Dual diesel filtering fitments

[coopec]

"I've heard it said that if a filter suddenly blocks, and you switch over, it's very probable that the other filter will block very quickly too. ".

Just to make sure I am understanding (fuel system my next job) I have Port and Starboard tanks and the fuel from the injectors will be returned to the same tank that it came from.
I presume what you are saying only applies to a boat with one tank?

 

[pvb]

Bear in mind that small diesel engines can only pull a very small vacuum. ie - My 1gm10 lift pump can pull a vacuum of 60mmhg = approx 1.3 psi. Most cheap guages are 0 - 1 bar ( 29.5 psi ) Find one 0 - 0.1 bar and you will be paying for it !

That's not my experience at all. Volvo lift pumps, for example can typically pull around 0.5bar. There's a reason why Racor specified a 1.0bar full scale deflection for their vacuum gauge, and why the red sector of the gauge starts at around 0.35bar.

 

[prv]

I presume what you are saying only applies to a boat with one tank?

Certainly we're thinking of one tank, as that's the norm on most yachts.

With two, it simply depends if both are equally dirty.

Pete

 

[rogerthebodger]

"I've heard it said that if a filter suddenly blocks, and you switch over, it's very probable that the other filter will block very quickly too. ".

Just to make sure I am understanding (fuel system my next job) I have Port and Starboard tanks and the fuel from the injectors will be returned to the same tank that it came from.
I presume what you are saying only applies to a boat with one tank?

I have 3 tanks port starboard and keel. Each have a primary filter water separator the fuel then passes through a duel 3 way 4 port valve that allows the selection of each tank with return to the same tank, even through my engine has very little fuel flow back to the tank. My vacuum gauge is teed into the outlet of that selector valve.

The fuel then passes through my single mechanical lift pump to a secondary set of filters with a change over arrangement so I can select each filter on the fly.

I don't have a vacuum gauge on these filters as in effect the fuel is under a slight pressure at this point due to the output of the lift pump. I would love to fit a gauge across this set of filters but due to the output pressure of the lift I think it would need to be a differential vacuum gauge which ore quite costly.

Did consider a low pressure gauge but the overall pressure could change at the speed of the engine changes so would be difficult to determine if the secondary filter becomes blocked which is very unlikely due to the primary filters.

If I have a block in the primary filter I would just change tanks so to keep running while changing the blocked filter. I also have electric prime pumps for each tank that could be used if the mechanical pump fails.

All fuel into my tanks is pumped in using a Jabsco gear pump which has an in line strainer and an in line fuel filter similar to outboard motor in line filters but bigger.

 

[prv]

I don't have a vacuum gauge on these filters as in effect the fuel is under a slight pressure at this point due to the output of the lift pump.

Agree, you can't easily fit a gauge after the lift pump.

I've still found the pre-lift-pump gauge useful for diagnosing a blockage in the post-lift-pump filter, though. If the engine is making sounds of fuel starvation, but the gauge is reading near zero, then it's very likely the second filter that's blocked. Without the gauge, it could be either filter or indeed the dip tube. In my setup I have a further (unplanned!) diagnostic in that when the dip tube blocks the primer bulb collapses.

All fuel into my tanks is pumped in using a Jabsco gear pump which has an in line strainer and an in line fuel filter similar to outboard motor in line filters but bigger.

That's interesting. Do you always fill up from drums or something? Otherwise how does it work when you tie up to a fuel berth which is expecting to stick a nozzle in a tank filler?

Pete

 

[rogerthebodger]

That's interesting. Do you always fill up from drums or something? Otherwise how does it work when you tie up to a fuel berth which is expecting to stick a nozzle in a tank filler?

Pete

We used to have a fuel supplier with a berth in the marina but it got condemned by the local authority. Any way the diesel had a lot of water due to old tanks located in the ground which at HWS the bottom of the tank was below water level.

We have no special price for boat fuel like you and suppliers to the road transport industry sell a lot cheaper than the average garage so better to get from truck stop where turnover is much higher and cheaper.

