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Fuel manifold supply
Jas
Posted: Friday, May 18, 2012 9:39 PM
Joined: 15/06/2011
Posts: 17


I have a new 2" fuel fill/supply system, connected to two 4 1/2" manifolds, one 12 valve manifold serves for tank suction to supply a Alfa Laval MIB 303s 13 fuel separator and a fuel transfer pump and the other for tank supply to fuel tanks. On system test, transfer pump struggles to self prime itself ( only after 5 mins ) and a mirrored response with the Fuel separator suction. We can increase the fuel transfer pump size and install a check v/v on the 1 metre supply line to the pump from the suction manifold. But this will not help the fuel sep with the same issue. Once you open up a new desired suction v/v from a tank you automatically lose the supply manifolds already primed capacity to the new un-primed line. Both the transfer pump and the fuel sep have 1" supply lines from the manifold. Is a larger fuel transfer pump our only option for transferring fuel, and possibly a supply line to a direct desired tank with the standard 1" supply line for the fuel sep also the only other way ? This system has all newly just been fabricated and is the result of the first tests. Thankyou. We would be appreciated any advice of options to overcome this pump suction problem from the large 4 1/2" manifold.
Rusty Wrench
Posted: Friday, May 18, 2012 10:09 PM
Joined: 21/09/2010
Posts: 207


By the sound of your description of the fuel system, this is Italian engineering logic.

 

 

A Benetti, I presume?


Jay
Posted: Saturday, May 19, 2012 1:11 PM
Joined: 15/06/2011
Posts: 17


Actually it is Turkish, we are in Turkey on the new build!
Rusty Wrench
Posted: Sunday, May 20, 2012 5:46 PM
Joined: 21/09/2010
Posts: 207


Does the owner have a surveyor employed?

 

Who approved the drawings?


Anonymous
Posted: Sunday, May 20, 2012 8:30 PM
very important point..surveyor!!!!
Chief
Posted: Sunday, May 20, 2012 9:36 PM
Joined: 02/06/2008
Posts: 342


"... options to overcome this pump suction problem... "


Lift check valves (sometimes called stop-checks) on the suction manifold.


Which of course means fabricating a replacement for the existing improperly designed manifold.
Anonymous
Posted: Tuesday, May 22, 2012 10:06 PM
Do you have a suction gauge fitted to the manifold, if so what does it read when you finally have a prime for your transfer pumps. Does this value fit the max suction lift value stated for your alpha laval sep. The value will be in the tech data section of the manual. It will be shown in m wg which is old school Meters of water gauge. This link http://www.sensorsone.co.uk/pressure-measurement-glossary/mh2o-metres-water-column-4-deg-c-pressure-unit.html translates it into something we can use. I might be wrong but i believe that the main issue here is the suction lift pressure required , this is governed by the height that fuel needs to be lifted from the tank more than the dia / vol of the pipework. So if it wont suck from a full tank it will be worse with half full tanks. Also not sure about the use of the check valves on fuel suction lines as this would mean you would have to fill prime the system should you ever need to suck the tanks dry. Would be good if someone could clarify this as i have also worked on a boat where the alpha would not suck from a tank that was below half full.
Jesse
Posted: Thursday, May 24, 2012 6:58 AM
Joined: 24/08/2011
Posts: 4


This may seem like a no-brainer, but fuel pumps all PUSH fuel very well, and PULL fuel very badly.  Is there any way to move the pump itself either lower or closer to the tanks/source?  As tough as it is to tear stuff out and move it around, you may end up having to do something like this, especially if it's a new build so you don't know the original design even works at all.  Check valves have a way of failing in the "closed" position eventually - not a good idea if you can avoid it.  Stick with basic physics and gravity every time.

Chief
Posted: Thursday, May 24, 2012 11:52 AM
Joined: 02/06/2008
Posts: 342


Do you guys worry about the valves in your bilge manifold? Is your bilge pump below the level of the rosebox?


Lift checks in a fuel transfer manifold are identical to those in a bilge manifold. If that is too scary, use self-priming pumps.


If this is a newbuild why is the builder not dealing with the issue? Surely there is someone involved in the project who can say "the fuel transfer system has to work properly ... make it happen" why does anyone have to post a question on a crew forum to find a solution to a problem that shouldn't even exist?

Anonymous
Posted: Thursday, May 24, 2012 1:21 PM
Chief we are not "Scared" of check valves we use them all the time in appropriate places, however the fuel system should be able to suck from any tank at any time without having to have been primed first. Jas can we have a bit more info like the size of the yacht, the distance to the tanks from the transfer pumps/alpha and the height from the bottom of the tank to height of the highest piece of pipework it passes through to get to the alpha. Again the suction pressure shown on the gauge will really tell you if the alpha is up to it. As far as moving the pumps/Alpha closer to the tanks that sounds a little bit impractical. Also lowering the height of the pump is not going to help if there is still a high point in the manifold/pipework . Agreed though this really is problem the yard should be working out. Its a defective fuel system and there i no way it should be signed off.
ratpack
Posted: Friday, May 25, 2012 7:02 PM
Joined: 03/03/2011
Posts: 100


Is this that new build in Turkey that is looking for a Y3 engineer and offering the dizzy heights of 5k a month ? Glad I said no no no
Jay
Posted: Saturday, May 26, 2012 6:19 AM
Joined: 15/06/2011
Posts: 17


Thank you all for your advice, yes the shipyard is continuing trying to figure out the situation, it has become quite frustrating, when asked about the surveyors input on the fuel system - this area he was not involved in ! The suction lift height for the testing is @ no more than two and a half meters from the bottom of the tank, with a distance of around 5-6 meters at the closest tank. At this stage I have found out that when the pumps were purchased for the build they were purchased from Gianneschi, Italy in a package ( in 2010 ) deal, with out any specs or thought gone into the fuel pumps capacity requirements. Hence the CP 30 type that they used, we now have upgraded to a ACM 451 + flow control v/v ( for two purposes ) which should be very adequate as it is also has good self priming capability. This now should solve the fuel lift inadequacy. Supposedly, this closest tank was to be the clean fuel tank @ 6.5000 L, that alfa was to deliver too. We can only now reconfigure the tank arrangement plan, for instance, changing the clean fuel tank from a alfa delivery tank into a alfa supply tank by having a direct supply line to alfa and reducing the diameter supply pipe work to what is appropriate for the standard alfa pump, all the way from the tank and by-passing the 4 1/2" fuel supply manifold. Basically the clean fuel tank will become a settling tank for the alfa to take from and deliver to the day tanks. The new build is 36m and it is a huge yacht for a 36 meter, all custom. We have used ck valves sparingly but where reasoned best. Ratpac, this is not the position you thought it was. Thank you everyone, appreciated.