Category: Rigging Inspection & Maintenance

Sling Selection & Working Load Limits: What You Need to Know

Sling Selection & Working Load Limits: What You Need to Know

Chain slings are a combination of chain, hooks, rings and other attachments used primarily for overhead lifting applications. Slingssling selection are often used in conjunction with cranes and other lifting devices and allow riggers to create custom configurations to lift loads depending on the needs of that specific application.

Standard chain sling configurations consist of chain branches that are affixed on one end to a master link or ring with some type of attachment. When building a sling, ASME, NACM and OSHA recommend that only alloy steel chain is used. Columbus McKinnon’s Herc-Alloy chain, available in Grades 80 and 100, is made of superior triple alloy steel and is a strong and durable option for building chain slings.

All chain slings should come with a metal identification tag that is affixed to the chain. The tag should include the following information: sling size, reach, working load limit, serial number, manufacturer name, grade of sling and number of branches.

Proper Chain Sling Selection

When choosing a chain sling there are a few things to consider:

  1. Weight and configuration of the load(s) to be lifted
  2. Type of chain sling required, according to weight and configuration
  3. Size of the body chain according to the working load limits. Be sure to take into consideration the effect of the required angle (see information below).
  4. Reach required to give the desired angle. This is measured from the upper bearing surface of the master link to the bearing surface of the lower attachment.
  5. The share of load on pick points and location of the center of gravity

What Determines a Sling’s Working Load Limit?

The working load limit indicates the maximum load that should be applied to the sling and should never be exceeded during use to ensure operator safety.
Sling working load limits are determined by the following:

  • Type of hitch
  • Material strength
  • Design factor
  • Diameter of curvature (D/d)
  • Angle of loading

The working load limit of a sling can also be affected by the conditions the sling is used in. For example, rapidly applying a load can produce dangerous overloading conditions. Also, the twisting and knotting of links or sling components can decrease a sling’s working load limit. Environmental conditions, such as elevated temperatures, can affect the working load limit of a sling as well.

Since slings are most often used at an angle, let’s review an example of how angle of loading affects a sling’s working load limit. In the diagram below, the percentages shown represent the maximum working load limit of the sling when used at the designated angle. In some instances the working load limit of the chain is reduced to 50%!

For example: One 3/8″ Grade 80 double sling used at 90˚ would have a working load limit of 2 times the working load of a 3/8″ Grade 80 single or 2 x 7, 100 lbs. = 14,200 lbs.

The same double sling used at 35º would have a maximum working load limit of 57% of 14,200 lbs. or .57 x 14,200 lbs. = 8,094 lbs.

sling selection

For another example of how the angle of use can affect the working load limit of a chain sling, check out this past blog post: What is the working load limit of a 2 legged chain sling?

Want to learn more? View our Safety Webinar on Chain Sling Inspection

Tim Lewis

Tim Lewis is a Business Development Manager at Columbus McKinnon Corporation.

What Is The Working Load Limit Of A 2-legged Chain Sling?

What Is The Working Load Limit Of A 2-legged Chain Sling?

2-legged chain sling Richard asks:

What is the working load limit of a ½ “ – G80 2-legged chain sling when both legs are used in a choke?

 

Peter answers:

The first thing that you want to do is to look at how the choke is rigged or rendered.  Working load limits shown on charts or tags for vertical chokes are based on the angle of choke being 120 degrees or greater.  If there is less than a 120-degree angle of choke, the choke rating must be reduced further. Once we determine the correct choke rating, we can take into account the angle of loading.

2-legged chain sling

First, you take the choke rating and multiply it by the SIN of the angle x 2 = Rating of a two leg sling used in a choke.

Example:
Our charts show that ½” grade 80 chain is good for 9,600 lbs when pulled vertically with a choke hitch of 120 degrees or greater.   Let’s assume when this double sling is rigged at a 60-degree angle it has a choke hitch of 120 degrees or greater.   Our working load limit for this sling is 9600 lbs x .866 ( sin of 60 degrees) = 8314 lbs x 2 legs = 16628 lbs.

Another way is to take the rating of the sling at a 60-degree angle and reduce it by 20%. Again assuming 120-degree angle of choke, ½” Grade 80 double sling chain is good for 20,800 lbs (at a 60-degree angle) x .8 (20% reduction):  rating: 16640 lbs.

