Different tanker shapes

It is a reference to the shape of the barrel. A straight round looks like a paper towel roll and discharges from the rear. Some plants combine loading docks w/ the tanker unloading areas so any place where you back in and down you need a rear un-loader for drainage. Some have the air bags with internal blocks that were made to stop van trailers from 'dock walk' and a dump valve that drops the rear another few inches for added drainage on level ground.

Double conical tanks look like two water cooler cups top to top so the bottom slopes from the front and back to the center. These give better drainage on level ground and will often have a 'heel' if backed into a pit as all the product can't drain. Matlack had some conicals set up 40-60 so the 'center' belly outlet was physically closer to the tractor so you needed less suction hose to reach the tractor mounted product pump.

All tanks for Haz Mat are built to 'spec'. Both the aluminum elliptical gasoline wagons and the big round un-insulated stainless solvent tankers are built to the same spec [DOT 406] and are not made for pressurized unloading so the need to be pumped off +/or gravity drained

Acid [DOT412] and general chemical [DOT407] trailers are built for pressurized off loading. 407s are often insulated and equipped w/ a belly steam pan for stationary steam heating +/or in-transit heating using the tractor coolant and engine temp.

Acid wagons are usually smaller 'cause the corrosives are heavier [sulfuric acid is 15.63lb/gal] and heavier so they can loose some thickness over time. Ultrasonic thickness testing is required to make sure they meet 'spec'.

All 'spec' trailers have some form of rollover protection to keep the dome lids intact in an accident. 406 & 407 have self closing internal valves and the piping has a 'shear' section so it can be ripped free in an accident with out tearing the belly of the tank apart.

Sanitary or food grade wagons won't have crash protection built up over the dome lid and have a simple outlet valve and are designed for ease of cleaning rather than crash protection. You don't see many double conical sanitary trailers, they are usually straight round barrels.

Any stainless tank with a smooth exterior is insulated and the real tank is covered with a wrapper skin protecting the insulation.

There is 1001 variations but this covers the basics though you can see that the added engineering put into tankers makes them cost much more than a 53' box. It is also why they usually are 42' to 45' max as the barrel is also the frame and making them longer weakens them instead of adding payload.

 

Gives new meaning to having a "hot" load!!!

 

That link and this thread are great! I've passed and been passed by tankers many times and didn't really think too much about what could be inside unless I notice any markings or descriptions on the sides or back.

 

In short, double conical tankers are fat in the middle and narrow on the ends. Kinda like two cones placed wide-end to wide-end. The idea is to make it easier to unload on flat ground. With the straight barrel tanker I pull, I have to dump the trailer suspension and sometimes place blocks under the landing gear and jack it up, to unload on flat ground.

 

Actually that was a new classification a few years ago when they decided to add "HOT" label to some of the molten products that had no other hazard classification, just a white diamond w/ the word HOT on it...like Liquid Molten Sulpher, it wasn't classified under any other hazard but it gets solid around 290 degrees and is shipped around 350 degrees...just to identify the potential thermal hazard...

 

We did not use placards or stop for railroad tracks when I hauled aluminum in the 1980s. I know of several accidents that caused the lid to detach spilling hot metal in the ditch or on the road. Two telephone company executives died when their car slid into the pool of molten aluminum that covered the road at Berrien Springs. Placards would not have saved them, but perhaps installing placards would have reminded the truck driver of his responsibility to drive safely.

 

WE actually noticed a thermal danger w/ non-placarded items too, Had a hose burst and spray a driver w/ surfactant [soap ingredient] that was just heated to 200degrees after being turned away that morning for being too cold...his terminal sent him to us [closest company terminal to the customer] for steaming and them he re-delivered that afternoon. He had his splash suit on and still had a nice first degree burn and a few 2nd degree where the product got at the edges and reached his skin.Lots of ways to get hurt w/ liquids.