Diesel Polishing

[Simi 60]

Originally Posted by s/v Jedi

Yes, US. The worry is bilge pumps pumping leaked diesel overboard.

Could just as easily leak from any one of a dozen other fittings.

[Uncle Bob]

Originally Posted by Simi 60

Could just as easily leak from any one of a dozen other fittings.

Mate, yah gotta stop being logical, we are talking Merica here.

[Pete7]

Originally Posted by a64pilot

Put an outboard squeeze bulb on it occasionally and suck some fuel out to inspect.

I thought they were dangerous and vertboten in 'Merica, despite everyone else in the world using them including many European car manufacturers

[Steve DAntonio]

Originally Posted by Bundyon

I am about to cut a 12 inch square to my built in metal tank of 1000litres (270 US gallons)
This fuel tank has never been cleaned since the boat was built (1991) I purchased the boat last year and carried out a major refit prior to sailing the 600odd nm back to my home port. During the refit I had installed a Racor 500 as my primary filter and a single CAV 796 was already fitted to the engine, this became the secondary filter. The tank had approximately 900 litres of diesel in it at the time of purchase, I topped it up prior to departure and also poured some top quality biocide in for good measure. New filters were fitted (10micron in the Racor).
Due to sail & rigging problems that we wanted to sort out back in my home port, it was decided to run on the engine back to our home base. Engine is a 4-236 Perkins 80h.p.
At the end of every day, whilst on anchor, I would drain the water from both filters with the electric fuel pump running to flush the filter bowls. No blockages at this point. Coming out of the Southport Bar at 0730 straight into 5 metre seas pounding us on our Port beam as we ran down the coast making for an uncomfortable run, heading for Iluka, we arrived off Iluka/Yamba Bar at midnight and decided to racetrack 5nm off the coast until slack on the high tide at 0700 before tackling the notorious bar. The Perkins was blowing a fair bit of black smoke which indicated to me that the fuel filters were blocking up, not surprising, considering the almost 24hour severe shake up the fuel tank had just had.
We made it into Iluka Lagoon and anchored up. With only another day run to get home, I decided to replace the filters. The fact that the Perkins could still run on the state of these blocked filters and the state of the water diluted diesel is testament to old school engineering. I have no doubt if this was a modern electronic diesel with Common Rail , we would have been doing a filter change every day and would definitely have had an engine failure at sea. I have enclosed several photo's of the Racor and the CAV upon removal at Iluka. Once I have cut the tank open, I will post up more pic's of what I find!
I was quoted between 3-5K to polish the fuel in my tank. Being on a Military pension & a mechanic, I am happy to do it myself. Expensive multi banks of filters aren't needed imho, on sailing boats. Start with a clean fuel tank, maybe a sediment bowl then a quality Primary filter followed by a quality secondary filter & regular maintenance/ checks. A visual Check on the sediment bowl will tell you the state of your fuel. 250ml of quality biocide per 1000litres will keep the bugs in check.

Don't cut a square hole! These inspection port kits are a god send Seabuilt - Access Plate Systems

I've used hundreds, they work very well, never leak, even in tank sides, as long as the surface is true.

I'd add one item to your list of things to keep a tank clean, a stripper tube, detailed here https://stevedmarineconsulting.com/c...-diesel-tanks/

[Steve DAntonio]

Originally Posted by a64pilot

A “proper” polishing system will remove a lot of impurities and much of any water, but it’s not going to remove biological growth, you can’t really remove most bacteria, just kill it, it’s too small to effectively filter without exotic means like centrifuges.

Strictly speaking, that's incorrect, a well-designed polishing system will remove the byproducts of biological growth, however, more importantly, it will prevent biological growth by removing water. Without water, you can't have biological growth. Even a stripper tube will do this. And, once again, without water no biocide is needed.

I hear this often, "Never had a fouled tank or filters in 30 years, all this filter, polishing mumbo jumbo is a waste of money or a scam". While I don't doubt there are folks who never have fuel issues, there are plenty who do, it's a fact; I have hundreds of photos of tanks that are as black as coal pits with asphaltene and bio-fouling, I have photos of aluminum tanks that have failed as a result of the acidic byproducts created by bacterial tank fouling. It does happen.

Until you have seen the inside of your tank, you don't know its condition. If you are forced to change filters because of high vacuum before you've used 1,000 gal of fuel, i.e. a lot for a small sailing vessel, your tank needs to be cleaned. Many don't discover their tanks are fouled until they are in a seaway, where the agitation churns up years' worth of accumulation.

