Understanding Working Load Limit and Breaking Strength

Safety is first and foremost in the shipping industry. Logistics professionals use load-bearing equipment such as rachet straps and chains to secure cargo during transit. Every rigging component comes with a working load limit and breaking strength to determine its safety factor ratio. If you are unfamiliar with these terms, we will explain their purpose and significance in this guide.

Defining Working Load Limit

The working load limit (WLL) is the maximum amount of weight a piece of equipment can handle under normal conditions without posing any safety risk. When determining the WLL, logistics professionals should assess the equipment’s material, design, and the conditions under which it is used. For example, temperature and humidity can compromise a strap’s ability to retain tension for securing cargo in a semi-truck trailer. Regular inspections and maintenance are crucial to ensure the equipment remains within its safe operating limits.

Defining Breaking Strength

Breaking strength simply refers to the maximum load a material or component can withstand before it fails. While you should never aim to reach this point, knowing your equipment’s breaking strength helps you understand its overall durability. A piece of rigging equipment’s breaking strength will always be higher than its WLL.

It’s key to understand that every element of a cargo securement system has its own breaking strength, and rigging components are only as strong as their weakest element. For example, if rachet straps and their tensioning device have a breaking strength of 12,000 pounds, but the end fittings have a breaking strength of 10,000 pounds, the overall breaking strength is 10,000 pounds.

What Is Safety Factor?

Safety factor is a concept in the logistics industry that combines WLL and breaking strength to assess a piece of rigging equipment’s operating limits. It is represented in a ratio that indicates how much stronger a system is compared to the required strength for a given load.

For instance, if a piece of equipment has a breaking strength of 20,000 pounds and a working load limit of 4,000 pounds, the safety factor is 5:1. This means the equipment is designed to handle loads five times greater than its WLL, providing a considerable margin of safety.

Understanding WLL and breaking strength is crucial for the safety of cargo and logistics professionals. Adhering to rigging equipment’s WLL reduces the risk of equipment failure, extends its lifespan, and helps maintain compliance with industry standards.