Our first example is a little more conservative.

If you want to learn more about rigging, check out our rigging training.

Peter Cooke

Peter Cooke is a Training Manager specializing in Rigging & Load Securement for Columbus McKinnon Corporation.

Columbus McKinnon now certifies Advanced Riggers & Examiners for CIC

Columbus McKinnon now certifies Advanced Riggers & Examiners for CIC

DSCF2226

CMCO recently hosted a Crane Institute Certification (CIC) Advanced Rigger Practical Exam and Examiner Workshop. The hands-on workshop was held at our CMCO Niagara Training Center in Western New York. The instructor for this session was Mike Parnell, President and CEO of ITI. Mike is a qualified rigger and examiner for CIC. Mike is also the Chairman on the Rigging Certification Committee for CIC.

Candidates who participated in the workshop had to lift three types of loads: direct connection, indirect connect and bundled load.

Each candidate was evaluated for:

  • proper rigging inspection,
  • proper rigging technique and application,
  • pre lift meeting,
  • proper use of hand signals,
  • load control, and
  • post rigging gear inspection.

A defined set of rigging equipment per CIC guidelines was made available to each candidate. The choice of rigging to use was determined by the candidate. A 21 ton Terex mobile crane, supplied by Clarke Rigging of Lockport, NY was also used for the workshop. The mobile crane and practical testing course were set up on the two acre property at the CMCO Niagara Training Center.

CMCO is pleased to announce that Peter Cooke (CMCO Rigging Training Manager) and Henry Brozyna (CMCO Corporate Trainer) are now Certified Advanced Riggers and Examiners for CIC Advanced Rigging and Signal Person Practical Exams. Chris Zgoda (CMCO Trainer) also completed his basic rigging signalperson certification. The CMCO Niagara Training Center is now a CIC practical exam site. This will assist construction crews in becoming compliant with the new OSHA Cranes and Derricks in Construction Regulation.

The CMCO Niagara Training center is a hands on training center located 15 minutes from Niagara Falls, NY. The facility has two 3 ton overhead crane systems, 2 Loderail work station cranes and a jib crane. It features a two acre lot for mobile crane set up. In addition to the cranes, the facility houses an overhead crane display with a Yale Global wire rope hoist. This display is a great tool for the hoist/crane technician workstation which is used for hoist and crane inspection and maintenance certification. The Yale, Budgit, Shawbox hoist history museum is a must see when training at this center. The museum features many of the original hoists from this product line.

Columbus McKinnon is hosting a Qualified Rigger Training Workshop on Oct 25 – 27, 2011. The course consists of rigging gear inspection, basic rigging, hand signals and advanced rigging. Participants can choose to take the CIC certification exam as an option on Oct 28. Register here or call 1-800-888-0985 ext. 5540.

For more information on Columbus McKinnon’s complete training program please visit http://www.cmcodepot.com/

Peter Cooke

Peter Cooke is a Training Manager specializing in Rigging & Load Securement for Columbus McKinnon Corporation.

Is it Possible to Mix Chain Grades on a Sling?

Is it Possible to Mix Chain Grades on a Sling?

mixing chain gradesBen from Chicago asked the following question about mixing chain grades:

Is it possible to mix grade 80 chain and grade 100 components on a sling assembly?

Peter answers:

In simple terms, yes –  BUT the assembly can only be rated at the grade 80 WLL.  Here is an example:  A sling is made with grade 100 chain and the hooks used for the sling are grade 80. This sling would need to have a tag with a grade 80 working load limit (WLL) of the weakest component.

For your reference I have provided the following applicable standards:

ASME B30.9, 9-1.5.7

When components of a sling have a lower rated load than the alloy chain with
which it is being used, the sling shall be identified with a rated load consistent
with the lowest load rating of any of the components.

OSHA 1910.184(e)(2)(i)

Hooks, rings, oblong links, pear shaped links, welded or mechanical coupling
links or other attachments shall have a rated capacity at least equal to that of
the alloy steel chain with which they are used or the sling shall not be used
in excess of the rated capacity of the weakest component.

Peter Cooke

Peter Cooke is a Training Manager specializing in Rigging & Load Securement for Columbus McKinnon Corporation.