I am in no way suggesting every or even most sailing vessels need polishing systems, it's the exception, however, I am saying if you need a biocide you have a water contamination problem, not a biological problem. Adding biocide to deal with water-born growth is like repairing a leak from inside the hull, it's a short term fix, and while it works, and you can keep doing short term fixes, removing the water is the long-term solution.

The final photo is of a Sea Built inspection port being installed. For a complete tank cleaning, you'd need to obtain access to every baffled chamber.

For cleaning, I have found squirting diesel fuel coming out of a common transfer pump doesn't provide enough pressure to properly clean a heavily fouled tank wall or bottom. That requires mechanical abrasion using plastic scrapers, ScotchBrite pads, non-metallic brushes. Never use metal tools to clean the inside of an aluminum tank, doing so can leave traces of that metal, which is cathodic to aluminum and can lead to corrosion if water enters the tank, and never wipe the inside of a fuel tank with an oil absorbent pad, it will leave behind fibers that are very difficult to see when wet (I've cleaned these impacted fibers from Racor selector valves shortly after a tank was cleaned). Or, for larger tanks, use a hot water pressure washer, it works like the proverbial charm and requires no cleansers or solvents.

[sailah]

Steve,

On these access plates, how are the bolts sealed? I have one on my 44 gal tank but never removed it. I did add a small fitting I machined to adopt a separate pickup tube for my polisher. I bedded it in RTV and added a small amount to the theads. Since my fitting was so small, I drilled and tapped the tank. No leaks so far.

When I first ran the polisher, I found all the aluminum chips in the first filter from the hole saw needed for the fitting.

[a64pilot]

Originally Posted by Simi 60

Could just as easily leak from any one of a dozen other fittings.

No, because those other fittings are not on the bottom of the tank, and a properly run fuel line goes uphill and cannot start a siphon.

[a64pilot]

Originally Posted by Pete7

I thought they were dangerous and vertboten in 'Merica, despite everyone else in the world using them including many European car manufacturers

I never said leave it on, and even if you did, there is no fuel flow through this line, I’d put an outboard fitting on the tank and only click on the bulb whenever I wanted to sump the tank, which isn’t often. Maybe once a month in a quiet anchorage.

Automobiles do many things that are not allowed on a boat as they would be unsafe. One for example is the entire fuel system is pressurized, cause the pump is in the tank. That would be very unsafe on a boat, The reason that it would be unsafe is that any leak would spray fuel from the leak.
I choose not to apply automotive standards to my boat, but apply Marine ones.
In order to comply with the USCG requirement that a motor must suck fuel from the tank, some outboards have had to get creative, for example, the Mercury Verado has a tank on its back, this tank is kept full by a level float that switches a low pressure fuel pump on and off, (just like a toilet tank) the high pressure pump lays in this tank and provides high pressure fuel for the fuel injection system.
An automobile simply puts the high pressure pump in the tank and the entire fuel system is under high pressure.

[a64pilot]

Originally Posted by sailah

Steve,

On these access plates, how are the bolts sealed? I have one on my 44 gal tank but never removed it. I did add a small fitting I machined to adopt a separate pickup tube for my polisher. I bedded it in RTV and added a small amount to the theads. Since my fitting was so small, I drilled and tapped the tank. No leaks so far.

When I first ran the polisher, I found all the aluminum chips in the first filter from the hole saw needed for the fitting.

I know you didn’t ask me, but do NOT use RTV on fuel, fuel softens it and makes it expand, makes a mess.
https://www.permatex.com/faqwd/can-u...unit-gas-tank/

Diesel will as well, just slower

[Wotname]

Originally Posted by a64pilot

.......
In order to comply with the USCG requirement that a motor must suck fuel from the tank, ......

Just to be sure I understand this properly, does this mean a gravity feed day tank is not allowed by the USCG???

[a64pilot]

Originally Posted by Steve DAntonio

Strictly speaking, that's incorrect, a well-designed polishing system will remove the byproducts of biological growth, however, more importantly, it will prevent biological growth by removing water. Without water, you can't have biological growth. Even a stripper tube will do this. And, once again, without water no biocide is needed.

I hear this often, "Never had a fouled tank or filters in 30 years, all this filter, polishing mumbo jumbo is a waste of money or a scam". While I don't doubt there are folks who never have fuel issues, there are plenty who do, it's a fact; I have hundreds of photos of tanks that are as black as coal pits with asphaltene and bio-fouling, I have photos of aluminum tanks that have failed as a result of the acidic byproducts created by bacterial tank fouling. It does happen.

