How do truck drivers carrying a liquid load combat the force of the liquid moving around in the back of the truck when turning or braking?
In: Engineering
The training for such loads tells them to do everything as smoothly as possible to avoid problems with the inertia of the liquid, and keep extra space.
Also, these tankers are usually as full as possible, which limits sloshing, and they also have internal baffles which also help a lot.
Some tanks are actually divided internally, so the effect of sloshing are limited.
But even for single tanks, they have rings called slosh baffles that dampen the effect. [Here’s an animation](https://www.youtube.com/watch?v=56cxOzgl-mc) showing sloshing with and without baffles.
Usually tanks designed for transporting liquids will have “baffles” within them. These are plates or barriers which have relatively small holes in them so that large movements of liquid are slowed while still allowing the tank to be filled and emptied as normal. Otherwise as you suspected sloshing of liquid would be a big problem.
A fun thing to think about is that trucks that carry bulk food loads (like milk carriers) are not allowed to have baffles due to difficulty of cleaning. There’s often special training for milk trucks due to the load being more free.
Former propane delivery guy here.
There are baffles in the thank. Think of them as walls that only let some liquid through at a time. Either having a large hole or being half walls. That helps with the front to back inertia. The side to side isn’t as much an issue as long as you are on flat land. Uneven terrain like a customers rough driveway can make it very noticeable sloshing side to side. Got a just go slow and be careful on those.
I work in party rental and that was a big thing they would drill into the heads of the drivers. I think they called it either ‘flux” or “surge” or something like that. When you have 500 8’ tables standing on end they can shift right and left with each turn, and it’s essentially like carrying a large load of liquid, without the forward and backwards inertia. You take a corner too fast and it feels like the giant box truck is gonna flip.
You learn to drive smooth. No sudden throttle no sudden brakes. You plan all your moves way farther ahead then when you just have a 50ft with freight behind you.
In fact when i drove semi the load most guys hated was hanging meat. Since they hang from the top of the trailer when you go around a corner they swing like a pendulum. Very easy to end up wrong side up.
Per my understanding, the tank has to be full. I imagine there’s ways to work around it, but that’s what I recall from my attempt at a CDL.
An article on the nuances of driving hazardous liquids …
[A Fleet of One: Eighty Thousand Pounds of Dangerous Goods](https://archive.ph/5GIIg)
>*Just as the body of a fish tells you how that fish makes a living, the body of a tanker can tell you what it contains. In Ainsworth’s words, “The architecture of the tank says what is in it.” If a tank has gasoline inside, it has a full-length permanent manway on top, and, seen from the rear, is a recumbent oval. If a truck is a water wagon, the tank—rear view—is rectangular. A perfect circle ambiguously suggests asphalt, milk, or other food. If the vessel is all aluminum and shaped in tiers like nesting cups, it is a food-grade pneumatic hopper full of flour, granulated sugar, and things like that. If stiffeners are exposed—a series of structural rings circling and reinforcing the tank—the vessel is uninsulated, generally operates in a warm climate, and often hauls flammables and combustibles. Ainsworth said, “That is what mine looks like without the designer dress” (the stainless mirror sheath). The double conical side view speaks of chemical hazmats. Since September 11, 2001, all these shapes have scattered more than fish.*
>*Backing blindsided at the Peterbilt dealer’s in Missouri, he said, “Sometimes you do this by Zen.” He had never been to driver school. “I’m a farm boy,” he explained. “I know how to shift. There are two things you need to know: how to shift, and how to align yourself and maintain lane control—exactly how much space is on each side. In city traffic it’s critical.” In the open country of western Kentucky, he said, “Out here, you look way ahead. It’s the same as steering a ship. There’s a silver car about a mile ahead that I’m looking at now. When you steer a ship, you don’t look at the bow, you look at the horizon. When I’m in a four-wheeler, I stay away from trucks, because if a tire blows or an entire wheel set comes off I’m going to Beulah Land.”*
>*From Harrisburg, North Carolina, to Sumner, Washington, the load in the tank behind us kicked us like a mule whenever it had a chance. The jolt—which he called slosh, or slop—came mainly on surface streets and on-ramps when gears were shifting at low speeds. On the open road, it happened occasionally when we were gearing down, mashing on the accelerator, stepping on the brakes, going downhill, or going uphill. Ainsworth minimized the slosh with skills analogous to fly casting. “You coördinate shifting with the shifting of the load,” he said. “You wait for the slop or you can pretzel your drive line.” The more ullage the more slop. The density of the monoethanolamine had allowed us to take only six thousand gallons in the seven-thousand-gallon tank. The ullage was the difference was the mule.*
Bulk milk trucks do to sanitation issues have no internal baffles. When they are half empty the milk will slosh and push the truck 3 or 4 feet forward then back. The only thing the driver can do is go slow and leave lots of room to stop.
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