Diesel tank vent

[Manny]

A coworker that owns a few boats down at the Jersey shore was showing me some pictures of the damage from the Nor' Easter that came through this past weekend. Looking at the shots of the boats getting pounded and some that sank at the dock got me thinking. I have done as much as I can think of to minimize any environmental damage that could occur if, god forbid, my boat sinks. Any spare oil onboard is kept in ziploc bags, even my oil change pump is in a ziploc. All cleaners are tightly sealed, some are in ziplocs, the kind with the spray nozzles are always set to "off" after use. I have a port-a-potty which isn't vented or plumbed to a pump out fitting so it cant leak. Oil pads abound in the bilge and under the diesel engine. I can't do much with my batteries, I cant see how to seal them in a manner that wouldn't be a safety issue. I take the fuel tank for the outboard home with me. The only thing that I can see being a major concern is the diesel fuel tank. I would imagine that the fuel could/would leak out the vent line if submerged. I only keep a couple of gallons in there but that would be enough to cause harm not to mention the massive fines from the EPA. So my thought is, can a valve be placed on the vent line to shut it off while not in use? A side benefit would be keeping the fuel "fresher". Would this be a safety issue? I could see it being dangerous with a gas tank but diesel is pretty stable. Any thoughts?Thanks,Manny

 

[Ray]

The vent is a must have item.

The vent on the fuel tank serves two functions. The first is to allow air to excape from the tank while fueling. The second is to allow the tank to remain at atmospheric pressure while the temperature fluxuates inside the tank.A shut off valve would cause the tank to possibly rupture at high temps or to collapse at the cool end to the temp range.Raising the vent line upward is one solution, but rather clumsy. Dual foot valves, one in the intake and one in the exhaust, would be an easier remedy but also wierd.Freshness doesn't play in this question as the the air within the tank itself is enough to fowl the fuel if it wants.The best all around awnser to the question is to prevent the boat from sinking in the first place.I applaud your goal of protecting our environment and wish more people felt the same. Keep up your ideals and enjoy the wonders of breezes.Ray

 

[tcbro]

How about a loop...

...in the vent line. Run the line up higher than the vent then back down to it. This would create an airlock if the boat sank. This should work if it stayed fairly upright.

 

[RichH]

Ray is correct ....

to put a vent valve on a fuel tank the tank must be rated for 'full vacuum'. Otherwise the tank can collapse upon extremes of pressure temperature when the valve is closed. What can be done (with still some risk for collapse) is to apply a filter capsule with a hydrophobic membrane system. Such will 'automatically shut down' when water touches and blocks the membrane, when no water touches the membrane the membrane will pass air. The difficulty/risk would be if any free water (or oil) gets in there from normal 'atmospherics' or spray which will 'lock up' the membrane ... and you still collapse the tank during 'normal' usage if the membrane becomes wetted. I apply hydrophobic membrane filter capsules to my water tanks to prevent microorganisms from entering and fouling the tank. An example: http://www.pall.com/datasheet_biopharm_32890.aspAn alternative would be to apply a long 'U tube' bend to the vent line with the U inverted and at the top of the 'run' of tube and mounted at the very top of the cabin ceiling, etc. The geometry of the inverted U would trap air in the top of the inverted U when the boat is submerged ... all bets are off if the boat is submerged and laying on its side.

 

[Banooma]

where and when were the boats damaged?!

nm

 

[Manny]

Thanks for the ideas

I will try to make a loop or an inverted "U" in the vent line. My vent currently is a pretty straight run to the transom. I should be able to raise it pretty high under one of the coamings (sp?). Pretty interesting stuff on the pall.com website. I agree with with Ray that the best answer is to prevent the boat from sinking. I always make sure to inspect when leaving the boat all the thru-hulls/sea-cocks, the stuffing box, the bilge and keel bolts, rudder stuffing box, and the scupper hoses. I check the float switch on the bilge pump and also make sure the battery is fully charged. Banooma, the pictures of the storm I saw were mainly down in the Cape May/Wildwood area. One of the sites my coworker showed was thebassbarn.com - there were a few different postings in the forums with pictures, I think one was called something like "not fit for man in cape may". He showed me a couple of other sites with pictures but I don't remember what the sites were. The storm was from Sunday into Monday. His marina called him to let him know that his boat was okay. A friend of mine that keeps his Oday on the Delaware River got a call on Monday morning from the marina manager that his jib had unraveled during the storm and had torn to shreds. In a way he was lucky, his boat was still on the hard and it didn't get knocked off the stands!!!!!Manny