The D/d Ratio ---The D/d Ratio is the ratio of the diameter around which the sling is bent divided by the body diameter of the sling.

The D/d Ratio is the ratio of the diameter around which the sling is bent divided by the body diameter of the sling.


Example: A 1/2" diameter wire rope is bent around a 10" diameter pipe; the D/d Ratio is 10" divided by 1/2" = D/d Ratio of 20:1

This ratio has an effect on the rated capacity of slings.

When a wire rope is bent around any sheave or other object there is a loss of strength due to this bending action. As the D/d ratio becomes smaller this loss of strength becomes greater and the rope becomes less efficient. This curve relates the efficiency of a rope diameter to different D/d ratios. This curve is based on static loads and applies to 6-strand class 6x19 and 6x37 wire rope.

Eye & Eye Slings The LOOP of an eye & eye sling has nearly DOUBLE the strength of it's body. For this reason the D/d ratio in the LOOP is just half as critical as opposed to when the sling is used in BASKET hitch. In most cases the shackle or hook over which the sling is placed will have a sufficient D/d ratio. On the other hand, do not place too LARGE an object into the sling eye as this will result in splitting forces affecting the sling splice and sling safety. The object (a shackle, a crane hook, a steel bar,....) you place into the sling eye must not be larger than 1/2 of the sling eye length. When a sling is used in a BASKET- or CHOKER HITCH with D/d ratios smaller than listed in the capacity tables, the rated capacities (or WLL's) must be decreased. For example: The BASKET and CHOKER hitch capacities listed (in all Standards and Regulations) for 6-strand ropes are based on a minimum D/d ratio of 25:1 An object you place into a 1" diameter 6-strand wire rope sling using a basket- or choker hitch must have a minimum diameter of 25". If the object is smaller than the listed 25:1 D/d ratio the capacity (or WLL) must be decreased. Table A) illustrates the percentage of decrease to be expected. Note: The minimum D/d ratio for GATOR-FLEX® and for TRI-FLEX® slings are just 5:1. If you need to lift small objects and don't want your sling to kink or bend permanently use these types.

Eye length must NOT be smaller than twice the object (e.g. a hook) diameter.   If the shackle body has AT LEAST the same diameter as the sling (D/d 1:1) the capacity need not to be adjusted   If the object lifted with a 6-strand wire rope sling in a basket hitch is at least 25 x larger than the sling diameter (D/d 25:1) the basket capacity need not to be adjusted.   If the shackle or object has 2 times the diameter of a 6-strand wire rope sling (D/d 2:1) the basket sling capacity must be reduced by 40%   It is better to use a larger shackle or a Wide Body shackle type. If the shackle or object has at least 5x the sling diameter (D/d 5:1) the basket sling capacity must still be reduced by about 25%.

Crosby® Wide Body shackles are available in capacities ranging from 75 tons to 1000 tons.   Standard shackles have round stock bodies and come in capacities ranging from 1/3 tons to 400 tons   Load Hooks must have sufficient thickness to ensure proper sling D/d ratio, particularly when using slings in an inverted basket hitch; that is the sling BODY is placed into the hook and the sling EYES are facing downward
Endless Slings Endless (or Grommet) slings DO NOT HAVE A LOOP which has double the strength of the sling body. Prior to EVERY lift YOU, the user, has to determine if the D/d ratio is equal or higher than the ones listed in the capacity tables. For endless 6-strand and Gator-Flex endless type wire rope slings the rated capacities have already been adjusted to be used at a D/d Ratio of 5:1. See the WLL Tables for details.
Use large enough hooks AND large diameter shackles to avoid crushing and kinking of the sling.   If possible use Wide-Body shackles. They increase the D/d ratio and you gain sling strength.   Proper D/d ratio for the sling capacity. If the sling is too short you may have to adjust the capacity because of the sling angle.   Small diameter shackles reduce the sling strength and, most likely, that small diameter shackle also has insufficient capacity for that job. Shackle or not, objects to be lifted and all hook up points MUST at least ensure a D/d Ratio of 5:1.

The Fire Triangle

In order to understand how fire extinguishers work, you first need to know a little bit about fire.

Four things must be present at the same time in order to produce fire:

Enough oxygen to sustain combustion,

Enough heat to raise the material to its ignition temperature,

Some sort of fuel or combustible material, and

The chemical, exothermic reaction that is fire.

