Engine cooling thermostat, how does it work

[kashurst]

Anode erosion is a problem of quantum mechanics - electrons have a spin property based on electromagnetic momentum as the electrons orbit the atomic nucleus. (like the earth going around the sun) When your propellers are also spinning the electrons spin in sync and all is well. However once everything comes to a stop the electrons keep spinning. This creates an electro-magnetic potential difference (Clarke Maxwell Law) which causes a current to flow from the props to the sacrificial anode. It is well known that the electron spin value in zinc is higher than propeller electron spin speed and the zinc atoms migrate to the slower propeller electron/nucleus because of entropy in an open field.

does that clear things up?

edit 21/07/09 - just in case anyone ever bothers to re-read this thread - this post is complete made up nonsense.

 

[Lon nan Gruagach]

Anode erosion is a problem of quantum mechanics - electrons have a spin property based on electromagnetic momentum as the electrons orbit the atomic nucleus. (like the earth going around the sun) When your propellers are also spinning the electrons spin in sync and all is well. However once everything comes to a stop the electrons keep spinning. This creates an electro-magnetic potential difference (Clarke Maxwell Law) which causes a current to flow from the props to the sacrificial anode. It is well known that the electron spin value in zinc is higher than propeller electron spin speed and the zinc atoms migrate to the slower propeller electron/nucleus because of entropy in an open field.

does that clear things up?

But they spin the other way south of the equator so you need anodes of a less noble metal instead of more noble of northern hemisphere.

 

[kashurst]

But they spin the other way south of the equator so you need anodes of a less noble metal instead of more noble of northern hemisphere.

True however as a bit of a fudge / get you home, you can fit the anodes the other way around - after all they are gravitationally polarised. You sometimes see this in the Northern hemisphere on boats with trim tabs with the anodes fitted underneath rather than on top.

 

[jfm]

T
Question is can it easily find a partner to bond to in fresh ?
Your Zincs are having potential partners / mates to bind with flushed away

But freshwater isn't an electrolyte (to any meaningful degree cf seawater), so they don't need to find partners/mates. With no electrolyte, you do not have the "battery" that LNG describes in #90. The electrons just stay where they are, married to their atoms (ie no ions), as is the case with the dissimilar metals inside your watch or your toaster.

If your theory were correct, a brand new engine just finished at the factory and never having seen any water or a boat, just full of air, would somehow be corroding due to not having seawater inside it.

 

[Portofino]

But freshwater isn't an electrolyte (to any meaningful degree cf seawater), so they don't need to find partners/mates. With no electrolyte, you do not have the "battery" that LNG describes in #90. The electrons just stay where they are, married to their atoms (ie no ions), as is the case with the dissimilar metals inside your watch or your toaster.

If your theory were correct, a brand new engine just finished at the factory and never having seen any water or a boat, just full of air, would somehow be corroding due to not having seawater inside it.

Sorry for the L post .

The chemistry still occurs with plain dock water but not as aggressive.
The greater dissimilar metals in contact the bigger , faster reaction too and current created .Extra ions in salts just facilitates the process , the process starts with plain water , and only needs plain water .Current flows more easily in salt water than it does in fresh water. This is because salt water, an electrolyte solution, contains more dissolved ions than fresh water, meaning electrons can move more easily. Since corrosion is all about the movement of electrons, metals rusts more quickly in salt water than it does in fresh water
So it depends on a few variables how much corrosion you are gonna get .

Corrosion is a given with dissimilar metal contact and water .


Aside the electrolytic potential of dock water is plenty enough to set it off .Ever read the label on Evian ?
Or seen how quick rain corrodes bare iron ?
But obviously not as strong as sea water and even seawater varies ,the Med being more salty than most .
So flushing may be effective for only 5 mins at tickover certainly reduces the electrolyte concentration .
But it reduces the same pathways of the e,s from the nearby Zincs .

But there should be enough Zinc e,s readily in continuity to cope with the motor running .
I think some e,s will travel through the metal casing but some are needed in solution to snuff out the initiators + ve charged OH 4 + ,s in the water .
It’s theses that are grabbing e,s from your boat bits .

Hence if it’s dry impossible in a boat it won’t corrode .


