Freeboard for sloshing in API Tanks

[JoseAcevedo]

Does anyone can tell me the criteria to evaluate if the tank roof and shell are designed to contain the sloshing liquid?

By the other hand I would like to know what happen if the sloshing height is bigger that the freeboard.

 

[IceStationZebra]

First - post this in the "fluid power engineering" section. Bud will see it and he is the Zen master of all things hydraulic.

Back to you question - "what happen if the sloshing height is bigger that the freeboard?" Happens all the time in off-road equipment. If you have a choice put the long axis of the reservoir perpendicular to the axis of travel to minimize problems. There are two issues to watch out for:

1. Make sure that the pump inlet is not uncovered. Usually not a big deal unless you have a shallow oil level.

2. Position of the breather and dipstick ports are very important. The dipstick will be OK if it has an O-ring seal (which it should anyway for cleanliness reasons).
The breather can be a very tricky problem. I have worked on many different types of machines where aggressive driving can have oil dripping out of the breather.
-- First line of defense is to put the breather port as close as possible to the center of the roof. If that is not possible seriously consider an internal pipe.
-- Next make sure that any plumbing for the breather will drain back to tank. Low spots create a P-trap which will "pump" oil out. The pumping action is provided by both the oil during sloshing and air during cylinder retraction. (note that even on 2-way cylinders the rod displaces oil, which goes back into tank, which forces air out.) I calculated an exiting air speed >40mph on one machine during the worst case cylinder retraction. Put your hand out the window at 40mph to get an idea of how much oil it can push!
-- In the same vein you can make the breather line larger. This decreases the air speed.
-- You can try a breather with built in low pressure check valves. Note that this will only work if you can guarantee that you will not be displacing air out while the sloshing is occurring.
-- You can try an expansion chamber, but I've had bad luck with the simple/cheap designs. I did design a very effective one on my last project though. It was a somewhat complicated rotomolded job, but it solved the problem and only cost $1.50 (for 10k units/yr).

Let me know if you have a more specific question. ISZ

 

[IFRs]

API 650 tanks are large cylindrical flat-bottom above-ground storage tanks. If the slosh height exceeds the freeboard, the liquid will slosash out of an open top tank (perhaps damaging the external floating roof if there isons), out the shell vents if present on an internal floating roof tank or up against the roof of a fixed roof tank. You may get better answers in the API Code Issues forum. API tanks can also be pressure vessels (API 620) and many other shapes and types. For a better answer, please describe more fully your tank configuration and the basis for your question.

 

[IceStationZebra]

Sorry, I didn't realize this was a large storage tank. Waaaay out of my league. ISZ

 

[IFRs]

I did not mean to assume that he was talking about API 650 tanks or suggest your answer was wrong. Just trying to contribute in case he was looking at 650 tanks.

 

[IceStationZebra]

No problem. ISZ