Chains have long been used to hoist, tie-down, and tension cargo in numerous applications. Whichever industry the chain is used for, whether it is for the logging industry or transporting machinery, it is critical to know a chain’s working load limit.
The working load limit is the quantity of force that chains are able to withstand prior to them breaking. Chains have a third of their break strength’s working load limit. For purposes of safety, different chain grades and materials have been properly differentiated, as well as their specific applications. Safety standards and proper regulations for the use, testing, manufacturing, and repair of chains were published.
What are the chain grades?
Chain grades were placed on a variety of chain products as a safety measure. These grades help identify a chain’s ultimate breaking strength. They appear as G70, G30, G100, etc.
The number seen after the letter should be read as Newtons per millimetre squared or N/mm2. It represents the chain’s maximum stress at ultimate strength. Three things to consider when choosing chains are the following: metal tensile strength or grade, chain thickness or diameter, and opening size or coil.
- Chain grade is the metal’s tensile strength. Manufacturers use the grade number to indicate a chain’s break strength. When a chain’s grade is high, the greater is its break strength. A galvanized chain indicates the quantity of carbon present in the steel.
- Galvanized “hot dip” steel is a common metal finish that is suited for use in saltwater. Stainless steel is mostly seen on deck and usually used for anchor chains. Galvanized steel is literally dipped into a zinc bath at a temperature of 800 degrees. The molecular alloy produces a resistant corrosion metal.
- Chain links also vary and need to fit at mid-chain and not at the end link. Longer links allow shackles bolts to fit in any place along its length compared to standard coils that have shackles that suit the end links. Plus, long links allow the chain to weigh lighter compared to a standard chain with an equal length.
The Facts About Working Load Limit
A chain’s working load limit (WLL) is used as a safety measure to identify the chains which are sufficiently strong for overhead lifting. The process of lifting a load could be lethal especially if the incorrect equipment is used.
Moving a heavy load across the ground is beneficial as the ground helps support the load. The coefficient of friction must be overcome in order to effortlessly move the load. Also, the working load limit of the chain needs to match the load’s weight. The chain must manage the applied tension.
Once the load is lifted off the ground, gravity must be overcome. The working load limit of the chain must be sufficiently strong to support the load’s weight as well as any added forces from the hitch types and angles used.
- A chain’s WLL is the maximum tension that can be placed on an undamaged or brand new chain. The WLL’s rated capacity is shown in pounds.
- The WLL is computed by dividing the chain’s minimum breaking strength by its assigned safety factor rating.
- The chain’s WLL is determined by its diameter and grade.
- Factors that affect a chain’s WLL is constant wear, use, twists, alteration, corrosion, misuse.
- Chains must be inspected regularly to make sure it is safe to use.
- The WLL is different from the tensile or breaking strength. Chain manufacturers set the WLL to determine the maximum force that can be used on the product.
- The WLL is a quarter or a fifth of the chain’s breaking strength. When a ratchet with a chain is used, the WLL is the lowest rating of the components utilized.
The Importance of Chains
Chain binders are important equipment used by the flatbed transportation industry for heavy hauling. Truck drivers have the responsibility to secure their loads for the purpose of safe and proper transport.
In the event that a driver fails to have his load secured, he could be subjected to fines, load damage, or worst – injury or death.
Different Types of Chain
The American Society for Testing and Materials requires alloy chains to be elongated to at least 20% prior to its fracture. Chains used for overhead lifting must either be Grade 100 or Grade 80.
- Rated trailer chains can be had in 8 to 13 mm sizes. These chains have a standard galvanized finish. Such chains are not suited for lifting but are ideal as safety chains for trailers.
- Grade 30 chains are affordable multi-purpose chains that are also referred to as Grade 30 Proof Coil chains. It is used in barrier chains, light construction as well as the marine industry. These chains are not recommended to be used for overhead lifting. Grade 30 chains possess less carbon and are an effective service duty chain.
- Grade 43 chains are also referred to as High Test Chains or Tow Chains. These chains are commonly used in logging industries and towing industries. These chains are not safe to be used for overhead lifting. Also known as Grade 40, these chains possess more tensile strength and is resistant to abrasion. It is also more costly.
- Grade 70 chains, also known as transport chains or truckers chains, are used for load securement in over-the-road hauling. These chains are also not safe for overhead lifting. Grade 70 carbon chain is heat-treated and has no alloy elements included in the steel. Such chains have the ability to elongate prior to breaking. It possesses no properties for overhead lifting. These chains are utilized as tie-down chains or transportation lashing. Its chromate finish resists corrosion against the elements as well as the harshness of winter road salts and highway use. Though any chain grade can be utilized for tensioning or tie downs, Grade 70 is considered as the ideal chain for securing a load. It is also important to have knowledge of your tensions to allow you to choose the correct chain.
- Grade 80 alloy chains is specially treated with heat to make it safe for overhead lifting. These chains are used for heavy-duty towing.
- Grade 100 chains are premium quality chains that provide a workload limit that is a quarter higher compared to Grade 80 chains. These chains are considered safe to use for overhead lifting.
- Grade 120 chains are new types of chains that are considered 50% stringer compared to Grade 80 chains. Grade 120 chains are also stronger than Grade 100 chains by 20%. These are also more abrasion-resistant compared to Grade 80 as well as Grade 100 chains. Grade 120 chains are safe to use for overhead lifts.
There is a slew of chains as well as fittings present in the market. Besides the chains listed above, there is a chain that can change colour when it is exposed to harsh or extreme temperatures. Fortunately, safety standards are constantly improving as chains are continually evolving. Having sufficient knowledge of chain grades’ working load limits allows you to know which to use for your cargo. Make sure to select the chain that fulfills your specific requirements and needs.
Related article: How To Safely Use Chain Binders To Securely Tie Down Heavy Cargo