Right now, you’re probably surrounded by items made of plastic—phones, pens, eyeglasses, yogurt cups, you name it. Practically every ounce of that plastic started as a load of resin pellets or powder transported on a bulk trailer. Many other dry bulk commodities—sand, clay, limestone, starches, fertilizers, to name just a few—play a crucial role in industry and agriculture.
Dry bulk is an important component of today’s supply chains, and transporting it is no simple matter. Even if you’ve shipped these kinds of products in boxes, drums or totes in a dry van, that doesn’t prepare you for the challenges of managing tank loads of dry bulk.
For newcomers to dry bulk shipping (and for more experienced people who just want to refresh their knowledge), this article covers its equipment, processes and responsibilities—and also offers tips on choosing the right partners to help.
The first, obvious thing that makes a dry bulk commodity different is that it doesn’t come packaged in boxes, barrels or other small containers. Loading and unloading 40,000 lbs. of pellets or powder takes a whole different skill set, and entirely different equipment, than you need to move packaged product on and off the back of a box trailer.
But the most crucial difference with dry bulk involves the danger of contamination. This is especially true with plastics. Let a half-ounce of clay sneak into a load of plastic pellets, and you could make the whole load—worth maybe $40,000—completely useless. After you unload a conventional trailer, just sweep it out and it’s ready to move something else. But most of the time, before a dry bulk trailer takes on a new load, it needs a thorough washing at a certified facility.
Other factors that make dry bulk shipments different from dry van shipments include:
There aren’t nearly as many dry bulk trailers on the road as box trailers. And due to concerns about contamination, carriers often devote certain trailers to specific materials—like black plastics, white plastics, sand or clay, hazardous materials, and food-grade commodities. So, when you need a truck, it might take longer to find one that can carry your specific load.
If you’re new to dry bulk, you may be shocked by the price quotes you receive. Rates are higher for several reasons:
The driver will need at least a tanker endorsement. If he’s hauling hazmat or waste, he’ll need endorsements for those as well. And he’ll need special skills to manage the equipment on a pneumatic trailer.
A carrier hauling non-hazardous dry bulk should carry at least $1 million in liability insurance. For hazardous materials, the minimum is $5 million. You’ll also require cargo insurance, which varies with the value of the load.
A dry bulk trailer is basically a metal cylinder, but with a series of cone-shaped hoppers at the bottom. The trailer comes with a series of openings called manholes, which are used to load the product. There are generally three to six manholes distributed along the top of and back of the trailer.
At the bottom of each hopper is a valve, opening into a pipe that runs below the trailer. Those valves are closed when a shipper loads the truck. When it comes time to unload, the driver opens them, letting product run out of the hopper and into the pipe.
Some shippers insist that each dry bulk trailer they use have a catwalk installed on top. The catwalk is a safety device that looks something like a ladder laid flat across the top of the trailer. When an employee climbs to the top of the trailer to load product into the top manholes, the catwalk helps to keep him from falling. As a further safety measure, some carriers also provide popup railings, which they raise on top of the trailer before loading.
Dry bulk trailers come in different sizes. One manufacturer, Polar, sells models that range in capacity from 550 cubic feet with a single hopper to 2,800 cubic feet with six hoppers.
As we noted, contamination is the bane of dry bulk shipping. A responsible carrier diligently visits the truck wash after each load, but there’s always a chance that a little stray material—a few beads of plastic or a bit of clay residue—will survive the wash, stuck deep in the piping.
What happens then?
Picture a load of white plastic pellets shipped in a trailer that still has a few black pellets lodged in a crevice. If those black pellets get dislodged, they’ll mix in with the white product. Then, when that plastic goes through a manufacturing process—say, to produce shampoo bottles—you’ll get an ugly black slash across hundreds of units. The customer will have to toss those bottles, and someone—possibly you, the shipper—will pay for that loss.
Now imagine if the customer doesn’t send that contaminated load straight to production, but instead loads it into a silo that is already largely filled with white beads. Those few black beads could ruin hundreds of thousands of pounds of white plastic. At a dollar or more per pound, imagine the liability then.
That’s why carriers that move bulk plastic pellets reserve some trailers for white pellets, some for black, some for blue, and so on. Then they dedicate other trailers to loads, such as sand or clay. It’s all right to load those less-finicky products one after another, as long as the carrier gives the trailer a good wash-out in between.
