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Detroit Diesel Heat Exchanger Failure

Discussion in 'Engines' started by CappyP, Dec 11, 2013.

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  1. CappyP

    CappyP New Member

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    Hello Forum members:

    This morning, 35 minutes after getting underway, we had a catastrophic failure on the heat exchanger on one of our Detroit Diesel 16V-71N engines. The front of the housing blew completely out, resulted in significant damage to various areas in the engine room. The explosion lifted the floor panels of the salon, which is over the engine room. The good news is that we had no fire or crew injury, and returned to our last port on the other engine. Yesterday, we had a fire drill and today my crew was outstanding in dealing with this event.

    We found the following:

    The raw water pump impeller had failed, which stopped the water to the heat exchanger.

    I had no over temperature alarm prior to the event.

    The pressure relief cap looked serviceable, and the cap receiver port was clear.

    There is no coolant or diesel fuel in the engine oil.

    Later, I ran the engine for 20 seconds and there is no over-pressure in the crankcase venting out the oil filler.

    None of my diesel technical friends have an explanation, or have ever heard of, or how the pressure could have gotten to the point to explode the heat exchanger. I am looking to this forum for any similar experience with this anomaly. We are working to effect repairs, but do not want to miss something before replacing the unit.

    Thanks to all in advance.
  2. dennismc

    dennismc Senior Member

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    Do you have any interface with domestic water, hot water tanks etc ?
  3. Capt J

    Capt J Senior Member

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    The only thing I could conceivably think of would be A LOT of crankcase gases in the coolant system. Fuel in the coolant system from a fuel cooler failure or something and the heat ignited it? I really do not know as this is a new one on me.
  4. dennismc

    dennismc Senior Member

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    Is it possible to tell which side failed ? salt or fresh.
  5. RT46

    RT46 Senior Member

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    can you post pictures?
  6. K1W1

    K1W1 Senior Member

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    Hi,

    Do you have any idea what the temp was just before it fell apart?

    Did the Hi Temp Alarm go off after the failure?

    I would test the Hi Temp Alarm Switch and Temp Sender before re assembling and hoping everything was good.
  7. K1W1

    K1W1 Senior Member

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    Hi,

    Is it possible that the SW outlet was somehow blocked or closed?

    The Jabscos are a positive displacement pump and do not take kindly to running against a closed valve.

    The whole system might have got to a pretty good old pressure and as there is no relief on the SW side, the weakest part failed and the ensuing explosion of water flashed off into steam to an extent on contact with hot surfaces and the flying parts caused some damage.

    Also, if the SW goes to the exhaust you would have had this entering the fray once the system was open via the spray ring or whatever injection device is used on your application adding to the mess.

    The Jabsco Impeller would not look good after 35 mins of running against a closed valve.
  8. CappyP

    CappyP New Member

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    Failure

    There is no connection to the domestic water system.

    There were a few small pools of coolant in the engine room and these there was no evidence of diesel fuel or crankcase oil. There was no indication of flame or fire in the space.

    The engine coolant side on the heat exchanger failed. The salt water core looks ok and we are having it pressure tested today.

    The high temp alarm did not go off before or after. It did test fine afterwards. I do not know at what temp it would activate.

    The SW outlet appears unobstructed.

    I had looked at the engine gauges about 15 minutes before the event and they looked normal.

    In discussions last night we are wondering if there could have been a crack in the housing and if it failed prior to the 7 PSI relief valve in the cap venting. We have most of the pieces and may get some forensic opinion on this at a later date.

    We are working to get a new unit installed and are hoping that there is no internal engine damage.

    Attached is a pps showing the damage.

    Attached Files:

  9. Marmot

    Marmot Senior Member

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    That's impressive.

    It looks like your seawater flow failed and the coolant overheated, did not relieve or alarm and the tank ruptured. As K1W1 suggested, the hot coolant flashed to steam and created an overpressure that seemed like an explosion.

    The FW side is sealed tightly but the cap should have relieved at least part of the pressure, and your hi temp alarm should have worked. A flow switch in the raw water side might have been a good investment given the propensity of Jabsco impellers to fail.

    That tank is a fairly thin casting and had probably been subjected to quite few pressure cycles over its lifetime so I would chalk that bizarre failure up to metal fatigue and bad luck given a bit of a boost by inoperative protective systems.

    What you need to determine next is what damage may have occurred by the overheating as it must have been fairly substantial. Also, find the impeller blades before they contribute to another overtemp condition.
  10. Pascal

    Pascal Senior Member

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    15 minutes interval between checking gauges seems like a recipe for disaster.

    I would carefully check th exhaust system before running that engine after the HE is replaced as things must have gotten very hot in the there with no flow.

    Impellers rarely fail suddenly, either they fail over a time period or something else makes them fail suddenly. Sometimes, slowly rising gear temperature will be the first thing to show limited raw water flow or an impeller which is shedding bits and pieces. At least this has been my experience on cat 3412s

    Has any cooling system maintenance been performed on that engine? Strainers? I ve had two instances where a raw water pump failed to reprime after the system was opened. In one case, the coolant never got hot enough as we were running slow on the way out but a cat mechanic down below touched the pump cover and realized it was burning hot (sea trial after maintenance). I now check the raw water pump cover for temperature after most cold starts and after haul out or strainers clean up and monitor coolant and gear temp for even rise after start up.
  11. SeaEric

    SeaEric YF Historian

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    That damage looks to me like what you would expect from freezing. I agree with Marmot, it is impressive.
  12. Capt J

    Capt J Senior Member

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    The damage is impressive I agree. BUT the shape of the piece that came out. It really looks like that piece was cut out previously and welded back and ground smooth and painted for some unapparent reason. It's strange how the edges are so straight and not jagged. Unless the part that stayed happens to be a thicker part of the casting. I've never seen anything like it on a DD heat exchanger housing.
  13. RT46

    RT46 Senior Member

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    It is hard to tell from the pictures.