Otherwise you are inferring the motors corrode when the salt concentration is highest ? When they are running at near WOT , mega
med seawater flushing .
Once rinced with seawater , after the first start up it there’s no going back to new or bone dry .
They don’t dissolve away ( normally ) if the anodic protection is there ,loadsa good e,s from the Zincs .

Remember all the crevices in all the joins a flush with tap or even RO and those microclimates which I mentioned earlier will still be pretty active salt concentration wise so there are still e,s being ripped out .Small currents galvanic activity etc .

But where’s the cavalry ? Why cut the Zn e,s out ? Reduce there supply route s
If your anodes dry out ( like the early CAT CAC,s ) then the cases supply of e,s is cut off because the Zinc is dry it can’t see a ion in solution to mate to so stops spewing protective e,s into the boat bits .
With insufficient numbers of protective e,s to backfill e,s start being ripped out of your boat a piece of boat starts reacting , that reaction is initially with positive charged OH molecules from the water , any water .

By fresh flushing ( sure with good intent ) from a corrosive POV all you are doing extending your anode life .

But @ what price ? That’s my point ,it’s been my point on the first thread on this from a corrosion POV .

So if an e is taken out of a crevice / flange / joint on a heat exchanger or CAC it’s replacement needs to be right there my continuity point
If there aren’t enough e,s donated e,s from the Zincs getting through A positive reactive piece of copper++ or Al ++ or likely any tiny constituencies of iron ++ from a boat part will jump out and start to mate with the water .
You don’t need salts the corrosion chemistry occurs with dock water .
Even RO , it starts with water the metals in the boat parts initially loose e, s to the loose reactive positive charged OH ,s in the water .

But crucially as I said earlier you anodes are “not ornaments “ much to MapisM,s consternation, they do a job of supplying extra e, to bond with the boat parts .
Infact a salt solution will facilitate the movement of those e,s good e,s

Fe → Fe2+ + 2e−

O2 + 2H2O + 4e− → 4OH−

2H2O + 2e− → H2 + 2OH−


Your e,s from the Zinc can prevent this thats if there’s continuity that’s the idea and if the Zincs are in good shape leave them alone .

It’s a balance if the metals are extra dissimilar ( accidental poor design / manufacturer etc ) and pencil anode protected like many if the Zincs can’t cope for what ever reason ( dry out too tiny not replaced in a timely manor ?? ) then it’s a net loss as they can’t cope with the speed facilitated by the salt solution THEN to win that battle if your supply of e,s is insufficient an attempt at reducing the electrolyte concentration by flushing is your last resort .
But bear in mind running the motors is working against you as you will have max seawater electrolyte.In this case it just a matter of time not if a coolers gonna go .

Not your first resort if the metal dissimilarity is fair to low and there’s plenty of Kgs of Zinc on the scene nearby extra conductivity of the sea water like if left MANs is helpful That’s my position at the mo .

I want my Zincs to deplete I want seawater to facilitate the transmission of there good protective e,s .

So it’s not a one regime suits all that’s what I,ve been pushing back depends on your set up I would say and you and MapisM have different set ups anodic protection wise .
Your set up with local pencil anodes bearing in mind the weighted history of CAT CAC flushing might be the best option .
If it appears to be beneficial( I hope it is ) it’s most likely working I suspect because you are not actually totally removing the salts with a low flow and low time it’s reducing the electrolyte concentration but is or was it ever enough? It might be below a critical level to slow corrosion down but maintain a strong enough concentration for sufficient good e,s supply from the Zincs nearby.

Suppose you could scape back paint to metal on different external “ boat parts “ and fix a sufficiently low calibrated multimeter and record voltage when flushing against time .Also recheck next day , week etc .
If there’s little V drop after the 5 mins or it’s back where it was a week later then
Don’t worry your “ Zincs aren’t ornaments “ they are slowing it down .
Ideally if the Zincs are working there should be zero volts .
If there’s zero v before then why flush ?
If there’s V after a flush then you have a problem.


What are your plans @ year 7 btw ?
Have you opened a CAC up and peeked inside recently?

Para 2
You need water to initiate corrosion metals get them wet think rain and cars .
If it’s dry kept in a dehumidified environment like say a classic car then it won’t corrode , I hope - don’t ask !
How ever if it got wet and struggled to ever get dry it would , it’s got not Zinc .
But some marques have retro fit galvanised chassis as J Rudge has pointed out .A lot of modern cars are Infact zinc coated theses days even Italian cars .

