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Tension Links 101

A tension link load cell is commonly used in lifting, both for short and long distances, and weighing applications. This type of load cell sensor generally has capacities ranging from 2.2K lbf to 1.1M lbf (5 to 500 metric tons). All tension links are available in custom versions and large capacities based on the customer’s project requirements.

Interface’s Tension Link series is manufactured from high tensile aluminum and stainless steel. Matched to shackle sizes, the load links have a rugged design for uses in harsh environments on the surface and in water. The tension links are environmentally sealed to IP65, IP66 or IP67. There are higher ratings available upon request.

A major benefit of Interface tension links is the option for custom designs in dimensions, ratings and capacities. The tension links are easy to install and are highly accurate.  They are compact in size and light weight. Another benefit is the options available, which include standard, wireless and self-indicating, giving the operator a variety of application use cases for quick measurement readings.  Self-indicating tension links have a built-inaudible alarm, which can be set by the operator to warn when an applied weight or force is met.

Often, customers will integrate the tension links with an Interface Crosby styled load shackle for robust applications that require accurate and reliable force measurement used for lifting, weighing, hoisting or towing apparatus that need sensors for safety and monitoring.

Wireless options are growing in acceptance for all types of uses. Interface provides wireless tension links that are compact and reduce the overall product weight based on the casing used to house the small alkaline batteries, which can be easily accessed by removing the telemetry housing cover while the internal electronics remain completely sealed. The antenna is also internally mounted, protecting it from accidental damage during use and handling, which is ideal for harsh environments.

Watch this discussion to learn more about the wireless features of the Interface Tension Links and Load Shackles.

Interface’s most popular tension links include:

WTSTL Wireless Tension Link Load CellDesigned for lifting applications requiring short or long distances. This product can transmit wirelessly up to 600 meters in distance (clear line of sight) to a handheld display or USB base station. Model WTSTL is available in capacities ranging from 11K lbf to 220K lbf (5 to 100 metric tons). Custom versions and larger capacities are available upon request.

WTSLTL Lightweight Wireless Tension Link – This smaller version ranges from 1 to 300 MT (2.2K to 661K lbf) and uses a lightweight aluminum construction, with an internal antenna and 1200 hours batter life using standard AA batteries.  It has high accuracy and uses license free 2.4GHz radio. There is an option to use this with telemetry and/or software for readout and reporting.

ISITL Self-Indicating Tension Link Load CellManufactured from high tensile aluminum to minimize weight, the ISITL is great for lifting and weighing in rugged or harsh environments.  The self-indication tension link load cell is ideal for mobile use cases.  It is simple to install and is matched to standard shackle sizes. They have a built-in display for applied weight or force in tons, kgs, lbs or kN. Interface can also offer a custom software to meet any specific application requirements for digital display or readouts.

ITL Tension Link Load Cell – This basic tension link can be amplified with 5VDC, 10VDC or 4-20mA Outputs. It can also be made to meet ATEX requirements. Model ITL is available in capacities ranging from 11K lbf to 220K lbf (5 to 100 metric tons). Custom versions and larger capacities can be requested at no additional charge, based on the exact specifications needed by the customer.

To learn more about our wide variety of load pins, load shackles and tension links, please visit www.interfaceforce.com/product-category/load-pins-tension-links-and-load-shackles/.

 

 

Understanding One-Cell Force Measurement Systems

When it comes to load cells and force measurement systems used to test and validate product designs, the options for different configurations is nearly endless. In fact, Interface has tens of thousands of force measurement products in standard, modified and custom-made configurations.

In our recent post, Considerations for Steel, Stainless Steel and Aluminum Load Cells, we detailed materials used in load cell construction. These considerations are important based on the project specifications for accuracy, quality and reliability in test and measurement.

Similarly, understanding the system configuration is another critically important factor to setting up the correct test for receiving accurate data.  A simple system configuration used for less-complex testing is known as one-cell or single load cell system.  They are popular for performance and durability testing.

How do one-cell systems work and what are the benefits and trade-offs?

One-cell systems are developed by using a tension cell and mounting it through a rod end bearing and clevises. If the cell is properly oriented with the dead end going to the support, the only other major consideration for this system is the elimination or reduction of possible parallel load paths. This type of simple system is attractive to some testing engineers and product designers because it is cost effective and can provide very accurate measurements when using Interface precision load cells.  It is important that the load meets the criteria for the test system.

