SMX double multi-stage fuel filtration problem

[dave]

Hi All,

   Looking for some help here….I have a single engine boat with two SMX double multi stage fuel filtration systems labeled A and B.  They’re plumed to the same fuel manifold; the active filtration system simply selected by managing the associated ball valves.  When the A filter system is “off'”, isolated with its ball valves closed, and the B system in use, the A system 19513 filter suction gage shows suction gradually growing to about the beginning of the red arc over 5 hours or so, with the 1000 filter side showing a lesser value after a few hours.  This…on a system that shouldn’t have any fuel flowing through it.

If I select the A system, the same thing happens.  I’ve replaced both filter canisters numerous times, cut them open, and found no contaminants.  I’ve also cleaned out and rebuilt the fuel manifold.  I have not taken the filter housings apart or attempted to clean out the housing.  There are no fuel leaks anywhere in the system.  I’ve used the fuel priming bulb to pressurize the A side and the vacuum gages respond…so I know it’s not an indication problem.   Any ideas?   Thanks in advance….

Topic

[Rob Schepis]

Do you have isolation valves on “both sides” of each filter set?

[dave]

Gene,

     Thank you for this….yes, I think the set up missed the original intention, or at least what I would guess was the original intention, of changing filter cannisters on the fly.  In this case it has resulted in the simple ability to switch the active filter system underway from A to B or B to A, but the engine would have to be shut down in order to actually change a filter cartridge.

     With respect to your observation about equal pull on both systems….that’s what puzzles me…why should the A set show a vacuum when the B set does not?  This is the case whether we’re using the A or B set, which just validates that the suction is applied equally from the engine up to the shut off valves upstream of both filter systems.  If the A shutoff valve isn’t completely closed I could understand the suction indication, but when the A system is used with its supply valve “open”, we get the same indication.  I’m wondering if that valve is broken in a partly closed position, and have ordered another one to replace it.  Any other thoughts?

thanks,

dave

 

 

[Gene Fuller]

This one has an easy answer.

If your diagram is correct both sets of filters are always tied together at their outputs. Therefore the vacuum seen by one set of filters will be the same as the vacuum seem by the other set. The engine lift pump is pulling on both sets at the same time.

There is no flow through the filter set that has its input closed, but the vacuum is still there all the same.

I believe most dual installations isolate both the input and output sides. Indeed, it cannot work correctly otherwise. If you tried to change filters underway there would be a major air leak and suction loss when a cartridge was removed.

[dave]

Tony,

   Thanks for this….answers:  1)  single CAT 3116TA.  Fuel fed from two tanks to single common manifold.                                                                 Filtration system draws from common supply manifold.  See diagram                                                                             attached. 

                                                     2)  System was installed by one of the previous owners.  Have not seen a                                                                       problem until last year / 30 running hours ago.

 

                                                     3)  Twin systems were installed in order to allow changing of filter elements                                                               while cruising without shutting engine down

 

                                                     4)  Last four years vessel operated about 75 hours a year

 

Can’t understand why the engine feeds normally through the B system whil still pulling suction on the A system with the supply ball valve closed to that side.  Is it possible that valve needs to be replaced?  All hoses have been removed and found to be in good condition.  What about the common brass manifold fed by the filtration systems for distribution….I have a hard time imagining it being fouled because the filters have not been contaminated.

 

 

[dave]

Thanks Clark, I’ve been wondering about that…..it makes as much sense as anything.

 

dave

[Clark Leighs]

I may be all wet but I am guessing that the ball valves are not fully closed for some reason.

I have seen valves with deformed seats that would allow leakage.       Only a very few times in over several hundred B.V.    but it may happen.   

 

 

[Tony Athens]

You are leaving out some very important info to trouble shoot what you are chasing. Your issue is not inside the filters or filter heads–it is in some part of the plumbing external to the filters..  Need these 7 answers to start the troubleshooting process.

1. Exact model engine is ?
2. did you ever measure fuel vac before you installed the DD systems?
3. what was the reason you thought you needed “twin systems”? 
4. what issues did you have with your past system that made to decide you needed the DD system,  let alone put in “twins”
5. average hours per year you use the vessel?
6. type of application is the vessel used for?
7. past history per year / total fuel per year  has been? 

Tony

 

 

 

 

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