seawater cooling circuit monitoring Q

[vas]

evening all,

quiet working and busy setting up the features of a new arduino based black box for each engine that will do the following:

• gearbox oil pressure (got the VDO sender ok, but no gauge on lower helm nor space to add another two 52mm VDO gauges...)
• gear selector in order to park fins when reversing (ordered 2 uber cheap chinese rudder sensors to mount next/behind to the g/b selector lever)
• EGT (have the K-type thermocouples and tiny boards, tested working)

and a few temps...
Now then, I've already bought a dozen DS18B20 temp senders following recommendations in PBO, already used one on the fins, got to find what to do with the others before starting stuffing them in fridges
These are 6mm dia and approx 30mm long ss sensor leading to a 2m long cable.
So for each engine I'm planning for:

• g/b oil temp
• two of these babies to check the seawater temp though the cooling circuit.

Bear with me.

If I fit one on the endcap of the charge air cooler (that's the first one where the seawater goes after the strainer and pump and where you fish bits of vanes...)
and I fit another one at the endcap of the coolant heat exchanger (that's the last one before the mixer). Through my Ivecos seawater goes cac, g/b oil, oil, coolant, mixer

Then cant I get the delta Temp and when it's more than something get an alarm ringing?

Also by monitoring these temps I can see if there's something abnormal in the cooling circuit.

Does the panel agree or am I missing something?

Now if we agree, I have a problem to solve!

these cylindrical senders are a bitch to get them in half-decent contact to something else. I guess they expect them to be freestanding on air or dipped in a reasonable liquid.
So was thinking of spotting some blanking nuts (I've seen them around in the heat exchangers) and get my machinist to redo them in bronze much thicker and drill a hole (that doesn't go all the way through obviously!) in order to fit with a bit of heat transfer compound that we use for el. chips heatsinks.

Makes sense?
I'll spot the ones tomorrow onboard, undo them and measure, should be fairly straight forward.
any ideas on that?

For the record, all that data will go to a Maretron DSM250 display on the f/b kindly donated by JFM, once more many thanks John!
Unfortunately as I've mentioned before although I really love my Garmins, they wont be able to present ANY of that data as they are only supporting the part of the NMEA2000 protocol that they do have sensors for, which is a bit poor imho and even g/b oil pressure which they do support have a v.low limit that wont cut it.

cheers

V.

 

[jrudge]

Sounds like a good idea.

At the risk of the bleeding obvious the delta will rise with engine power demand, but assuming you have rpm you could even have max reference delta for given rpm bands.

The only thing to bear in mind is that all you are compensating for as opposed to measuring the temp at the output is sea temperature which will vary by only say 15 degrees c depending on season, so you are only getting a small additional warning when the sea temp is cold

 

[vas]

Sounds like a good idea.

At the risk of the bleeding obvious the delta will rise with engine power demand, but assuming you have rpm you could even have max reference delta for given rpm bands.

yep, will do some monitoring and then setup custom NMEA2000 alarms in my code which will take under consideration the rpm (already got that in NMEA2000)

The only thing to bear in mind is that all you are compensating for as opposed to measuring the temp at the output is sea temperature which will vary by only say 15 degrees c depending on season, so you are only getting a small additional warning when the sea temp is cold

Jeremy, lost you here I'm afraid...

what I'm trying to do is spot when seawater is not going through the system (blocked strainer, seacock off - unlikely as I never turn it off..., seawater pump buggered, or whatnot)
I'm assuming that if there's a blockage (say bag in skinfitting) then temps will rise quickly and I get a warning. I'll obviously have warnings on high temps on any of these sensors (just a matter of getting decent values on all)
only worry is that say bag in inlet, pump will flush all the water out of the system (doubt as there wont be anything to push through and get the water out...) and temps rise slowly letting other things take the strain.

I could have a simpler solution by plugging one of these sensors on the flex exhaust hose after the mixer, but I'm not too keen on drilling holes on this 127mm id pipe tbh.

cheers

V.

 

[Portofino]

what I'm trying to do is spot when seawater is not going through the system (blocked strainer, seacock off - unlikely as I never turn it off..., seawater pump buggered, or whatnot)
I'm assuming that if there's a blockage (say bag in skinfitting) then temps will rise quickly and I get a warning. I'll obviously have warnings on high temps on any of these sensors (just a matter of getting decent values on all)
only worry is that say bag in inlet, pump will flush all the water out of the system (doubt as there wont be anything to push through and get the water out...) and temps rise slowly letting other things take the strain.

I could have a simpler solution by plugging one of these sensors on the flex exhaust hose after the mixer, but I'm not too keen on drilling holes on this 127mm id pipe tbh.

cheers

V.

