2014 Sunseeker 115 Sport sludge tank... questions MTU

Bonjour,

So we have a 115 Sport powered by MTU 2000 series V16's

Sludge (waste fuel oil) tank has four engine connections to it and one from the fuel polish unit.
There is a pump out port (with a QD connector) on a pickup tube (as expected) and *a tank vent that is on a welded bung that has an pickup tube as well.

Now that is what I am wondering about, that tank vent on the other pickup tube. How does that work and is it the correct application??? Please explain how a 50 gallon capacity tank can vent, when that vent line is submerged by being connected to a pickup tube.
When at 8 (+/-) gallons indicated on the Tjessen that vent will offload into the bilge via that pickup straw like a squeezed juice box.

Now the engine to sludge tank connections:
On the B side of the engine,about half way, and under the exhaust manifold [ Designation F46 ] [ Leak fuel level ] is where the first sludge tank line connects.
The other sludge tank line is connected, again on the B side of the engine, towards the top, in the vicinity of the [ Designation B48 ] Fuel Pressure ( in rail ) and [ Designation YB33 ] Fuel Temperature.

It was suggested that one of those lines should be connected to return to the top of the fuel tank... Because if the emergency shut down were to happen at a high rate of speed, that the electronics will shut down ( the injectors will stop feeding the cylinders ) but the HP injector pump will continue to run for a short interval. Thus very high rail pressure will be jetting from the HP fuel valve, and so the vent line...

I believe there are two mistakes in this engine / sludge tank installation.

Please advise. Either educate me or confirm my suspicions.

Thank you for your anticipated replies...
cheers!

Update: As I research this problem further, I have found installation documentation that supports that the HP fuel rail (safety) valve should in fact be venting into the fuel tank ( top, above fuel level) and NOT into the sludge tank.

NOTE: as always, when I make these posts, I am not only trying to solicit help in solving a current problem from the community, but I am also aware that any information I can ascertain, may help the next bloke that googles along looking for similar answers to a similar fault.

Your participation and guidance is always greatly appreciated.
Cheers!

An idle run in the berth this morning did not replicate the high pressure fuel discharge that was experienced two nights ago whilst steaming along at 80% throttle. A similar discharge reportedly happened over a year prior that in fact did rupture the sludge tank

Update 17OCT2019,
It has been determined that our SunSeeker vessel was in fact assembled incorrectly at the factory, UK.
The sludge tank vent, a screen filter fitting, was installed to a suction stand pipe, a tank bung that is designated to draw liquids up from the bottom of the tank. This FAULT greatly diminishes the useful capacity of the sludge tank as we have found. When the tank got to the 24 liter unusable liquid (below the standpipe) then additional pressure would cause the contents to come up the straw, out of the tank vent, and discharge all over the bilge...

... well, sludge sprayed all over the bilge up to the point that the vent screen gets clogged with all the 'sludge' from the bottom of the tank.
If you can't imagine what happens from there, let me paint a .....paint a bilge with greasy crap:
Once that vent is clogged, additional pressure will increase until the tank seam get blown out. The tank exploded (well, it popped like a balloon). At that point, you will have all the sludge tank dumped into the bilge. And the cost of a new tank (or repair) to add insult to this mess.

If this were an aircraft, it would be mandated by the FAA that an AD (airworthiness directive, in the USA)(or a vehicle recall if we were talking US automotive sales/manufacturing)


SO, I would recommend all SunSeeker vessel engineers remove and inspect the sludge tank, the dirty oil tank, and the clean oil tank vent screens, to insure that they are not installed into a threaded bung atop the tank that is a lift tube (stand pipe).

Please report your discoveries here.
Perhaps this is enough of a problem that we can save many a crew the unsavory task of a messy cleanup, an environmental discharge, and/or, perhaps, an engine room fire (or worse)

Cheers
Remember, Safety is NO Accident!

Just another FYI, Is your engine high pressure fuel rail safety vent line connected to the sludge tank like mine was?
If you have a situation where engine faults are identified and the engine goes into protection mode (auto reduced RPM, "Limp Mode") (or an emergency shut down at high rpm)

Then perhaps this could happen to your SunSeeker when it is most inconvenient. SunSeeker has replied that they decided to plumb the MTU engine fuel rail safety vent hoses to the sludge tank.
MTU (engine manufacturer) said to connect that fuel line to the main fuel tank that the engines are pulling from.
SunSeeker's answer to my inquiry was that they didn't want that fuel oil to go back to contaminate the main tank...
...I can see where they are coming from, and going with this line of thought.

Right up to the point that I am floating oil sorb pads in the bilge!

Wow, I sure am glad I followed the adamant directions and filed my post in the SunSeeker bilge where it is unseen or unreplied to.

Thank you both.
I am new to SunSeeker and yachting myself, yet I have been a member of various forums for years.
I have found that they can be great and others not so good. It is the members that make, or break, a forum.
I am usually a proponent of reminding folks to please return and give feedback about how they finally corrected (or learned to live with) the faults they ask about. That makes the forum complete in my opinion.
Nothing more frustrating to perform a google search, find a posting of similar nature, perhaps a few folks join in and make suggestions, or post their experience and knowledge... then the post goes cold... Was it fixed? What was the answer?

I get it, I do, I know how folks get busy, the car, boat, airplane breaks down at the least inconvenient occasion. And we get in a tizzy to get it fixed. When finally we get it repaired, or give up trying to fix it ourselves and send it off to a shop, the imminent need for answers will quickly diminish.

Thank you both for your replies. I was curious to know if I were shouting into a canyon and if I could hear my ECHO Echo echo.
Cheers!

Cheers!

The incident in post #4. The burst sludge tank happened enroute from FtLauderdale to Miami boat show 17 or 18. The MTU service reps were sneaking aboard with tools hidden under their lab coats. RickObey "Nothing to see here... Let me show you the salon, look at this bar on the fly bridge, built in ice maker..."

So it is my belief (I was not crew at that point) that they did investigate the problem, repair the tank. Then, it seems that they connected everything the same way (sludge tank vented on a standpipe, geese) then when the fault could not be reproduced on a sea trial, the vessel was approved for return to service.

After a season in the Bahamas, the vessel was transported to Spain and the occurrence has happened again when transiting back from Mellorca. We made it back to the birth on the port engine. But still.

Thank you for your interest.
I'll let you know what we determine after consulting with Helmut and Rolf

Cheers