Until you have seen the inside of your tank, you don't know its condition. If you are forced to change filters because of high vacuum before you've used 1,000 gal of fuel, i.e. a lot for a small sailing vessel, your tank needs to be cleaned. Many don't discover their tanks are fouled until they are in a seaway, where the agitation churns up years' worth of accumulation.

I am in no way suggesting every or even most sailing vessels need polishing systems, it's the exception, however, I am saying if you need a biocide you have a water contamination problem, not a biological problem. Adding biocide to deal with water-born growth is like repairing a leak from inside the hull, it's a short term fix, and while it works, and you can keep doing short term fixes, removing the water is the long-term solution.

The final photo is of a Sea Built inspection port being installed. For a complete tank cleaning, you'd need to obtain access to every baffled chamber.

For cleaning, I have found squirting diesel fuel coming out of a common transfer pump doesn't provide enough pressure to properly clean a heavily fouled tank wall or bottom. That requires mechanical abrasion using plastic scrapers, ScotchBrite pads, non-metallic brushes. Never use metal tools to clean the inside of an aluminum tank, doing so can leave traces of that metal, which is cathodic to aluminum and can lead to corrosion if water enters the tank, and never wipe the inside of a fuel tank with an oil absorbent pad, it will leave behind fibers that are very difficult to see when wet (I've cleaned these impacted fibers from Racor selector valves shortly after a tank was cleaned). Or, for larger tanks, use a hot water pressure washer, it works like the proverbial charm and requires no cleansers or solvents.

Steve, nice post, although I’m seeing asphaltanes
But no one ever said that I’m aware of that you “need” a biocide, but that regular use of a biocide will prevent biological growth from ever occurring.
Think of it as Insurence.
However why is it you guys are against regular use of a biocide? It’s pennies of cost and does not harm the engine or the tank, and one container will treat over 2,000 gls of fuel, so it’s not even a problem to carry, it’s one half ounce per 40 gls of fuel.
Some better grades of fuel already are treated with biocide.

[sailah]

Originally Posted by a64pilot

I know you didn’t ask me, but do NOT use RTV on fuel, fuel softens it and makes it expand, makes a mess.
https://www.permatex.com/faqwd/can-u...unit-gas-tank/

Diesel will as well, just slower

Well the RTV sealant I used has now been in place 4 years and looks the same as when I installed it. There are zero indications it has softened, expanded or made a mess. I used Loctite 593.

[a64pilot]

Originally Posted by sailah

Well the RTV sealant I used has now been in place 4 years and looks the same as when I installed it. There are zero indications it has softened, expanded or made a mess. I used Loctite 593.

Well then for whatever reason , your good then. I’d guess as it’s at the top of the tank it rarely if ever gets fuel on it, the RTV that is.
My first experience with it with fuel was on an old Ford Military Jeep many years ago. Something on the fuel tank was sealed with lots of RTV, and inside of the tank was what looked and felt like Bass fishing worms, it was excess RTV. I guess it was a fuel pickup plate, cause I don’t think it had a gas gauge?

Although not illegal to be used on aircraft the FAA inspectors at the plant I worked at wouldn’t allow RTV on the plant floor, they were that concerned about it possibly getting into a fuel system.

[s/v Jedi]

Originally Posted by a64pilot

However why is it you guys are against regular use of a biocide? It’s pennies of cost and does not harm the engine or the tank, and one container will treat over 2,000 gls of fuel, so it’s not even a problem to carry, it’s one half ounce per 40 gls of fuel.
Some better grades of fuel already are treated with biocide.

The point is that a biocide does not prevent bacteria... it just kills them. Removing the water is what prevents bacteria, so all you have to do is remove the water, no additives needed. A sump drain or tube into the sump fixes it. Polishing fuel with a water blocking filter fixes it. Biocide just kills bacteria and leaves their remains on the bottom of the tank.
Also, in 3rd world countries the fuel is very rough. You need to recirculate it or it separates with heavier parts low in the tank. Some of that needs to be filtered out as well. It’s amazing what I remove from new fuel with a 30 micron filter element in places like Venezuela, Colombia, Panama. But I only paid $0.11 per gallon in Venezuela and that was delivered at the anchorage and pumped into my tanks

[Simi 60]

Originally Posted by a64pilot

No, because those other fittings are not on the bottom of the tank, and a properly run fuel line goes uphill and cannot start a siphon.

Tanks on ours are 6 ft tall - fuel into engines and filters is about 3ft, even if fuel pick up was from top of tank it could still syphon if a fitting was compromised.
Think syphoning out of a 44 gallon drum into a jerry can.

Oh, and our fuel out is at the bottom of the tank just above the sump - ex commercial vessel built to survey standards.