How to Determine a Chain’s Working Load Limit
Any job site that utilizes heavy-duty industrial hardware will have a higher rate of job site hazards than the average workplace. Construction zones, transportation services, and manufacturing plants that rely on industrial chains for hoisting, tie-downs, or tension can create dangerous scenarios if they are not mindful of the working load limit. Miscalculations can cause even strong chains to warp or even break – leading to dangerous and disastrous consequences.
According to the latest research, over 2.8 million workplace accidents are reported every year in the US. But over 20% of these injuries occurred on construction sites, many of which involved malfunctioning hardware or faulty setups. This is why organizations like OSHA have put regulations in place regarding equipment usage and inspection.
Properly calculating the working load limit for industrial chains is just one of the preventative measures to take to lower these risks. Even though these chains are made from incredibly durable materials, the load-bearing weight should never exceed or even approach the breaking strength. The working load limit (WLL) of a chain is a safety precaution to prevent this from happening.
Here’s what you need to know about the WLL, how it is calculated, and how to work with it in your industrial application.
1. Understand the Differences Between Industrial Chain Grades
Before considering or calculating the WLL of a chain, you first need to understand the differences between the various grades. The grading system for chains is a number that represents the maximum stress per square millimeter the chain allows for. Industrial chains are categorized into 5 main groups of grades: 30, 43, 70, 80, and 100. Higher grades do exist, but these are the most common grades used within construction, rigging, and transport.
Lower-grade chains (30, 43, and 70) are most commonly used for construction, tie-downs, towing and logging. While these chains are quite durable and have working load limits of up to 15,800 lbs., they are not safe for overhead lifting or rigging applications.
Grade 80 chains are made from a steel alloy, meaning it contains additional metals for added strength and durability. Grade 80 chains have a breaking load limit of up to 190,800 lbs. and a WLL of 47,700 lbs. They are extremely rugged and often come in a black lacquer finish, which protects the links from damage and wear.
Grade 100 chains are 25% stronger than Grade 80 and are most commonly used for chain hoists and overhead or even aerial lifts. This style of chain is available in varying lengths and diameters, which can change the breaking load limit and WLL of the entire chain.
2. Calculating the Working Load Limit
Apart from deciding on the grade, length, and chain link diameter required for the intended application, the WLL is one of the most important factors to note before purchasing. This number is the absolute maximum tension that can be safely applied to an industrial chain without compromising its strength.
The WLL is far lower than the maximum breaking strength of a chain. This is to account for added factors that will create additional tension on the chain apart from the load itself. These factors could include:
- Force of gravity
- Wind
- Load shock
- Rotation
- Speed of operation
- Abrasion or friction
If you are buying from a reputable industrial chain supplier, the WLL should be clearly stated for each chain style option. This number is determined by dividing the minimum breaking strength by the safety factor rating for the chain.
The safety factor is a ratio that states how strong of a weight force the chain can withstand before breaking. For most industrial chains, the safety factor will be 5:1, meaning that if its working load limit is 10,000 lbs. it can technically withstand 50,000 lbs. before snapping. However, this chain should never be used for a 50,000 lbs. load.
3. Only Use Approved Chains for the Job
You should never use an industrial chain for a purpose apart from the applications it is approved for. Lower-grade chains can safely bear thousands of pounds, but they are not designed for heavier duty uses like overhead lifting.
Grade 30 and 43 chains are approved for use with construction, securement, and agricultural use. Galvanized or stainless-steel chains may also be used with marine applications, as they are corrosion resistant. Grade 70 has a far higher strength than 30 or 43 and is generally used for transport tie-downs. And remember that overhead lifting is reserved for Grade 80 and higher-grade chains only.
Finally, be sure to consider other factors that could lower a chain’s strength, such as its age or condition. The WLL is calculated with brand-new chains, not ones that are worn from previous use. This is why close inspection of chains is always necessary before using them for a new load or application.
Over to You
The working load limit for industrial chains is not overly complicated, but you should understand the basic concepts when using this type of hardware. Before placing an order from an industrial chain supplier, always double-check the WLL along with the accurate load calculation.
Finally, be sure that you’re buying top-quality chains made from solid materials for the highest grade WLL. This also ensures the longevity of the chains, so you are safely able to use them over and over again.
Looking for great quality industrial chains or need help calculating the WLL? Elite Sales can help – simply connect with us online to get in touch with an industrial hardware expert.