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Rigging Training Workshop: Load Weight Estimation

  
  
  
  

Estimating a load's approximate weight is always an important part of any rigger's checklist and must be done before choosing the rigging system.

Have some fun and estimate the weight of the storage tank and its attached field stand below. To help you in your calculations we have provided Panel 6 of ITI Bookstore's Journeyman Rigger's Reference Card, which details weights of various materials and quick estimation formulas. Answers can be found below.

rigging workshop

Journeyman Rigger's Reference Card - Panel 6

journeyman rigger's reference card

Happy trails to all my crane and rigging friends,

Mike Parnell
ITI-Field Services

P.S.  This article was originally published in The Professional Rigger Newsletter - Find CG by Test Lift.

 

Answers:

rigging workshop answers

Rigging Training Workshop - Find CG by Test Lift

  
  
  
  

With four quick lifts, raising the load only a few inches, a rigger can confirm:

a) The load's estimated weight
b) The load's approximate center-of-gravity (CG)
c) The approximate load at each pick point

Find the approximate weight and the location of the CG of the load in the diagram. Answers provided below.

rigging workshop

Happy trails to all my crane and rigging friends,

Mike Parnell
ITI-Field Services

P.S.  This article was originally published in The Professional Rigger Newsletter - Find CG by Test Lift.

 

Answers:

rigging workshop answers

Rigging Training Workshop - Rig Right, Load Right!

  
  
  
  

This workshop requires the reader to consider the CG (center of gravity) of a load and the desired weight distribution to the tractor and trailer axles respectively. Often a rigger and truck driver must work together to land a load which produces a desired axle loading allowing the truck and trailer to legally travel over the road. In this example, the truck driver would like to end up with 22,000 lb on the driving axes and 18,000 lb on the trailer axles. The question is: Where do you place the load and in which orientation to achieve the loading requirements?

Study the information in the diagram, referring to the panels from the Journeyman and Master Rigger Reference Cards pictured below. Assume a frictionless system. See if you can arrive at the best solution of the three loading options provided. The answer is provided below.



rigging workshop

 

Journeyman Rigger's Reference Card Panel 2:

jrrc p2

 

Master Rigger's Reference Card Panel 9:

MRRC panel9

 

Assignment: Place the package where it produces proper loading for the rear and driver axles.

Loading Options:
A) Place the electric motor end of the package 1.5 ft from the trailer's rear bumper.
B) Place the pump end of the package 2.5 ft from the trailer's forward end.
C) Place the electric motor end of the package 4.5 ft from the trailer's rear bumper.

The best solution to achieve proper axle loading is Option # _____ .

 

Happy trails to all my crane and rigging friends,

Mike Parnell
ITI-Field Services

P.S.  This article was originally published in The Professional Rigger Newsletter - Rig Right, Load Right!.

 

Workshop Solution:

rig right load right answers

Rigging Training Workshop: Determine CG

  
  
  
  

rigging workshopA crew must load out a short bridge column which will be used in a creek bed to support one end of a light bridge deck. The crew rigged the precast column at two locations about 20 feet apart. Using two cranes, they have decided to determine the location of the column's center-of-gravity so that they can load the column onto an over-the-road trailer. By properly placing the column onto the trailer, the resulting axle loading allows the tractor trailer to not exceed any travel limits.

Use Panel 2 of the Journeyman Rigger's Reference Card to help solve the question about the column's CG. Instead of using Run1 and Run2, consider replacing them with Weight1 and Weight2, to arrive at the percent distribution, times the total span of 20 feet. To double-check your work, remember "Short Stout, Long Light". Translated, that means that the CG is a short distance from the stout (heavier) end, and a long distance from the light end.

Journeyman Rigger's Reference Card Panel 2

journeyman rigger's card

Assignment: Estimate the location of the column's center-of-gravity from the "head-end". (Answer below)

The CG is ______ ft from the head end.

 

Happy trails to all my crane and rigging friends,

Mike Parnell
ITI-Field Services

P.S.  This article was originally published in The Professional Rigger Newsletter - Crane & Rigging Quiz.

 

Answer:

rigging workshop answers

Rigging Training Workshop: Center of Gravity & Load Tension

  
  
  
  

Many things affect the distribution of weight being lifted at various pick points on a load:

  1. Where the slings or lifting attachments are secured in relationship to the load’s CG.
  2. If the pick points are not equidistant from the CG, then the weight distribution will probably be unequal.
  3. If the slings lifting the load are not in a straight vertical plane, there will be added tension in the slings due to the angle.

