Diesel engine room blowers

[BruceK]

I'm replacing my engine room blowers that haven't worked in a while due to shot / corroded fan bearings.

What is the best configuration for a cramped diesel engine room?

Both fans in
Both fans out
One intake and one exhaust.

Engine room contains house batteries etc.

 

[Andy Cox]

Funnily enough, this also on my winter list. I believe I have two inlet fans and two outlet fans. I know at least two of them aren't working due to being seized like yours.

I also have batteries under the engine room sole.

Andy

 

[BruceK]

Hi Andy. There is a discussion on this from a couple years ago : http://www.ybw.com/forums/showthread.php?458840-Engine-Room-Fans-Suck-or-Blow

Unfortunately it didn't seem to reach a consensus and ended up being more of a confirmation that diesel cooling was great. Still worth a read and I am hoping that a consensus can now be reached.

 

[jrudge]

Fairline on the s58 and s65 have 2 blow and 2 suck.

The t40 had fans as well and I have no idea what they did as it was a while ago but at a guess they blow and suck also.

 

[Hadenough]

Consensus, on here? In your dreams
Anyway, for a bit of TD should they suck/blow from the top or the bottom of the engine bay? Or one from the top and one from the bottom?

 

[Andy Cox]

That's interesting reading Bruce.

I have two fans located at the fwd end of the engine room which blow in. At the rear of the compartment are another two fans that extract.

The inlet and outlet circuits are switched separately, therefore I could and perhaps should run the inlet fans whilst underway to help introduce cool air in to the compartment and then after shutting down the engines switch over to the extractor fans to expel excess heat and odours etc..

Makes sense to me.................at least I think it does?

Andy

 

[Seastoke]

BRUCE ,To say you have more than one fan is a joke Theresa May has more fans and don't forget you are Welchhhhhhhhhhhhhhhhh .SS

 

[BruceK]

BRUCE ,To say you have more than one fan is a joke Theresa May has more fans and don't forget you are Welchhhhhhhhhhhhhhhhh .SS

No just 2 Roy. Although there is ducting for 4

 

[BruceK]

(Yer not baiting me)

 

[Assassin]

For diesel engines you need air blowing in and ideally at the lower end of the engine room with sufficient capacity to supply sufficient volumes of air with the engines running at full chat, basically you're pressurising the engine room by a tiny amount and allowing the surplus air to escape through the ductings, lower down because hot air rises and this creates vortices which rise and attract other emissions and drags them out.

 

[PilotWolf]

For diesel engines you need air blowing in and ideally at the lower end of the engine room with sufficient capacity to supply sufficient volumes of air with the engines running at full chat, basically you're pressurising the engine room by a tiny amount and allowing the surplus air to escape through the ductings, lower down because hot air rises and this creates vortices which rise and attract other emissions and drags them out.

All our vessels have between 4800 and IRC 11000 hp with either 2 or 4 engines and all the fans draw in and vent at the opposite end of the engine rooms. There seems to be no standard or logic as to whether the fans are at the fwd or aft end.

W.

 

[Portofino]

For diesel engines you need air blowing in and ideally at the lower end of the engine room with sufficient capacity to supply sufficient volumes of air with the engines running at full chat, basically you're pressurising the engine room by a tiny amount and allowing the surplus air to escape through the ductings, lower down because hot air rises and this creates vortices which rise and attract other emissions and drags them out.

I can’t see that , the pressurising of the ER

https://www.widman.biz/English/Calculators/CFM.html

Using this my engines at 1850 rpm suck 35400. L / Min .So 70,000 + beingdrawn in .
Can’t see any electric pump(s) with sensible dia tubing 24 V being able to get anywhere near that .
And the sucker outer set of blowers likewise ,think about it there’s 70000 L being drawn in through the ER hull vents per min ,are you telling me those out fans are gonna be effective when running normally against all that flowing t,other way in ?

So why fit them ?
Well they certainly are useless when the engines running so maybe they are a bit useful after shut down to mitigate against heat soak now the water pumps stopped or just exhaust and latent fumes .
As said at design rpm they feel useless the maths regarding the huge vol of air , those blowers just piss in the wind .

