In industries from mining and manufacturing to construction, transportation, and agriculture, the need to weigh or measure inputs, outputs, and applied force has grown in recent decades to improve production safety and control costs.
What follows is a quick primer on what design engineers need to know about measuring weight or force with load cells, load pins, and tension links (also known as tension cells), and why working and consulting with the right vendor partner can be a critical choice in the process.
The Basics
Load cells can range from versatile single-ended shear beam, which can be used in weighing applications such as blenders, hoppers, and floor scales, to double-ended shear beam, which can be used in applications such as tank weighing and large capacity platforms.
Standard load cells and tension links are typically used if the system is standard or an engineer can adapt the system to an off-the-shelf item. This occurs in applications where there is some design flexibility in the early stages of design. Most load cells, load pins, and tension links are custom when they must be adapted to fit existing systems. Additionally, designers should consider the benefits of custom load cell solutions for new designs where their use enhances the overall system integrity, safety or performance.
Avoiding Pitfalls
To avoid pitfalls, it is advisable for engineers to insist on a regulatory-approved quality management system that traces the load cell manufacture at each critical step from start to finish. Engineers should also request a design flow checklist from any weighing system vendor to ensure that nothing critical or even desirable is missed.
Design engineers benefit from asking weighing system vendors to validate the output of their load cell component against simulated real world conditions. To ensure output stability, engineers also need to know how the load cell output may vary depending on material strain over time. Conducting a creep test to determine how stable the output is over time can also be important.
Because the accuracy of any load cell is only as good as its calibration, it is vital that the reference cells in any testing system be traceable to a trusted standard such as that of The National Institute of Standards and Technology (NIST). To guarantee that your supplier complies with the Verified Conformity Assessment Program (VCAP), a program proposed by the National Conference on Weights and Measures, it is also a good idea to ask for a copy of the VCAP auditor’s report.
As design engineers respond to the growing need to weigh or measure inputs, outputs, and applied force to improve production safety and control costs, working and consulting with the right vendor partner can be a critical choice in designing weigh systems with the optimum load cells, load pins, or tension links.
Massload Technologies Inc.
www.massload.com
Filed Under: Test & Measurement Tips, Safety systems + components