    Using Panel 2 of ITI’s Journeyman Rigger’s Reference Card, find the solutions to the problems below. Focus on identifying how the weight of each load is distributed in regard to the respective pick points. If an angle is involved, how much additional load is introduced to the sing(s)?

     

    6 2 CG & Sling Tensions 2 resized 600

    For the answer to this workshop scroll below.


    Happy Trails to all of my Crane and Rigging Friends,

    Mike Parnell

     

    P.S.  Center of Gravity & Sling Tensions are demonstrated in our Journeyman Rigger Training and Master Rigger Training Courses.

    This is an article from The Professional Rigger newsletter, 1991. To download this issue of The Professional Rigger, click Center of Gravity & Sling Tensions.

     


     

     

     

     

    CG & Sling Tensions Workshop Solutions:

    #1

    To find tension in A
    6+6=12, 6/12=.5  .5x8, 200=4,100 lbs
    (minimum wire rope diameter = ½”)

    To find tension in B
    6+6=12, 6/12=.5  .5x8, 200=4,100 lbs
    (minimum wire rope diameter = ½”)

     

    #2

    To find tension in C
    6/4=1.5, 1.5x(22,00/2)=16,500 lbs
    (minimum wire rope diameter = 1”)

    To find tension in D
    6/4=1.5, 1.5x(22,00/2)=16,500 lbs
    (minimum wire rope diameter = 1”)

     

    #3

    To find tension in E
    4+6=10, 6/10=.6  .6x16,000=9,600 lbs
    (minimum wire rope diameter = ¾”)

    To find tension in F
    4+6=10, 4/10=.4  .4x16,000=6,400 lbs
    (minimum wire rope diameter = 5/8”)

     

    #4

    To find tension in G
    7+3=10, 3/10=.3  .3x30,000=9,000  9,000x(8/4)=18,000 lbs
    (Minimum wire rope diameter = 1 1/8”)

    To find tension in H
    7+3=10, 7/10=.7  .7x30,000=21,000 21,000x(5/4)=26,250 lbs
    (minimum wire rope diameter = 1 3/8”)

    The R's of Rigging Managment

      
      
      
      

    The R’s of Rigging Management

    Review:  Be methodical in your approach to any rigging task.

    Research:  Be a student of your profession.  Load and rigging data – Don’t start until you get it; don’t stop until you get all of it.

    Responsibility:  Be willing to give it and receive it.

    Reinforcement:  Show support for those who work for you and those you work for.

    Require:  Demand thoroughness of yourself and others for each rigging assignment.  Show by example, not by lip service.  Require continuing education for everyone.

    Reserve:  Be cautious in making decisions.  Hold your judgment until all of the available information is known.

    Resist:  Resist the temptation to make decisions for people who need to make them as part of their learning process.  Be patient.

    Respond:  Respond quickly to those who are seeking answers or help.  Be wise in how to lend assistance.

    Reward:  Be liberal in your praise and compliments.  Let others know when a job has been done well.  Be consistent in your praise of things done, i.e. equal praise for equal jobs.

    Happy Rigging, Mike Parnell.

    This is an article from The Professional Rigger newsletter, 1988. To download this issue of The Professional Rigger, click The R's of Rigging Managment.

    Crane & Rigging Accident Workshop

      
      
      
      

    Enjoy this fictional rigging workshop, it makes for great safety meeting instruction.

    An open top container made of ¼” steel plate (10 lbs./sq. ft.) measuring (3’H x 6’W x 10’L) was being used at a construction site to transport scrap materials off the top of an 80’ building.  A rented mobile crane (when outriggers are extended, they form a 20’ x 34’ stand) would lower the container to the ground twice a day for unloading.  The container’s pad eyes had been damaged beyond use.

    Two synthetic web, eye & eye, 20’ slings (each having a safe working load capacity of 2,000 lbs. in a single vertical hitch) were basketed around the container.  All of the sling eyes were gathered in a 1” shackle with the pin down, and the shackle bail was attached to the crane hook.  Each sling was in a basket hitch slung around the broadsides of the load, straddling the approximate center of gravity, and the slings were approximately 4’ from each other at the underneath side of the load.

    The container held 2 half-full, 55 gallon drums of water and 3,300 lbs. of steel cutting scraps.

    Immediately after the shackle had been put on the hook, the operator picked up the load.  The container swung and made slight contact with the crane’s boom structure.  The operator then swung the boom 90 degrees to his left.  The conclusion of his swing placed the load off the rear of the crane.

