How to Balance Mix from the Truck
BY John Ball
With workers in short supply, not every paving crew has the luxury of a dump man in addition to a paver operator on the job. Whether you have a miscommunication between the haul truck driver and paver operator or an improperly loaded truck bed giving you trouble, you can adjust to compensate for a poorly charged hopper or other unbalanced mix movement before it gets out of hand. Here are some tips to overcome the problem.
In this picture, we see the U-shaped truck bed has allowed the mix to move without getting stuck in corners or along tracks. What’s happened, though, is a triangle shape has formed in the center of the bed. The material is flooding the center of the hopper and conveyors. Because the mix is in the middle of the head of material, you can expect to have an unbalanced screed.
To correct the unbalanced screed, first look to the flow gates. Not all pavers are equipped with flow gates, but the machine in this picture is a Blaw-Knox paver with them. Raising or lowering the flow gates will influence the amount of material moving through the conveyors to the center of the screed. For the problem here, lower the gates about 4 inches. This will reduce the mix in the middle of the augers, balancing the head of material.
The next option the paver operator can try is to manipulate the speed of the conveyors. Is it at 60 or 70 percent? If the conveyors are overfilling, you’ll want to slow them down.
Balanced Charging. In this picture, you can see the mix leaving the truck bed is organized in an almost straight line, meaning it’s moving in an almost balanced manner through the paver and to the screed. This shows me I’m using a good flow of material across the width of the screed.
A third option is to check the feed sensors for height or distance from the head of material. The feed sensors are typically set 18 inches from the top of the pile and they “tell” the mix to come to the endgate or to slow down. If the endgate area needs more material, the feed sensor will “tell” the mix to come on in and fill that area. You may need to adjust the feed sensor height or distance to the head of material briefly to encourage its messaging—to encourage it to tell the mix to come to the endgate.
The final option is to check the feed sensor for speed. We want the augers to run 100 percent of the time, but not a 100 miles per hour. Instead, check the auger speed and adjust the feed sensor so that it directs the material to move to the endgate appropriately.
In this second image, we can see a straight line of mix near the “end” of the truck’s dumping load. You want the material to move as a mass out of the truck to charge the hopper and you want to see that line across the bed so you know the balance of material moving through the paver is perfect.
If you can get dump the trucks in this manner, so that the line of moving mix is straight across the bed, then you can bet the material behind your screed is balanced.
John Ball is the proprietor of Top Quality Paving & Training, Manchester, New Hampshire. He provides personal, on-site paving consulting services around the United States and into Canada. For more information, contact him at (603) 493-1458 or tqpaving@yahoo.com.