Wire Ropes, Chains, Slings And Their Working Load Limits Flashcards
What identifications are on a wire rope tag?
Length Diameter Composition Pattern Formation Grade
Example: 300m (1000ft) 19mm (3/4in.) Diameter, 7×31 Warrington, reformed, improved plow steel, fibre core, right regular lay
How do you measure the diameter of wire rope?
How do you identify the composition of wire rope?
At its thickest point.
There are 3 ways to identify wire rope composition:
- number of strands
- number of wires in each strand
- pattern of the wirse un the strand
What are the 4 patterns?
Ordinary
Seale
Warrington
Filler
What do the ordinary and Seale pattern look like and how is Seale better?
Ordinary has all the wires in the strand the same diameter.
Seale has thicker wires on the outside and thinner wires on the inside. The Seale pattern provides greater resistance to abrasion than does the ordinary pattern. The thinner wires on the inside increase the strands flexibility.
What do the Warrington and Filler patterns look like? And what are they good for?
Warrington has alternating thick and thin wires. This provides greater flexibility as well as more resistance to abrasion.
Filler wires have very thin wires between layers of thicker wires to prevent the outer wires from crowding into the valleys of the inner wires, making the rope resistant to crushing.
Explain the differences of preformed wire rope and Non-preformed
Preformed has each strand bent or moulded to match the shape it will have in the completed rope. As a result it can be cut without the ends untwisting.
Non-preformed rope is made from wire just as it comes out of the spool. Twisted to form strand, which in turn are twisted to form rope, they have a tendency to return to their straight form
What are the different grades of wire rope?
100/110 plow steel, 110/120 improved plow steel, 120/130 extra improved plow steel
The stronger the grade of rope is the less the rope is able to withstand repeated bending
What are the 2 different types of center cores and they differences?
Fibre core
Fibre cores are made of fibre rope. Most common fibre cores are sisal and Manila but they can be synthetic as well such as polypropylene or nylon. They offer more flexibility than other cores but are more easily crushed.
Independent wire rope core (IWRC)
the wire rope core is a small wire rope. It produces good flexibility and resistance to crushing
Describe what the ropes “lay” is
“Lay” is the direction the wires and the strands are wound to make the rope. Both lays are available in right and left styles.
Regular lay has the wires of the strands wound in one direction while the strands are wound in the opposite direction.
Lang lay has both the wire and the strands wound in the same direction
There is also a rope called “non-rotational” this rope has an outer layer of strands wound in one direction and an inner layer wound in the opposite direction. It’s designed not to spin when a load is applied to it
When should a wire rope be replaced?
If there are 6 or more randomly distributed broken wires in one rope lay or 3 or more broken wires in one strand in one rope lay (A rope layer is the length along the rope in which one strand makes a complete revolution around the rope).
It should also be replaced if there are 1 or more broken wires near an attached fitting
What are the 4 different types of wear a wire rope can have?
Peening- when wire rope strikes against a structural part of the machine or beats agaisnt a toe or itself.
Scrubbing- the displacement or wires and strands caused by wire rope rubbing against itself or another object.
Fatigue fracture- when a wire breaks with square ends and shows little surface wear. Usually caused by contact between adjacent strands. In almost all cases, these failures are related to bending stresses or vibrations.
Corrosion- usually occurs internally before there is any visible external evidence. Usual cause is lack of lubrication. If you see pitting on wire rope immediately remove the rope from service. Slight discoloration from rusting means the rope needs lubrication. In situations of extreme corrosion it maybe be necessary to use galvanized wire rope
What are some ways the strands can be damaged?
“Bird caging” is caused by sudden stops. Kinks are usually cause by faulty handling. Bulging indicates that there is core slippage ir “turns” are being put into or taken out of the rope. Replace the rope if it has any of these damages or any gaps between strands or if the core is sticking out.
Heat damage will cause lubrication loss and damage the core if its fibre.
Electrical damage will fuse wires together and should be replaced
What are some qualities about chains that might make them better or worse than wire rope?
They can better withstand high temperatures and abrasion. They store easily and grip the load well. They resist abrasion and corrosion better than wire rope and are good at lifting rough loads. Chains have no elasticity and are very poor at withstanding shock loads.
How are chains graded?
By its stock diameter and grade. The minimum grade acceptable for overhead hoisting is system 8 chain grade A. Each link must bear an “8” stamped into the surface. It maybe also bear the letter “A” along with the number 8 (8A). The standards for chain are established by the National Association of Chain Manufacturers
Where should a chain be put out of service?
When the amount of wear equals 5% of the links diameter fir chains less than 22mm (1in.) Or 10% for chains over 1in.
Never place a load on a twisted or knotted chain. If possible avoid sharp bend, they tend to overload the links at the bend. If any link shows stretching of 3% its original size, do not use it for lifting.
Heat will also have adverse effects on the lifting capacity of chain. “A chain sling must not be exposed to a temperature above 260C (500F) unless otherwise permitted by the manufacturer”-WorksafeBC (See page 53 for full chart)