Take a look at the following diagram, called the "Fire Triangle"

 

Oxygen, heat, and fuel are frequently referred to as the "fire triangle." Add in the fourth element, the chemical reaction, and you actually have a fire "tetrahedron." The important thing to remember is: take any of these four things away, and you will not have a fire or the fire will be extinguished.
Essentially, fire extinguishers put out fire by taking away one or more elements of the fire triangle/tetrahedron.
Fire safety, at its most basic, is based upon the principle of keeping fuel sources and ignition sources separate.

Fire extinguisher iinspect & maintenance

Inspect fire extinguishers at least once a month (more often in severe environments).
Fire extinguisher maintenance is important for everyone’s safety.
You must ensure that:

• The extinguisher is not blocked by equipment, coats or other objects that could interfere with access in an emergency.
• The pressure is at the recommended level. On extinguishers equipped with a gauge (such as that shown on the right), the needle should be in the green zone - not too high and not too low.
• The nozzle or other parts are not hindered in any way.
• The pin and tamper seal (if it has one) are intact.
• There are no dents, leaks, rust, chemical deposits and/or other signs of abuse/wear. Wipe off any corrosive chemicals, oil, gunk etc. that may have deposited on the extinguisher.

Some manufacturers recommend shaking your dry chemical extinguishers once a month to prevent the powder from settling/packing.
Fire extinguishers should be pressure tested (a process called hydrostatic testing) after a number of years to ensure that the cylinder is safe to use. Consult your owner's manual, extinguisher label or the manufacturer to see when yours may need such testing.
If the extinguisher is damaged or needs recharging, replace it immediately!

IMPORTANT: Recharge all extinguishers immediately after use regardless of how much they were used.

What is the difference between a fire extinguisher inspection and fire extinguisher maintenance?

INSPECTION
An inspection is a “quick check” to give reasonable assurance that a fire extinguisher is available, fully charged and operable. The value of an inspection lies in the frequency, regularity, and thoroughness with which it is conducted. The frequency will vary from hourly to monthly, based on the needs of the situation. Inspections should always be conducted when extinguishers are initially placed in service and thereafter at approximately 30-day intervals. 

MAINTENANCE
Fire extinguishers should be maintained at regular intervals (at least once a year), or when specifically indicated by an inspection. Maintenance is a “thorough check” of the extinguisher. It is intended to give maximum assurance that an extinguisher will operate effectively and safely. It includes a thorough examination and any necessary repair, recharging or replacement. It will normally reveal the need for hydrostatic testing of an extinguisher.

Rigging Jobs

Proper Rigging Safety Techniques...

There are significant safety issues to be considered, both for the operators of the diverse "lifting" devices, and for workers in proximity to them. To a crane operator, few experiences may be as frightening as when a crane becomes unbalanced while a load is being lifted or when the crane collapses under the weight of an excessive load.

• Check limit switches before rigging the load
  
• Make sure the load does not exceed rated capacity.
  
• Know the center of gravity of the load.
  
• Attach load above the center of gravity for stability.
  
• Select hitch that will control the load.
  
• Know the rated capacities of rigging and slinging
  
• Inspect all rigging before use
  
• Protect the sling from sharp corners.
  
• Allow for increased tension due to sling angle.
  
• Equalize loading on multiple leg slings
  
• Allow for load reductions when using choker hitches
  
• Attach tag line prior to lift.
  
• Keep personnel clear of lift area.
  
• Wear hard hats when making overhead lifts.
  
• Lift load a few inches and verify rigging.
  
• Check for any loose items.
  
• Know limitations of hoisting device.
  
• Start and stop SLOWLY! Watch for obstructions (not only hook and load but outboard end of the bridge).
  
• Check pathway is clear before making a lift (use a spotter for blind spots).
  
• Verify hook completely closes.
  
• Use appropriate hand signals.
  
• Maintain load control at all times.
  
• Report suspected drum wrappings immediately (if drum has fewer 2.5 wraps remaining).
  
• Never leave load unattended.
  

