I never had issues like that with either rock or granular salt. And we rarely delivered same day and many times sat over the weekend with it on the truck. My longest run was KS to Lemoore CA and it unloaded like normal.
oh yeah, well, that is the easiest way to get unjammed. it reverses the flow from blowing stuff out through the bottom pipe to sucking stuff in through the bottom pipe back up into your hoppers.
it makes it possible for a person to hook a hose up to a train car and suck cement out of the train car and put it into your tanker, then when your tanker is relatively full, you can take your tanker and pump the cement, or slag, or flyash, or what have you, into a silo.
here is a video that shows a guy unplugging his tanker by reverse pumping. its all about creating high pressure in your bottom pipe and low pressure in your hoppers.
when you reverse pump to actually fill your entire tanker, all hoppers, you will have to open the latches on one of the hatches on the top of your tanker. it will let trapped air out as you are pumping the product in..
I showed that that trick to a guy that's been doing cement for 5 years. He thought i was just yanking his chain LOL. "Man i wish i knew this sooner" I always did the last tier 1st in case i plugged off. Doesn't have to travel as far then. And if for some reason its winter and you can't get all the product off you still weight on drives