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Old 12-08-2011, 12:09 PM   #1
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silicon bronze

I have been working on my heat exchanger. The bonnets on either end of the exchanger are of bronze. The bolts used to hold everything together are of steel. They are rusting. Are silicon bronze bolts a good substitute for the steel ones? Are they strong enough.

I Realize that the casing for the exchanger is cast steel. The issue is two dissimilar metals.

If I replace the bolts with the bronze I have bronze bolting through steel.

If I use steel bolts I still have steel going through bronze.

Comments?

SD
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Old 12-08-2011, 12:26 PM   #2
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RE: silicon bronze

Just buy some stainless bolts from the hardware store. They are stong enough, they won't rust and look nasty and will last longer than you will.

Besides, how come they are getting wet in the first place? If it's because your engine room is damp then you need better ventilation or you need to clean and paint the heat exchanger properly.

Since you own a boat in Alaska, you have more important things to worry about.
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Old 12-08-2011, 12:43 PM   #3
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RE: silicon bronze

Thanks Rick, That is just what I am doing.

Major refitting of the engine room I have repainted it and the engine, and am now working on the heat exchanger.

Pulled the tube bundle and hot tanked it. Found a leak.**That will address my overheating and coolant loss.

Now for the reassembly.

So you think three dissimilar metals will be OK?

Stainless bronze and cast steel.
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Old 12-08-2011, 01:02 PM   #4
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RE: silicon bronze

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skipperdude wrote:So you think three dissimilar metals will be OK?
Stainless bronze and cast steel.
It should not be any problem at all. They are not submerged in seawater and will be clean and dry when you finish the job.

The only time you really need to worry about dissimilar metals is when they are submerged in seawater or constantly wet with seawater. Steel is perfectly fine as long as it is kept dry or has a good protective paint coating on it.

There should be a zinc in the end caps to protect the core. The cast steel housing is corrosion resistant by its nature. After all it only sees engine coolant, just like the engine block itself. Don't forget there are plenty of brass and copper bits threaded into the block and they don't rot away over a long weekend either.
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Old 12-08-2011, 01:09 PM   #5
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RE: silicon bronze

Gotch ya. Sounds good to me.

*Plus the new stainless bolt heads will look nice.

SD
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Old 12-08-2011, 02:49 PM   #6
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RE: silicon bronze

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skipperdude wrote:*Plus the new stainless bolt heads will look nice.
I was going to say that but thought I would keep it all professional like*. I would do exactly the same if it were mine. if you want to have some fun, polish the heads and*use threaded stock instead of hex head bolts then you can use SS or brass acorn nuts and really make it look good. Paint the cast steel housing or have it powder coated. It will look like a museum piece worthy of Benn's Gardner.

I like to use polished copper or copper nickel pipe for larger vent lines and such. You can buy really nice brass railing and flanges for a lot of engine room applications where a traditional "shippy" look works well.
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Old 12-08-2011, 03:06 PM   #7
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silicon bronze

It would look cool. I thought about going that rout. Especially when I used the wire wheel on my Knife grinder (Hobby I Make Knives out of old chainsaw bars) *to remove the paint from the end caps on the exchanger. Cast bronze.

But then I figured they would just turn green and I didn't want to have to polish them all the time so I repainted them. I thought a clear coat would keep them pretty but I didn't.

But hey it's never to late. *I may get to something like that.

My first mate (Old Navy Man) wants to color code all the lines he said he has all the color codes for navy ships. Green for raw water violet for fuel and so on.

I told him to have at it. We shall see he talks a lot.

I'm more into the servicable kind of thing as long as it serves it's function.

when I get her done I post some pics.

SD


-- Edited by skipperdude on Thursday 8th of December 2011 04:12:20 PM
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Old 12-08-2011, 03:31 PM   #8
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silicon bronze

It will take a while to go green and a quick touch up with a brass wire wheel keeps them looking good, but clear coating is a guaranteed disaster.

Color coding the lines can go either way. If you use a single wrap of colored tape discreetly applied in*places where it actually provides useful information it can be very*useful. A directional arrow to show flow is also good*with the same caveat.

Attaching numbered brass disks to valves is a good way to help document systems and procedures. The disks are cheap and a set of number stamps work well to mark them. When you make a system drawing*all you have to do is*show the valve number. A separate index tells what the valve type and system is.

p.s. Don't wrap tape around SS tubing, it will corrode underneath it.


