The Impact of Thermal Expansion on Truck Scale Accuracy and Longevity

Truck scales are vital for a wide range of businesses and industries, serving purposes from ensuring axle weights comply with legal limits to facilitating the buying and selling of truckloads of goods. Workflow needs quick, accurate, and dependable weights, and businesses rely on truck scales to process frequent traffic daily without downtime. Regular maintenance for these scales is often neglected until a problem arises, forcing traffic to be rerouted, drivers to pay for weights at another scale, or the site to be shut down until the issue is resolved. Often, the truck scale issue is due to a physical bind that occurs between the scale and the concrete foundation. For much of the year, the typical cause of a bind is dirt, debris, or spillage that has fallen through the gap and accumulated over time. Another contributing factor of binds to be aware of is thermal expansion, and the effect it will have as the weather heats up, and materials left in the sun start to undergo a physical change.

What is Thermal Expansion?

Thermal expansion is the natural tendency of materials, e.g., steel and concrete, to expand when heated and then contract when cooled. As the scale heats in the summer, a steel-deck truck scale, along with any metal support components underneath and the foundation it sits on, will expand and decrease the tolerances for scale movement. As the scale grows, the binds with the concrete foundation will begin to cause weighment issues, leading to problems the scale was installed to avoid. This thermal expansion affects steel-deck truck scales most but can also cause problems with concrete-deck scales. Thermal expansion is typically not an overnight issue after the first hot day and will often worsen as summer progresses. 

How Thermal Expansion is Detected on a Truck Scale

 Most steel-deck truck scales are exposed to the elements and take direct sunlight throughout the day. The steel can reach extreme temperatures, causing

Binding or rubbing between the scale and the foundation

As temperatures rise, the steel deck expands lengthwise. This may cause the deck to press against the headwalls, whether the scale is pit-mounted or above ground, limiting or preventing essential front-to-back movement.

Shifting or misalignment of load cells

Depending on the type of load cell system used, i.e., canister or link-style, expansion may prevent proper seating or alignment, leading to inaccurate and inconsistent weighments.

Creaking or Grinding Noises:

Unusual noises when a truck enters the scale often indicate that the deck is rubbing against the foundation or headwalls. This can also signal a buildup of debris.

Real-World Effects of Thermal Expansion on Accuracy

 Any expansion in steel can cause measurable weight discrepancies. If the deck becomes misaligned or applies uneven pressure on the load cells, the scale may exhibit:

• Fluctuating weights as temperature changes throughout the day
• Sudden changes in batched weighments without adjustments made
• Challenges with the scale holding zero or wild swings in weight
• Negative weights after a vehicle leaves the scale

How to Manage Thermal Expansion

Thermal expansion cannot be prevented from causing physical changes to a truck scale. However, steps can be taken to avoid stoppages or a decrease in production brought on by the changes due to thermal expansion: 

• Proper Gap Tolerances
  During installation, a minimum ¾-inch gap should be left between the truck scale and foundation to allow for seasonal changes. This is the responsibility of the scale installer and cannot be easily fixed without extensive work and site downtime. Any gap issues during installation will be exacerbated by thermal expansion, so scales with known clearance issues should be maintained more frequently. 
• Regular Inspections
  Check for rubbing, binding, buildup, or shifted components, especially during seasonal temperature swings. This should be done frequently by internal personnel, with a more thorough inspection performed by licensed scale technicians on a scheduled basis. 
• Routine Calibration
  A truck scale should be tested and calibrated regularly to compensate for environmental effects. During this service, the checking system, suspension, and mounts will be inspected to ensure proper adjustment of the bumper bolts and sufficient serviceable life remains for the components. Any concerns observed during the internal regular inspections will help the technician keep the scale running optimally. 
• Remove Physical Obstructions
  Issues arising from dirt, debris, or spillage between the scale and foundation walls can become more frequent during thermal expansion, and the scale should be cleaned regularly. Daily spot checks help prevent multiple-day cleaning services due to build-up. 

Many truck scale manufacturers use a checking system consisting of bumper bolts with accompanying strike plates to help restrict lateral movement from traffic, protect the headwalls from damage, and re-center the scale for the next vehicle. These bumper bolts are recommended to be adjusted as the temperature shifts and the spacing required to maintain proper scale movement changes. Adjusting for hot weather during summer, the bumper bolts need to be retracted to allow the scale to move freely and maintain proper gaps with the strike plates embedded in the foundation. Once the weather cools again at the end of the year, the bumper bolts will need to be readjusted to restrict the available movement, keeping the scale centered on the foundation and its load cells. Scale movement that is not properly restricted, or “checked,” by the bumper bolts hitting the strike plates due to too much gap from the summer adjustment can lead to excessive and abnormal wear of the scale’s components. This wear can cause expensive repairs and unnecessary downtime, due to prematurely failing parts.

What We Recommend

The best offense is a good defense, and, just like we should all get regular checkups to catch health concerns early, a truck scale needs routine, preventative maintenance to keep it working and business flowing. Having a licensed service provider maintain the scale at scheduled intervals is the best way to keep the scale healthy with consistent weights. Between these service visits, regular internal inspections can help identify signs of thermal expansion and binding before they become problems. The frequency of maintenance required depends on the site and usage rate of the truck scale. We recommend that any truck scale with a checking system be maintained at least biannually to allow for bumper bolt adjustment and help avoid issues arising from thermal expansion.