In this figure, it shows a high-impact one-cell system platform. This one-cell system can withstand the high impact of rough treatment from certain applications such as large drums, LPG tanks and more.

The downside to using a one-cell system is that the center of gravity of the load must be placed directly on the mark for the system to work properly. However, this can be accounted for by positioning the fences as shown in the high-impact one-cell platform diagram, so that the center of gravity is located properly when the application you are measuring is shoved up against fences.

The actual load at the center of gravity for your application will be factored by the lever arm (as shown below):

The one-cell system works simply because the location of the center of gravity is under control. If the force on the primary axis of the load cell bears the same relation to the location of the center of gravity and the load under all conditions, the scaling will be correct. Whether using a one-cell or two-cell system, the system must be designed to retain its integrity.

This has been a brief overview of a one-cell system, which is detailed in Interface’s Load Cell Field Guide.

To learn more about these systems and to determine if your application test can utilize the simplicity and cost savings of a one-cell or two-cell system, contact our systems experts and application engineers.

Considerations for Steel, Stainless Steel and Aluminum Load Cells

In the world of force measurement and load cells, one size certainly does not fit all. There are thousands of different options for size and force ranges, and our load cell configurations vary widely based on the requirements of your project. Whether you are designing and testing products for the medical industry, or measuring force deep within a mine shaft, users need to be aware of certain force product details to ensure their getting the right tools for the job.

One of the critical considerations in the load cell selection process are the materials used in the construction of the load cell. If you did not already know, load cells can be made from several different metal materials. This list includes aluminum, steel, stainless steel, titanium, Inconel®, and even glass or carbon fiber.

Each material used depends on the end-use requirements and the need for strength, resistance, hysteresis, environmental concerns, output signal, size and weight, and budget.

For this post, the focus is on the three most used materials for load cells: aluminum, steel and stainless steel. Below is an outline comparing the different factors that make one material better than the others based on the testing requirements and use case.

Aluminum

Aluminum is a light and inexpensive metal, making it the most budget-friendly of the three. It is also the easiest to machine, as it does not require a heat treatment or secondary machining. Aluminum has a higher thermal conductivity, which can be a good or bad thing depending on your need. The hysteresis of aluminum load cells is also the lowest on this list. The most prominent benefit is that it can be used for constructing smaller load cells, so if size, weight, and total volume of the load cell is a key consideration for your project, aluminum would be the metal we’d recommend.

In adverse, when dealing with aluminum load cells it is important to understand that it is the softest material on this list, which means it is more susceptible to damage. This also means that it cannot handle as much stress, resulting in a lower output signal.

Steel

Steel is a stronger metal, so it is a bit more expensive than an aluminum load cell. It is still comparatively cost-effective. It also has the highest strength of the three materials outlined here. This means it is the least susceptible to damage and has the highest signal output. It also has higher environmental resistance than aluminum and less heat conductivity, which once again can be good or bad depending on the project.

The downsides to steel include the fact that it is more complicated to machine and requires a multi-step heat treatment operation. Compared to aluminum, the hysteresis is generally slightly higher for certain load cell designs. This can be remedied with additional engineering. It also does not provide the benefit of size, weight, and total volume flexibility that lighter aluminum provides.

In our opinion, steel provides the best value for a load cell in terms of money and performance, if size, weight and total volume is not an issue with your project or application.

Stainless Steel

Stainless steel is a stronger material than aluminum; however, it is not as strong as steel. The output signal performance for stainless steel load cells is somewhere in the middle of steel and aluminum. The main benefit of stainless steel is that it is the best material to use in a corrosive environment because of the metal’s environmental resistance properties.

The downside to stainless steel is that it is a bit more difficult to machine but does only requires a simple heat treatment process. It is also the most expensive metal of the three and has the highest hysteresis. We would recommend stainless steel when the user needs to collect data in a hazardous environment. Read more here about our Ex Rated products.

Understanding the difference between these materials is critical to getting the most accurate data from your force tests based on the environment and the nature of the product or system you are testing.

If you’re unsure about the requirements your project demands, be sure to reach out to us at 480-948-5555, or visit our website to be connected with an application engineer. We can discuss your specific challenge and help you select the load cell with the right material for your needs.

Contributor Ken Vining, Chief Engineer at Interface