What I have std with the MAN is a “ seawater inlet pump pressure” reading one of the pages of the MMDS Man maintenance,Diagnostic System.

So any change in that pressure outside normal triggers an alarm immediately.

That’s what you need to attemp to measure .

Also handy to actually if you are bothered to record it regularly you could use it to check impeller health .

So no waiting for overheats , look at the water pump pressure ,
The pump is not specifically a MAN in house jobbie it’s a generic bolt on seawater effort ( sorry can’t remember which type )
So it’s either got a taped hole already in the body or there’s a taped hole somewhere in the pipage to accept the sensor .

 

[vas]

What I have std with the MAN is a “ seawater inlet pump pressure” reading one of the pages of the MMDS Man maintenance,Diagnostic System.

So any change in that pressure outside normal triggers an alarm immediately.

That’s what you need to attemp to measure .

Also handy to actually if you are bothered to record it regularly you could use it to check impeller health .

So no waiting for overheats , look at the water pump pressure ,
The pump is not specifically a MAN in house jobbie it’s a generic bolt on seawater effort ( sorry can’t remember which type )
So it’s either got a taped hole already in the body or there’s a taped hole somewhere in the pipage to accept the sensor .

nice idea Porto,

where do I source a seawater capable pressure sensor, and second, what sort of range would that have, I doubt it's high, I guess a 1-3bar at most pressure should be fine.
Wonder if it has to be special to withstand the salt 24/7...
It would be v.easy to fit on a blank on the cac front endcap (entry to cac)!
would be nice if you would find any specs on such a sender as I had a go at WIKA and couldn't find something that specifically says it will survive sea. FWIW, even if WIKA did such sensors (may do, dunno!) it would be prohibitively expensive (over 100euro a pop...)

Also have to see what I can treat it as in the NMEA2000 PGN protocol though, will check!

cheers

V.

 

[Portofino]

View attachment 75672

2.6 bar here .

Theses supply OEM MAN sensors , and many more .
https://www.mandmcontrols.com


Here = https://www.mandmcontrols.com/060g3125
Bit pricey?

 

[vas]

thanks!

a 0-5bar should be fine I guess.
Happen to remember at what rpm was that pic?
or remember if there's a great variation as revs go up?

danfoss (from the link you posted) is ONLY 200quid each "suitable for marine environment" which doesn't even mean it can survive seawater IN it and not around it...

found this, hope it's cheaper, but at these prices I probably skip and use my twin temp approach.

and further, unfortunately I can only report such pressure as:
EngineCoolantPress
which is not quite right (but I don't have a coolant pressure sensor anyway )

cheers

V.

 

[Portofino]

Click on the data sheet 316 SSteel the bit in contact with the seawater . MAN engines are littered with Danfoss OEM sensors .see the approval list too , Pukka sensors the real deal .
https://www.mandmcontrols.com/media/attachment/file/m/b/mbs33m.pdf

 

[vas]

thanks, got the code(s) I'd need, will ask on Monday at the local hydraulics shop and get a quote for two of them.
If they're silly price, I can always get 3-4 chinese ss ones for a 12quid each
Apparently there's a market for such sensors (but will odd custom plugs and highish prices) for the largish outboards that I assume are rawwater cooled and they keep track (or probably the ECU) of the raw water pressure. I note that these are yellowey coloured and definitely not ss.

we shall see!

V.

 

[vas]

another update...

Seems that seawater specific pressure sensors cost an arm and a leg, upwards 250quid all the way up to 400 ffs!!!
I find it a bit too much and considering it's not mission critical, I'll order half a dozen ss sensors for under 100quid (for the lot!) and see how long they last. I may remove, wash and store every winter, but for the price you cannot go wrong I guess.
Porto, do you happen to know where they are fitted in the circuit, I mean early on after the seawater pump, halfway through the heat exchangers or at the end of the route?
Second Q, are they dipped in seawater all the time, or are they fe at the top of the topmost endcap and dry out when engine is left to rest?

BTW, one of the two VDO 25bar g/box oil pressure senders is broken, so I'll get a couple of ss ones as well 4-20mA and wire them up...
I'll use the VDO on the generator's yanmar to monitor engine oil pressure recycling...

cheers

V.

 

[Portofino]

I think they are after the seawater pump on a metal pipe v close to the impeller out house. I would think they are always immersed as the SW pumps are low near the strainer relative height wise .
The other stuff SWCAC and HE , s are about as high as you can get them relatively to the WL , these drain out when the engines are stopped .
The water pump don’t drain as they as said low and about WL height- so primed always wet ready to go .

