Detroit Diesel Heat Exchanger Failure

Hi,

Yacht Jockey, Marmot was asking if it were Kafue that had seen the fire and the engine replacement.

I was just pointing with the use of a part of your post that it was info in a post originally by you where the words came from not his own words.

Aqualarm makes a good and reasonably priced selection of raw water flow alarm systems.

AQUALARM :: OnLine Store :: Comersus

The easiest thing to do would be to put a pressure switch on the output side of the raw water pump, where if the pressure drops below say 3 psi, the alarm will sound. I don't remember what pressure you should see on 12v71's at idle speed on the raw water side, but the alarm switch should be a couple of lbs below that and sound an alarm. MAN uses them on both the raw water and coolant on the common rails (a pressure switch that the computer sounds an alarm if it's too low).

I think the problem with paddle type flow switches is the build up of salt on the arm and where the arm joins the body, this always makes in line sensors subject to falses when in a hostile enviro. I have a pipe mounted thermostat on all cooling water exits from HEX's set at 140 F or whatever temp it will go off at during normal op temps. There may be in line sensors available that are immune to the salt enviro. Had a steam boiler blow up once due to failure of the water sensing probe due to a lack of proper chemical treatment, the probe was just encased in hard crystalline material and failed to sense a low water condition.

In addition to coolant temp alarm, exhaust temp should also be alarmed. (Note Aqualarm sells those too. Or for complete monitoring something like this; one of the few to monitor coolant level and pressure in addition to temp.

Diesel Engine Protection | Engine Monitoring | Engine Saver | Flight Systems, Inc

I prefer a raw water pressure sender just aft of the raw water pump, over the paddle type sensors for reasons already mentioned. The pressure senders seem to be pretty reliable. I've seen a lot of the paddle type sensors go bad in watermakers and get stuck and stop turning and then they create a little bit of a flow restriction also. The Jabsco style raw water pumps are pretty darn relaible, IF people change the impellors every 200 hours like they're supposed to.

A lot of them eh?

If your paddle type flow switch starts turning you have other problems ... What kind of watermaker uses a paddle switch for flow metering anyway? Most of them use pressure as an alarm source since output of the boost pump and high pressure pump is related to pressure.

There is a difference between a paddle wheel flow rate sensor and a paddle type flow switch, or a turbine flow meter. Besides, most units use a rotameter as a flow indicator for the operator.

Flow metering is used to protect the membrane and give an indication of the pressure required to obtain optimum output which depends on temperature and salinity.

A paddle flow switch is used to monitor the existence or lack of water flow. It does not measure it.

Are you sure what you were looking at?

I have also seen clogged heat exchangers cause impellors to fail prematurely in addition to what everyone else has said.

I had an issue with a 12v92 with overheating and impellors and the first stop after the raw water pump was a fuel cooler and upon inspection it was packed with broken off zincs even though it was pass through, broken off impellor blades can also get blocked at the entrance as well. I also had an issue with a westberbeke 20kw and it's heat exchanger was also packed with zincs. Something to look at. I also had an overheat issue that was intermitten on an 8v71, eating impellors and it happened to be a 2" spacer that bolted to the r/w pump and air was leaking in there and causing the pump to cavitate.