Field Trip: Inspecting Heavy Truck Scales

by | Jun 15, 2015

Heavy Truck Scale inspector Glen Farmer uses a     cart to check scale accuracy.

Inspector Glen Farmer uses a six-wheeled, gas-powered, steel test cart to check scale accuracy. The cart, along with the 1,000-and-500-pound weights together equal 25,000 pounds.

Recycling old appliances, aluminum cans and other heavy metal items not only keeps these items out of our landfills, it sends the customer home with a little spending money. We recently met with Glen Farmer, a heavy scale inspector with N.C. Department of Agriculture and Consumer Services, to learn how scales at scrap metal facilities are checked annually for accuracy.

The Standards Division checks any scales where “money changes hands.” This would include scales at grocery stores, livestock scales, buffets, agricultural-supply centers, highway patrol weigh stations and scrap metal facilities. Scales are checked on an annual basis or by complaint. The only exception is stockyards, which are checked twice a year.

When consumers bring unwanted appliances, metal debris or even old vehicles to a scrap metal facility the items are generally weighed on a truck scale. At some facilities, this scale can record up to 100,000 pounds of weight. The entire weight of the vehicle, trailer and scrap metal is recorded on the scale. After unloading inside the facility, the consumer then drives the emptied vehicle and trailer back over a scale at the exit and this weight is recorded. The consumer is paid for the difference of the two weights. Depending on the amount of scrap brought in, the amount could be a couple of hundred dollars.

To check a heavy truck scale, Farmer uses a six-wheeled, gas-powered, steel test cart. A hydraulic arm is used to fill the cart with certified 1,000-pound and 500-pound weights. For the test, he uses a known weight (the cart plus added weight) and test different quadrants of the scale. A five-section scale would have 18 different test points. There are two different types of truck scales, mechanical and load. To test a mechanical scale, Farmer must move his cart side to side to record weight. To check the accuracy of a load scale, he moves the cart down the center of the scale.

Old appliances, aluminum cans and other metal scrap brings cash to consumers.

Old appliances, aluminum cans and other metal scrap brings cash to consumers.

The Standards Division uses National Institute of Standards and Technology guidelines to determine tolerance levels on the scales. A tolerance level is the amount of weight a scale is allowed to vary. For a scale that can measure more than 25,000 pounds of weight, the tolerance level would be 60 pounds. A scale that does not pass inspection must be pulled out of service until the facility fixes the problem. “Many times the issue is debris buildup in the crevices of the scale,” Farmer said. “Pine straw, cans and other debris can cause the scale not to weigh correctly. Our advice to the company is to power wash or use an air hose to clean the area around the scale.” If the scale is still recording incorrect weights after cleaning, the facility may call a scale-calibration company to fix the problem. Some facilities will have a representative from their scale company go along with the standards inspector on the day of their inspection. This means that most problems can be fixed immediately, and the facility doesn’t have to endure a prolonged shutdown of a scale if problems are found.

Two 1,000-pound weights are used to check the smaller 4x4 scales.

Two 1,000-pound weights are used to check the smaller 4×4 scales.

A smaller amount of weight is used to check the accuracy of the 4×4 scales. These scales are used to weigh smaller metal amounts, such as aluminum cans, and have a much lower tolerance level. For a scale that will weigh up to 500 pounds, the tolerance level is just 1 pound. “My advice to consumers would be if you only have a small amount to weigh, use the smaller scale,” Farmer said. “Its lower tolerance level makes it more likely to be close to the accurate weight, and get you more money.”
Farmer also offers the following advice to consumers when going to a scrap metal yard:

  1. Make sure the scales are clean and that dirt and debris have not gathered in the sides of the scale.
  2. Look to see that the scale is at zero before moving onto the scale in your vehicle, and make sure the number doesn’t fluctuate too much while your items are being weighed.
  3. Know the deductions beforehand. The facility is required to post them clearly. Make sure you understand the deductions for tare, water or foreign materials. Also, know what the facility is paying per pound for metal.
  4. Several locations use newer ATM-like machines for payment. These machines do not give change so they will round up or down to the nearest dollar. There should be a sign informing the consumer that they can request full payment by check if desired.
  5. Call ahead if you have a big load. The facility will appreciate it and offer advice on separating materials.
  6. If you suspect the scales aren’t accurate, call the Standards Division at 919-707-3225.