Tag: alloy chain

In-Depth Alloy Chain Sling Inspection Part 4: Stretch and Chain Elongation

In-Depth Alloy Chain Sling Inspection Part 4: Stretch and Chain Elongation

This article is Part 4 of a 5-part blog series that will cover what professional riggers should consider when performing an in-depth alloy chain sling inspection. Today, we’ll discuss stretch and chain elongation.

Stretched Links
Stretched Links

A visual link-by-link inspection is the best way to detect dangerously stretched alloy chain links. Reach should also be measured from the upper bearing point on the master link to the bearing point on the lower hook. The smallest sign of binding or loss of clearance at the juncture points of a link indicates a collapse in the links’ sides due to stretch. Any amount of stretch indicates overloading, and the chain should be removed from service.

Note that a significant degree of stretch in a few individual links may be hidden by the apparent acceptable length gauge of the overall chain. This highlights the importance of link-by-link inspection.

Alloy steel sling chain typically exhibits well over 20% elongation before rupture. The combination of elongation and high strength provides energy absorption capacity. However, high elongation or stretch, by itself, is not an adequate indicator of shock resistance or general chain quality and should not be relied upon by riggers to provide advance warning of serious overloading and impending failure. Overloading must be prevented before it happens by selection of the proper type and size of slings. Again, any amount of stretch is overloading and the chain should be removed from service.

There is no short-cut method that will disclose all types of chain damage. Safety can only be achieved through proper inspection procedures. There is no adequate substitute for careful link-by-link scrutiny.

Additional Resources:

In-Depth Alloy Chain Sling Inspection Part 1: Twisting & Bending
In-Depth Alloy Chain Sling Inspection Part 2: Nicks and Gouges
In-Depth Alloy Chain Sling Inspection Part 3: Wear & Corrosion

To learn more, view our Chain Sling Inspection Safety Webinar.
Want to get trained? Check out our Qualified Rigger 3 day Workshop.

In-Depth Alloy Chain Sling Inspection Part 3: Wear and Corrosion

In-Depth Alloy Chain Sling Inspection Part 3: Wear and Corrosion

This article is Part 3 of a 5-part blog series that will cover what professional riggers should consider when performing an in-depth alloy chain sling inspection. Today, we’ll discuss chain wear and corrosion.

chain wear
Figure 1: Inspection for interlink wear can be easily detected by collapsing the chain.

When used in rigorous material handling applications, chain can easily become worn or corroded. It is important to inspect chain for defects on a regular basis to avoid an unsafe lifting condition or even operator injury. When corrosion and wear occur, it results in a reduction of link cross-section which can lead to decreased strength of the chain.

Corrosion can occur anywhere chain comes in contact with harsh chemicals, water or when it is used in tough environments.

Wear can occur in any portion of a link that is subject to contact with another surface.

The natural shape of chain confines wear, for the most part, to only two areas. These are, in order of importance, (a) at the bearing points of interlink contact, and (b) on the outsides of the straight side barrels that may be scraped from dragging chains along hard surfaces or out from under loads.

Figure 1 illustrates the condition of interlink wear and shows how to inspect for it. Notice how easily such wear can be detected by collapsing the chain to separate each link from its neighbors. An operator or inspector can also check for corrosion using the same method.

When chain wear or corrosion is observed, the next step is to determine how severe the damage is and if the chain can still be safely used.

General surface corrosion can be removed by cleaning and oiling the chain. If pitting is observed after cleaning and oiling, remove from service. Next, the operator should take a caliper measurement across the worn section of chain and compare it to the minimum allowable dimension for that chain.

See the chart below for minimum section dimensions or chain wear allowances for Grade 80 and 100 Chain. If the chain does not meet these minimum dimensions, it should be removed from service and replaced.

chain wear

Stay tuned for our next part in this series where we’ll talk about Chain Inspection.

Additional Resources:

In-Depth Alloy Chain Sling Inspection Part 1: Twisting & Bending
In-Depth Alloy Chain Sling Inspection Part 2: Nicks and Gouges

To learn more, view our Chain Sling Inspection Safety Webinar.
Want to get trained? Check out our Qualified Rigger 3 day Workshop.

Understanding the Difference between Chain Grades and How They’re Used

Understanding the Difference between Chain Grades and How They’re Used

chain grades
Chain has been around for over a thousand years. It is one of the most versatile and reliable ways to lift, tension and tie down materials in a variety of applications. In the past, people would use any type of chain to lift something, tie down a load or tow a vehicle. Proper inspection, safety procedures and general standards of practice for chain were lacking.

In recent years, due to safety concerns and regulations, the industry has begun to differentiate between various materials and grades of chain and the specific applications they should be used for. ASTM (American Society of Testing & Materials), ASME (American Society of Mechanical Engineers) and OSHA (Occupational Safety & Health Administration) began to publish safety standards and regulations for the manufacturing, testing, use, inspection and repair of chain.

Chain Grades

One of the safety measures implemented was to place chain in Grades based on the ultimate breaking strength of that chain. This number is what we see today G30, G43, G70, G80 & G100 and the common chain grades. The number after each letter is N/mm2. For example, G80 means that the maximum stress on the chain at ultimate strength is 800 newtons per millimeter squared.

