How To Choose a Load Cell for Harsh Operating Environments

There are a huge number of factors that can affect the performance and accuracy of the load cells in your industrial scales and weighing equipment. Regular servicing, testing and calibration are important, however, it’s even more crucial to choose the right equipment from the start.

Choosing the right equipment isn’t always about brand names or equipment cost, though having a quality brand manufactured by your supplier with localised production is often a good choice. It’s really about doing some research and getting long-lasting, accurate equipment that can handle the environment in which they’ll be used, hot, cold, wet, dry, humid or explosive.

How Can Load Cells Be Damaged?

When we talk about harsh environments, what exactly does that mean? A number of factors can cause damage to load cells, so you need to consider where, when and how it will be used. A harsh environment certainly isn’t restricted to dusty outdoor conditions. Some of the factors to consider are:

• High temperatures
• Extreme cold temperatures
• Humidity
• Presence of corrosive chemicals
• Large amounts of moisture (from washing down)
• Uneven loads
• High vibrations
• Shocks from sudden heavy loads

This list isn’t exhaustive, but it gives you an idea of the things that can damage load cells in certain environments. It’s essential to understand your operating environment when choosing load cells to ensure your weighing equipment remains accurate and in good working order and fault free.

Load Cell Features to Consider

When selecting weighing equipment, whether it be for small-scale laboratory weighing or larger applications like weighbridges, you need to take into account the specific features of your load cell. Accuracy is important, and damaged components are sure to affect accuracy. Here’s what you should consider.

Materials

A load cell is a metal element. However, there are different metals used for different load cell applications. The most common are steel alloy, aluminium and high-grade stainless steel.

Steel Alloy – This is the most commonly used metal for load cells, but it is best suited for dry environments. It offers excellent performance and is cost-effective. However, it doesn’t handle moisture well, with corrosion being a major concern and thus premature failure in the wrong environment.

Aluminium – Load cells made from aluminium are found in low-capacity applications with high accuracy. While it performs well in the right environment, water and chemicals can wreak havoc on it, so you should only consider aluminium for dry applications or wet applications with higher IP rated IP67 and above, but avoid applications with harsh chemicals that attacks the aluminium body.

Stainless Steel – For wet applications, you can’t go past stainless steel. Not only is it strong, but also resistant to corrosion. It will handle water from washing down and most chemicals that it would be exposed to. In severe wet environments choose loadcells that are hermetically sealed with an IP rating of IP68 or IP69K.

High-temperature Components

Most quality load cells are designed to remain accurate between -20°C to +80°C, but when using a scale or weighbridge for legal for trade applications the OIML standard requires testing from -10°C to +40°C, if the temperature exceeds this there is no guarantee that the loadcell will remain accurate for legal trade applications, unless you have a high quality loadcell that has been temperature compensated during the manufacturing process.

For super high-temperature environments, you need a specially designed load cell that features strain gauges, wires, solder, cables and resistors that are made for temperatures up to 200°C.

Cables

Every load cell has a cable connecting it to the weighing system controller, but they aren’t all created equal. These cables can suffer from water or dust ingress, so they should be rated accordingly.

If you’re operating in an environment of high temperatures of chemical exposure, you should look for cables that are coated in a protective material such as Teflon.

For weighbridges that are mainly located outside in all weathers and the cables have the possibility to be attacked by rodents, also consider stainless steel over-braided cables or anti-rodent cables, and if your cable is detachable from the loadcell as is the case with many Digital Loadcells, ensure that the connector is rated IP68 and is stainless steel to avoid corrosion.

Size

Even in a weighing system with multiple load cells, you need to ensure that each cell can handle the required weight. Every weighing system should have a maximum live load (full scale) and dead load capacity (empty scale), and the load cells need to support that weight.

The general rule is to add the live load and dead load limits together, then divide by the number of load cells. This is the weight that each load cell must be rated to handle. The best practice is to add another 30% to 50% to this number, as it can help protect against shock loads, overfilling or unbalanced loads.

For specialist advice on the most suitable weighing equipment for your needs, contact Weightron Bilanciai. We deliver world-class precision instruments, along with expert repair and calibration services to all typed of industries. To find out how we can help, contact our friendly sales and support team today.