Heat exchanger repair

[rogerthebodger]

Now steady on there - I spent most of my youth being forced to go sailing . I attribute much of my love today to stockholm syndrome . As is the natural order of things, I pay it forward to my children, who now in turn love it also (once prised away from the Playstation!...(Okay, so we do now sail with a Nintendo Switch also...)). And yup, my daughter is just as interested in the servicing of the engine and all the other practical wonders of boat work (who wouldn't love sticking their (gloved) fingers in sikaflex?...)...

My comment was based on my grown up daughter not when we would go cruising in the UK when daughter was little and would supervise dad when servicing the engine on my boat and cars. She was 4 to 5 years old at the time now over 40 y o a.

We were away from any form of boating for nearly 20 years while 600 km from coast and job, family and business got in the way.

When we got back into boating/sailing daughter was at university 1000 Km away so joining us was very limited.

There is a time in children's lives when they are old enough to help/get involved in what eer passion attracts them helping dad in his passion and hopefully the same. Then other attractions and responsibilities come in to play.

My Father wa a fisherman and enjoyed horse racing I never took to fishing and have no interesting in horse racing but went along but nevered forces to get involved yet my brother did all his life.

Girl or boy friends, university. work, marriage, family all take the toll until the time comes when you have time and or money or both to go back to what you enjoyed

I put the ages when children and dads start to enjoy pastimes together is 8/10 to about 15/16 or older if you are lucky.

My point is it's all about choice and opportunity for the children with maybe some genital encouragement and loads of respect and acceptance if they don't wish to partake

Back to your heat exchanger is it all OK now or are you still waiting for it back and fitted.

 

[MagicalArmchair]

£400 and the good folks at the Goto Engineering nearly have it all flush and ready to go. Both chambers pressure tested to 15psi fine.

Pressure testing the freshwater chamber:

Pressure testing the raw water chamber:

Original flange pre welding:

Welding process started:

Studs out and ground back:

More building up and final machining and polishing will be done later today, ready for pick up tomorrow!

 

[rogerthebodger]

Looking good.

 

[RichardS]

Great news. Should be virtually as good as new. A good gasket and perhaps checking every couple of years should be the way forward.

Richard

 

[Beneteau381]

£400 and the good folks at the Goto Engineering nearly have it all flush and ready to go. Both chambers pressure tested to 15psi fine.

Pressure testing the freshwater chamber:

Pressure testing the raw water chamber:

Original flange pre welding:

Welding process started:

Studs out and ground back:

More building up and final machining and polishing will be done later today, ready for pick up tomorrow!

A good story for PBO! They do pay for these

 

[Beneteau381]

Ive seen pics of people cleaning back to good metal and building up with weld. It takes quite a bit of courage but it is do able. Plastic metal is for a get you home or sell it quick job.

Good to see it actually being done

 

[dankilb]

Think they left the studs in while welding because they knew the heat would help in getting them out later?!

 

[MagicalArmchair]

A good story for PBO! They do pay for these

Quite a relief - I'm looking forward to getting the engine back together again. I've done a few articles in my time - I'll write this one up too - one of the benefits of lockdown, a surplus of time... (although with the 'crew' at home and homeschooling, there is less of that than you might think...)

 

[PaulRainbow]

Think they left the studs in while welding because they knew the heat would help in getting them out later?!

Definitely help, but also stop blowing the sides out of the threaded holes.

 

[Bobc]

£400 and the good folks at the Goto Engineering nearly have it all flush and ready to go. Both chambers pressure tested to 15psi fine.

Pressure testing the freshwater chamber:

Pressure testing the raw water chamber:

Original flange pre welding:

Welding process started:

Studs out and ground back:

More building up and final machining and polishing will be done later today, ready for pick up tomorrow!

Good stuff. All looking good. Glad to see that you've managed to get it fixed and that it's holding pressure.

 

[rogerthebodger]

Definitely help, but also stop blowing the sides out of the threaded holes.

That is the main reason especially when welding aluminum with its relative low melting point.

 

[vas]

400quid is a bit steep though, no?
well done fixing it, make sure you remove the elbow often from now on

V.

 

[MagicalArmchair]

It was the pressure testing that put the price up, as they had to fabricate plates etc. Email from the shop:

We don’t have machining facilities but in the first instance we will aim to get it as flat at possible on our side. I can also get a quote in from one of my suppliers to do this if that would be useful.

