Fuel polisher questions

[RichH]

Ken
Racor (Parker) makes relatively very accurate filter elements - these do come with 'cost' and the replacement cost per filter element is relatively 'high' (includes 'hefty' distributor costs). You dont need such accuracy in a recirculation polisher. Racor filters are probably the 'best available' for in-line fuel filtering; but, are simply too costly, 'too accurate' and without much overall economic benefit in a recirc.-polisher.

Notwithstanding the above comments ..... ANY measure of recirculation-polishing will be of great advantage to any fuel system: protects the 'in-line' filters from becoming plugged, rapidly returns/recovers the tank to 'normal' particles in case of a 'particle storm' when the crud breaks loose from the walls (sometimes in minutes), removes the 'seed particles' that form and which agglomerate into continually large and larger particles, continually removes the aspirated (through the vent) fungal 'spores' that are linked to most 'tank fouling'. Your choice on 'how expensive'.

Dont forget to 'get in there and clean out the tank now and then'.

 

[Hermit Scott]

Some say having a partially empy tank causes the moisture to condense on the walls of the tank with changing temps and then the water runs down the sides falls to the bottom of the tank and is trapped there. It can't evaporate back into the air in the tank.
What do you think about that Rich?

 

[RichH]

Hermit -

... and some simply dont know their chemistry.


If the tank fill port is intact, Where does the water come from?

Oil is cracked and distilled at extremely high temperatures ... it becomes almost totally dehydrated in the refinery.
Left alone in contact with the atmosphere it will eventually become 'saturated' with water vapor --- all due to 'chemical equilibrium' and no matter how large the surface area of the oil in contact with the atmosphere. Fuel that is apparently condensing on tank walls means that the oil is fully saturated with water (molecular water and emulsified water). The water that settles by gravity to the bottom is an extreme case of saturation. Equilibrium is driven by the MASS of the dehydrated fuel and the rate of equilibrium dependent on the degree of dehydration/saturation AND to a lesser extent the contact surface area between oil and air.

The simple answer is: saturation with water is dependent on TIME, the degree of prior dehydration .... and contact with the atmosphere (through your tank VENT). If you dont store fuel for a long time in your tank, keep the minimum amount NEEDED, you will have less moisture in the fuel.

 

[Hermit Scott]

Assuming you are buying fuel from a place with high turnover, how long are we talkning about the fuel reaching 100% saturation and than having water condense?

Also by ABYC standard, to have a 'bottom drain' it must be a dip tube going down into a indented place in the tank right? So no pet cocks like a motorcycle.

How much water do you see in the bottom of your water/fuel seprater filters?

Also in your 5th sentense is the first word supposed to be water, or did you mean feul.

 

[kloudie1]

Some anecdotal notes concerning diesel.. Lots of diesel is straight cut and not cracked and much of what is at the pump is a mixture of those.. The market value of the components determines the blend, and the cracking units can be tweeked to make more or less diesel depending on whether heating oil or gasoline components are worth more.. When the stuff is made, one of the last things that happens is it is exposed to steam to get out some hydrogen sulfide and a couple of other nasties.. so it is saturated with water pretty much before it goes into the big storage tanks.. The tanks typically have holes in the roofs that leak rainwater so again there is a place for water and algae to get in.. It settles to the bottoms and is drawn out, but the tanks are stirred so before the fuel leaves the refinery, it is saturated with water and probably has algae in it..

 

[DanW9494]

Day tank

I've heard of cruisers having a second fuel tank in their system, that they fill up with polished fuel adequate until the next anchorage. This tank can be mounted above the engine for gravity feed. This tank needs to be removable easily for cleaning, or smaller tanks can be glass or clear. This sometimes called a day tank. Then if there is a violent seastate or the fuel pump gives out, just switch to this tank. Or if it is a day passage, just use this fuel tank for the day to keep it clean. This keeps you from worrying about your engine when your attention is needed at the wheel. In those times, how often do you want to go down to change filters and restart the engine. No matter how many filters or parallel filters are in your system, you really don't know how long they will last in rough water if you aren't sure that your main tanks are very clean. And who knows how long they stay clean after a few fuel docks.

 

[Hermit Scott]

Has anyone else noticed that every subject that has to do with a sailboat has an encyclopedia of things to learn about it?

 

[Roger Long]

I've heard of cruisers having a second fuel tank in their system, that they fill up with polished fuel adequate until the next anchorage.

Putting one of those in my boat is on my winter to-do list. I'm planning on one good for just about an hour's running since I have an on board fuel polishing system.