So yes I do fill from 25lt cans and pump from mooring finger into boat tanks.

We do have a guy with a trailer tank that can fill boats but due to my draft I can't get close to where he can get.

I run a diesel 4x4 and fill cans at the coast as the fuel (diesel & petrol) much cheaper at coast than inland where I have a home.

Petrol price is Government regulated but not diesel so you can shop around foe diesel but petrol is all the same price in an area.

 

[lw395]

"I've heard it said that if a filter suddenly blocks, and you switch over, it's very probable that the other filter will block very quickly too. ".

Just to make sure I am understanding (fuel system my next job) I have Port and Starboard tanks and the fuel from the injectors will be returned to the same tank that it came from.
I presume what you are saying only applies to a boat with one tank?

I was commenting on two filters fed by a single tank.
With twin tanks, the risk would only be there if you witched to an equally dirty tank, and if it had been shaken up similarly.

Switching to a full tank would probably buy a lot of time, as it would probably not be agitated like a half full tank?

 

[prv]

We have no special price for boat fuel like you

Our boat fuel price is no longer particularly special . We get to pay a reduced tax rate on 40% of it, in a nudge-nudge, wink-wink arrangement that assumes it's being used for heating and generating, but given the limited competition and turnover compared to a road garage, the suppliers make up most of that difference in increased basic price.

Pete

 

[charles_reed]

I am constantly amazed by the esoteric knowledge and wide experience of marine disasters that seem to be commonplace with fellow posters.
In 32 years of sailing and about 10K hours of motoring I've never had a blocked filter.
I've frequently had a blocked tank inlet and, in hope, I have a water separator and 3 filters on the fuel line. But never a blocked filter!!!
I've only once found a little (iron oxide) debris in the final filter.

 

[lw395]

I am constantly amazed by the esoteric knowledge and wide experience of marine disasters that seem to be commonplace with fellow posters.
In 32 years of sailing and about 10K hours of motoring I've never had a blocked filter.
I've frequently had a blocked tank inlet and, in hope, I have a water separator and 3 filters on the fuel line. But never a blocked filter!!!
I've only once found a little (iron oxide) debris in the final filter.

I've never had a completely blocked filter stop a yacht engine.
I do know people who've had mobo engines stop due to diesel bug blocking the filter.
I've seen a few blocked filters on generators and agricultural motors.

I have been in the position of being on a yacht, knowing there was a good deal of crud in the tank, and declining to take it out into a rough, narrow channel because I thought it likely the filter would block.
In those circumstances, I don't think a second filter would have helped much.

 

[Grumpybear]

I am constantly amazed by the esoteric knowledge and wide experience of marine disasters that seem to be commonplace with fellow posters.
In 32 years of sailing and about 10K hours of motoring I've never had a blocked filter.
I've frequently had a blocked tank inlet and, in hope, I have a water separator and 3 filters on the fuel line. But never a blocked filter!!!
I've only once found a little (iron oxide) debris in the final filter.

I am clearly doomed to suffer all these things in the next few days' sailing as my experience mirrors yours. I have, however, suffered an airlock in the fuel supply due to the shameful failure of the tank level to stay above the bottom of the dip tube (duff fuel gauge, yer 'Onour, honest!). We had a cracking beat home though, and got some respeck for sailing into our berth.

 

[prv]

(duff fuel gauge, yer 'Onour, honest!).

We once ran out of fuel in a charter boat despite it supposedly having been full when we picked it up two days earlier, as confirmed by the gauge. Turned out that the terminals on the top of the tank sender had been shorted with a bit of scrap wire, pegging the gauge at full. The charter company were having some difficulties with the locals at the time, a dispute over hiring there versus shipping in lots of young brits, and it seems the local guys given dozens of boats to refuel in a morning had taken the easier route of sabotaging some of the gauges and assuming there was enough in the tank for the next charter. Might work for a week or two, but not indefinitely...

Pete