Frequent sampling of Racor fuel filter.

[ss2016]

My VP D6 has a Racor 500 pre filter, My query is about daily draining. I don't, though I do look at the bowl for water or debris. To date, 180 hrs, I have found no water and minimal debris at service. Daily draining of a small quantity especially when using a 'strange' supplier does make sense to me, however there is a problem, which leads to my question.
Since the fuel level in the tank is slightly below the filter (perhaps not when it is full), if I open the drain valve at the bottom of the Racor, a dribble of fuel comes out but an equal (or possibly greater) amount of air goes in. Clearly shutting off the tank would ensure equality but it's hard to get to. Either way I have a small amount of air in the Racor. Now the book says take the top off and top it up. I am loath to do that since frequent removal risks damaging the two O-rings both of which need to be intact. Not refilling the Racor means air will build up over time with frequent sampling reducing the amount of the element 'working'.
So my question is what is normal practice? Am I missing a trick? A subsidiaries question, will the tiny amount of air in the filter get cleared through the engine or could it in fact bring it to a halt if not bled?

 

[Bandit]

The important thing is to know your fuel system so you can see any difference.

Drain a bit of fuel off from time to time into a white plastic container to see is any water in the fuel.

From Time to time remove the lid to be able to lift the filter element to see if any crud in it or dust.

Always dose with a biocide. carry three spare fuel filter elements on board and keep on checking.

The rubber seal ring is fairly robust.

 

[Plum]

My VP D6 has a Racor 500 pre filter, My query is about daily draining. I don't, though I do look at the bowl for water or debris. To date, 180 hrs, I have found no water and minimal debris at service. Daily draining of a small quantity especially when using a 'strange' supplier does make sense to me, however there is a problem, which leads to my question.
Since the fuel level in the tank is slightly below the filter (perhaps not when it is full), if I open the drain valve at the bottom of the Racor, a dribble of fuel comes out but an equal (or possibly greater) amount of air goes in. Clearly shutting off the tank would ensure equality but it's hard to get to. Either way I have a small amount of air in the Racor. Now the book says take the top off and top it up. I am loath to do that since frequent removal risks damaging the two O-rings both of which need to be intact. Not refilling the Racor means air will build up over time with frequent sampling reducing the amount of the element 'working'.
So my question is what is normal practice? Am I missing a trick? A subsidiaries question, will the tiny amount of air in the filter get cleared through the engine or could it in fact bring it to a halt if not bled?

With a transparent bowl I visually inspect every time I open the seacocks and never drain unless I see something that needs draining. In fact I have never needed to drain in the last 8 years although I have once completely removed the bowl for cleaning as there were some very small bits of black in there stuck to the sides but were not at the bottom so would not have drained out. I put in a new filter every 200 hours and fill the top to the brim before fitting the lid. I shut the fuel ballvalve before opening the lid so none can drain back into the tank.

www.solocoastalsailing.co.uk

 

[Portofino]

First any air at the top will just stay there .1-3 cm .It will not effect the filter or get into the engine .It’s a myth they need to be brimmed .
You are right to worry about the risk of inadvertently disturbing o rings so they malfunction .Sods law is never far away from boats .

Just wait until the level of tank is sufficient or move the racor lower if you wish to continue to regularly drain off .
Or examine them with the engine running ,as the engines fuel pump will draw some through to fill it if the tank level is lower .Assuming it’s safe for you in the ER with engines running ?

ASAP will supply water in fuel sensors type bowls and probes etc .So you could convert the bottom 1/2 of your existing to WIF with a dash gauge to boot ? This adds a fall back safety feature , takes the emphasis off a daily eyeball .
There is still a reasonable distance from the probe tips before the fuel is sent to the engines .

Or stick with what you have and buy a large syringe from a motor factor ( used to with draw brake fluid or fill g box oil ) connect a tube to this and the racor bleed tap .Open the tank cock and bleed tap and draw via a vacuum slowly the bowl contents out .Slowly.This will stop air going back and draw the lower fuel level in the tank through to the racor …..which if I understand your dilemma is what you desire ?

 

[ss2016]

Thank you for your replies. I think I will do less draining and just rely on a visual check.

 

[kashurst]

Yes, you can try too hard. Racors are good at separating out gunge etc. If after regular checks you do not see any water, stop worrying.
If you are still a bit wary, shine a torch through the clear bowl after the engines have been on a trip for an hour or so, once you are all tied up etc.
If there is any water in the fuel the diesel will be hazy. If there is no water it will look clear like wine.

Again unless you see water in the bowls don't get too worried.