You won’t find a more Danfoss infested marine engines than MAN , it’s there Achilles heal on one hand and on another great to be able to see a zillion parameters, like “ seawater inlet pressure “
Like I said the system even tells you if there s a sensor error so kinda self diagnosing. So if you accidentally pull a wire off say a oil pressure sensors it’s tells you rather than alarms and goes into a limp mode .You operate the boat as normal ( sans oil pressure ) and sort it at your leisure .
They are all Danfoss from that link I posted .

 

[MapisM]

Porto, do you happen to know where they are fitted in the circuit, I mean early on after the seawater pump, halfway through the heat exchangers or at the end of the route?

V, I half remember to have read (years ago) that in the Mercury 496HO which powered my Fountain the sensor was fitted just after the raw water pump, because this way it can give also an early warning on a dirty heat exchanger.
In fact, the first effect of that, well before any overheating in the closed circuit, is that the raw water pressure gets HIGHER than normal.
IIRC, the alarm was actually triggered only by LOW pressure, but it was still nice to be able to check also that it didn't increase, over time.

 

[vas]

V, I half remember to have read (years ago) that in the Mercury 496HO which powered my Fountain the sensor was fitted just after the raw water pump, because this way it can give also an early warning on a dirty heat exchanger.
In fact, the first effect of that, well before any overheating in the closed circuit, is that the raw water pressure gets HIGHER than normal.
IIRC, the alarm was actually triggered only by LOW pressure, but it was still nice to be able to check also that it didn't increase, over time.

yep, makes sense P.
trying to combine this approach with a sensor drying position, so plan to put them on the top of the circuit on the first endcap before entering the charge air cooler. Will sent pics in a month or so (got to wait for the senders to arrive...)
Easy to have a low and a high alarm as well.

cheers

V.

 

[MapisM]

trying to combine this approach with a sensor drying position, so plan to put them on the top of the circuit on the first endcap before entering the charge air cooler.

Actually, I'm not so sure about what is better for any metallic parts, between:
1) being submerged in salt water and then dried + exposed to air, till the next time the engine is turned on, and so forth, or
2) being constantly submerged in water - which in this case could as well be salt water just for a relatively short amount of time, if you have a convenient way to flush the circuit with fresh water.

We already debated this in the past also for heat exchangers/intercoolers/exhausts, and IIRC Portofino rooted for self-drying stuff and considered fresh water flushing useless. But having had several boats both on the lake and at sea, I know where I would rather keep my boat, if it were just a matter of choosing what is better for her...

 

[vas]

Actually, I'm not so sure about what is better for any metallic parts, between:
1) being submerged in salt water and then dried + exposed to air, till the next time the engine is turned on, and so forth, or
2) being constantly submerged in water - which in this case could as well be salt water just for a relatively short amount of time, if you have a convenient way to flush the circuit with fresh water.

We already debated this in the past also for heat exchangers/intercoolers/exhausts, and IIRC Portofino rooted for self-drying stuff and considered fresh water flushing useless. But having had several boats both on the lake and at sea, I know where I would rather keep my boat, if it were just a matter of choosing what is better for her...

nice one P, you understand you're not being exactly helpful, do you?

The easy option for me, like remove a plug and stick it in 1/8 thread ready there waiting is on the third heat exchanger and low down so, always submerged. First is CAC, then it's gearbox oil, and then engine oil, last being engine coolant.
The not so easy option is to remove the pipe going uphill from seawater pump to CAC and weld a M10X1 nut and cut a hole in there obviously, still always submerged.
Third option is removing the CAC front cap where the seawater comes in, drill and tap and fit the sensor above the drying point.

Further, after two days of searching the web and contacting various companies, US, IT, GR the conclusion is for that sort of job you need "super duplex stainless steel as 316 wont work as it will corrode at Med seawater temps". Problem is that these costs 400-500euro each and I aint spending that much for sure!
Plan is to order half a dozen chinese "stainless steel" sensors (I guess they are 303 stainless or dunno do they do a 302 ) at around 20euro a pop and see how long they last Even if the 20euro one lasts a couple of seasons, my son will be reaching retirement before I'd recoup the cost and I'd have to be 100+
I also understand that these guys selling the super double whatever SS ones are selling high accuracy and well calibrated devices and I don't really give a damn if the coolant pressure is 3.23 or 3.235bar, so I'm searching on a non-existent market it seems...

Oh well, will order this week, should have them on before the end of March gives me enough time to prepare a few other things in the e/r

cheers

V.

 

[MapisM]

nice one P, you understand you're not being exactly helpful, do you?

LOL, am I more helpful if I tell you that I'd go for your easy option?
That, coupled with a fresh water flushing system, which I'd rather install regardless of sensor.
But you already fitted that, IIRC?