Of course, companies that transport hazardous materials or food-grade dry bulk need separate trailers for those, too.
A trailer that is used to transport plastics carries a vacuum unit on the back. About six to eight feet tall, this unit suctions the plastic pellets or powder through the bottom pipe and along a hose to the silo or other vessel where the receiver stores product. Trailers for other kinds of commodities, such as sand or clay, come equipped with blowers, which are about half the size of vacuum units and less powerful.
Dry bulk carriers generally use hoses, four inches in diameter, to blow material into and out of a trailer. When loading product from a rail car or offloading to a silo, those hoses may need adapters to connect them to other equipment.
In the old days, blowers would build up a great deal of heat as product flowed through them. The resulting hot air would sometimes melt plastic pellets, deforming them slightly. To eliminate that problem, more modern blowers come with built-in cooling systems.
Those differences have big consequences for transportation. If you’re shipping a product that weighs 20 lbs. per cubic foot, and you fill a 1,500-cubic foot trailer to capacity, that will make your load 30,000 lbs.—well below the amount you can load to stay within the Department of Transportation’s 80,000-lb. limit on gross vehicle weight. But if you load that same trailer with sand, at 100 lbs. per cubic foot you won’t even fill the tank by one-third before you hit 45,000 lbs., about as much as you can load to stay within the legal limit.
If you’re moving perlite, you can fill the whole trailer without worrying about overweight fines. But you might need a couple of trucks to move as little as 12,000 lbs. of product.
The newer trailers come with onboard scales. These aren’t precise enough to tell you exactly how much product you’re delivering to a customer, or how close a loaded truck’s gross vehicle weight comes to the legal limit. But they indicate approximately how much weight you have onboard, accurate to within a couple of hundred pounds.
To get a precise measure of the product you’re shipping, the driver first takes the empty truck to a certified scale to obtain a “light weight.” Once you’ve loaded the product, the driver returns to the scale to get the loaded weight, which is printed on a scale ticket. Of course, that number, minus the light weight, gives you the weight of the product.
Before you start looking for equipment to move a dry bulk shipment, make sure you can answer the questions that your carrier or broker will ask, including:
Sand, clay and many other materials can be simple to load into a dry bulk trailer. Usually, the driver pulls the truck under a chute attached to a silo, and gravity does most of the work as the material drops through the manhole. The process moves from one manhole to the next, to fill the trailer evenly.
Loading plastic pellets or powder from a rail car is trickier, as it involves the use of air pressure to move product through the hose and into the trailer. It takes a skilled worker to pressurize the trailer in just the right way and then gently adjust the air to get the product moving. Turn the pressure up too fast, and product will jam up in the hose. Then you have to stop the process and take everything apart to unclog the lines.
Usually, the shipper assigns an employee to take charge of loading. But before anyone starts that process, you need to inspect the trailer carefully to make sure it’s clean, dry and odor free. To confirm that the trailer has been cleaned correctly, ask the carrier for a wash slip. Also, check the seals on the manholes and the valves on the hoppers to make sure they’re closed tightly, so no product can leak out.
Unloading is generally a driver’s job. Every piece of equipment is different, and the driver is the expert on how his particular equipment behaves.
When the driver arrives at a plant or other receiving site with a load, his first stop is the office. He shows his paperwork and confirms that the product on the truck is the same product the company expected. Then someone directs the driver to the unloading site. With help from plant personnel, the driver verifies that he is preparing to offload to the correct silo. A smart driver will get an authorized person to sign a form attesting to that fact, to make sure he’s held harmless in case of a mistake.
Someone should also make sure there’s enough room in the silo to receive the load. Usually there is. But every now and then, the pressure of an incoming load will blow the top off an overfilled silo, spewing product and dust all over the cars in the parking lot. (It’s happened!)
The driver brings the truck as close as possible to the silo. If proper planning has occurred, the driver will have enough 20-foot lengths of hose to connect the trailer to the tank.
Finally, it’s time to start the vacuum or blower, carefully adjusting the pressure to get the product flowing smoothly through the hose. That hose connects to a pipe that leads into the silo, sometimes by a long route that includes the occasional elbow.
Although product blown off a dry bulk trailer is usually clean, some receivers insert filters into the hoses and piping to catch any unwanted material.
