5. Herramientas de Windows
5.2. OSForensics
Due to the occurrence of large number of accidents, workers and managers must know the correct procedures for material handling and storage to protect their health and safety. The safety professional must evaluate employee fitness and job tasks to determine the specific material-handling engineering and administrative controls and personal protective equipment required. To reduce the number of injuries caused by material handling, the project managers should try to minimise the manual handling of material as much as possible. They can combine or eliminate operations, introduce ergonomic principles to job design, and move material mechanically whenever possible. For hazards or jobs that cannot be mechanised, workers must learn safety techniques to reduce their risk of injury.
Although physical differences make it impractical to establish safe lifting limits for all workers, some general principles can be applied. In manual lifting, worker should make sure the route they must travel with the object is clear. Next, they should inspect the object and determine how best to grasp it to avoid sharp edges slippery surfaces, and other injury-producing factors. 1f mechanical aids are required (slings, block and tackle etc.) they should be secured before any lifting is done.
Guidelines for lifting must satisfy four criteria: - Epidemiological,
- Bio –mechanical, - Physiological and - Psycho-physical
Squat lifting emphasises correct placement of feet, straight back and bent knees, load held close to the body, correct grip, chin in, and use of body weight to move the object.
Team lifting and carrying emphasises two or more people working in unison to avoid injuries.
Accessories for manual lifting include hand tools (hooks, crowbars, rollers), jacks, and hand trucks. Jacks must be inspected regularly for signs of wear o defects. They should be placed on a clean, level surface and used with shims and blocks to prevent accidents.
Hand trucks include two-wheeled and four-wheeled carts and trucks. Workers should be aware of the main hazards
(1) running wheels off bridge plates or platforms, (2) colliding with other trucks or obstructions, and
(3) jamming their hands between trucks an other objects.
Temporary and permanent storage of materials should be neat and orderly to eliminate hazards and to conserve space. Materials storage must be carefully planned to allow adequate ceiling clearance under sprinklers; to keep aisle and exits clear; to install adequate bins, racks, and shelving; to secure mechanical lifting aids; to establish warning signs and signals; and to develop disaster and emergency planning procedures.
Rigid containers such as metal and box pallets, fibre board/cardboard boxes, barrels and kegs, rolled paper and reels, and compressed gas cylinders must be stored to conserve space and to provide easy access when the material is needed. Uncrated stock, such as lumber, bagged materials, pipes, and sheet metal, presents special storage problems. Supervisors must ensure that these material are secured and will not fall or come loose and injure workers when being removed from storage.
Hazardous liquid and combustible materials stored containers require special handling and storage methods to ensure worker’s safety and health. These containers must be protected from
using, or filling these containers. They must be taught to follow proper safety procedures and wear protective clothing.
Handling and storage of cryogenic liquids:
The storage and handling of cryogenic liquids (oxygen, nitrogen, argon, helium, and hydrogen) require careful planning and worker training. These liquids can cause frostbite on contact with skin and (except for oxygen) displace breathable air in an enclosed workspace. To reduce the risks in handling these materials, workers must know the nature and properties of each cryogen, know how to operate the equipment, use only approved and compatible materials, use protective clothing and equipment, know emergency medical techniques, and be prepared to deal with emergency situations.
Cryogenic liquids should be stored only in the containers designed for the particular gas. Containers should be transferred slowly into a warmer environment to prevent thermal shock to the containers and equipment. Workers must avoid dropping warm solids or liquids into cryogenic liquids, never breathe vapours from cryogenic sources, always check containers for leaks or loss of insulating vacuum, and use only approved transfer lines to move the liquid from one container or point to another.
Supervisors of shipping and receiving areas must be aware of appropriate regulations and labels. Floors must be level, able to bear the weight load required, and kept clean and slip resistant. Ramps must have slip-resistant surfaces, be equipped with handrails, and be clearly marked. Aisles should be wide enough to allow employees to move about while handling materials and to allow passage of loaded equipment. Warning signs, mirrors, and directional markings can ensure that workers avoid collisions and blind corners.
Workers in shipping and receiving must be trained in the proper use and handling of such common items as dock-boards, machines and tools, steel and plastic strapping, burlap and sacking, glass and nails, pitch and glue, barrels, kegs, drums, and boxes and cartons.
Common personal protective equipment used in material handling includes safety shoes, gloves, goggles, aprons, and leggings to protect against the most common injuries to hands, feet, extremities, and eyes. Where workers handle toxic or irritating materials, they should take showers or wash hands and face thoroughly at the end of their shifts. The management / contractor should provide a change of clothing or laundry facilities at the site.
Treating Cold-Contact Burns
Workers will rarely come in contact with a cryogenic liquid if proper handling procedures are used. However, in the event of contact with a liquid or cold gas, a cold-contact ‘ Burn ’ may occur. Actually, the skin or tissue freezes.
• As soon as is practical, immerse the affected part in warm water (not less than 105 F or more than 115 F, 0 C to 46 C ). Never use dry heat. The victim should in a warm room, if possible.