Hoisting and Rigging Safety
Selection of the sling is only the first step in the rigging process. Hoists are often used when materials are too heavy or bulky to be safely moved manually. Because hoists rely upon slings to hold their suspended loads, slings are the most commonly used materials-handling apparatus. In part because of the complex nature of the seemingly simple task of lifting an object, an effective program is necessary to lift and move heavy loads safely.
Workers involved in hoisting and rigging operations should receive training in the following:

• Sling and hitch types
  
• Sling capacity determination
  
• Equipment inspection, care, and maintenance
  
• Load weight and center of gravity determination
  
• Safe lifting techniques
  The crane regulations cover a number of areas, including:
  

• Ground conditions.
• Assembly and dis-assembly.
• Work around power lines
• And inspections.

They also address:

• Signaling.

• Fall protection.
• Work area control.
• Operator certification.
• Qualifications for "signal persons" and maintenance personnel.
• Training.

While you should be familiar with all of the provisions of the crane regulations that affect you and the people that you work with, some of the recent changes in the regulations are particularly notable.

Before a crane is positioned or assembled, it must be verified that the "ground conditions" are firm, drained and graded so that the crane can set up safely.

Crane assembly, disassembly and set-up must be overseen by personnel who are "competent" and "qualified". There are new restrictions as to how far a crane must be from power lines when it is being assembled, operating or traveling.
Generally it must be at least 20 feet away at all times. But this can vary depending on the amount of current going through the lines). By November 10, 2014 all crane operators must be "certified" by either:

• An accredited testing organization.
• A licensed government agency.
• Or a qualified employer program.

"Signal persons" must be "qualified" based on the criteria OSHA has specified in the regulation, by either:

• A "third party qualified evaluator".
• Or their employer’s own "qualified evaluator".

Pythagoras Formulas

Theorem of Pythagoras: a² + b² = c² c² - b² = a² c² - a² = b² c = √(a² + b²) a = √(c² - b²) b = √(c² - a²) Hypotenuse sector p: p = ( a² ) / c Hypotenuse sector q: q = ( b² ) / c Height h: h = √(p * q ) Perimeter: a + b + c Surface area: ( a * b ) / 2 Angles: α = arccos( (b² + c² - a²) / 2bc ) β = arccos( (a² + c² - b²) / 2ac ) γ = 90 ° α + β = 90 °

Hypotenuse: c Catheti (legs): a,b

A 500 tonne Liebherr LTM1500 collapsed

A 500 tonne Liebherr LTM1500 all Terrain crane overturned, a 35-year-old crane operator died after the crane in which he was working collapsed.

The machine was short rigged and only had one section extended, in fact it appeared to have been setting up when it went over.



The boom came down across the road striking an overpass.

PROCEDURES AND PRECAUTIONS FOR LIFTING OPERATIONS

When the signalman desires to give the operator any instructions other than those provided by the established  signal  system,  the  operator  should  be instructed to stop all motion FIRST.


Hand signals can be used effectively when the distance between the operator and the signalman is not great,  but  two-way  radios  should  be  used  when  the distance  or  atmospheric  conditions  prevent  clear visibility. Adequate   lighting   and   signalling arrangements  must  be  available  during  night  work,  and the equipment must not be operated when either is inadequate.

PROCEDURES AND PRECAUTIONS FOR LIFTING OPERATIONS



The  most  important  rigging  precaution  is  to determine the weight of all loads before attempting to lift them, to make ample allowances for unknown factors, and to determine the available capacity of the equipment  being  used.  In cases where the assessment of load weight is difficult, safe load indicators or weighing devices should be fitted. This chapter also includes a section dealing with the estimation of load weights.

It is equally important to rig the load so that it is stable. Unless the center of gravity of the load is below the hook, the load will shift.

The  safety  of  personnel  involved  in  rigging  and hoisting operations largely depends upon care and common  sense.  Remember  these  safe  practices.

1. Know the safe working load of the equipment and tackle being used. Never exceed this limit.
2. Determine the load weight before rigging it.
3. Examine all hardware, equipment, tackle, and slings   before   using   them   and  survey   defective components.  Discarded  equipment  may  be  used  by someone not aware of the hazards or defects.
4. Never can-y out any rigging or hoisting operation when the weather conditions are such that hazards to personnel, property, or the public are created. You must carefully examine the size and shape of the loads being lifted to determine if a hazard exists during high wind speeds.  Avoid  handling  loads  that  have  large  wind- catching  surfaces  that  could  cause  loss  of  control  of  the load during high or gusty winds.  The wind can critically affect  the  loading  and  load-landing  operation  and  the safety of the personnel involved (fig.).