Swiss Watches are made of noble metals and usually keep dry inside and immersed in the sea for short periods .The cases are noble enough as they are to not need anodic protection, a zinc bolted on the back .Well mines hasn’t got a zinc and it’s in the sea all the time swimming etc .
Your toaster needs to be dry or simple paint to protect it .
There’s moisture in the air too so another sources of OH

Bleach contains hypochlorite ions they actually accelerates metal corrosion more than ordinary water because it liberates even more positive charged OH molecules ( or derivative ) which are what start the process as they are the ones ripping e,s out metals inc SS .

 

[markc]

Holy cow L, you really need to get back working, you have far too much time on your hands! I can't read all these pseudo science lectures, especially when I need to be building my patented Bodge System!

 

[jrudge]

This thread has defended into chemistry of corrosion

Remember the second bit. No critters In the water taking up home on my heat exchangers. My aim is first and foremost to stop that. Extended anode life is a bonus but they are about £5 each and I have 4 so the flush plates cost me about 3 years worth!

 

[markc]

So, I've sourced everything needed to do this, and it comes to less than £150 including new strainer lids, ball-valves etc in bronze, and all Gardena Profi 19mm hose connections for maximum flow. Thanks MapisM for the various links and info! I just need to decide if I should plumb the hose into my domestic system (I already have a hose plumbed into the domestic side in the engine room) and just use when the boat is connect to dock water, or connect a hose to the dock supply when needed.

 

[kashurst]

I would plumb it into the domestic system, then when you are leaving the boat possibly short of time, it's that bit easier to do without faffing about with the hose pipe.

 

[jrudge]

So, I've sourced everything needed to do this, and it comes to less than £150 including new strainer lids, ball-valves etc in bronze, and all Gardena Profi 19mm hose connections for maximum flow. Thanks MapisM for the various links and info! I just need to decide if I should plumb the hose into my domestic system (I already have a hose plumbed into the domestic side in the engine room) and just use when the boat is connect to dock water, or connect a hose to the dock supply when needed.

I think the issue is the system will not give the required flow and hoses will collapse

My d12s are happy on a hose pipe. Other way is to bypass the pump and suck from the water tank

 

[jfm]

@ #105 - OMG - I don't have the time any more. I didn't read beyond the 10th line. I'm folding. Let engines be stewed in brine :encouragement:

 

[MapisM]

Thanks MapisM for the various links and info!

My pleasure, M. :encouragement:

To recap, the BCI (BodgeFlowTM International Club) includes so far representatives in 4 Med Countries, involving no less than 5 engine brands - with apologies in case I'm forgetting someone:

Jfm (Cat)
Vas (Iveco)
Jrudge (VP)
Markc (MTU)
Mapism (MAN)

Porto, don't get distracted by sub-atomic particles, quantum mechanics and all other trivial details.
At this rate, belonging to this club is going to be de rigueur before you know it.
Otoh, an open boat would fit nicely in our collection of (so far) flybridges only.
A win-win situation, if I've ever seen one.

May I interest you, as a cherry on top, in a free subscription for the first year?
Don't be shy, go ahead and show us some pics of your BFTM implementation!

 

[MapisM]

I just need to decide if I should plumb the hose into my domestic system (I already have a hose plumbed into the domestic side in the engine room) and just use when the boat is connect to dock water, or connect a hose to the dock supply when needed.

I don't think it makes a meaningful difference, M.
Provided of course that your fresh water pump can supply a decent flow, which I bet it does.
Or that you can arrange a direct connection to the tank and let the engine suck water directly from it, as Vas did.
Can't remember, have you got a watermaker onboard?
If yes, feeding the BFTM from a tank filled with RO water (as jfm mentioned) would be a nice touch, but that's beyond hair splitting!

 

[markc]

I don't think it makes a meaningful difference, M.
Provided of course that your fresh water pump can supply a decent flow, which I bet it does.
Or that you can arrange a direct connection to the tank and let the engine suck water directly from it, as Vas did.
Can't remember, have you got a watermaker onboard?
If yes, feeding the BFTM from a tank filled with RO water (as jfm mentioned) would be a nice touch, but that's beyond hair splitting!