• If the exposure has been massive and the general body
temperature is depressed, the patient should be totally immersed in a warm-water bath. Supportive treatment for shock should be provided.
• Frozen tissues are painless and appear waxy and yellow. They will become swollen and painful and prone to infection when thawed. Do not re-warm rapidly. Thawing may require 15 to 60 minutes. For white people, thawing should continue until the pale blue tint of the skin turns pink or red. For black people, assess frostbite by the swelling and blistering of the skin. Reduction of swelling indicates alleviation of frostbite. Morphine or tranquillisers may be required to control pain during thawing and should be administered under professional medical supervision.
• If the frozen part of the body thaws before the doctor arrives, cover the area with dry, sterile dressings and a large, bulky protective covering.
• Alcoholic beverages and smoking decrease blood flow to the frozen tissues and should be prohibited. Warm drinks and food may be administered.
7.1.1 Winch :
Crabs and Winches may be either hand operated or electrically driven. Some form of braking or safety lowering device should be installed, and portable units should be installed securely against the pull of the hoisting rope or chain.
Under Rule 59, The Building and Other Construction Workers (Regulation of Employment and Conditions of Service) Central Rules, 1998 provides the statutory requirements to be complied with while using the winch. A schematic diagram of the winch is given below
The following are some of the guidelines given for the safe operation of the winches:
• The Safe Working Load of the winch should be marked and
this should never be exceeded.
• Barricade guard should be installed to protect the operator against flying strand of wire and the recoil of broken ropes. The operator should also be protected against extreme weather condition.
• It should be placed on a firm base and properly anchored.
• The brake, ratchet arrangement, gear and pinion including
The operator of this car puller winch stands behind the shield, which protects the employee if the rope breaks.
• Ratchet arrangement should be kept in position while hoisting a load.
• Tie rod should be adjusted not to allow drum movement
causing clutch arrangement to slip.
• The locking pawl on the ratchet of a winch frequently
presents a serious hazard to fingers of the operator particularly when he attempts to disengage the pawl. To reduce this hazard, a small lever may be welded to the pawl so that it can be safely grasped.
• Hand operated equipment that has a crank handle instead of a hand wheel poses a major danger if operator loses control while lowering the load (struck by the revolving handle). Provide a dog to lock the gears. A pin through the end of a crank will keep it in the socket during hoisting operation. • Providing strap brake will be useful when load is to lowered
7.1.2 Reeving :
If more than one tackle block is used in material handling, the process of connecting them is termed as REEVING;
Block and Tackle :
A safety factor of 10 is recommended for determining the safe working load of Manila rope (falls) in a block-and tackle assembly. This large safety factor allows for
(1) error in estimating the weight of the load,
(2) vibration or shock in handling the load on the tackle, (3) loss of strength at knots and bends, and
(4) deterioration of the rope due to wear or other causes.
The governing factor usually is the safe working load of the blocks, rather than of the falls (rope).
By multiplying the number of sheaves and rope parts, the weight of the load that can be handled by the rope multiplies but does not correspondingly increase the strength of the blocks. Calculations show that, in most instances, using a safety factor of 10 for the rope automatically makes the load on the blocks correspond to the rope size within safe work load limits. (Mark blocks with their safe working load. as specified by their manufacturers.) The total weight on the tackle should never exceed this safe load limit. The safe work loads for rope used in block-and-tackle assemblies conversely 1 / 10th of the block's breaking strength, based on a safety factor of 10.
To find the required breaking strength for new rope, proceed as follows:
1. For each sheave of 3 in. (7.6 cm) in diameter or larger, add 10% to the weight of the load to compensate for friction loss. 2. Divide this figure by the number of ropes or parts running
from the movable block.
2. Friction loss (10% for each sheave) = 40% or 800 lb (363 kg). 2,000 + 800 = 2,800 lb (1,270 kg), which divided by 4 (the number of parts at the movable block) = 700 lb (3 1 8 kg). 3. Applying the safety factor of 10 (10 x 700) gives 7,000 lb
(3,200 kg), the required breaking strength of the rope.
4. New Manila rope of 7/8 in. (22 cm) has a breaking strength of 7,700 lb (3,500 kg) and, therefore, is the proper size for the load. Synthetic fibres would have greater tensile strength. The safe work load limit for two double blocks made for rope Of 7/8- in. (22-cm) diameter is 2,000 lb (900 kg)-the equivalent of the total load in the example.
Attach the rope to the block with a thimble and a proper eye splice. A mousing of yarn or small rope should be placed on the upper hook of a set of falls as a precaution against its accidental detachment.
Inspect blocks thoroughly and frequently, paying particular attention to parts that are subject to wear.
Figure below shows how tackle blocks should be reeved.
If the sheave holes in blocks are too small to permit sufficient clearance, excessive surface wear of the rope will occur.
Likewise, excessive internal friction on the fibres will occur if the diameter of the sheave is too small for the rope.
When using block and tackle in confined spaces, provide guards on the pulley block so that a person's hands cannot be caught between the pulley and the rope.