Get it machined? Surely sanding it flat (it being soft ally) and polishing flat will be enough?

 

[rogerthebodger]

It was the pressure testing that put the price up, as they had to fabricate plates etc. Email from the shop:



Get it machined? Surely sanding it flat (it being soft ally) and polishing flat will be enough?

I machined the welding of my heat exchanger with a belt sander for the flat part and a half round file for the O-ring chamfer

 

[PaulRainbow]

Get it machined? Surely sanding it flat (it being soft ally) and polishing flat will be enough?

Depends if you want it to turn out like your bleed screw

Get a price to have it machined, should not cost much to mill the surface at 90 degrees to the studs.

 

[MagicalArmchair]

Get a price to have it machined, should not cost much to mill the surface at 90 degrees to the studs.

Thanks, You are the professional - I defer to your wisdom sir. More money! Can't spend it anywhere else I suppose...

 

[Bobc]

It was the pressure testing that put the price up, as they had to fabricate plates etc. Email from the shop:



Get it machined? Surely sanding it flat (it being soft ally) and polishing flat will be enough?

Get it machined flat. After spending all that money on it, it's not worth risking it for the sake of another £50.

 

[MagicalArmchair]

Mr Volvo responded, claiming its not galvanic corrosion:

Galvanic corrosion is caused by two dissimilar metals which are in direct physical contact with each other and are immersed in an electrolyte (a liquid that conducts electricity, such as sea water). The joint between the exhaust elbow and exhaust manifold is not in a solution of sea water, the sea water is injected at a lower point into the exhaust stream. We believe the corrosion of the exhaust elbow and manifold is due to moist air mixing with elements in the exhaust gases to form a solution that over time can cause corrosion. Hence our point this failure is age related. At the end of the boating season we suggest points to check in addition to the annual servicing, VP workshops will have access to this information.

• Check for leakage: fuel/water/exhaust. • Check hose clamps and bellows. • Check cable connections. • Inspect through-hull fittings/cocks. • Check the cooling water cock: opening/closing. Replace if stuck. • Clean off fouling growth (drive/hull/propellers). • Clean the battery terminals; remove oxide. Check the electrolyte level. • Clean the engine and engine compartment. • Clean the fuel tank. • Drain/replace the fuel pre-filter. • Functional check of other electrical systems. • Check the drive and propeller(s).

I responded with:

Hello Volvo,

Thank you for the response and happy new year.

The failure was not caused by age, as such, it was caused by corrosion elsewhere: The exhaust elbow raw water injection point.

The elbow is a hollow casting with 3 core plugs. Internally the cast iron corrodes as it is hot and wet and passes warm sea-water. The scabs of iron oxide build up inside the elbow. These can block the water injector ports ( one on top and one below). In this process it’s quite possible for pumped sea-water to spray backwards toward the exhaust manifold. The resultant hot sea-water corrodes the aluminium all around the flange to the elbow where it sits next to the dissimilar and more noble stainless steel gasket. See the injection elbow in my below picture:

On removing the elbow, all looks fine, until you removed the stainless gasket:

The spray would sit and gather just inside the gasket. We now have the perfect conditions for galvanic corrosion.

I posed them a few more questions also, lets see if they come back with anything more useful.

 

[rogerthebodger]

We believe the corrosion of the exhaust elbow and manifold is due to moist air mixing with elements in the exhaust gases to form a solution that over time can cause corrosion. Hence our point this failure is age related.

An interesting point is the sulphur in the fuel turns to SO2 (sulphur dioxide) which when combined with water (normally in the atmosphere) becomes acid rain or

Sulphuric acid (H2SO4)

Even dilute sulfuric acid reacts with many metals via a single displacement reaction as with other typical acids, producing hydrogen gas and salts (the metal sulfate). It attacks reactive metals (metals at positions above copper in the reactivity series) such as iron, aluminium, zinc, manganese, magnesium, and nickel.

 

[MagicalArmchair]

It's plausible what our friend at Volvo said, I just don't buy it. I think it would have eaten that flange in a very different way - the corrosion would not have just focussed where the dissimilar metals meet. Additionally, Parts4Engines gave the specific reason they supply that composite gasket, and to chuck the stainless one supplied away, that they are well aware of the galvanic corrosion issues of this area of these Volvo engines. Added to that, on the other thread related to this issue, a Vetus owner, who had a 30 year old engine, noted Vetus fit as standard a composite gasket and his exchanger flange to the elbow was "as new".