Choosing the Correct Rocker Column Load Cell Cups

Load cells used in truck scales or rail scales are exposed to temperature-induced expansion and contraction. Canister load cell technology couldn’t account for the temperature-induced errors, so rocker column load cells were developed to replace them.

Rocker column load cells have rounded upper and lower loading surfaces that are spaced out from the strain gages. This is to avoid stresses from the high contact areas. Spherical radii are either placed on the loading surface or where the load measurement is made and at the outer extremities. This is to avoid dispositioning as the column rocks and minimize errors caused by weighbridge shortening. It is important to choose a rocker column load cell that will compensate for when the load cell is offset. Rocker column load cells should also be hermetically sealed at both the strain gage location and cable entry. Compensating for load errors are vital to obtaining accurate measurements and meeting quality standards.

Truck scales are often used to sell products by weight, so they need to meet NTEP quality standards. It is important to have the correct load cell cup installed! Here’s a video to help you make sure you have the right cups for your rocker column load cells. Contact us for your truck scale calibration or installation. We’d be happy to help!




Increasing the Efficiency Rate of Water Consumption in Agriculture

 

 

 

 

 

 

 

 

According to the Food and Agriculture Organization of the United States, Agriculture accounts for 70% of all water consumption; however, the efficiency rate of that water consumption is very low. Most of the water drains off or is evaporated. Only a small percentage of that water consumption is actually used for plant growth.

What effect does this have on the Agriculture industry? A lower efficiency rate results in wasted resources and decreased productivity. As fresh water supply becomes increasingly limited as the years go on, it is imperative for the Agriculture industry to strategize ways to increase water consumption efficiency for sustainability.

A University measured plant performance based on efficient water consumption. Their goal is to secure future food production no matter what climate challenges are faced. Potted plants were monitored continuously for their water consumption during growth and weighed in ambient conditions.

The measurement system needed to be resistant to temperature noise to provide reliable and accurate results. Load cells that were specifically tailored to greenhouse conditions were used to track small increments in weight over a long period of time. These load cells withstood the temperature fluctuations and high humidity environmental conditions. This measurement system is expected to save costs by optimizing nutrient delivery and boosting crop yield, due to early detection of stress and reducing water and fertilizer use.

Though this was not a Solutions Project GRM was involved in, this goes to show how metrology is used to solve various problems. If you’d like to decrease wasted resources, increase productivity and efficiency, we’d love to help you strategize! Our Solutions Team specializes in process automation and custom measurement systems to meet your specific goals.

 

 

SOURCE:

“Load Cells Help Optimize Water Efficiency In Stressed Climate.” Weigh & Measure, Apr. 2019, pp. 10+.

5 Factors to Consider When Choosing a Load Cell

Determining The Correct Load Cell

To determine the correct load cell, there are several factors one needs to consider.

  1. Observe the environment your weighing system will be in and make note of the conditions. Is this a hostile environment with extreme temperatures, corrosive chemicals, excessive moisture, high vibration, or unequal loads?
  2. Will your weighing system be washed down with cleaning chemicals or at a high pressure?
  3. Load Cell Material
  4. Cable Composition
  5. Size

Using these conditions to determine the correct load cell and components will allow the weighing system to operate reliably.

Load Cell Material

A load cell is typically composed of tool steel, aluminum, or stainless steel. Tool steel is best for dry conditions because excessive moisture can rust the steel. This is the most common material for load cells. It is suitable for single and multiple load cell applications, and limits creep and hysteresis.

 

Aluminum is used for low capacity, single point load cells, and isn’t suited for moist or harsh conditions. Both 2023 Aluminum and 4340 Tool Steel are popular options because they return to their starting position after weighing.

 

Stainless Steel may be the more expensive option, but it performs the best in harsh conditions. It can withstand corrosive chemicals and excessive moisture. There are some pH levels that attack even the stainless steel, so you may want to check to see if you need to apply a coating to the stainless steel load cell.

Cable Composition

Now to think about the cables, strain gauges, resistors, wires, and seal options.

 

Most cables are made with a polyurethane jacket that protects against moisture and debris. If you need a cable to withstand extreme temperatures or corrosive chemicals, you will need a cable made with a Teflon jacket.

 

When it comes to sealing, there are several options. There’s a rubber boot, a glued cover, a potted strain gauge cavity, or a hermetically sealed load cell. The rubber boot, glued cover, or potted strain gauge cavity filled with material will keep the load cell protected from debris and moderate moisture. The hermetically sealed load cell will protect against chemical applications and excessive moisture. These load cells are typically made of stainless steel and has a welded barrier to cover the strain gauge cavity. The welded barrier further protects the load cell from harsh environmental conditions.

Size

The last factor to consider is the load cell size. Will this load cell be subjected to overloads, excess weight to one side, shock, or live and dead load miscalculations? You’ll want to be sure your load cell can deliver reliable results even under these conditions.

 

To determine the right load cell size, add the live load and dead load and divide by the total number of load cells. “This gives the weight that each load cell will be subjected to when the vessel is loaded to its maximum capacity.”

To account for overfilling, shock or unequal loads, add 25% to the number calculated. To account for excess weight on one side, have all load cells in the system account for the larger capacity. All load cells must have the same weighing capacity.

 

These are factors to consider when choosing the correct load cell for your application, but this is just part of the process. The installation is a critical component to ensure accurate weighing. You will want to seek out a professional to do the installation correctly. Give us a call to discuss your load cell application or request a quote!

A Load Cell & PLC Solution

An agricultural company Grand Rapids Metrology has a long-standing relationship with contacted us with a need for a customized solution. Based near Grand Rapids, MI, they previously had four silos in place that incorporated a fast load out system which was originally crafted by Grand Rapids Metrology. Throughout the years as technology advanced, the system needed updating. The customer trusted Grand Rapids Metrology to continuously work with them and update the fast load out system numerous times.

In recent years, the company invested in eight more silos each with a capacity of roughly 225,000 pounds. GRM partnered with a third-party contractor to install the eight new silos and solely installed four new load cells under each silo with indicators, one dedicated for each group of four silos. The previously updated fast load out system was replicated and implemented twice during this project totaling to three systems with twelve silos. Our extensive relationship and knowledge of this company has allowed us to scale to their growth and continue to implement such projects.

One of the company’s biggest requirements for the new system was the desire for printed tickets to include the product name and product code. GRM has vast experience with Ethernet IP and PLC (Programmable Logic Controller) communication as well as incorporating PLC’s and indicators. We were able to create communication between the PLC and the scale indictor utilizing Ethernet IP which allowed the printed weight tickets to include the product code and product name, just as the company had hoped.

A challenge encountered during the process was working to certify the company’s outgoing products on their trucks for Legal for Trade. GRM worked closely with the customer and the State of Michigan to fulfill the requirements of having products Legal for Trade, one of those being an accurate weight measurement. The new communication system and load cells produced extremely accurate results. Our Solutions Team also integrated an auto- adjusting and auto-learning pre-act system that allows the measurements of product to become more and more accurate as time goes on.

The use of load cells has applications in numerous industries as does a communication system similar to the Ethernet IP and PLC one utilized here. For inquiries about our custom engineered solutions, please contact of Director of Operations, Terry Benjamin by email at terry.benjamin@grmetrology.com or by phone at 616.249.1210.