My system is set up so that turning a single valve starts fuel flowing from the polishing system to supplement the flow from a clogging filter. I figured out a way to put this tank in so that the engine would automatically start drawing from it if the polishing filter started to load up. It's a belt, suspenders, and loop of rope over the shoulders kind of approach but so easy to implement that it seems silly not to do it.

More here:

http://www.rogerlongboats.com/FOpolishing.htm

BTW note that I just got my own domain name and thus a new website address. The old site will evaporate shortly and some of the links from my older posts will break. If you can't find something, go to:

http://www.rogerlongboats.com/RWL.htm

or email me and I'll edit the post link.

 

[MoonSailer]

Two smaller tanks is a great ideal and probably cheaper than fuel polishing. Say 2 X 10 gallon tanks instead of one 20 gallon tank. Pump one tank until it is near empty before using the other tank. Theoretically this would cut your average fuel age in half. AND one tank could be left dry most of the time and only filled for trips. If my 22 gallon tank ever requires replacement I will install two tanks of 11 gallons each or maybe a 5 gallon and a 18 gallon tank leaving the large tank empty most of the time.

 

[Ron20324]

Scott, we used to have a wall hanging at work:

"There has been an alarming increase in the number of things I know nothing about."

 

[Stu Jackson]

Two smaller tanks is a reasonable idea

however, one would have to figure out the appropriate method of fuel return for a diesel engine to the right tank. There was a post just last week about someone having fuel return back to a "full" tank and overflowing. Careful management is required of both the supply and return lines as well as the magnitude of the contents of each tank.

Either we've been very lucky or our fuel suppliers have clean fuel. In the past 10+ years we have had no problems with fuel, and have filled up with either our usual half a tank 10 gallons (23 gallon tank) or, when not able to do our usual, have maxed out at 17 gallons in one or two refills.

That said, guess what could happen next...

 

[Bill Roosa]

condensation in tanks

Well it is a little known fact that water can't condense inside a tank if there is no water.
So how would water get into the air above the tank you ask? As the fuel cools and heats up with the daily/weekly/seasonal temp changes the diesel fumes expand and contract. When they contract they draw in atmospheric air which has water vapor in it. If you have a mostly empty tank then the problem gets worse because the air space above the fuel is larger and "breaths" more. that means more outside air entering over time.

You could put one of those dehumidifier crystals in a container attached to the tank vent to TOTALLY prevent the entrance of water. This might also take some of the water already in the fuel (kluoid1's post) but that is a big might.

 

[Roger Long]

As the fuel cools and heats up with the daily/weekly/seasonal temp changes the diesel fumes expand and contract. When they contract they draw in atmospheric air which has water vapor in it. If you have a mostly empty tank then the problem gets worse because the air space above the fuel is larger and "breaths" more. that means more outside air entering over time.

Several authorities are on record as stating that this is a myth and my direct experience supports them. For nearly a decade, I flew a plane parked a few hundred yards from the ocean. As the manager of the aircraft for the club, I checked the tanks several times a week and religiously before every flight by drawing out a sample through the bottom drains. Despite sometimes going out and finding frost so thick on the wings that we had to pour RV antifreeze over them, I never found a drop of water except after one heavy rain when someone didn't tighten the fuel cap. This was over the fulll range of New England seasons.

These tanks were similar to boat tanks in that they were separate aluminum tanks inside the wings. Some planes do have problems with water in the fuel but they are usually those with "wet wings" where the wing skin is the tank.

My boat diesel tanks sat half full much of last winter as I was building my fuel polishing system. When I started it up, no water. I've never found any water in the sediment bowl for that matter.

 

[Hermit Scott]

I am starting to get a sneaking suspicion that most water present in marine tanks comes in at the fill cap.

 

[RichH]

Re: condensation in tanks

Bill

Take a quart of diesel fuel, heat it to ~300 deg. for 4-6 hrs, let coo,l then weigh it to the nearest gram.
Put it in a container with an small open top, let sit 3-4 months, then weight again.

Guess where the extra weight came from? atmospheric water vapor.


Oil is essentially a dehydrated liquid when it leaves the refinery, because of the high production, etc. temperatures. Air is usually saturated by water vapor (to a varying daily % relative humidity). Equilibrium is the driving force and its all mass dependent and dependent on the partial (vapor) pressures vs. the temperature of the fuel/mix. Simple chemistry totalization of partial pressures.

regards
RichH

 

[KandD]

I've been designing a system for my boat for about a year now... We have 2 tanks totaling 55 gallons; so it'd be pricy to toss all the fuel.

