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Old 03-03-2009, 15:47   #1
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Bukh Engine Exhaus Elbow

We have just spotted a crack in our exhaust elbow and looking on the web, some owners have replaced this with a fabricated S/S unit.

Do any members have experience of replacing this item or have comments on the advantages/disadvantages of a cast unit vs a S/S one.

Thanks
Hi guys A freind of mine has posted the above on another (Very Small) forum, and I thought it would be intereting to get some feedback here.
I have seen elbows made from iron pipe and stainless steel apart from the fact the iron pipe is probably cheaper to have made what are the advantages and disadvantages of either system.
Thanks
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Old 03-03-2009, 16:02   #2
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I have owned a Bukh ME10DE since 1980 and I had to replace the elbow in 2007. As I'm in Canada our parts source for Bukh is Crinion Marine ( hope I spelled it right ) don't recall the price, didn't break the bank. This is the only time I have put a wrench on it other than oilchange and water pump impeller.

Used the phone call to order the origional Bukh warning lamps for the control panel as the sun had done them in.

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Old 03-03-2009, 16:17   #3
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Hey Cacique! I am fabing a new elbow/stack right now (for a Nissan diesel)! Dave Gerr says 316L stainless or better. I bought my elbows at Grainger, and my plate for the flange at Speedy online metals here in the USA. Gerr says use Schedule 80 pipe, I measured my old plain steel rusted elbow, and settled on Schedule 40. All told; $220 us for the materials, and should be around $80 for the welding. This was for 2 1/2" nominal pipe (63mm) Hope this helps if you need to make your own, Chris


http://www.speedymetals.com/pc-2557-...teel-annealed-
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Plumbing > Fittings > Stainless Steel Pipe Fittings and Accessories > Elbow,90 Deg,2 In,316L Stainless Steel : Grainger Industrial Supply
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Old 03-03-2009, 16:54   #4
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Be very careful with 316, it is not the right material for this application. The combination of high temperature, salt water and sulphurous exhaust components will soon see crevice corrosion in welds followed by the material proper breaking down.
Best material - one of the Incoloy family, for the budget user mild steel galvanised (should last 10yrs)
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Old 03-03-2009, 16:58   #5
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Quote:
Originally Posted by Christian Van H View Post
...Gerr says use Schedule 80 pipe, I measured my old plain steel rusted elbow, and settled on Schedule 40.
I am assuming the elbow is in a wet exhaust and the raw water exiting the engine is injected there - ignore the following if not the case.

I have no direct experience of using 316L ss in that particular service as all the new builds I have been involved in with wet exhausts requiring the injection parts to be fabricated from new have been large power boats and specialist ss's have been used for which standard fittings cannot be had. But I have had quite a lot of experience with the failure of ss in hot and drying situations where chlorides exist.

SS is very susceptible to corrosion when exposed to chloride solutions (eg seawater) at higher than ambient temperatures and especially if there are wetting and drying cycles allowing a coating of precipitated chlorides to form.

It is normally even more vulnerable to corrosion in regions where there are stress raisers due to welding.

So, for myself, if going to fabricate such a fitting I would follow the advice and use Sched 80. If it were the case that the engine manufacturer made their elbow using a resistant alloy (cast in one piece) then I would always use that and swallow my pride regarding the cost, however I understand that the standard fitting in your engine's case seems to be steel so that option is not available.

I also would be interested in any feedback regarding any experiences of long term use of 316L in the application. I have known of a couple and in both cases the experiences were bad - but it may only be because they were bad that I got to hear of them .

EDIT: 's for Marinheiro, we posted at the same time so didn't see yours before I hit the send button - is nice to find someone who agrees with me for a change .
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Old 03-03-2009, 17:14   #6
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Sorry Midland, my elbow is dry. I'm only quoting Dave Gerr here. He said 316L is acceptable. There are several other metals that are even better. Unobtainium seems to be the best of the best...do you know where we might get some? I HAVE seen a ton of custom SS exhaust parts in my day though...
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Old 03-03-2009, 17:50   #7
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Sorry Midland, my elbow is dry...
Yes, no real problem in that case then, just don't play tennis with it .

I have a big selection of Unobtainium fittings here, tell me what you want and I'll send you some - payment required in advance .
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Old 03-03-2009, 18:32   #8
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I'm not sure I could even afford the shipping! That stuff is HEAVY!
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Old 05-03-2009, 16:12   #9
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Thanks for the input so far guys
This systen is an exhaust elbow that is injected with warm salt water.
It sounds like the iron system might be better.
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