    Reacting to a ground signalman, the operator was “booming down” to place the container at a greater radius.  The operator soon felt the crane getting “tippy”.  He reversed the action and began “booming up” while lowering the load.  He felt the tires settle back down to their original position.

    One sling began to slide towards the other.  Immediately the “moving” sling parted and the load tipped almost on end and started to slide out.  Then the second sling parted, dropping the load to the ground.

    1. How many OSHA violations can you find given the above information?
    2. What actions would you consider to be poor, improper, or dangerous rigging practices?
    3. Who was at fault for losing the load?  Was it: the building top workers, the crane rental company, the construction company owners, the crane operator, the ground level signalman, the sling manufacturer, or someone else?

    Feel free to leave comments below with your answers.  Crane and Rigging Accident Investigations have been a staple of ITI for over 25 years.  

    This is a workshop from The Professional Rigger newsletter, circa 1987.  To download this issue of the Newsletter, click here.

    Engineered Sling Protection - Oh the Variety!

      
      
      
      

    Engineered Sling Protection Companies in a variety of industries use different types of rigging equipment to handle loads of all shapes and sizes. Certain loads require the use of a specific type of sling. Often, employees in steel manufacturing and welding/fabrication use chain slings to rig and move ingots, slabs, plate, pipe and finished products. The work environment is rough and tumble, often at elevated temperatures which require rigging that will withstand the affects of corners and edges of materials in a dependable manner.

    Other industries that depend on chain slings as the material of choice include stevedoring, shipbuilding, and heavy construction. Metal mesh slings are generally restricted to manufacturing where dipping and product cleaning is practiced. These flexible slings handle objects that may be in bundles or in-process lengths. They are fairly dependable in limited heat and chemical applications and are typically used in pairs from the ends of a lifting beam in choker or basket hitches. They are resistant to load corners to a degree and can be coated with synthetic rubber-like material to provide friction when handling smooth objects. Wire rope slings are flexible and reasonably durable, but have a “memory” often taking on the contour of the load they are rigged to. Because of wire rope’s round shape, very few protectors have been developed for defending the wires and strands from load edges. Wires are often ripped or shredded resulting in some loss of strength and this condition can present a hazard to employees who handle the slings.

    The construction world often uses wire rope slings when utility loads such as steel beams, rebar, concrete or steel pipe, and wood or concrete piling are picked and handled on a repetitive basis. Newco Manufacturing makes a host of wire rope sling protectors to help defend the wires/strands during lifting (photo 1).

    Sling Protection 1#1

    Also, Interfron from Italy offers an aluminum “hinged” magnetically connecting device with a large groove to help form an arc, for the wire rope to bear against at load corners (photo 2).

    Sling Protection2#2

    Synthetic rigging such as flat web slings, synthetic roundslings and synthetic rope slings are common in many industries. They are flexible and lightweight when compared to their counterparts and easy to store. The volume of synthetic rigging in toolrooms and gang boxes has grown substantially since the 1960’s and will continue to do so in the foreseeable future. By nature of the material, they are susceptible to cutting and friction damage against load edges and surfaces. Of the 60 crane and rigging accident cases investigated by ITI in the last 25 years, 30 have been related to sling damage/failure and 30 were associated with rigging hardware, wire rope (crane operating ropes) and crane/rigging procedures. Of the sling related accidents, 87% involved synthetic web slings or synthetic roundslings. During our investigations, no synthetic slings failed due to improper manufacture or fabrication. To date, we have not found any cases yet where loads at high temperatures (1800+F) were the primary cause of failure. A handful of accidents involved ultraviolet ray degradation that caused significant loss of tensile strength resulting in a dropped load. In the lion’s share of cases, the cause of failure could be directly tied to external abuse. Load edges and super rough surfaces often created localized friction or cutting damage to the synthetic sling muscle, whether web fibers or core yarns. A significant contributor to synthetic sling damage is sling sliding, which can often melt or cut through even engineered sling protectors.

