Three strands of rope

A. Marine fibre rope

1. Type, purpose and characteristics of fiber rope

1) natural fiber rope

(1) white brown rope: made of wild plantain or tequila, it is light yellow.

Purpose: generally used as cargo hauling rope.

Advantages: soft, light, elastic.

Disadvantages: after damp, will expand hair hard, and easy mildew change.

(2) cotton hemp rope: a mixture of cotton and hemp treated with anticorrosive treatment and twisted into small strands, then woven into a rope with a few small strands.

USES: used as a rope, a rope, etc.

Advantages: soft, smooth, difficult to twist.

Disadvantages: lower strength, less elasticity, less corrosion resistance.

(3) oil hemp rope, hemp, soaked with tar corresponding water imbibition, elasticity and strength is low, the ship is only used for binding wire rope, Manila rope or femoral head, in case of funiculus.

Three strands of rope

2) synthetic fiber rope

Synthetic fiber rope is also called chemical fiber rope, or chemical fiber rope. The ship's custom is called nylon rope. At present, the synthetic fiber rope has almost completely replaced the natural fiber rope in mooring, and the commonly used synthetic fiber rope is nylon cord and polypropylene rope. Their advantages are light weight, strong strength, anti-mildew, corrosion resistance, good flexibility and elasticity. The nylon rope has the highest strength and friction. The weight of the chemical fiber rope is the lightest, which can float on the water surface and not absorb the strength of water. Therefore, it is especially suitable for Marine mooring rope. The polyamide rope is heavier and less elastic than the previous two. It is commonly used as a tackle.

2. Specification and strength of fiber rope

(1) diameter

The thickness of the fiber rope is expressed in its diameter, in millimeters (mm). Some places like to use the English unit inch (in), the measure is the circumference of the British unit, when measuring the diameter, use the size of its largest place, with 1/4, 1/2, 3/4 in, in less than 1in. Because:

1 in = 25.4 mm

D = perimeter c/PI

The conversion equation of circumference and diameter can be simplified as:

Perimeter C (in)/diameter D (mm) = 1/8

The conversion of rope diameter and circumference with this conversion equation is simple, convenient and practical.

(2) length

The length of the fiber rope is the length of the whole bundle of new ropes, and there are both metric and English.

Metric: 1 bundle is 200m, or 210m.

British system: 1 bundle is 120 (720ft), equivalent to 220m.

(3) quality

The quality of the fiber rope is estimated by the following formula for each bundle of 200m.

The quality of each bundle of rope is:

W = 0.15 D&sup 2; (kg)

In the formula: D -- -diameter, mm.

The quality of each bundle of rope is:

W = 0.121 D&sup 2; (kg)

In the formula -- D diameter, mm.

Three strands of rope

2. The strength of the fiber rope

In order to avoid the danger of breaking the cable, we must understand the strength of the rope before using it to ensure the safety. The strength of fiber rope can be divided into breaking strength and strength.

(1) breaking strength: the force of the cable is gradually increased to the strength of breaking.

(2) intensity of use (also called work intensity) : refers to the strength used to ensure the safe use of fiber rope, which is generally taken as 1/6 of breaking strength and the safety factor is 6.

Use strength = breaking strength/safety factor

This is the conversion formula for the strength of the new rope. If the fiber rope has been used, the safety factor should be increased according to its specific conditions to ensure the safety of the rope.

When the strength of the fiber rope is not understood, the following formula can be used to estimate the strength and the actual difference, but it is generally more secure.

(3) estimation of fiber rope breaking strength

Breaking strength of white brown rope = 53 D&sup 2; (N)

Breaking strength of synthetic fiber rope = 137 D&sup 2; (N)

In the formula: D -- the diameter of the rope, mm; 1 kilogram (KGF) (non-statutory measurement unit) = 9.8 Newton (N)

Example 1: a 30mm diameter white coir rope allows the lifting of multiple objects?

Solution: according to the calculation formula, the breaking strength of white coir rope is 53 D&sup 2; (N), the use strength is 1/6 of the breaking strength, and the mass of the object which can be hoisted by a 30mm diameter is:

53 D&sup W = 2; (N)/(6 x9. 8) = 811 kg

A: a 30mm diameter white brown rope can lift an object of 811kg.

Example 2: object 1.5 t, ask how much size of chemical fiber rope to hang?

Solution: 137 d & sup2; / 6 = 1500 x9. 8

D = 25.4

Answer: the diameter of the chemical fiber rope is 25.4mm.

(4) factors to be considered when estimating the strength of chemical fiber rope

New and old: the above estimation formula is based on the new rope, the old rope is smaller than the new rope, the new rope will be stored for two or three years, and the strength will be reduced by 15%.

Wet condition: after damp, the intensity of white brown rope will decrease by about 25%, and chemical fiber rope will be reduced by 5%.

If the force is used suddenly, the strength should be calculated according to the original 50%.

Whether or not to knot: after knot, use should also reduce the use intensity.

Three strands of rope

3. The use and storage of fiber rope

1. Use and storage of white brown rope

(1) when the white brown rope is damp, it will be shortened, rainy, foggy, and should be relaxed in the open air, so as to avoid the contraction of the twill or easy to loosen.

(2) wash and dry with fresh water when wet or muddy. If the surface is dry, the rope is still stiff, which is still damp in it, so it must wait for the rope to dry out and become soft before collecting the storage. Inventory should be pay attention to the ventilation, dehumidification, with 10 to 21 ° C temperature inside advisable;

(3) prevent the white brown rope from contacting acid, alkali and other chemicals, so as to prevent the fiber from being stale, especially when it is directly related to the high rope of personal safety, jumping rope, insurance rope, etc. It should be hung up in case of mildew, and it must not be used for any other purpose, nor can it be worn on the deck;

(4) the left hand rope should turn the steering wheel counterclockwise, and the right hand rope should be clockwise to avoid kinking.