My boat has not got any blowers at all .
It’s got one presumes adequate air vents in the hull to handle the incoming sucked air .These vents can be closed / sealed as part of the fire control regime. Adding blowers would just complicate sealing the ER in the event of a fire .Not saying it’s impossible , just added complications.

So we need the vol of theses blowers in or out to compare with what the engines gobble to work out if they are useful or chocolate teapots .

 

[PilotWolf]

I can’t see that , the pressurising of the ER

https://www.widman.biz/English/Calculators/CFM.html

Using this my engines at 1850 rpm suck 35400. L / Min .So 70,000 + beingdrawn in .
Can’t see any electric pump(s) with sensible dia tubing 24 V being able to get anywhere near that .
And the sucker outer set of blowers likewise ,think about it there’s 70000 L being drawn in through the ER hull vents per min ,are you telling me those out fans are gonna be effective when running normally against all that flowing t,other way in ?

So why fit them ?
Well they certainly are useless when the engines running so maybe they are a bit useful after shut down to mitigate against heat soak now the water pumps stopped or just exhaust and latent fumes .
As said at design rpm they feel useless the maths regarding the huge vol of air , those blowers just piss in the wind .

My boat has not got any blowers at all .
It’s got one presumes adequate air vents in the hull to handle the incoming sucked air .These vents can be closed / sealed as part of the fire control regime. Adding blowers would just complicate sealing the ER in the event of a fire .Not saying it’s impossible , just added complications.

So we need the vol of theses blowers in or out to compare with what the engines gobble to work out if they are useful or chocolate teapots .

First the caveat I'm not talking pleasure craft.

Our engine room fans shut down when or before the fire system activates ( depending on which boat - some manual some auto). But usually the first sign of a fan failure on the boats that don't have fan failure alarms is the rising engine temps.

Also the Mate will or should do an engine room check at each port ( roughly 90 minute intervals), and trust me the moment you go into the engine room you know if the fans are working or not!

Our basic SOP for a fire is fans stopped, dampers closed, engines shut down and activate CO2 or the the halon replacement. Crews will not (or should not), activate the extinguishing agent except under direct instruction from bridge team for various reasons.

Not trying to teach anyone to suck eggs but unless fans are off, dampers closed and engines shut down before letting off the gas it's going over board one way or another rather than smothering the fire.

W.

 

[Portofino]

First the caveat I'm not talking pleasure craft.

Our engine room fans shut down when or before the fire system activates ( depending on which boat - some manual some auto). But usually the first sign of a fan failure on the boats that don't have fan failure alarms is the rising engine temps.

Also the Mate will or should do an engine room check at each port ( roughly 90 minute intervals), and trust me the moment you go into the engine room you know if the fans are working or not!

Our basic SOP for a fire is fans stopped, dampers closed, engines shut down and activate CO2 or the the halon replacement. Crews will not (or should not), activate the extinguishing agent except under direct instruction from bridge team for various reasons.

Not trying to teach anyone to suck eggs but unless fans are off, dampers closed and engines shut down before letting off the gas it's going over board one way or another rather than smothering the fire.

W.

Yeh agree we know that .I did not want to drift into the fire side of blowers just touched upon it as said briefly “ just added complications “ which you have reinforced that view .

The main point was I can’t see how you can pressurise the ER with the IN blowers ( no chance with the OUT sucking ) while the engines are running .
Yours is just scaled up can you use the link to get a comparative vol , I don,t know your cubic capacity or typical rpm of those 7000-11000 Hp engines .
That link for my 700 ,s as said works out at over 70 ,000 L / min of air ( turbo diesels )
So go on any marine pleasure craft equipment site find a 24 V x 2 IN or 4 inc two suckers OUT - pumps some suitable ducting appropriate sized for a 4.2 x 14 M boat - what 6 inch , 8 inch !?
Then see if when they run how close vol wise ,they are to the main engines drawing 70 ,000 L / min from the vents in the sides of the hull .

Imagine if you were an air molecule in the ER - where would you end up ?