I Don't understand the specifics though... If my Racor is a 2um then for polishing I want 10-20um correct? I want a higher flow rate because I'd like to build in a pressure wand I can insert through the sending unit (no access panel) to help get the crud off.

How do I know what filters are compatible with which cartridges?
Are filters interchangeable? back-washable?
Is there a difference between filter and water separator?
What is a good source for supplies?
What do I need to look for in a pump? I was going to hit up used auto yards, but I'm not sure that will work anymore.

Thanks for your advise!

 

[Roger Long]

Thanks for your advise!

A lot of your questions are answered back up in the thread. Filters are not back washable.
Don't use Racors for polishing, elements are too expensive and you want depth; not surface filtering.

Review the thread and look over my system (link above in the thread). Come back with remaining questions.

 

[KandD]

ok, I've re-read a little closer, there is about 3 different subjects here. I'll pose my question this way and ya'll can tell me if I'm right.

1) I need 10-20 micron filters at 1-3 gpm to clean the fuel for my 2 micron target

2) Shelco filters have the benefit over Racor because they use standard size cartridges - 2.5" by 10" (or 20, 30, ext) or 2.75" by 9.75" (or 19.5", 29.25", ext)

3) Depth filtering uses wound filters that are thicker and hold more crud where surface filters are pleated and clog quicker

When looking for a wound filter, does it need to be rated for fuel? What materials are no-good? I'm not sure I can justify buying 60 filters to the admiral.

When matching a pump to the system, a 10" filter is rated at 10 gpm; so do I need to keep the capacity of the pump below or above that? Is that WAY too much?

Will a depth filter remove water?

 

[jibes138]

A buddy of mine bought a new Selene 36 trawler and the fuel system was awesome. Allows him to polish the fuel whenever he wants, of course he probably has a 250 gallon tank or more. The new Caliber boats also come with a really nice system with dual MA 500 Racors that allow switching to a new filter and keeping the boat running while changine an element, might be able to polish also, not sure. Seems like the new boat guys have figured this out, all us old boat guys need to do is duplicate the systems they are putting in new boats, then send a check to the bank every month to pay for the loan it will take to buy all the components and hardware for installation. I am really considering putting in a 6 gallon tank (instead of 30 gallons) like those used for an outboard, adding a return fitting to it for the return line and then just carrying jerry cans for the capacity of the trip I'm taking. I've only had two years in 25 years that I went through more than a tank of fuel in a year mostly because my boat was at a marina with a very short distance to get to sailing grounds. I contend that most boats have far too excess fuel capacity and would benefit from smaller tanks and thus fresher fuel. Less weight, easier to maintain, less space occupied, cheaper, etc. Just my two cents.

 

[Roger Long]

ya'll can tell me if I'm right.

You got it mostly right. Everything I know about filters I learned from Rich H here who is a real expert, the kind who advises other filter experts. Do a forum search for "fuel polishing" "filters" etc. and you'll get an education.

You can buy blown melt polypropylene filters that have more capacity than the wound string filters. Shelco will only sell them in large lots but you can get them in smaller quantities here:

http://www.freshwatersystems.com/p-3692-hytrex-9-78-filter-10-mic-gx10-9-78.aspx

One filter lasted a whole season for me last year, nearly 2000 miles, about 60% under power.

You should put in the 10" standard length housing. I only went with the half length because of space restrictions and getting the half length filters is a pain. Size matters. Longer is better.

Filters are not like screens. A 2 mu filter will let much larger particles through. Rich describes it as like trying to catch golf balls with a pile of golf clubs. Even some baseballs will get through. That's why systems that run the fuel around and around are so much better than ones that just filter it once before it goes into your engine. Many passes of a 10 mu filter will clean smaller than a single pass of a 2 mu filter that is straining your fuel pump.

I've forgotten how effective the Shelco set up is at removing water. The Racor will do that in any event. I've never seen any in my fuel.

Those blown filters are used for filtering drinking water and come in sealed sanitary paper packages. They have nothing in them that can leech into your fuel. I think Rich said the string wound filters are slightly better at removing water but not by a significant amount.

I have two seasons and a lot of motoring (I basically operate like a motor sailer) with the system now and it's amazing how clean the tanks and system are.

You should still change your Racor and engine mounted filters every season because the elements degrade even if they are not being challenged by particles of crud.