A direct tank connection would be a right pain, so that's not on the cards. I have a Gianeschi Ecojet which I think does 40lpm so that may be OK, and yes I do have a watermaker so if I took from the tank then I could fill with RO water. I can't remember how the current engine room hose is connected, buts it's right by the strainers so that'll be my first investigation when I'm on the boat in a week or so.

 

[Zing]

As to the part of the original question asking if a thermostat is an on/off device. If you do nothing but watch the temp gauge for a considerable period of time, it won’t budge by even a degree. If the thermostat were an on/off device like a bimetalic switch there would be a noticeable up down movement of the temp gauge within a range representing the thermostat’s hysteresis. As that isn’t the case it has to be essentially a proportional control device.

 

[MapisM]

Interesting observation, because during the last seatrial we made some stress tests, like cruising at 2000rpm and reduce one engine at a time by 400rpm.
The chap in the e/r with the IR gun did not notice any unusual temp increase in the more stressed engine compared to the other one with lower rpm, but at the helm I did notice with one of them an up/down movement of the cooling liquid temp.
Unfortunately, the accuracy of analogue gauges leaves a lot to be desired, but the behaviour was indeed noticeable.
I would say in a range of at least 5 degrees, if not more.
Increasing slowly (within a minute or so), and decreasing rather rapidly (some seconds), and so on.
When it was the other engine under stress, nothing like that was visible on the gauge.
Should I be concerned about the thermostat conditions? :ambivalence:
As I said, according to the chap in the e/r with the IR gun, all temps were fine at all times, but I guess that when measuring the metal rather than directly the liquids some inertia is inevitable...

Btw, the overall results of the seatrial (after a full cleaning of HE+aftercoolers, and a calibration plus nozzles replacement of all injectors) were excellent.
Smoke upon cold start is less and disappears faster, transom soot is overall reduced, and engines are somewhat smoother at idle, in spite of the fact that two different MAN engineers confirmed me that they were ok also in the past.
For the records, both told me that V8s aren't as smooth as V12s, but V10s were the worse - in fact, they were phased out.
Besides, we reached exactly the same performance recorded in the first startup protocol made on the brand new boat back in 2004 (33kts @ 2300).
Bottom line, at first glance it seems that the injectors refurbishment was worth doing, in my case - as opposed to other forumites who reported no changes at all, like petem and jrudge, IIRC.
Time will tell if that improves also fuel burn, though it was already pretty decent and in line with boat specs, so I'm not holding my breath.
My impression is that perfectly tuned injectors are more relevant at both ends of the scale (idle and WOT), but not so much at normal cruising speed.
Just gut feeling, though.

 

[Zing]

A problem with thermostats is they usually fail unsafe, i.e. to fail closed, which will cause a boil-over and engine incapacitation or maybe worse. I found a failsafe type. I think it is a good idea:

https://motorad.com/tech-tips/fail-safe-thermostats/

How bad would it be for the engine if it ran with the thermostat open fully and therefore over-cooling the engine to some degree?

 

[TheOrs]

As to the part of the original question asking if a thermostat is an on/off device. If you do nothing but watch the temp gauge for a considerable period of time, it won’t budge by even a degree. If the thermostat were an on/off device like a bimetalic switch there would be a noticeable up down movement of the temp gauge within a range representing the thermostat’s hysteresis. As that isn’t the case it has to be essentially a proportional control device.

Or just suspend one in a kettle and switch on. You can see it open slowly. Switch off & let it cool & watch the thermostat close slowly.

Play with the switch and you can get the thermostat to stay open varying amounts depending on the temp of the water. Quite fascinating if you are shallow like me!

 

[MapisM]

How bad would it be for the engine if it ran with the thermostat open fully and therefore over-cooling the engine to some degree?

Constant over-cooling would not be good, but better than constant overheating, I suppose...
Otoh, I don't think to have a choice in the thermostat replacement (if needed), because afaik it's engine-specific.

 

[Assassin]

All this talk of electrolytes (lucozade sport has them) and Zn which is found in vitamin tablets has bored me to tears and given me an idea.

Sod the coolant as I am filling mine with a combination of multivitamin tablets dissolved in Lucozade sport and this should cure all my problems, and it should make my engines healthier.