Obviously proportionally your ducting and fan motors will be bigger but the dia of the duct I tell you now a man can,t stand up in neither will it 6 inch .
What I,am saying is the vol of air moved by the engines drawing in outblasts any other forced IN fans .
As said probably makes the suckers useless .

When running at what ever rpm is normal place a smoke source between the engines and see where it goes .
Obviously when the engines are off then the blowers will dictate the smoke flow and cool the ER as the heat soaks up the block into the what was cool coolers since the sea water has stopped .So there is some merit of ER directional blowers after shutdown to keep the ER temp down , minimise heat build up I can see that .

It’s just running I can’t see any point of blowers because the air is gonna move only way towards the air filters on the engines .
This is because of the relative huge difference in flow vols between the diesels at cruise rpm and the blower motors + ducting .

 

[BruceK]

I can’t see that , the pressurising of the ER

https://www.widman.biz/English/Calculators/CFM.html

Using this my engines at 1850 rpm suck 35400. L / Min .So 70,000 + beingdrawn in .
Can’t see any electric pump(s) with sensible dia tubing 24 V being able to get anywhere near that .
And the sucker outer set of blowers likewise ,think about it there’s 70000 L being drawn in through the ER hull vents per min ,are you telling me those out fans are gonna be effective when running normally against all that flowing t,other way in ?

So why fit them ?
Well they certainly are useless when the engines running so maybe they are a bit useful after shut down to mitigate against heat soak now the water pumps stopped or just exhaust and latent fumes .
As said at design rpm they feel useless the maths regarding the huge vol of air , those blowers just piss in the wind .

My boat has not got any blowers at all .
It’s got one presumes adequate air vents in the hull to handle the incoming sucked air .These vents can be closed / sealed as part of the fire control regime. Adding blowers would just complicate sealing the ER in the event of a fire .Not saying it’s impossible , just added complications.

So we need the vol of theses blowers in or out to compare with what the engines gobble to work out if they are useful or chocolate teapots .

Using that calculator 29000 litres per minute at cruise revs
Each fan pumps 7650 litres per minute theoretically
So If I used all 4 instead of just 2 I would theoretically just exceed demand at cruise revs.

That is of course if Assassin is correct.
Trouble is I am not sure exactly how hot my engine room is getting when underway considering the amount of air it is sucking in. My I/R gun thermometer is useless for that. What I can say is if you enter the engine room on shut down via it's access hatch rather than open the engine bay door it's hot enough to immediately drench you in sweat. So 50C plus which cant be good for that battery banks.

All that of course is if you were trying to charge air directly into the engine. I'm not sure about that. I think the fans are either to maintain a close to ambient temp during cruise or to extract heat after shutdown. Problem is the owners manual doesn't even mention fans in a diesel context. Only the warning for petrol engined variants.

My boat isn't a large passage maker but a 34 foot sports cruiser with a cramped engine bay.

 

[Portofino]

Using that calculator 29000 litres per minute at cruise revs
Each fan pumps 7650 litres per minute theoretically
So If I used all 4 instead of just 2 I would theoretically just exceed demand at cruise revs.

That is of course if Assassin is correct.
Trouble is I am not sure exactly how hot my engine room is getting when underway considering the amount of air it is sucking in. My I/R gun thermometer is useless for that. What I can say is if you enter the engine room on shut down via it's access hatch rather than open the engine bay door it's hot enough to immediately drench you in sweat. So 50C plus which cant be good for that battery banks.

All that of course is if you were trying to charge air directly into the engine. I'm not sure about that. I think the fans are either to maintain a close to ambient temp during cruise or to extract heat after shutdown. Problem is the owners manual doesn't even mention fans in a diesel context. Only the warning for petrol engined variants.

My boat isn't a large passage maker but a 34 foot sports cruiser with a cramped engine bay.

Just two are IN ?

If so that’s 15.300 L Against the engines 29000 . So about 1/2 the vol ish .

And if the other two suckers are on , that’s my point where’s the + ve pressure coming from ??

To get +ve you need the pair of IN ,s to exceed the 29 K the engines are gobbling,and presume suckers off or bunged up !

