Rigging &InspectionConsiderations for Industry
The following information is forpresentation and demonstration purposes only, not intended for actual field application.Thisis notacrane and rigging guideormanual.This presentation isnot intended to replace or add on toany regulationsorguidelines set for the by themanufactureror any regulatoryagencies.For crane operation and rigging guidelines always refer toup-to-dateequipmentmanufacturerinformation, regulatory guide lines, qualified rigging manuals, and proper training.
Rigging Plan Basics
Responsibilities for rigging/lifting setup & executionLoad weight, gravity, # of cranes, load calculations, head roomWork area conditions, crane & rigging inspections doneLifting equipment/gear appropriate for taskTag lines needed for control, sling protection usedCorrect communications used for the type of liftPersonnel out of the area where the lift is being performed (Safety watch)
With a hook, maximum sling angle should be 90°With a master link or shackle, 120° is maximum angle.
It is allowable to use a shackle in a situation where it is being side loaded, as long as the rated lifting capacity decreases by the percentage shown below.
Good working conditionMust be properly engaged into threadsDo not shock load eyeboltsDo not mix SAE and Metric typesCountersink eye bolt holesDo not overtighten, undercut, or force eyebolts into placeUn-shoulderedeyebolts shall only be used for vertical loads (no side loading beyond 5 degrees from vertical).Only shouldered eyebolts shall be used for angular loading.
When used in a tapped blind hole,theeffective thread length shall be at least1 1/2 timesthe diameter of the boltfor engagement insteel. Thefirst 1/2 diameter length of threads do not fully engageresulting in reduced strength and should never be counted as part of the engaged length of thread. Thisimageshowsthe tip of an eyebolt with a long unthreadedarea nearly 1/2thread diameter in length.
The eyebolt should not wobble or require extra force while being screwed in.
When tapped holes are in softer materials additional thread length must be provided to ensure sufficient strength is achievedMinimum thread engagement for holes tappedthrough in various materials(ASME B18.15):Steel - 1 thread diameter,Cast iron, brass, bronze - 1.5 thread diameter,Aluminum, magnesium, zinc, plastic - 2 thread diametersIf the threads are in a tapped blind hole, an additional 50% of thread length/depth is needed.
Onlyshouldered eyebolts shall be used for angular loading.Align eyebolts within ± 5º of the direction of pull
To help get the eye properly aligned with the sling angle, a shim can be added under the eyebolt shoulder. It is recommended that the shim should not be more than(1/2 turn of the eyebolt)to achieve thecorrect orientation.
Donot over tighteninan attempt to get it in to proper alignment or to keep it from rotating.Onlyfirm hand pressure should beused to snug it down
Many manufacturers of electric motors warn that the eye bolt supplied on a motor is designed for lifting the motor only and not designed to lift an assembly such an MG set or motor pump assemble.An assembly of this type should be designed and fabricated with engineered lifting points on the assemble base.
Eye bolt load capacity is reduced when loaded at an angle.Note that eye bolts are not created equal, always use WLL and angle load information for the brand of eye bolt being used.Proper thread engagement is also important for maximum strength.
Note that the capacity for Crosby eyebolts is different than the capacity of the Chicago eyebolts, DO NOT use the Crosby table for Chicago eyebolts.
In this example of a3/4” eyeboltused at45degrees, it has a rating of 1500 lbs.Because thesling isreevedthrougheacheyebolt, its effectiveslingangleis reduced to a load angle of around22.5 degrees. This now increases the load toover 2,600lbs.persling leg.
Do not reeve sling through eye bolts or attachment points.
Come-a-long/Chain Fall (Hand operated)
A Come-A-Long isNOTdesigned for lifting.
A lever“hoist”isdesignedfor lifting.
LeverHoist(Chain Fall, Come-along, etc.)
Swivel Hoist Ring
Whenusing a swivel hoist ring,applythe proper torque to thebolttoensurethe hoist ring andboltwill achieveitsrated capacity in any allowed position used.
Wheneverabolt-on deviceis used it is always best to consult with the devicemanufacturer,or a qualified engineer to ensure thedevice’s attachmentbolts arethe right grade fortheapplication, installed, and then tightened correctly.
Sling Load Angle Factor
To Calculate Load Angle Factor:NOTE:The number of legs used for sling load calculation is not to exceed 3 legs, even when 4 or more legs are rigged.
When the sling angle can be measured, use a LAF table for your rigging configuration.Always round the measured value down if it is not on a listed number.Example: Angle of measure is 34°, round down to 30°. This gives a slightly higher sling load, but will increase your margin for error in the calculations.
Sling Angle Factor
Below are some visual reverences to sling angles and there effect.
Whenthreeor more sling legs are used, the sling angle ismeasuredperpendicular to the centerline of the load line and hook, not in the plane of the adjacent sling.
Sling Angle Factor
When using a choker hitch withmultiplesling legs, the sling leg and choke angle must both be factored in to sling load calculations.
Sling Angle Factor
DO NOTuse a horizontal sling angle less than60°onan inverted basket.
When rigging a sling in an invertedbasket,the horizontal sling angle must begreaterthan60°,to minimize the possibility of the sling shifting on the hook.
Thepreferred method when two sling leg are used, is to use two slings that terminate at the hook, providing the best possible load control and stability.Whenadditional sling legs are needed, a master link and shackle may needed to prevent sling bunching on the hook and to even out sling load distribution.
DO NOT Wrapthe sling around the hook in any manner
D/d – Is the ratio between the curvature of the part being riggedDand the diameter of the sling being useddThisratiois important in because it effects both the load carrying capacity of the sling and its ability to resist damageAn excessively small D/d ratio with wire rope and chain sling will be permanently damaged the sling.TheD/d ratio for wire 6 x 19 rope is 25/1.Othersling type havedifferentD/d ratings, such as 6/1 for chain slings or 5/1 for grommet slings
D/d? Flat Web Slings
Flat web slings have no diameter and therefore no D/d ratio.All web sling manufacturers recommend some form of edge protection be used between web slings and load edges to protect the sling against damage, such as cutting.Some manufacturers suggests that at minimum the edgeradiusof the load contact point should be at least the thickness of the sling at the point of contact.If the sling is 3/16” thickwebbing,the contactradiusshould be 3/16” or greater.If the sling is 2 or more ply’s in thickness, it is the total thickness of all the ply's at the contact point of the sling and load that constitutes the sling thickness.A chamfered edge is not the same as a radius, it still has sharp edges.
All slingstypes mustbe protected from sharp edges of a load, and any other damaging forces.Many types of protection are available and can be improvised, below are some examples
Sling Strength Loss
Shown here are test results from two different sling manufacturers, showing the loss of ultimate strength of the sling do the various sizes of edge cut in a 2 inch wide single ply sling.
Sling Strength Loss
To help put things in perspective:The red wire represent 12 randomly spaced wire on a wire rope sling, this equates to about 10-1/2 % of the wires in the sling.
The image below represents the cross section of a 1 inch wide by .147 inch thick web sling, the blue area is about 10-1/2 of the sling fabric a cut of about ..015” deep, this is about the thickness of two business cards.
The image below is about what the sling cross section would look like in your hand.