In the lifting and rigging industries, understanding the concept of forces is paramount for safe and efficient operations. Two fundamental types of forces encountered in these industries are tension and compression. While both involve the transfer of loads, they differ significantly in their nature, calculations, and applications. We explain these differences further and provide valuable insights on how to measure these two forces to keep you safe.
What is Tension Force?
Tension force occurs when an object such as rope, cable, or wire is pulled in opposite directions along its axis, or length. The force passes through the object and acts to elongate or stretch it, placing it under tensile stress. Normally, this happens in lifting jobs where a crane or other equipment hoists the heavy load with proper lifting slings across a certain area. The tension force that occurs levels out with the weighted object, creating an equilibrium within the setup.
Calculating tension force requires using the basic principle of Newton's second law, which states that force (F) equals mass (m) multiplied by acceleration (g):
Tension Force (F) Formula: F = mg
In the case of tension forces, the mass refers to the lifted load, and acceleration refers to the gravitational force that pulls down the object in the opposite direction of the lifting direction. Additionally, factors such as friction, wind, and dynamic forces must be considered to ensure accurate calculations.
Graphic from ScienceFacts.
A simple lifting setup shows the weight of the object pulling down on the rope, causing it to become taut. The heavier the mass of the load, the higher the tension becomes. Therefore, make sure to always check the rated load capacities for your lifting equipment before you start a job. This prevents any accidents from occurring and promotes a safer workplace.
NOTE: Keep in mind, more complex lifting systems requires additional calculation such as trigonometry and vector analysis. This helps determine the tension forces in different parts of the rigging system. These complex lifting systems involve multi-leg lifting slings, their angles, and additional dynamic forces.
What is Compression Force?
Unlike tension forces, compression forces act to push together, or compress, and object. With forces applied inward rather than outward, the molecular composition of the object changes, as well as the amount of kinetic energy. As the outward forces push inward, the compression force increases.
To calculate compression force, take the total weight of the material (P) and divide it by the area of the material resisting the load (a):
Compression Force (F) Formula: F = P/a
In this formula, the weight of the object is evenly distributed across the given area. An example of this would be outrigger pads, where a flat surface lays flat on the ground underneath an outrigger. The weight of the outrigger arm presses down on the pad while it makes contact with the ground. Because of this, the force from the arm creates and equal opposite force from the ground - one of Newton's Laws. Therefore, compression force occurs, as shown in the graphic below.
Graphic from Tekscan.
Compression can be found in numerous applications in our everyday lives. An example of this includes spring applications, where springs compress underneath weight, increasing the compression force and kinetic energy. When the weight is release, the spring expands causing kinetic energy release and the compression force to decrease.
Compression forces are critical in stabilizing and supporting loads in lifting and rigging operations. Structural components such as beams, columns, and frames withstand compressive forces while maintaining stability. For instance, in construction projects, cranes exert compression forces through hydraulic cylinders to lift heavy loads and place them in position. In the lifting and rigging industries, compression forces occurr when stacking objects, using hydraulic jacks, or supporting loads with columns or beams.
Calculating compression forces also involves understanding the properties of the materials involved and the structural design. Engineers consider factors such as the material's compressive strength, dimensions, and load distribution to calculate the maximum compressive force safe for application. Structural analysis methods such as finite element analysis (FEA) help to ensure structural integrity.
Testing Tension and Compression Forces in Lifting & Rigging
Many engineers deal with tension and compression forces across the lifting and rigging industry, as well as construction, mining, staging, shipping, drilling, and military operations. While these forces are very common, they must be carefully managed to prevent overloading, excessive stress on equipment, or catastrophic failures. Testing these products for their tensile and compressive strengths is a common practice to ensure the materials hold up in different applications.
Safety measures such as load calculations, inspections, and regular maintenance are essential to ensure safe lifting practices. Understanding the limitations and properties of materials is vital to prevent structural failures and ensure worker safety.
Measuring Tension and Compression Forces
When it comes to keeping your equipment and personnel safe on the job, it's important to measure the tension and compression forces of your applications. StraighPoint Load Monitoring Cells allow you to measure the tension and compression of your equipment, prolonging its working life and keeping the area safe from potential damages or accidents.
Below are two types of transducers used to measure these two forces:
- Tension Load Cells measure tension in overhead weighing, testing, bollard pulling, cable tensioning, and heavy lift applications. These state-of-the-art devices handle tension reading capacities between 1-ton to 500-ton, and are available in different models, including cabled, wireless, and Bluetooth versions.
- Compression Load Cells work by calculating the center of gravity of large and heavy objects used in structural weighing. Measuring loads up to 1,000-ton, these durable compression load cells handle heavy-duty loads while remaining compact in size. These models come in wired or wireless makes to keep you safe during load testing.
We offer additional load cells to suit your load monitoring needs including line tensionmeters, running line dynamometers, shackle load cells, and more. Get in touch with our product experts at their contact information listed below to answer any questions around StraightPoint Load Monitoring Cells, as well as tension and compression forces in your setups.