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Old 08-11-2017, 05:03 PM   #1
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Repair HX Raw Water socket

I have a standard Sen-dure HX on my Cummins 6BTA's. It is cupro-nickel and the raw water sockets (the In and Out barbed hose connectors) appear to be made of the same copper-rich material.

One of my raw water sockets has badly corroded at its lip (see photos below) and I want to get it repaired before I re-install the raw water hose that runs off this socket to a wet exhaust elbow.

I'd appreciate the advice of TF members as to the best repair technique. Rather than just show up with the HX to the local radiator shop & hand it over, if a particular repair approach is preferred I'd like to find a shop with experience in that technique. I understand that brazing with bronze 'filler' may be one option; and that TIG welding with a special welding rod might be another. Also that the HX casing itself needs to be heat-protected during the operation to avoid damage to the tube bundle inside.

Of course, if I'm over-thinking this and it is a job any local radiator shop does every day...please tell me that too! I have absolutely no machine-shop knowledge...as many will have already recognized!
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Old 08-11-2017, 07:52 PM   #2
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That nozzle is probably bronze as is the shell of the heat exchanger. Only the tubes are cupro-nickle. Once they get that corroded you are better off replacing the whole thing.

David
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Old 08-11-2017, 08:11 PM   #3
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Paul, I had the outlet on my F/Lehman FW circulation pump corrode such that the mechanic had a tube welded on to replace degraded and lost tube length. A check of the other engine revealed it had already been done too. Of course yours is RW not fresh, and I`m sure replacement as djm suggests is the best route, but a skilled repair and your observation might last you quite some time.
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Old 08-11-2017, 08:21 PM   #4
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David: the rest of the HX exterior and the other nozzles and the tube bundle itself are all in good order. Tube bundle is gently rodded every 12 months and mild acid-washed every 4 years. New replacement end-caps & gaskets are ready to go on. I don't think a corroded nozzle alone justifies replacing the whole shebang for 2+ boat bucks!!
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Old 08-12-2017, 05:29 AM   #5
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There are devices that can be put in the tubing end that will expand and bring it back into a round shape.

I would then find a copper tubing size that fit the outside of the fitting and simply solder it on.

Epoxy would work if you don't solder.

A too large size can be slit and shrunk carefully with channel locks.

It now will have good contact area and should not crush with a hose clamp on the rubber.

Next time use a hose removal tool, instead of brute force.
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Old 08-12-2017, 11:26 AM   #6
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FF: it is an oddity/distortion of the photo making the nozzle look like its been bent out of round by force. In fact the corrosion at the end of the nozzle is so severe the copper has broken away in sections. In fact the hose came off a little too easily once the clamps were removed. I think you may be right that a copper tube could be used to sheath the existing nozzle if it were cut back to solid material. I'd never use expoxy in this application though. I think it must be brazed with bronze....so late next week when I can get back to the boat, I'll dismount the HX and take it to a shop that does bronze work & see what they say.
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Old 08-12-2017, 02:57 PM   #7
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I would fix it, too, but I come from a time when we fixed things. Silver soldier is another way to attach a new nipple. Much stronger than regular soldier and much less heat than welding.
If the nipple is brass and corroding before other metal, I'd check my engine anodes.
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Old 08-12-2017, 05:41 PM   #8
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Thanks Lepke. ...funnily enough I've been reading about silver solder too. Seems like a stainless hose barb could be attached to the copper remnant nozzle using silver so that's certainly another option. Nozzle is copper or cupro nickel or bronze, not brass. Anodes are checked & replaced before they expire so no problem from that source. I haven't had that raw water hose off that nozzle for 4 years and the HX is 19 years old so i think hot salty water has just done its thing. I'll be pulling the same hose off the other engine's HX so I won't be surprised to find the same thing there.
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Old 08-12-2017, 05:50 PM   #9
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Greetings,
Mr. A. Since the original hose barb lasted 19 years it IS feasible, IMO, to replace it with copper again rather than going to SS. Both copper and SS are readily attached with silver solder (silver brazing is another term for the same process). Copper is easier to silver braze than SS although a competent welder should easily be able to accomplish both.
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Old 08-12-2017, 06:20 PM   #10
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OK many thanks RTF...you, Lepke & FF have contributed the 'technique' info I was hoping for. I have found a source for a 2" x 1 1/2" copper reducing coupler. I'm thinking that the 2" end will slip over what is left of the original nozzle (perhaps split and crimped in tight as FF implied) and can be brazed on. I'll then have a 1 1/2" outlet again. I'm guessing the hose 'barb' can be added as a fine brazing line at the edge of the 1 1/2" section.
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Old 08-15-2017, 07:43 PM   #11
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It may not be worth it for $2k. But is it worth it for under $800usd???
3866719CN Cummins Heat Exchanger

