Chains

Among flexible rigging elements, chains play an important role. These are steel elements of round-link form. The main characteristic is diameter, which determines the calibre. Products are divided into calibrated and non-calibrated.

Calibrated chain is manufactured with links of uniform size and minimal tolerances, which is why it is used in load-lifting mechanisms, as well as for operation on drums with various drives.

Types of chains

Steel chains are part of electrical and mechanical equipment used in loading and unloading operations. Chains are divided into categories by the following characteristics:

• design features;
• material;
• link calibre;
• dimensions of the connecting device.

Common types:

• plate chains with open pins;
• flexible plate rigging with concealed pins;
• round-link chains.

Chain links consist of an even number of plates and are fixed to the pins by a hinged design. Individual plates are additionally secured. Round-link chain may include studs that increase the operating load. There are short-link and long-link models.

Application

Chains manufactured to GOST 30188-97 are not permitted for use as slings. The standard sets technical requirements for chains to withstand a load of at least 800 megapascals.

Marking

Flexible rigging is marked by chain calibre — the diameter of the metal rod from which the element is made. Typical calibres:

• 4 millimetres;
• 5 millimetres;
• 5.6 millimetres;
• 6 millimetres and above.

Check the load rating of the chain against the operating conditions and national standards.

How to choose correctly

A steel lifting chain is selected taking into account the type of metal alloy, the design features of the links and their strength. Safety of the work depends on this characteristic. There are conventionally three classes by operating conditions:

• Class 8 may be used at temperatures up to 200 °C. Safety factor — 4:1.
• Class 10 is suitable for the same temperature conditions. Maximum load — up to the full calculated load weight +30%.
• Anti-corrosion variants are made from austenitic steel with increased resistance to rusting. Heat treatment is not required for them.

Selection is made based on the main characteristics of the chain, maximum load capacity and other parameters. Modern lifting chains comply with GOST 30188-97 — this is class T8.

Before purchasing, the maximum load the chain will be subjected to must be assessed. When used for suspension, a safety margin is required.

Chains manufactured in accordance with GOST or DIN requirements should be chosen. Under these standards, links must have a minimum pitch and be manufactured by welding. Burrs at the joints must be removed, and after welding chains undergo heat treatment, with the exception of anti-corrosion variants.