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
Just fill the trucks with school lunch size cartons of milk?
Baffles in the tanks – lots of tanks however do not have baffles, called smooth bores, usually for food grade tanks as the baffles make it hard to clean.
Very careful driving with all tanks but especially smooth bores. Even with baffles when you come to even a moderately fast stop you can feel it push you.
The bonus though is that you can run overweight and the scale houses won’t be able to tell if you jam the brakes when you go to stop on it, they’re not going to wait a couple minutes for the surge to die down
Just anticipate it and ride it out. The closer to full, topped off, it is the less slosh. Some tanks have baffles some don’t. For instance most chemical tanks are smooth bore. It’s super important that they get a good clean out between loads of different product. Any extra edges ledges or corners make places the washout won’t reach. Different products handle differently. Depends on viscosity and density of the liquid. For instance, crude oil isn’t that bad. Water is terrible, so it is antifreeze. Sometimes it slams so hard after stopping you swear someone just ran into you.
While you always want a full tank your limited by how heavy the product is. A 200 bbl tank with a day cab can be topped off and still legal on weight. But if you load Water or brine in same tank your at 80k with a little over half a load.
I drove a unbaffled 7000 gallon tanker for 4 years and the max fluid I hauled was around 5500 gallons. You just learn to drive slow and shift smooth and brake only has you have to. But what doesn’t help is when we are in traffic and we leave a gap to stop and cars keep jumping in front of up and making us slam on the brakes. And it isn’t bad unless we take off and slam on the brakes again. Then we get the bounce of the liquid sloshing around. But I have never been around a turn to fast for it to make my truck jerk sideways. But I always pictured me driving a 80s caddy taking grandma to church just taking my time.
My husband drives a tanker without baffling, he said that most food grade tanks won’t have it due to the cleaning issue. He says most of it is really just always allowing extra time for everything – drive like you’re in bad weather all the time, give yourself extra time to slow down, to turn, etc.
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.
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.*
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.
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.
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.
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