If an intermodal yard has three IM tanks or three 20 foot containers and the lower well must be assigned two per the AAR Intermodal Loading Guide, how is the third intermodal tank or container handled? Would it have to wait for another IM tank or container or be held for the next train?
Well cars are usually in three unit or five unit groups (considered one car). The third tank simply goes in the next well.
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I'm not sure I understand this question. If you have only one well and three 20' containers, you'd put two in the well and stack the third on one of them with four IBCs.
If you had 2 20s and "anything else" (40/48/53) you have to put the 20s on the bottom, where there are intermediate corner castings for support, and lock the four outermost corners of the pair of 20s to the "40' spaced' center 'corner castings' on the long container with the IBCs.
You can't put two 20s on top of anything except two other 20s: current boxes aren't stressed with midspan support.
I thought you wouldn't put a 20 on top of a 20 on a railcar. Not in the sense that you can't physically do it, but more in the way of "find another place for it instead of shoving 3 20s in this car."
My interpretation of the question was that you only had the one well (two 20') to 'populate'.
My opinion is that, since the well is 'rated' for at least 4 TEU between empty and fully loaded, there would be little dynamic problem in suspension with three vs. two 20' containers in a well. This is somewhat amplified if any of the containers in question 'cube out before they weigh out'.
Transversely there is little if any 'balance difference' between a stack of 20' and a stack of something longer, and it is unlikely (NOT like the Hancock building!) that any tipover will be on the long axis of a container. There is nominally twice as much support in the well, and twice as much retaining force from twistlocks, in two 20-footer stacks in one well as in anything bigger.
If you can get the whole train single-height, the air resistance can be decreased, perhaps substantially, vs. wells with single containers poking up. There is also some picking effectiveness if most of the containers are immediately accessible to a crane spreader. So there would be reasons to stack the three 20s in the question across wells if you have the actual space. On the other hand, block-swapping and container-crane handling are both improved if wells in a given unit are stacked full before the next unit starts to be loaded -- you see this in the many trains that are built full but then have bare-table stock (hopefully toward the rear of the consist with nothing behind them!!)
Some early discussions of stack equipment involved the use of forks like some PiggyPackers to handle containers with transverse fork pockets, and those don't work well if at all for containers sitting in wells. I don't know of any current operations that sideload ISO containers domestically, but it would certainly be interesting to read about them.
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