    I really would like to seem some close ups of the cracks and breaks.

    The edges of the metal do not appear to have failed from excessive interior pressure.

    I would expect a failure of a hose clamp or hose before the HE fails from high pressure.

    Is it possible that metal fatigue or electrolysis cause the metal to fail at a fairly low pressure?

    How effected was the floor above? Is there significant damage and movement of the floor?
  14. Yachtjocky

    Yachtjocky Senior Member

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    Impressive

    15 minutes between checking gauges is impressive, not checking water flow after "opening up the system" is even more so !.

    I would check the lengths of the bolts that secure the pipe support on the front of the heat exchanger. If these are too long and are "bottoming out" they could cause stress cracks in the casing.

    Although the photos are kind of hard to tell but there are small stains on the edge of the broken piece but not all the way across which may indicate cracks have been there and unfortunately during this run the casing let go.

    Most temperature senders will not alarm if there is no water and in one case I was involved in the DD got so hot the wiring harness went up in flames, burnt all the way up to the fly bridge, Halon system went off, shut downs did not work and engines sucked the good old halon in resulting in two new engines and two new generators.

    The cause in that case was the complete failure of a fresh water hose which dumped all the coolant, no water no alarm

    Good luck.

    Please send close up photos of the welded casing ;) which failed lol
  15. K1W1

    K1W1 Senior Member

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    It is that invisible welding and the disguising of the grinding on the inside that really gives away that process isn't it.

    Its Cast Iron which is actually quite brittle if mis treated, beat one with a Sledge Hammer and you will see similar results.
  16. Marmot

    Marmot Senior Member

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    Welding indeed. It was obviously done by laser proton stir welding in a NASA vacuum chamber them micromachined internally in order to disguise the old repairs and make the failure look exactly like the type one would expect to see when a thin casting with a large flat surface is over pressurized.
  17. CappyP

    CappyP New Member

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    HE Failure

    There is no evidence of prior welding, and as pointed out it would be impossible to grind the weld on the inside of the housing. Plus the boat has passed by NASA, but never stopped in.:)

    There was raw water being pumped from both engines after start. We always check this during the warm up phase. Obviously that did not last.

    The metal fatigue/crack theory seems the most likely at this point. There are some questionable marks on the edges of the case remnants. The surface area of the failure is about 190 square inches, so at 7 psi that would be more than 1300 pounds of outward force. With a crack, maybe that would have done it.

    I am curious what temp the alarm is supposed to trip. And, how the sensor works. The test mode works, which I think just shows continuity of the circuit and the light and horn are functional. If the sensor did not work, for instance a failed bimetallic element, then no warning would have been evident.

    I have a DD mechanic arriving today to start the replacement. I hope to get more information on the temp system from him.

    Stay tuned.
  18. Capt J

    Capt J Senior Member

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    I'm quite familiar with cast iron. Cast Iron is pretty strong when done right, especially the new MIM process. It definately is not nearly as strong as a piece of forged metal, but you couldn't create a tank of that shape out of forged metal back in the day, or at least a cost effective one. With today's CNC machines it could be done fairly easily out of forged, but you'd still have to have a weld somewhere due to it's shape. However cast iron does suffer from porous castings and weak castings when not done right, which is evident on the top edge where it's rusty and appears water has almost been seeping through the casting there for years. I said it almost looks like it was cut and welded. The other question is why didn't a rubber hose blow first or the relief valve on the cap, but I guess the casting was weak to begin with and 2 decades of age set in. I've never seen a 16v71, but have seen many 16v92's and even a 24v92 which was an engineering disaster on DD's part.
  19. P46-Curaçao

    P46-Curaçao Senior Member

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    Woww I’m extremely worried now :eek: Al-Qaeda infiltrates in Detroit engines…I will put some extra surveillance on my 6-7's :D
  20. Capt Ralph

    Capt Ralph Senior Member

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    How cold was it when you started? When this happened were you still in a river? Water temp?

    With allot of imagination please bear with me;
    Old stressed tank.
    Water temp coming up. Expanding cast.
    Then a blast of real cold sea (river) water. (cold eddi) Contracting cast.
    Then warm water again. Expanding (exploding) cast/tank.

    It may not have been allot of pressure, just allot of thermal flexing.
    Note the heavy cast areas are intact. Slower to react to quick temperature changes. The thin areas that could have taken a drop or hit 20 years ago or even a cast blem, then a drastic thermal.
    Q C on this tank when new involved what? Eyeball and it held water. Nobody x-rayed this after it was made. No audio or ping on it.
    Yes modern technology is a whole different world on HEs now. There was not much high tech (todays standard) around when this tank was made.
    Find another one, bolt it on and go back out.
    As these ole Detroits (and others) pick up more years, we may start seeing more bazaar failures like this.