Working Load Limit (WLL) of Chain

The other safety measure was identifying which types of chain are appropriate and strong enough for overhead lifting. Anytime we move or lift a load it is dangerous. Moving a load along the ground has the advantage that the ground is supporting the load. We have to overcome the coefficient of friction to move the load. The chain’s working load limit does not have to match the weight of the load. It needs to be able to handle the tension applied, which is based on the surface that it is being moved over plus some fraction of the weight of the load. This can be calculated using formulas.

If we lift that same load off the ground, we now have to overcome gravity. The chain’s working load limit will have to be of sufficient strength to support the weight of the load plus any additional forces imposed by angles and hitch type(s) used.

Which Chain Grade Should Be Used for Which Type of Application?

Alloy Chain Grade 80 or Grade 100 should be used for overhead lifting. ASTM states that alloy chain shall be able to elongate a minimum of 20% before fracture (7.3.5). To ensure that alloy chain consistently meets this requirement, ASTM requires the use of certain alloying elements in the manufacturing of the steel for alloy steel chain. These alloys can vary from company to company, but some key requirements are specified by ASTM. The alloy properties also improve the wear and tear that the chain will experience.  Note that when chain is in use, no amount of stretch is allowed.

Carbon Grade 70 chain is a “heat treated” carbon steel chain that has no alloying elements added to the steel. This chain will elongate before breaking but does not have the properties needed for overhead lifting; therefore, Grade 70 chain is not intended for overhead lifting. This chain is designed for use as a tie down chain or lashing for transportation. Grade 70 chain has a gold chromate finish to help resist corrosion from continuous exposure to the elements and the rigors of highway use, such as road salts in the winter.

When any type of overhead lifting is required, use only alloy chain slings unless specified by the manufacturer.

The preferred chain for load securement is Grade 70, but any grade of chain can be used for tie downs or tensioning. You have to know your tensions in order to select the proper chain. Refer to load securement safety standards FMCSA (Federal Motor Carrier Safety Administration), CVSA (Commercial Vehicle Safety Alliance), WSTDA (Web Sling Tie down Association) or the state regulations for more information.

Training is key in knowing how to properly size and use any type of chain for any application. Learn more about Columbus McKinnon training programs.

Watch our Safety Webinar on Load Securement.

In-Depth Alloy Chain Sling Inspection Part 1: Twisting and Bending

In-Depth Alloy Chain Sling Inspection Part 1: Twisting and Bending

twisting and bending

Twisted and Bent Chain
twisting and bending
D/d is the ratio between the curvature taken by the sling ID and the diameter of the component chain D.

 

 

 

 

 

 

 

 

 

This article is Part 1 of a 5-part blog series that will cover what professional riggers should consider when performing an in-depth alloy chain sling inspection. Today, we’ll discuss the effect of twisting and bending.

Consider that chain is evaluated by applying loads in a pure tensile link end-to-link-end fashion and rated accordingly. Rigging chain around edges or corners alters the normal loading pattern significantly. A lack of proper padding or consideration of the D/d ratio (see above) for chain can result in twisted and bent links. Once a chain is twisted or bent it will alter inner link stresses which can result in failure. For this reason, all chain containing twisted or bent links must be removed from service immediately.

National Association of Chain Manufacturers (NACM), representing domestic manufacturers of welded and weldless chain since 1933, has conducted D/d testing on alloy chain. As a result of this testing, the NACM came out with the chart below which shows reductions in working load limits based on D/d ratio of alloy chain rigged around an edge or a corner. Consult the manufacturer for any D/d below 2. The latest revision ASME B30.9 2014 released for sale this month has adopted this chart into the new standard.

twisting and bending
Using proper sling protection, following the D/d capacity reductions and exercising proper rigging practices will eliminate damage to your alloy chain slings.

To learn more, view our Chain Sling Inspection Safety Webinar.
Want to get trained? Check out our Qualified Rigger 3 day Workshop.

NACM Conducts D/d Testing on Alloy Chain

NACM Conducts D/d Testing on Alloy Chain

National Association of Chain Manufacturers (NACM), representing domestic manufacturers of welded and weldless chain since 1933, has conducted D/d testing on alloy chain. D/d is the ratio between the curvature taken by the sling D, and the diameter of the component chain d. NACM alloy chain manufacturers supplied Grade 100: 9/32”, 3/8” and ½” and Grade 80: 3/8” for testing. Until this point, no published information was available for chain regarding D/d. NACM wanted to publish information to make recommendations on the minimum pin diameter for proof testing basket chain slings based on link deformation and rating/ derating of baskets and endless slings vs D/d ratio.

NACM testing results are shared below.

Conclusions:

1) Effect of D/d is the same for all sizes and grades of alloy steel chain.

2) Strength loss is highly consistent with D/d ratio.

3) No damage to chain at WLL (working load limit) with a D/d as low as 2.

4) Minimum D/d pin diameter of 5 recommended for proof testing basket slings.

5) Strength loss is 10% or less once D/d is 5 or greater.

The chart below shows reductions in working load limit of an endless alloy sling based on D/d ratio. Consult the manufacturer for any D/d below 2.

image