Offloading usually takes about an hour to an hour-and-a-half, depending on the product. An inexperienced driver might take longer, especially if he turns the pressure up too high and has to stop the operation to unclog the hose or pipes.
This requirement adds extra time to every shipment. It also adds cost, partly because every shipment includes deadhead miles, and partly because the shipper pays for the wash. Because tank washes are few and far between, with little competition, they can generally charge what they want for their services.
For many products, the tank wash just needs to blast the inside of the trailer with water at high pressure. It does this by dropping a spinning device—something like a disco ball with water jets all around—into each of the manholes. After the wash, the trailer is blown dry.
If the driver has just dropped a load of sand or clay and is preparing to pick up a similar load, it’s often fine to skip the certified wash and visit a local business that washes down the tank with a high-pressure hose. In this case, however, the driver will need to use his own onboard blower to dry the inside of the tank.
But when a truck drops one commodity and picks up a different one—especially when moving plastics—it must go to a certified wash station, and it needs what is called a conversion wash. In that process, employees at the tank wash take off the pipe that runs along the bottom of the trailer, remove all of its fittings, lay everything on the ground and give it a careful cleaning. The conversion wash ensures that no stray bits of plastic or sand will be lurking anywhere in the assembly when it comes time to load a different product.
It takes a great deal of work to make sure that dry bulk shipping is performed correctly and safely. To avoid finger pointing, everyone involved needs to know where specific responsibilities lie. This chart explains which party is responsible for which aspects of the process.
| Shipper Responsibilities | Receiver Responsibilities | Carrier Responsibilities |
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Typically, the shipper is responsible for loading a dry bulk shipment, and the driver is responsible for unloading. But that might not be true for every shipment. When you book a load, establish right from the start who will load and unload, so there are no misunderstandings when the truck arrives.
An unqualified carrier always exposes you to risk, and that risk is significantly greater when you’re shipping in a tanker truck. Don’t invite trouble. Often, all you need is a short conversation with a carrier, asking the right kinds of probing questions, to figure out who’s a real expert and who’s just pretending.
When evaluating dry bulk carriers to haul your loads, consider the following:
It is also important to keep in mind that - due to the driver shortage and other factors - carriers may have limited capacity but a seemingly endless supply of shippers vying for it. In order to secure capacity for your loads, you may need to make your loads as attractive to the carrier as possible. See this blog post for 7 ways to do that.
If you’ve read this far, you know at least one thing about dry bulk shipping: it isn’t simple. Requirements vary from commodity to commodity, and there’s a lot more risk involved than you’d face with dry van shipments. Forget to nail down just one important detail, and you might find yourself in a world of pain.
Can you and your team handle all the ins and outs of dry bulk shipments on your own? Do you have the time and know-how to locate, evaluate and manage all the carriers you’ll need to source day-to-day and emergency freight capacity—and to do it all well?
If not, you’ll be glad to know that there are brokers who specialize in moving dry bulk shipments. Working with one of these brokers, you gain access to the following benefits.
Cut freight costs. Most freight 3PLs have very large networks of carriers. A 3PL can leverage the size of its network to find the best carrier for a shipper’s load based on experience, equipment and cost. 3PLs can essentially ‘comparison shop’ on behalf of their shipping customers.
Move freight fast. Again, the large size of a 3PL’s carrier network allows for greater flexibility in meeting the timelines of shippers. From there, communication is vital to iron out schedules that work for shippers and destination facilities. Brokers can also factor in stops to tank washes and other items.
Remove demands of traffic management. When a shipper books a load with a carrier, that shipper typically must allocate internal resources to track that load and manage the timeline and stakeholder expectations. Brokerages can handle those tasks on the shippers’ behalf.
Maintain carrier information. For shippers going it alone and working with different carriers directly, there can be a lot of work that goes into maintaining the carriers’ licensing, insurance and regulatory compliance information. Some 3PLs have a dedicated team whose responsibility it is to keep these records updated and ensure that the broker’s TMS system assigns shippers’ loads ONLY to carriers that are up-to-date and qualified to handle them.
Most of all, the right freight broker provides expertise developed over years of moving just about every dry commodity you can think of. For you and your safety conscious, performance-conscious company, that expertise delivers the ultimate benefit: confidence that everything will run just as it should.