Cold Chains
Ben Dobbs, Head of Global Standards and Legislation at LEEA, considers the arguments regarding an operating temperature of -40 °C being prescribed for 10G chain.
Lifting takes place everywhere – even in locations that can experience extremely cold temperatures, which can have a detrimental effect on lifting equipment. Metals are affected by temperatures and in temperatures down to -40 °C even extremely strong chains become more brittle, creating a risk of failure and potentially accidents without warning.
The acceptable temperature range of chains will vary depending on its grade and there will also be a variance in reduction of Working Load Limit (WLL), which is the maximum load that a chain is designed to sustain in lifting use.
Grade 10 (sometimes called grade 100) is approximately 25% stronger than grade 8 (also referred to as grade 80), which provides flexibility in terms of application – it can be used for heavyweight as well as lightweight lifting – to offset its greater expense. This has made it more popular, though remember: the repairs and maintenance regime will be the same. But what about using 10G in very cold temperatures?
Some take the view that an operating temperature of -40 °C should be prescribed for 10G chain without reducing WLL. There are, however, strong doubts about the reachable safety level, in addition to different requirements for grades 10G and 10X used under the same conditions but with the same valuation base used by consultants.
By going beyond all well-known and used standards, this view defines a new characteristic and therefore requires very close consideration of safety, since lower requirements are placed on the alloying elements for this type of chain.
With the 10X chain, a nearly identical product to the well-known and BG-proven PAS chain will be available, which fully meets the specified usage requirements, but obviously at a higher price due to the alloys that give it greater strength. PAS 1061(Publicly Available Specification) completes the standards of the series referring to DIN EN 818 (European safety standard for chains), and defines in detail the requirements for short link and medium tolerance round link chains that can be used for chain slings and for general lifting purposes. Any extension of the use of 10G to the same level of 10X/PAS is inevitably cost-driven.
Summary of the pros and cons
While there have been no negative experiences in the past with extended use of 10G down to -40 °C without reductions, the state of the art is represented by PAS 1061 and related BG-certification since 2006. 10G will not reach these requirements.
Detailed explanations from experts on the basis of the ISO-TR Technical Reports give rise to significant doubts as to whether 10G chain can provide a safe breaking force level and toughness behaviour.
Based on current experience, using 10G down to -40 °C leads to a safety level lower than grade 8 chains at -40 °C. To maintain the safety level at -40 °C, it is necessary to reduce the nominal stress at WLL for 10G from 250 N/mm² down to 200 N/mm² (equal level of grade 8). However, no current foreign standard covers this requirement. However, 10X chain, as an easily available product, fully covers it.
It is easy to understand, and should not be ignored, that the situation for countries where lower operating temperatures are common, such as those in the Nordics, is not simple. Obviously, manufacturers here support the use of a chain that is outside a standard on their own risk. This procedure would not be eliminated by an EN standard in future, though that is a matter for legislators.
However, there are alternatives for solving this problem. The lowest operating temperature for 10G is -30 °C at full WLL. Minimum Charpy values (these provide characteristic values for the impact strength of a material at high strain rates in the form of a surface area related energy value) shall be of 30 J at -30 °C. While 10G can operate down to -40 °C, this reduces WLL to 80% with minimum Charpy values of 30 J at -40 °C.
Ultimately, it remains vital that careful attention is always given to selection of chains for use in very cold temperatures. A good place to start is always to look for the LEEA logo from chain suppliers as they will be members of the Lifting Equipment Engineers Association and, therefore followers of best practice.
LEEA Members wishing to submit their technical enquiries to the Technical Triage can do so through the LEEA chatbot, which is available on the homepage of leeaint.com and the Connect App.
