This is the fourth in a series of blogs discussing factors to consider when designing modern lift trucks.
Lift trucks operate in a wide range of harsh environments. Depending on the use-case, the lift truck’s electronics can be subjected to a range of severe shocks and vibrations. They can also face wide and rapid swings in temperature and humidity, moving from freezers to outside temperatures in the middle of summer. Ingress of water, dirt and chemicals can also pose a risk to sensitive electronics. These factors can potentially damage the components, such as on–board battery chargers, which is why prudent lift truck designers should design their products for worst-case operation.
Causes of Component Failure
Components onboard a lift truck can experience failure due to vibration, shock, temperature, humidity and condensation.
- Every lift truck exposes the components to different vibration profiles, which vary significantly in frequency. For on–board battery chargers, vibration can shake the components inside the charger loose or cause damage, leading to charger failure.
- The lack of suspension in most lift trucks can lead to significant mechanical shock. Repeated shock can damage the components – from the lift truck being driven over a speed bump, hitting a heavily loaded pallet, or running into a wall.
- Lift trucks operating in high– or low-temperature environments can cause components to overheat or fail quickly.
Hot environments can create significant humidity. Batteries and other components can overheat and fail when they are exposed to excessive heat and humidity.
Internal condensation can occur when a lift truck is driven from a drive-in freezer into a hot warehouse – condensation can lead to electrical shorts and material degradation.
Any damage to the battery, charger or other electrical components in the machine can result in severe and costly maintenance issues. Lift truck designers should choose components that are designed and tested for maximum reliability in the harshest environments.
Testing for Lift Truck Reliability
Charger and other component manufacturers should validate their product‘s reliability and assess its tolerance to “worst-case” operational conditions while mounted onboard a lift truck. Many test methods can simulate real-life stressors on the component to confirm that it will not fail during everyday use.
Appropriate mechanical tests determine how shock and vibration can impact the performance and robustness of electrical and mechanical components. These tests are used to demonstrate mechanical weaknesses and pinpoint areas prone to degradation. Thermal tests verify that the component will continue to operate after prolonged exposure to a wide variety of temperatures, whether operating or not.
Component manufacturers should design their mechanical test suites based on published protocols and standards, setting test levels to represent strict user requirements. The International Electrotechnical Commission (IEC), for instance, has developed international test methods to test a product’s ability to withstand a wide range of shock and vibration profiles. Another useful series of tests is defined in GMW3172, an automotive standard created by General Motors to test electrical/electronic devices with circuit boards in stressful environments. These tests subject a large sample of products to extreme shock, bump, vibration, humidity, and temperature cycling at an automotive-grade level. They also accelerate the on-board component’s ageing to prove that they will meet the design life objectives.
Battery chargers and other electrical components onboard the machine must be designed and tested for maximum reliability in the harshest environments.