cylinder,the timing of admission is controlled by the starting gear and the required direction of rotation.

To reverse rotation, the starting gear changes the firing sequence of the engine so that it rotates in reverse.

So, to start the engine - on older ships - select rotation, pull the air start lever and watch the cam end untill you see it rotating, then put on the fuel and take off the air and hopefully it goes! The knack was (is?) getting them going using a minimum of air from the receivers.

To start a newer engine - ask BB 

Engine cooling water is a closed system so that corrosion can be inhibited, this in turn cooled through sea water coolers.

Dredging the grey cells for this - its 25 years since I dried my boots off!

Ian

[john strapp]

Bluebird - it was an experience on Doxford "j"'s but I'm a turbine man at heart. Having said that, my first ship was a T2,  give me "Waverley" anyday!

[Bunkerbarge]

I haven't actually seen a reversing engine for about 20 years now.  Currently the plant is diesel electric, which is normal cruise/ferry practise, and before that it was a CPP set up.

Medium speeds very much favoured for speed of response when manoeuvring and for Diesel Electric.  We have five engines so can use any combination for optimum loading depending on speed required.

Starting is by compressed air, on one bank of the "V" only, through air start valves, timed by a distributor on the end of the camshaft.

Starting is usually from the control room but you can start them locally and they are usually left on auto-start as back up.  

Large slow speed engines are a whole differrent ball game.  As Ian says starting a large slow speed diesel was an art and if you were maneouvring from the platform while on stand by you had to ensure that you used just enough air to start it without having it fail to start, in which case you just wasted a load of air, or you were too cautious and you used too much air to get it going.  The knack was to use the minimum amount of air for each start.  Obviously if you used too much there was always a danger of running out and then the ship couldn't manoeuvre until the air bottles were filled up enough.

I was once on a ship with a 7 RND 90 engine, total power, 20,300 bhp.  Not big by todays standards but the buzz you get out of manually starting something like that is unbelievable.  All huge brass levers and hand wheels and the pressure of getting it just right and being responsible for getting all that engine moving.  Great experience.

[Colin Bishop]

Interesting stuff. Of the three Denny built Isle of Wight ferries built 1948-51, the third one, Shanklin was built without gearboxes to save money. This meant that every time she touched base on each side of the Solent, the engines had to be stopped and restarted in reverse to give astern power. Not the most efficient arrangement on a half hour crossing which led to her being used mainly for cruising and being sold off before her slightly older sisters.

[Bryan Young]

Just a touch off topic, but still on engine starting. Perhaps an ex-army guy can help out here. When I was on the LSLs, prior to discharging a full load of tanks, all the tanks fired up their engines with an explosive charge. Quite impressive and logical as a tank would'nt have space for an air-start system. My query is...did (or do) any ships use the "explosion" method? BY.

[boatmadman]

Not in my (limited) experience!

Ian

[Shipmate60]

Bryan,
Yes.
We used to operate an old fast passenger boat RMAS Osprey, she was powered my marinised Rolls Royce Aircraft Engines and had cartridge start.
These were like a 12 bore cartrudge and after about 5 starts the starter had to be stripped and cleaned.

Bob

[DavieTait]

We had a 6 cyclinder 500hp air start Mirlees Blackstone ERS6MGR in the David John ( my families last trawler ) and to start her we had to use a long bar to rotate the crankshaft round till cyclinder 1 was TDC ( Top Dead Center , right at the top of its stroke ) before ( making sure you had stowed the bar..... ) you hit the starter valve. She usually started first time but if we had been stopped over Christmas and it was very cold we always made sure the Gen sets were warmed up and both air bottles were absolutely full as i've seen us just getting her going just as the last of the air runs out 

[Stavros]

This is what Mayhem is all about keep it up chaps very interesting reading

Stavros

[polaris]

Bryan,

Just to briefly mention that single cylinder Marshall agri. tractors used cartridge start (these 1930's to mid-40's - not that I was around then you understand!). Quite a few early stationary engine mfrs. used this method.

Ruston used air on their big engines very early on - definitely in the 20's anyway - something is at the back of my mind that they bagged some tech. ideas off the Germans after WW1.

Suction gas engines used a hot plug 'sort of system' (canal barges used to use the same on the early oil engines by blow lamps), but there were other ways of starting gas engines but I have forgotten - will dig out the info. I have on these out of curiosity and to refresh memory! Suction gas wasn't used as marine propulsion, because of it's bulky eqpt. and obvious risks, but I could be wrong?

Regards, Bernard

[Bunkerbarge]

It's funny you should mention the cartridge.  A couple of years ago I was showing an old boy through the engine room, I can't remember who he was or what the connection was, but he asked me at one point how we started the engines.

I showed him the compressors, explained the air start system etc to which he said "Oh I wondered if you still used shot gun cartridges"  I was then convinced he had lost it but then he went on to explain that he was an RAF mechanic during the war and when they were test running lancaster engines they uses shot gun cartridges.  When I explained that one of our cylinders is approximately 70 litres and there are 16 to an engine he realised it wasn't going to work for us.

Apart from the usual list of air start motors, electric start motors and the normal timed air injection undoubtedly the strangest system I ever came across was an emergency generator on an old passenger ship. 

To start this you took a roll of old film and inserted it into a steel flask.  The flask was screwed onto the engine and the engine was turned to a specific starting point.  You inserted a lit taper into one end of the flask and quickly closed the flask and opened an internal valve that allowed the flame to contact the roll of film.  The film burned so quickly it released enough energy into the flask to pressurise it.  You then opened a valve on the flask that allowed to pressure to act on a piston that pushed a toothed rack across the toothed flywheel of the engine.  The rack turned the engine over as it flew out the other side as was collected in a cylinder.  Heath Robinson eat your heart out!!  When I was first told about this I thought it was standard sea going prank and informed the First Engineer I was too old to fall for crap like that.  So he showed me, and it worked.  I was absolutely speechless and cannot believe to this day that it worked. 

The engine was a large "V", certainly a lot bigger than most vehicle engines and you would be hard pushed to turn it by hand.

[sweeper]

Re: explosive starters.
These were derived from the type used for aircraft (Kaufman - spelling may well be wrong).
They were fitted to "Ton"class minesweepers/hunters. From memory, a rotating cylinder akin to that of a revolver with about six cartridges held in the cylinder. Electrically fired , next charge is put into line by rotating the cylinder by using a solenoid.
IIRC, the aircraft ones were used for three reasons (1) the size of the engines was increasing to the point that electrical starter motors were becoming strained, (2) using this method saves installing a heavy starter motor (3) they are not dependent on ground equipment (trolley accumulators).

Regards