-- Edited by RickB on Thursday 8th of December 2011 04:32:54 PM
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Old 12-14-2011, 10:51 PM   #9
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RE: silicon bronze

SD--- In addition to the good advice Rick has given you, another factor is that stainless and silicone bronze are fairly close to each other on the galvanic chart. The farther apart two metals are on the chart the greater the likelihood of electrolysis and corrosion. You wouldn't want to put stainless fasteners in aluminum assemblies, for example, particularly in an environment where they can get wet. Which is why stainless fasteners are never used on floatplanes, for example.

When we installed some additional bronze cleats on the fore and aft decks of our GB I was able to find bronze fasteners the right size to use for this. However the shipwright we used for various projects back then said that if we hadn't been able to find bronze fasteners stainless fasteners would have been the next best choice because of the proximity of stainless to bronze on the chart.
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Old 12-15-2011, 04:20 AM   #10
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RE: silicon bronze

My first mate (Old Navy Man) wants to color code all the lines he said he has all the color codes for navy ships. Green for raw water violet for fuel and so on.

Visit the power plant at JFK, if you want to see this done professionally.

EYE CANDY!
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Old 12-15-2011, 10:06 AM   #11
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RE: silicon bronze

I think I'd be more inclined to use galvanized cap screws. The heat exchanger "bonnets" need to come off fairly often so replacing the screws would be convenient and economical. Are you sure the heat exchanger is steel and not bronze? *I wonder why a manufacturer would put a bronze cap on a steel housing?*
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Old 12-15-2011, 11:29 AM   #12
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silicon bronze

It's bronze for sure one on each side thick and heavy with steel bolts and the zincs are threaded into brass square end.

The priming pump is Aluminum and the fuel line has steel JIC fittings going into*a small*aluminum block on top of the fuel pump.

SD


-- Edited by skipperdude on Thursday 15th of December 2011 12:52:58 PM
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Old 12-15-2011, 01:36 PM   #13
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RE: silicon bronze

Are you say'in the housing is brass and the caps are bronze??
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Old 12-15-2011, 02:09 PM   #14
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RE: silicon bronze

No. The housing for the tube bundle is steel the bonnets or end caps are bronze.

SD
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Old 12-16-2011, 09:45 AM   #15
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RE: silicon bronze

I think Rick's recommendation of stainless is probably best. SS would probably come out better than galvies after time but never seize would probably solve that problem. I know Rick knows a whole lot more about corrosion than I do so go w the SS.*
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Old 12-16-2011, 10:29 AM   #16
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RE: silicon bronze

The original bolts on the valve covers were steel through aluminum covers into the steel heads. they came with a built in washer on the tops of the bolts. I couldn't find the same in stainless so I am using 316 SS bolt with a washer.

I'm wondering what is the best gasket sealer to use on the heat exchanger.(Water and coolant)

I bought a tude of Permatex. it says on the tube for gas oil and a bunch of other things. ya think it will do?

SD

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Old 12-16-2011, 02:03 PM   #17
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RE: silicon bronze

Dude,

If it's a good gasket do'nt use any goo. It will be so so much easier to take off later. I would think a rather soft gasket thick enough for a bit of crush would do fine if the mating surfaces are very flat and not pitted ect.*
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Old 12-16-2011, 02:13 PM   #18
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RE: silicon bronze

Ok. Sounds good to me. As the old ones had no sealant. They are of rubber so can squish. Thanks Eric

I have a mechanic on board and I will follow his advice also.

SD
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Old 12-16-2011, 03:34 PM   #19
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RE: silicon bronze

Quote:
skipperdude wrote:They are of rubber so can squish.
*If they are rubber don't use anything on them*. Make sure the mating surfaces are clean and dry.

*An exception is if you have to prevent*the gasket from moving from the proper position while assembling, it is acceptable to use contact cement to hold a rubber gasket on on side.
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Old 12-19-2011, 03:21 PM   #20
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RE: silicon bronze

Quote:
RickB wrote:skipperdude wrote:They are of rubber so can squish.
*If they are rubber don't use anything on them*. Make sure the mating surfaces are clean and dry.

*An exception is if you have to prevent*the gasket from moving from the proper position while assembling, it is acceptable to use contact cement to hold a rubber gasket on on side.

*Didn't have contact cement so I used the form a gasket. I only needed it on one side because of the PCV valve. I couldn't flip it over quickly enough to land in the grove. I only used 4 little dots on the corners.

Thanks for the advice.

SD
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