I bought from these people and they are top notch!!! Excellent customer service as well. Now whether they will ship down under I do not know.
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Old 08-15-2017, 07:58 PM   #12
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Baker thanks for passing that on. No problem getting it here....adds about $250 to the cost which is not a deal breaker. Certainly cheaper than local alternative. I'll know more about repair feasibility/cost tomorrow when I take the HX to a specialist radiator shop that can do bronze brazing & silver solder work. One thing against the Mr Cool & Champ alternatives is that some BoatDiesel gurus say the materials in these are very inferior to the Sen-dure original. Still, at that price I could replace twice and still be ahead.
I'll post details of the repair feasibility and cost when to hand. Thanks again.
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Old 08-18-2017, 01:44 AM   #13
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Finding a shop that would even look at a bronze brazing/silver solder job took about 15 phone calls. I tried both radiator shops and 'specialist' welders. Finally found an outfit that said they did this kind of work and who agreed to at least look at it. On inspection, they said "Easy" and $100 and 24 hours later, I had a copper-sleeved, brazed, strengthened nozzle with a hose barb returned to me: photo below. For Aussies in Sydney, the outfit is Superior Radiators at South Granville; Justin is the man. He also services Cummins aftercoolers "the Seaboard way".

Baker in post #11, pointed me to Mr Cool for a new HX at relatively low cost, which sent me looking for OEM solutions. I found go2marine.com even cheaper, at around US$685. What with currency conversions and shipping, a new HX could have been landed here for $1350 local currency; vs $6k+ (yes, that's not a typo) for a unit from Cummins locally. So I'm pretty pleased with my $100 spend. Of course now I have to strip and paint the shell; fit new end-caps and gaskets...even so, I'm well ahead....sort of. All savings will, as usual, be applied to other boat projects! Thanks to all who helped educate me about this.
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Old 08-25-2017, 09:53 PM   #14
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OK, seen some good and bad input here, here's my input from 40 years of welding marine alloys and member of a welding institute NZIW,

1) There are two main grades of copper-nickel alloy used in marine service - 90-10 (10%nickel) and 70-30 (30% nickel).The 70-30 alloy is stronger and has greater resistance to seawater flow; but 90-10 will provide good service for most application sand, being less expensive, tends to be more widely used.

2) Copper-nickels can be readily welded by all conventional processes and, since they have a simple metallurgical structure, do not require preheat or post-weld heat treatment. However, it is essential that requirements for preparation, particularly cleanliness, are carefully followed and that welders undergo a period of familiarization with the particular characteristics of these alloys if they are not to encounter problems. Automatic welding, including orbital welding of pipe, may also be appropriate.In some applications, insurance and inspection bodies may require qualification

3)Since the predominant application of copper-nickels is in the form of relatively thin-walled pipe, the tungsten inert gas(TIG), otherwise known as the gas-shielded tungsten-arc (GTAW), welding process is frequently used, both for joining pipe sections and for attaching fittings and flanges.

4) Copper-nickel alloys are readily brazed by all processes, although torch brazing is the most common. Since the process relies on wetting the surfaces to be joined by the brazing alloy, absolute cleanliness is essential. Fluxes alone are not capable of removing all contamination, particularly those containing lead or sulfur, and oils, paint, etc, which should be removed carefully with solvents and degreasing agents. Oxides and dirt can be eliminated with emery paper or a chemical cleaning process.

5) While phosphorus-bearing brazing alloys are often recommended for joining copper alloys, they are not suitable for copper-nickels because the nickel reacts with phosphorus to form a brittle nickel phosphide phase. Silver-based brazing alloys (‘silver solders’) should be used. They offer a useful combination of melting range, flow characteristics and mechanical properties. They also perform well in brazed joints where copper-nickels are exposed to seawater.

6) Never even think of using a dissimilar metal combination here, if you silver solder for example a SS Nipple on. it will last only months(or less) before it falls off due to Galvanic Corrosion

7) You should strip the heat exchanger and remove the interior copper nickle tube stack prior to any welding

Cheers Steve(MIIMS,NZIW)
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