Ropes, Their Uses and Their Working load Limit Flashcards
Types of fibre ropes
Synthetic fibers- Nylon, polyester and polypropylene
Natural fibers- Manila and sisal
List the construction steps of rope
Fibers-twisted into yarns- yarns twisted into strands, and strands are twisted into lays. This construction is commonly called “laid” or “twisted” rope.
What does the term “lay of the rope” mean?
The direction that the lays turn. In a right-hand lay of rope, the lays are twisted in a clockwise direction, while in a left-hand lay rope the lays will he twisted in a counter-clockwise direction.
Name some descriptive features of Manila rope and its 6 grades
Its light yellow in color and has a smooth, waxy surface. Manila is about 35% as strong as nylon.
Yacht rope- highest quality, very pale yellow and expensive because of this it’s only used on special jobs.
Bolt rope- pale yellow rope
No.1 grade- usually identified by one or more color strands. Light yellow in color and is the lowest grade suitable for overhead lifting.
No.2 grade- slightly darker than No1 rope and doesnt have coloured identity strands. It loses strength more rapidly than No1 grade.
No.3- considerably darker than either No1 or No2 and loses strength very rapidly when in service
Hardware store rope- darkest and poorest grade of Manila rope. Since it is connected with a high percentage of short fibers, it has little strength, a short life and a much tougher texture with many fibre ends sticking up from the surface.
Other type of natural fibre rope and description.
Sisal rope. Almost white in color and has a course texture that is rough to the touch. Sisal rope is weaker than Manila rope and should be used only where cost rather than strength is the major factor. Sisal rope is NOT acceptable for construction rigging and hoisting.
About Nylon rope
3 times stronger than Manila rope. Usually pure white, soft, pliable and smooth to the touch. It has an elastic quality and will stretch up to 40% of its original length.
Nylon rope loses about 10% of its strength when wet, but regains its original strength when dried. Does not resist rot, unaffected by mildew and can withstand temperatures up to 150C (300F) without being damaged. It will be damaged by acids and alkalines.
The high elastic nature of nylon rope makes it capable of withstanding repeated shock loads. Can be a hindrance if you’re trying to lift loads in areas with restricted headroom
Aboyt Polyester rope
Similar to nylon rope in appearance. Not as elastic can only stretch up to 5% before breaking.
Polyester rope is 87% as strong as nylon, but because it’s not elastic, it can sustain only 60% of the shock load of nylon rope.
Polyester doesn’t lose and strength when wet, and it is not affected by acids or alkalines
About polypropylene rope
Commonly called “poly rope” is the most popular general-purpose synthetic fibre rope available in hardware stores. Available in a wide range of colors but most common is yellow. Smooth and somewhat slippery, lightweight and floats on water.
Polypropylene gradually softens as temperatures increase and loses 40% of its strength at the temperature of boiling water (100C or 212F). Higher temperatures will cause polypropylene to melt.
Polypropylene rope is 60% as strong as nylon and is capable of absorbing only 40% of the shock load of nylon. Polypropylene has the best insulating properties against electrical shock out of the ropes mentioned.
Formula for finding WLL for personal and materials
Design factor for materials- 5
Design factor for personal- 10
For materials-
WLL=breaking strength÷design factor
For personal-
WLL= breaking strength÷design factor
What is applied at the end of a rope to prevent unraveling? And name the steps
Whipping is the twine wrapped around the end of a rope to prevent unraveling. If it’s a synthetic rope it can also be melted or you can use tape.
The whipping should be 1 1/2 the diameter of the rope and should be half the diameter in from the end of the rope.
How much strength is lost when theres a sharp bend or knot in a rope?
What must be used if you have to hook a ring on to the rope?
50% and a thimble must be used