 

[BruceK]

yes if I port 4 fans in I can just exceed demand, theoretically. There is ducting for 4 from the 4 intake and or exhaust vents but when I got the boat two were only ever in use with fans so that is where I currently stand. I cant see blocking all ports to go via a fan is a good thing? I may be wrong there.

 

[Andy Cox]

I'm inclined to agree with PF, in that using fans to try and provide excess pressure in the engine room is quite improbable. I guess running inlet fans whilst underway will help provide additional air flow around the engine room and help keep the ambient temp down.

Running the sucker fans whilst underway wouldn't make any sense but they would be helpful to lower the post shut down temp in the compartment and prevent odours etc. making their way into the living spaces.

The other day I bought a gadget I saw at my local garden centre which is basically a digital indoor/outdoor thermometer with a probe on a 2m lead to measure the outdoor temp and the main unit measure the indoor. The reason being that my generator is not boxed and I want to make up a sound insulated box for it but I'm worried about a high temp build up and I thought this could be a good way of keeping an eye on it remotely. I'm sure there are wireless units out there and perhaps we should be thinking about having something like that on board to help keep an eye on engine room and generator unit temps whilst running?

The one I bought was about a tenner and looking me in the eye, so I bought, but I'm now starting to think more seriously about this.
Andy

 

[Portofino]

Yes it interesting to get to the bottom of ER blowers in liesure boats .
Some have none like me , some have both blow n suck and use them intermittently, some just either blow or suck .
Is there anybody out there that absolutely need a blower ie the engines seem to have impaired performance when they are not working ? Just curious .

My geny is air cooled the cylinder head has fins like old fashioned VW beetle and a big fan + cowl to direct the air .
It’s in a sound proof box ,but the box has no floor so with the cowling air is fanned about .
Thing is as you can imagine it’s v hot air after a run and shut down when the Med ambianct already say 30 outside .
There is seawater air / water HE looks like car small car radiator.So warm say 27 degree sea water circulated in the rad and them fanned by ER temp air or air warmed further after passing over the cylinder head fins .
It’s original 2003 and despite what seems like a pretty harsh environment the yanmar engine seems ok .
I guess the air is cooled from what ever the ER is 50/60 to sea 26/27 then this fanned over the windings and engine .

I guess a pair of suckers on after shutdown may lower ambient ER after shutdown.
Batts are in the ER they are gel maintenance free in theory and seem to last about 5 y .
Possibly one could argue extending the lifespan is stored in perfect ( not 50 degree + ) environment.
But there’s are many other variables to bat life that you have little control of .
Not currently feeling the urge to blower up the ER on a maybe get another year or so out of the batts .

Another thing while we are on ER ambiance temp ,have you ever touched the fuel tank after a long run or a couple of days running .
It’s like a radiator on full in the winter .This is because of the 80 or what ever % fuel returned eventually heats up the tank .
Oil holds the heat better than water so so have a huge heat sink issue .
Even in the morning it’s warmer than the iron engines .
So what I am saying blowing some air about for [ insert your timeframe ] after shutdown is gonna struggle to cool the contents of the fuel oil tank(s) .

Having said that some boats feel blower mad .
Those Med boaters have all heard Mangusta and Arno Lepeords arrive or depart from a what was a piece full Anchorage .
There ER fans are often heard 1 st before the engines when anchor doing manoeuvres .They wake up neighbours snoozing :ambivalence:
Really LOUD .

View attachment 74662

These are full on blower boats
They come in from 70 ft upwards

 

[Portofino]

View attachment 74663
Here’s a pic inside a gusta 130 ER .
On the port side you can see circled in red the IN vents , four .
If you look at the outside of the 165 above ^^^ at the grills you can see four squares .
They are all the same , just different sizes

I suspect the fans are in there ,they do sound like when you park you car in the summer and the rad fan runs on .
Kinda fan blade noise .But x 8 huge fans .
I,am assuming they are located in those boxes because google images of Mangusta ER show no other contraptions fan like or ducting associated with blowers .

You can see the Venetian blind effect flaps which form part of the fire control system , closing the boxes .

Hell of a noise they make .

Ps I bet they take that paper roll down for the RINA survey or fire prevention inspection for the ins Co ?