#6 HFO TANK, NEED TO LOWER SUCTION LINE TO RECOVER MORE OIL 1

[Cymatics]

This is a 137'wide X 48'high tank, the 10" suction line has a 90 degree elbow and is located in the center of the tank, the opening of elbow is 2.5' of the deck.

This leaves 263000 gallons of unusable product. A floating suction line would not work well going much lower than 2.5 feet with vortex issue and cavitation problems.

Has anyone heard of a sediment ring or a ring manifold that could be placed on the bottom of the tank? to get access to more 6 oil.

There are 4 bayonet heaters 2.5 off the deck 2 on either side of the suction inlet and a steam return reclaim heater that sits on the deck.
Thanks.

 

[MikeHalloran]

I have heard of using local depressions in the bottom (of much smaller tanks) in order to recover more product. E.g., a sump of a couple of feet diameter x a couple of feet deep surrounding the outlet, which would be flush with or below the bottom of the majority of the tank. In fuel tanks built into structural steel skids, this is accomplished by using plate for most of the bottom, with a channel inserted open side up at the drain location.

If you were designing a new tank, that might be an option. I assume this tank exists already. All that comes to mind for retrofitting an existing tank is:

A trumpet extending down from the current elbow to a plane much closer to the tank bottom. The vortexing/ cavitation is not a problem for a trumpet of sufficiently large diameter/circumference.

OR

Displacing the unusable product with some kind of filler that will sink in the oil, and still be light enough to not overload the bottom, covering most of the bottom except around the discharge to the depth of the now unrecoverable product. Big rocks or concrete blocks would fill the first requirement but not the second.

Along those lines, for a one-time recovery, it might be possible to build a dam around the discharge, seal it to the bottom, and slowly fill the resulting outer annulus with water.



Mike Halloran
Pembroke Pines, FL, USA

 

[Cymatics]

Thanks for your feedback, it helped me out. The 90 degree elbow is a trumpet now that I think of it. Thanks for giving me the name. The trumpet opening is facing up. I don't know if there is enough room to spin it 180 degrees and have it facing down and still have it off the deck and not cause any cavitation.

I did check an idea I had on the displacement option; basically placing those temporary rubberized blatter tanks inside the steel oil tank and fill them with water. They come with 3" cam lever lock connections and could be lowered down inside the tank by said hose and filled with water causing the blatter to sink and raise the oil level. But the problem was cost along with the possibilty of the blatter tanks moving around and coming in contact with the hot steam heating coils and springing a leak.

 

[racookpe1978]

If the tank could be drained and cleaned sufficiently, and if the total volume of the tank would be acceptable with less apparent capacity (BUT by using the untapped "sludge volume" now just sitting there getting the same useable volume), then you could

1. Empty and clean the tank.
2. Fill the bottom of the tank with a sloped concrete floor so the current drain (or one with a slightly lower bellmouth) is at the top of the new sloped concrete floor.
3. Wait for the concrete to dry, then refill. The new concrete won't be part of the "pressure boundary" of the tank as a whole - that's still the current walls and floor.

Alt: Fill the floor with 12" of sloped concrete leaving a small sump in the bottom that's 12 inches deep, but with a new drain pipe mounted in the side of the sump. Your sludge will accumulate in the sump, but it can be pump out with a separate small pipe to waste or to a cleaning system. The main drain will be catching the relatively more clean oil above the skudge and residue, but that residue loss will only be the little bit of volume in the sump.

And the bottom of the tank won't need to be cut out and rebuilt.

 

[Thealanator]

I assume that the suction opening is off the bottom so that the pump will not suck in water (from condensation?) Does this mean the tank is designed to handle the 2.5 feet of water? Can you pump water into the tank 2-2.5 feet deep? Oil (or most of it) would float above the top of the suction opening.

 

[tr1ntx]

Like the above poster, I was wondering if you know for certain that it is only oil in the bottom 2.5 feet. It could be water/sludge/sediment.

I assume from reading your posts that some sort of temporary hose suction is an option. How about a hose with one of those "fish basket" trash strainer ends, which should also serve as a vortex inhibitor? (or use some other sort of vortex breaker hose-end attachment)

Maybe just lay a piece of pipe along the bottom. You would put holes it in at certain distances from the end, smaller dia as you get further away from the end. You would want to cap the end, or maybe just weld in a half-opening plate. You don't really want a full-blown "perforated pipe" because you want to distribute the inflow along a certain distance, i.e., this is a poor man's manifold I guess. There might be someone who makes a "bottom scavenger" pickup, but you'll probably have to design one yourself if you want something like the sediment ring or ring manifold you mentioned. You might try checking with tank manufacturers.

 

[IFRs]

Would something like the attached work for you?