    In Photo 3 (right), note that sling sliding resulted in a failure that producedsling protection3 a fatality, due to heat generated between the load edge and web protector/enclosed web sling. As a general rule there are two basic rigging methods. The first method involves slings rigged directly between the crane hook and load shackles at the load. The slings touch only selected rigging hardware. The hardware needs to be “clean”, meaning no burrs, scoring or surfaces that can cause cutting of the synthetic slings. The second method generally involves rigging the slings directly to the load via basket or choker hitches. During the “direct contact” type applications we need to incorporate sling protection that will hold the sling away from edges or locations that can cause cutting damage. “Old school” practices allowed for sling protection to be made from retired slings (cut in 12” pieces), old fire hose or leather. We as users must start employing a more serious grade of sling protection, especially for synthetic slings. The material must be able to push or hold the sling away from the load edge during the lifting activity. A new type of rated and engineered sling protection in the marketplace is made by Linton Rigging Gear Supply. The patent pending design involves a piece of high density plastic round stock that is machined with a 900 notch designed to hug the load corner by lightly connecting with magnets.

    Also available is a style that fits to the flange of an I-beam (photos 4 and 5).

    synthetic sling protectionSynthetic sling protection

     

     

     

     

     

     

    #4,5

     

     

     

    The Meshguard by Lift-It Manufacturing incorporates metal mesh belting in a webbing sandwich (photo 6).

    sling protection  6 resized 600#6

    With contact pressures in the tens of thousands/lbs/inch/wide, the sling protection must be substantial and have the structural integrity to withstand the exerted force at the contact point. Often, the more important consideration may be the capacity of the engineered sling protection as the limiting factor, if it less than the sling in use. An important consideration is the overall width of the sling protection and its allowable loading per inch of width, when compared to the anticipated sling loading per bearing inch of width. Scott St. Germain of Slingmax notes that the Cornermax Pad has, “internal spacers that create a “tunnel” of cut protection, separating the pad and the sling from contacting the 900 load edge” (photo 7).

    sling protection7 resized 600#7

    This protection is designed with encased plastic rods that help create a barrier between the sling and load. Some sling protectors are made from super high density synthetic fibers sleeves (photo 8), which provide exceptional resistance to cutting.

    sling protection8 resized 600#8

    Other materials in the marketplace that are intended to provide resistance to abrasion and can be made from a radiator hose like material, steel-belted flat rubber, reinforced rubber conveyor belting or heavy duty webbing (photo 9).

    sling protection9 resized 600#9

    Slings can also be coated with neoprene or a rubberized compound to help fight abrasion and repel foreign matter like metal shavings. The owner/user of the synthetic rigging needs to investigate a variety of options and determine the best selection for their various applications. When employees grab synthetic slings for a job, a new axiom should come to mind, “Slings in the right hand, sling protection in the left hand”.

    Website addresses for the protection items noted throughout this article.

    Photo 1 www.newcomfg.com

    Photo 2 www.interfron.it

    Photo 3 Damaged sling protector (no web address)

    Photo 4 & 5 www.lrgsupplies.com/

     

    Photo 6 & 9 www.lift-it.com

    Photo 7 & 8 www.slingmax.com

    The author, Mike Parnell is the president of Industrial Training International, Inc. ITI provides crane and rigging training/consulting for hundreds of clients in the U.S. and around the world. Mr. Parnell is the ASME B30 Main Committee Vice-Chair, a member of five B30 Subcommittees, CIC Rigging Certification Committee Chair, and is a charter member of the Association of Crane & Rigging Professionals. He can be contacted at: 360-225-1100 or mike@iti.com.

    Rigging Quiz: Can you identify 5 hazards in this photo?

      
      
      
      
    Rigging Quiz photo

















    Check in next week for the answer!

    Horizontal Rigging - When Rolling a Load...

      
      
      
      

    As we begin to plan to move a load horizontally, using a set of industrial rollers, we should consider some options that can help ensure a success.

     

    1. Identify the weight and center-of-gravity of the load.

     

    2. Select a set of 3 rollers and “surround” the center-of-gravity at hard points underneath the load. When using three, we have continual pressure to the rollers’ bearing points, like a 3-leg milking stool. If the floor is uneven (undulations) and four rollers are in use, it is common for one roller to disengage causing diagonal loading of two rollers.

     

    3. If a single roller is near one end of the load, and the other two are opposing it on the other side of the center-of-gravity, the single roller is typically used as the “steering” roller. The shorter the “wheel-base” is, the more maneuverable the load. A long wheel-base causes challenges when turning corners. Think about the wheel-base underneath a school bus. With a short wheel-base, it can turn 90deg corners easily and efficiently.

     

    4. Ensure that each industrial roller has the necessary rated capacity to bear the amount of load intended for it.

     

    Happy trails my rigging friends,

     

    Mike

     

    Mike Parnell, ITI – Field Services

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