There is a small rail marshalling yard behind our office. This morning I was out on a smoke break and was looking at some rail cars sitting across the the fence and noticed the instruction written on the side of the cars. I don’t remember the exact words but it went something like – “Do not use sharp objects to clean inside. Enter car wearing soft soled and clean shoes.”
Maybe I can understand the part about not using sharp objects to clean. Probably the inside of the car is lined with something, an insulation perhaps. But I can’t imagine the reason for the second part . Why the imperative of “soft soled clean shoes” inside the car? It is a rail car used to transport stuff. What are these rail cars supposed to carry?
Perhaps it was a refrigerated rail car? I assume those would have an insulated interior, like you guessed, and that might be damaged by abrasion. Soft soled shoes would then be somewhat self-explanatory. I would guess that keeping them clean is a matter of not dragging in grit and small pebbles, which would then scratch up the interior as you walked on them.
It all sounds quite odd to me if it is was just an ordinary rail car, though.
I have seen that notice on hopper (tank?) cars used for pelletized plastic resin. The interior needs to be slick, so the contents can be completely emptied by moving air (vacuum) hoses. Also, any foreign matter tracked in will screw up the molding process when the plastic is used.
Yes it was a covered hopper car, something like the second picture in your wiki link.
I think AskNott’s answer is close because one of the cars also had ‘Plastic Granules’ labeled on it.
But I am still not clear about the reason. How would wearing, say wooden heeled shoes, make a significant difference. Even if the shoes were to scratch the surface, how would that cause a problem in emptying the car of plastic granules or balls? What size of balls are we talking about? Even if a layer was to remain behind and not get emptied, it would be tared out in subsequent loads, wouldn’t it?
And as to the ‘clean’ question, wouldn’t it make sense for the manufacturer to have some sort of a cleaning process for the raw material before using it, rather than rely on the carrier, especially if cleanliness is that important…
Perhaps it would also make more economic sense for the carrier because then it would not have make special rail cars for use only by some of its customers.
Hopper cars, except for some grain cars are not owned by the railways. They’re mostly privately owned. (if the initials end with an “X”, they’re private)
The cars have an epoxy lining mainly to prevent rust, which can stain plastic pellets. The car owners don’t want to have to pay out big claims for defective product.
I really can’t answer the soft shoe question; I’ve never been inside one. Plastic resin comes from the supplier as little cylinders, roughly 1/8" in diameter, and roughly 3/16" long. Naturally, there are smaller particles as well. If the molding plant were to filter out small particles, most of them would be plastic. The understanding is, the supplier provides a pristine (virgin) product. The molding plant must dry the plastic before using it, lest the moisture makes little “smear” lines in the mold.
The material is delivered in a variety of colors. It wouldn’t do to fill up a hopper with red, if it still had some clear in it, or vice versa.
As you probably know, there are many kinds of specialized train cars, that will always carry the same material, such as a certain acid, sugar syrup, soybeans, scrap iron, coal, and so on.
The hopper railcar is probably coated with Dupont FS-200HS, a tetrafluorethylene compound that makes them slippery. Like your frying pans, it’s hard to get this stuff to stick to the railcars, and they’d prefer you didn’t scratch it. It’s why you use plastic spatulas with nonstick cookware.