Vivid idioms are often centuries old. And sometimes the experiences behind them have become foreign to us, since they no longer have any practical relevance to our daily lives. This certainly isn’t true in the case of the often-quoted phrase “Every chain is only as strong as its weakest link”. For anyone who deals with lifting chains professionally, this age-old insight is still very true today. But, first things first…
Let’s begin with a simple question: What is a lifting chain anyway? Lifting chains belong to the group of lifting equipment, i.e. connecting elements between a load to be lifted and, for example, a crane hook. At the other end, the lifting chain, like any other lifting equipment, is ideally connected to a tested lifting point mounted on the load. In other words: Without lifting equipment, the transport of loads with cranes is practically impossible.
Lifting equipment: Which one is the right one?
Today, anyone who wants to lift or transport heavy loads can hardly manage without lifting chains. But this wasn’t always the case. After all, chains didn’t used to have the best reputation as a means of lifting. Their material strengths were low, and they were heavy and unwieldy. But those days are long gone. Modern lifting chains have high material strength, which means that they weigh considerably less for the same WLL. They are also very durable, economical and reliable. These properties alone make them the first choice when it comes to lifting and moving.
Nevertheless, the other options shouldn’t be neglected here either, i.e. the wire rope and the lifting belt or round sling. Today, wire ropes as lifting means are only found in Central Europe in a few special applications where light weight and inherent rigidity are important. Because they are pleasantly light, synthetic round slings are very popular with many users. However, they have decisive disadvantages in common with wire ropes. They cannot be shortened and are vulnerable to sharp edges. Furthermore, round slings don’t do well with rough surfaces or extreme temperatures. All these safety-related disadvantages do not apply to lifting chains -– provided they are used correctly. Above all, the length adjustability with additional components, so that, for example, asymmetrical centre of gravity positions can be easily compensated.
Quality grades for lifting chains
If you want to buy a lifting chain, you have to ask yourself several questions. One of them is which of the existing quality grades it should have? You should also be aware of what the currently available grades (QG) of lifting chains stand for. After all, the WLL of a lifting chain directly depends on its grade. Let’s start with quality grade 8, a standard which has been in existence since the early 1970s. Anyone buying a lifting chain from the Far East today will find that they are available there at frighteningly low prices. This also applies to lifting chains of grade 10, which have been available for close to 20 years. About 10 years ago, grade 12 was born – the highest quality lifting chain segment to date. This class enjoys a certain exclusivity because only a few manufacturers are still able to produce it (RUD is one of them). The decisive advantage for the user: Compared to grade 8, grade 12 always allows the use of the next smaller chain diameter. In practice, this means that the chain is lighter for the same WLL, which improves ergonomics for the user.
Because the quality of a lifting chain is not visible from the outside, it is given a corresponding stamp for each running metre during production. In the case of a lifting chain, this can be the “(H1) 8” stamp for grade 8 or “(H1) 10” for grade 10. The H stands for “high-strength” and is issued by the responsible trade association (TA). The number after the H identifies the manufacturer of the chain. For quality grade 12, the responsible trade association has issued a completely new stamp “(D)”. By the way, since the characteristics of a hoist chain differ considerably from those of a lifting chain, hoist chains are stamped with letters rather than numbers to indicate their grade. This is intended to prevent potentially dangerous mix-ups.
A modular system to enable individual configurations and simple repairs
Lifting chains are practically always part of a modular system. The advantage here is that both a fabricator (e.g. a specialist dealer in lifting technology) and the workshop of a lifting chain operator can quickly and individually install lifting chains of different configurations. One of the strengths of a modular system is that individual components can be easily replaced as required. The so-called fork head system is especially popular – and with good reason. Here components are connected with a special pin. The ideal safety feature is a fork head system with only one type of bolt for all components. The major advantage of this is that incorrect installation, as in systems with eyelet connection elements and connecting locks, is impossible.
Approval, marking and test certificates
Safety should always be paramount with lifting chains. Anyone who is safety-conscious will only use chains that are approved by the DGUV (German Statutory Accident Insurance). This can be identified in quality grades 8 and 10 by the above-mentioned H stamp and in quality grade 12 by the D stamp on all components. The DGUV only grants this approval if all technological safety requirements are met. Anyone who doesn’t pay attention or regard to this stamp, or even clear manufacturer identification, runs a considerable risk in terms of product liability and violation of normative specifications.
An equally important minimum requirement is that the individual components of a lifting chain are traceable via a batch code. A few manufacturers now also mark their components with an RFID chip for component-specific identification. In any case, it is essential for the operator to obtain a test certificate from the manufacturer in compliance with DIN EN 10204 2.1, a declaration of conformity and operating instructions with the lifting chains.
What makes a good lifting chain extra safe?
As we said at the beginning: A lifting chain is only as good as the sum of its components. For this reason, a lifting chain should not be assembled from components of different quality grades. Manufacturers rule out liability for a “mixed combination”. Neither should they be assembled from components from different manufacturers in the most cost-effective way. Especially with the high quality grades, the final strength depends on details that are only effective within a manufacturer-specific system. For each lifting chain, a visual identification tag is also mandatory, on which the WLL is documented. If this tag also has the function of an inspection gauge, this provides the user with yet another safety-relevant benefit.
But the most important thing is the chain itself, from which buyers and users can expect at least 20 per cent elongation at break (when coated) and high dynamic strength. This high elongation at break makes the lifting chain an exceptionally safe means of lifting, because overload can be detected with the naked eye.
Testing lifting chains
Anyone who binds themselves to a lifting chain for a longer period of time must have it checked by an expert at least once a year. “At least” means that, depending on the operating conditions, shorter intervals may also be necessary. After three years at the latest, lifting chains must then be subjected to an electromagnetic crack test, which is usually carried out by a certified specialist company. It is not advisable to carry out a test load instead of the crack test because cracks cannot be detected during this test.
Checklist for purchasing lifting chains
- What types of loads need to be lifted?
- At how many points can the loads be attached?
- Do the loads have rough surfaces or sharp edges over which the lifting chain will be placed?
- What are the maximum weights of these loads?
- How high is the WLL of the available cranes?
- Do the loads have asymmetrical centres of gravity?
- Do extremely low or high temperatures occur during operation in the environment where the chains are used?
- Should it be possible for the user to easily check the operational safety of the chains?