When blocks and falls are used to lift heavy materials or to keep heavy loads in suspension, as on heavy-duty scaffolds, wire rope is more serviceable than fibre rope.
7.1.3 Rigging:
In lifting the various materials and supplies, a number of standard chokers, slings, bridle hitches, and basket hitches can be used. Because loads vary in physical dimensions, shape, and weight a rigger needs to know what method of attachment can be safely used. It is estimated that at least about 15 to 50% of the crane accidents are due to improper rigging.
The contractor needs to train those employees who are responsible for rigging loads about the :-
1. Knowledge of the load 2. Judgement of distance
3. Selection of tackle and lifting gear
4. Proper operational directions to be given.
The most important rigging precautions are to determine the weight and the size of the load before attempting to lift it. This will determine the type of equipment and gear to be used and the method of slinging.
There are various methods of hitching the load to the hook through choker hitch, basket hitch etc. Some of the types of hitching / slinging are given below: -
Watch for broken wires in
A wire rope which has been kinked. A kink is caused by pulling down a loop in a slack line during improper handling, installation, or operation. Note the distortion of the strands and individual wires. Early rope failure will undoubtedly occur at this point.
A “ bird cage” caused by sudden release of tension and resultant rebound of rope from overloaded condition. These strands and wires will not return to their original positions.
A wire rope which has been subjected to repeated bending over sheaves under normal loads. This results in “fatigue” breaks in individual wires-these breaks are square and usually in the crown of strands
A wire rope which has jumped a sheave. The itself is deformed into a “curl” as if bent around a round shaft. Close examination of the wires show two types of breaks – normal tensile “cup and cone” breaks and shear breaks which give the appearance if having been cut on an angle with a cold chisel.
An example of “fatigue” failure of a wire rope which has been subjected to heavy loads over small sheaves. The usual crown breaks are accompanied by breaks in the valleys of the strands – these breaks are caused by “strands nicking” resulting from the heavy loads.
A fatigue break in a cable tool drill line caused by a tight kink developed in the rope during operation
Method of Attachment:
All hooks and rings used as sling connections should develop the full rated capacity of the sling.
Sockets and compression fittings, when properly attached with wire rope sling should develop 100% of the rated strength of the wire rope. Swaged sleeve sling endings should develop 92 to 95% of the wire rope’s strength. Compression fittings and swaged sleeve fittings are available from the wire rope manufacturers.
Hand tucked splices develop about 90% of the rope’s strength in ropes having diameter less than ½” and 80% for larger diameters.
The recommended load rating for a sling assembly is usually based on 1/5 the calculated strength of the assembly.
As a general rule, hooks and rings, oblong links, pear shaped links, coupling links and other attachments should be made of the same, or equivalent, heat treatable alloy steel as the chain itself. In most cases the attachments are provided by the manufacturers themselves.
When rigging irregular shaped loads or heavy loads proper rigging should be made. Some of the special rigging methods are shown below: -
The three most common hitches for all types of
slings are the Regular, Choker, Basket Hitch. Typical Double-chain sling Identification tag
Safe Slinging Practices:
2 – Leg Bridle Hitches 1 - Single Vertical
Hitch
NOTE: Load may be supported on only 2 legs while 3rd leg balances it.
3-Leg Bridle Hitch
Leg length can be adjusted with turnbuckles.
Single Double Wrap Basket Hitch
This hitch compresses the load and prevents it from slipping out of the slings.
Pair of Double Wrap Basket Double Wrap Basket Hitch
Not recommended Recommended
Right
“Double” choker Use to turn loads
Types of Slinging and SWL of this Mode
:
Sling with Choke Hitch SWL= 0.8 x SWL of rope
Load held on one part of rope
Load held on Two part of rope Packers to prevent chafe
Simple sling with two legs SWL= 0.8 x SWL of rope
Sling with two separate legs SWL= 1.25 x SWL of rope
Load held on two parts of rope
Endless Sling with Two legs and Choke Hitch
SWL= 1.60 x SWL of rope Load held on four
parts of rope Packers to prevent chafe Packers to prevent chafe
Endless Sling with Four Legs SWL= 1.60 x SWL of rope
Sling with Four Separate Legs SWL= 2.00 x SWL of rope
Sling Calculation: -
When this angle is greater than 450 SWL = SWL (of single vertical hitch) x 3/4
When this angle is less than 450
SWL = SWL (of single vertical hitch) x A/B
Determining capacity of single choker hitch
When this angle is greater than 450 SWL = SWL (of single vertical hitch) x ¾ x H/L x 2
When the choker angle is less than 450
Special Rigging / Heavy Rigging: -
Double, Triple, quad chain sling to handle loads of virtually any size or shape.
Out - of - balance load by a double sling with chain leg adjusted (Two short chains with grab hooks attached to the master links.)
Extreme wear at load bearing surfaces. Wear
Surfa
7.1.4. Test Certificates:
THE BUILDING AND OTHER CONSTRUCTION WORKERS