What is Chain Grade?
Generally the meaning of Chain Grade Numbers used by manufacturers designate one tenth of the actual grades or strength designations. This therefore indicates that grade 80 is 800; grade 70 is 700, and so on.
Know Your Chain Grade
Knowing the Chain Grade is extremely important when working with any kind of link chain for towing or lifting a load. Three considerations for choosing the correct chain grade for your job are grade, diameter and coil. You may also want to consider the finish for corrosion resistance.
- Grade refers to the tensile strength of the metal. The grade number is an indicator of the break strength of the chain. The higher grades indicate a greater strength. If it is galvanized chain it basically boils down to how much carbon is in the steel. For instance Grade 30 has less carbon and makes a good value service duty chain. While a higher grade like 43 or 70 will have a much higher tensile strength but will come with a much higher price. The higher grades will also come with a higher the price.
- Diameter simply means the diameter in inches of the metal used to form the chain links. Some common sizes are 5/16″, 3/8″, 7/16″, 1/2″ and 3/4″.
- Coil is usually referred to as Proof Coil but may also be known as Common Coil chain. This is the standard commercial quality of chain regularly stocked by hardware and industrial supply houses. Proof coil is chain grade 30 chain and is a general purpose chain for pulling or restraining applications. Proof coil is not recommended for overhead lifting or where maximum tensile strength is crucial to prevent failure. Basic carbon steel metal composition makes it the most popular chain grade for log chain and towing applications. The metal in these chains may look different depending on finish. You will see standard finishes that can be plain, colored, bright zinc or galvanized. The tolerances are not as stringent for inconsistencies in link size and diameter with proof coil so the price will be less than the precision chains.
Chain Grade and Working Load Limit
Chain grade may also be referred to as a certain working load limit.
- Grade 30 Proof Coil is a general purpose chain of standard commercial quality with a working load limit of 300. It is made from low carbon steel. This chain is most often used as tow chains and logging chains. When it fits the job it can also be used as tie down or binding chains. This type chain will be marked at various intervals with the manufactures symbol and grade marking of 3, 30 or 300. Proof Coil is not a chain grade that is ever recommended for overhead lifting for safety reasons.
- Chain Grade 40 is a High Test Chain. The strength level is the same as Chain Grade 43 but the dimensions of the chain links are smaller. It is primarily used for boat windlasses and has become a standard for that industry. The Grade Chain 40 designation was used until 2005 to designate High Test grade chain. This has since been changed and everyone uses Chain Grade 43 in keeping industry standards. This Chain Grade is hallmarked with “G4″ on every link and should not be used for overhead lifting.
- Chain Grade 70 is Transport Chain. As you would expect from the name Chain Grade 70 Transport Chain is mainly used to tie down loads when transporting them over the roads. They will have yellow chromate (gold) plating and will be easy to recognize from most any distance. Chain Grade 70 is made from heat treated carbon steel and has about 25% more strength than regular high test chains. They will be Hallmarked every 1 to 3 feet with the manufacturer’s symbol and grade markings of 7, 70 or 700. Chain Grade 70 Transport Chain is not for overhead lifting.
- Chain Grade 80 is Alloy. Chain Grade 80 is the first chain specifically designed for safety and approved by OSHA and other agencies for overhead lifting. It is an alloy, heat-treated steel that makes ideal material for making lifting slings and heavy duty tow chains. Chain Grade 80 is hallmarked no more than 3 feet apart with manufacturer’s symbol and grade markings of 8, 80 or 800 and is suitable for overhead lifting.
- Chain Grade 100 is Alloy. Chain Grade 100 Alloy is a new innovation in alloy chain metallurgy that provides about 25% higher working load limits over Grade 80 chain with some limitations reported in lower ambient temperatures. It is hallmarked no more than 3 feet apart with manufacturer’s symbol and grade markings of 10 or 100 and is listed as suitable for overhead lifting.
WLL or Working Load Limits may sometimes be referred to as SWL or Safe Working Load. Below is a chart giving comparisons by Chain Grade for several common size chains.
Our disclaimer to this information is that you should not wholly rely on it but use the manufactures recommendations for each chain because it is always subject to change. We d however, hope this has given you a better understanding of the term Chain Grade.