 

[Portofino]

LOL, am I more helpful if I tell you that I'd go for your easy option?
That, coupled with a fresh water flushing system, which I'd rather install regardless of sensor.
But you already fitted that, IIRC?

Depends!!!
There’s a fundamental difference between two engine anodic protection systems . It’s important to understand which type you have .
MAN use a huge hull anodes normally on the transom one for each side connected via a copper earth strap running through the bilges . There may be other stuff linked in too . Anode sized appropriately.

So in galvanic circuit the least noble will sacrifice. That’s the zinc bolted on the transom in the sea but it needs seawater to create a circuit for the movement of the various protective subatomic particles .

So cutting this circuit by subbing sea salts with a fresh water DIY ie a none OEM mods is madness .

It’s nice to minimise dissimilar metals all through the seawater circuit as much as possible to minimise local galvanic activity between components. Either use isolation gaskets or exact as far as poss metals in the components.

Or to hell with dissimilar metals shop from where ever - race to the bottom spec wise , sub out the components screw / bolt them together and run ! As a nod towards anti corrosion drill and tap shed loads of holes for LOCAL anodes and prey the operator changes them literally blindly on time .

All these zincs wear at different rates depending on as you say there immersion in salt and exactly what they are screwed into .So in say a CAT engine or Volvo D12 the pressure is now on to eliminate the salt solutions ie drain or / and flush and guess if the pencil anode is ( slang for sex beginning with F )
Or wash your hands of the multiple subcontractors that supply the components and blurt our the coolers are lifed for x years anyhow like CAT . I believe they recommend the Sea water charge air cooler is basically a throw away part every 5 years . Helps stop a US class action - sorry another class action for cooler corrosion. Cheap trick .

Those Germans ( MAN / MTU ) aren’t daft when it comes to marine engineering in a corrosion rich environment. Lurrsen used to make U boats btw . Wow haven’t they come far how ironic Philip Green swans about in one !

So recap
If it’s NOTv got pencil anodes it needs continuity via seawater to the transom anode . MAN like MapisM

If it’s got pencil anodes like your Onan geny or CAT or D12 etc then there may be some merit in attempting to dilute the salt solution connecting the zinc pencil to the components its trying to protect . Maybe ?

It’s not a one size - fresh water flush that fits all . Depends!!!!!

 

[MapisM]

So cutting this circuit by subbing sea salts with a fresh water DIY ie a none OEM mods is madness

R U suggesting that MAN engines aren't fit for purpose in lake boats?
You should inform several ferry operators about that...

 

[Portofino]

nice one P, you understand you're not being exactly helpful, do you?

The easy option for me, like remove a plug and stick it in 1/8 thread ready there waiting is on the third heat exchanger and low down so, always submerged. First is CAC, then it's gearbox oil, and then engine oil, last being engine coolant.
The not so easy option is to remove the pipe going uphill from seawater pump to CAC and weld a M10X1 nut and cut a hole in there obviously, still always submerged.
Third option is removing the CAC front cap where the seawater comes in, drill and tap and fit the sensor above the drying point.

Further, after two days of searching the web and contacting various companies, US, IT, GR the conclusion is for that sort of job you need "super duplex stainless steel as 316 wont work as it will corrode at Med seawater temps". Problem is that these costs 400-500euro each and I aint spending that much for sure!
Plan is to order half a dozen chinese "stainless steel" sensors (I guess they are 303 stainless or dunno do they do a 302 ) at around 20euro a pop and see how long they last Even if the 20euro one lasts a couple of seasons, my son will be reaching retirement before I'd recoup the cost and I'd have to be 100+
I also understand that these guys selling the super double whatever SS ones are selling high accuracy and well calibrated devices and I don't really give a damn if the coolant pressure is 3.23 or 3.235bar, so I'm searching on a non-existent market it seems...

Oh well, will order this week, should have them on before the end of March gives me enough time to prepare a few other things in the e/r

cheers

V.

Surely any zinc should go before any SS?
If it’s alleged cheapo SS then that’s gonna just speed up Zn depletion be it on the transom if it’s that type or pencilif that type .
The cheap SS will only go after the zinc (s) .
A best quality SS will be last before the metal casing and zinc .

Just monitor any zincs in the 1st year to get a handle on any changes in depletion rate .

 

[Portofino]

R U suggesting that MAN engines aren't fit for purpose in lake boats?
You should inform several ferry operators about that...

No use different anodes to reflect the lower substrate solution. Oh hang on they do ! Commonly referred to a AL .
Feels like you have not studied Chemistry. I spent a career working with dissimilar metals in a very special hostile environment . Painful if I got it wrong