Dual Racor Design?

[deano]

Dual switch-filter-while-running racor sets are $1k-ish...I already have two racors side-by-side in my engine compartment, one for the main engine (75 hp Yanmar 4JH3) and one for the genset, and two separate pairs of feed/return lines from the fuel tank.

Is it possible to duplicate the dual set up with my existing filters at much lower cost? Are there operational reasons not to?

Also, a diesel-rated bulb pump to more easily bleed after a filter change seems like a great idea.

Thanks in advance for your informed opinions.

[Talbot]

One of the lessons learnt when trying to find small air leaks in diesel fuel systems is to minimise the number of connections. There have been a number of occassions where the culprit was actually the on/off fuel cock itself.

Of course it is possible to duplicate the racor twin setup by teeing the supply line before the filters, then adding on/off fuel cocks before the filters, and after the filters, and then teeing the line together again after the second on/off cocks. The increased probability of problems means I would rather pay the premium.

Racor sell some filters that have their own integral pump - much better system than the squeezy bulb!

[Pblais]

One of the lessons learnt when trying to find small air leaks in diesel fuel systems is to minimize the number of connections. There have been a number of occasions where the culprit was actually the on/off fuel cock itself.

Been there too. My current system has two tanks and two racors. You manually switch everything. It was fine in 1991, but now as you say I'm tracking air leaks. They don't all leak just the one you can't reach or forgot to tighten the hose clamp on. I have one now that I'll replace the line and remove the shut off. Removal of extra unrequired connectors is just too good an idea to pass up.

If it's not there you can't break it by accident either.

Deano while you could use one dual filter system you could not use them at the same time for the engine and genset. Not sure why you would want to but it's another things to say no you can't. The twin racor 500 turbine filters are clearly the best possible combo. Not sure you need them on a genset though. Over engineering has some limitations where money spent yields little to return. It can go to the point where the additional complexity adds unreliability too.

I have twin filters now and I may get rid of them. Anything that could trash the racor that fast could do the second one in less time. I can't replace one and then switch it in without bleeding the system any way. It isn't practical to think you could swap filters one after the other to get some place. The idea that it may happen and save you the hassle of switching under way is one nice thing. The risk of chasing air leaks is far worse. They are never easy to find. The worst one I ever had was on the racor itself.

[Talbot]

Originally Posted by Pblais

Been there too. --snip--The worst one I ever had was on the racor itself.

You should try the old Lucas CAV filter - words fail me!

IMHO the best bet is to try to keep the contents of the tank as good as possible. I always have used a "smart" funnel between shoreside pump and fuel tank - This has not only a decent filtration in its own right, but will also stop water going into the tank.

The second most important point is to try to keep the tank topped up when possible, and especially when being left static for a while. (cuts down on condensation problems)

Most of the problems in a fuel tank start with water in the fuel providing breeding ground for the bug.

I also always use Fuel set additive

[Pblais]

The most common problem I've seen is you buy a used boat from up north. Dock space is so limited all for sale boats are hauled. They sit around condensing water for a good long time then get sold. The new owners apas the sea trial and clog the filters on the way home and need to get towed in.

Talbot I would have to agree with all you say about prevension. It's better insurance.

[Cheechako]

The dual setup allows you to switch quickly to one or the other ... right? You are setup with separate systems. If you are saying you just want the gen to take from the same filter as the main, I've done it with dual 500's. It is a bit messy but works. I used copper flared tubing. A hand bender is only about $15. Producing good flares is a bit of an art. Use two Kitz (3way) valves, one before the filters and one in your return lines. pretty simple really and less messy than two ball valves, one for each tank. I guess I've always been lucky, never had many air in fuel issues on any of my boats, two Volvos, four Yanmars, one Bukh, One Mercedes, and two Perkins... Now I've jinxed it!!

[motion30]

I don't undrrstand the don't do it comments I have duel filters on my motor and have been able switch when clogged in very rough water I do not believe I would have been able to change out the filters in those conditions I say do it and get a seperate filter fo the gen set

[Pblais]

I say do it and get a seperate filter fo the gen set

He already has one.

[Christian Van H]

I built one recently...Hope their are no leaks! Everything went together well.

[David M]

I think the money you MIGHT save in doing your own plumbing is not worth the price nor the increased chance of air leaks. I have dual Racors onboard, one pair for each engine. I like how they are, nice and compact and professionally connected to each other with a four way valve.

[deano]

Thanks to all for the feedback. I appreciate the leak issues (KISS!) and am endeavoring to keep the fuel and tank clean...and I'm really liking the idea of a single-movement, dark and stormy, first-mate-proof way to get the engine going again in an emergency, without getting gouged in the process.

Here are some simple diagrams of what I was looking at. It adds one tee connection to the genset's fuel line and one tee valve to the engine's fuel line.

Normal operation feeds the engine and genset from their own racors as currently installed. Moving the valve to feed from the other(genset) racor provides quick backup to a clogged filter. Alternatively, normal operation of both engine and genset from the genset's racor would leave the engine's racor unused and clean until needed.

The big engineering issue I see so far: Feeding the operating engine from the genset's racor will pull fuel back from the genset's high-pressure pump (genset off). Will this induce air and kill the engine anyway? Is a mechanism to prevent backflow absolutely required?

If I can get a definitive reason not to set it up like this I will move on to a dual filter dedicated to the engine fuel line.

Thanks again for the voices of experience...surely someone else has looked at this idea.

[David M]

I am not fond of your first or second system.

The way you have drawn up the use of your dual Racors is not how they were intended to be used. Their purpose is to quickly be able to switch fuel filters without introducing air into the fuel line...for one device that burns fuel. The solution is to get a second set of fuel filters for your genset.

Each device that burns fuel needs its own set of fuel lines and fuel filters. The reason is that if for the example the genset has a vacuum leak, then the air entering the fuel system will flow back to the filters and then shut down your propulsion engine. What you don't want is for crud in the polishing system filter to be able to shut down something else.

Completely separate fuel lines and filters starts at the fuel manifold (if you have two tanks and a cross over) or if you don't have a manifold, at the tank itself. Don't share your fuel filters between two or more different devices that burn fuel.

The same goes with fuel polishing. A fuel polishing system should not be tied in to a generator or propulsion engines fuel supply system.

Isolation is the key to prevent the failure of one system from shutting down another system.

I know some have tied all their devices that burn fuel into one set of fuel lines and fuel filters, but I am looking at it from what is best from an isolation standpoint.

To draw up an extreme example, without isolating your fuel systems, you have the potential of shutting down your two main engines, your genset and your diesel heater, all at the same time if you get a vacuum leak or something else happens.

[Dockhead]

I don't understand what's wrong with it. Please explain. The proposed second version seems to be an elegant way to give you emergency fuel supply to your propulsion engine, by taking over temporarily the genset supply. Where would air get into the system like this? It looks very good to me -- the only downside is you lose the genset fuel supply while in "emergency" mode.

The upside compared to the conventional dual racor setup is that you have greater redundancy -- the entire fuel system including pickup is changed when you switch over. Another upside -- cost. Looks great to me; please explain why I'm wrong.

[David M]

It would work...yes indeed. I was just trying to give you the ideal isolation perspective so that no one thing has the ability to shut down something else. The benefit of your system is that it would cost less money.

[Cheechako]

Looks great to me. KISS! You could put another 3 way valve at the tee from the gen if you are worried about leaks in the gen lines. Leaks? it's all about the connections