The small joint method is to disassemble the single strands of two flies and weave the strands of two rope ends together in a certain way. The rope pulled out in this way is that the strands of two ropes are combined together within the scope of the joint, so the end of the rope becomes thicker. Generally, the butted rope does not need to pass through pulleys, but is only used to increase the length of the rope. Its joint length is short, generally defined as (40 ~ 50) d, and for ropes used in important positions, the joint length can be extended to (80 ~ 100) d, so the docking method is also called short insertion.
The connection mode of large steel wire rope is mostly used for endless rope winch transportation, and the winch steel wire rope is connected with the joint. For example, the length of wire rope used in the endless rope transportation system in this mine requires 4 000 m, while the length of domestic wire rope is generally 1 000 m/ piece. In this case, it is necessary for users to order 4 000-meter-long wire ropes from manufacturers. If the manufacturer cannot deliver the goods to the site, it is necessary to connect two wire rope joints by extension. This kind of joint requires high quality. It is necessary to ensure that the thickness of the wire rope joint is similar to that of the original wire rope segment (actually slightly thinner), so that the wire rope can smoothly pass through the wheel groove and be neatly arranged on the drum during operation. Practice has proved that the tensile strength of the wire rope at the joint can completely reach the tensile strength of the original design wire rope.
Steel wire rope is a spiral steel wire bundle, which consists of steel wire, rope core and grease. Wire rope is a kind of rope which is twisted into strands by multiple layers of steel wires, and then twisted into a spiral shape by a certain number of strands around the rope core. In material handling machinery, it is used for lifting, traction, tensioning and bearing. The wire rope has the advantages of high strength, light weight, stable operation and reliable operation.
Wire ropes can be classified according to their materials, surface conditions, twisting methods and uses.
According to material classification
1. Carbon steel wire rope is made of high-quality carbon structural steel wire.
2. Stainless steel wire rope, which is made by twisting stainless steel wires.
Classification by surface state
1. Phosphating coated steel wire rope (China patent), referred to as phosphating steel wire rope. The phosphating film of rope steel wire weighs 3-60g/m2. Strands, steel cores and wire ropes are directly twisted without cold drawing after phosphating. Phosphating film can improve the wear resistance and corrosion resistance of rope-making steel wire surface and effectively inhibit fretting fatigue. For the phosphating treatment of rope steel wire, manganese series or zinc-manganese series phosphating is preferred. The phosphatized steel wire is directly twisted with phosphatized steel wire. Because the phosphating film makes the surface of steel wire more wear-resistant, and the phosphating film is not conductive, the corrosion resistance of steel wire can be improved at the same time. The service life of phosphating steel wire rope is 2-3 times that of smooth steel wire rope, and the fatigue resistance of steel wire rope is greatly improved. Phosphating steel wire rope [1] is not only an ideal substitute for smooth steel wire rope, but also can completely replace imported steel wire rope [2].
2. Galvanized steel wire rope includes hot dip galvanizing and electro-galvanizing. The protection of galvanized steel wire belongs to anodic protection, and the thicker the galvanized layer, the stronger the corrosion resistance.
3. Plastic coated steel wire rope: the outer surface of steel wire rope or strand rope is coated with plastic with a certain thickness, including polyethylene, polypropylene and polyurethane.
4. Smooth steel wire rope is obtained by cold drawing of raw materials after heat treatment and surface treatment (note: the phosphating film formed during pretreatment gradually falls off due to intense friction with wire drawing die during cold drawing). Without any surface treatment, the steel wire is directly twisted into strands, steel cores and steel wires, and production started in foreign countries 1834 and domestic Tianjin No.1 Wire Rope Factory 1939.
According to the method of wire rope twisting.
Single rope
Also known as single twist rope, it is made by winding the steel wire rope layer by layer on the central wire or hemp core, and can twist one or more layers of steel wire.
Double twisted rope
It is made by twisting two strands of rope around the rope core (steel core or fiber core), which can twist one or more layers of steel wire. It is the most widely used steel wire rope.
three stranded rope
Twisted with double twisted rope around the rope core into strand rope, which is mainly used for thick wire rope with diameter greater than 60mm, such as offshore wire rope.
The marking method of wire rope twisting method is as follows:
A right alternating twist ZS: the rope is twisted to the right, and the strand is twisted to the left. The twist direction of the strand rope is opposite to that of the steel wire in the strand, which is called alternating twist.
B left alternate twist SZ: left twist of rope and right twist of strand.
C right twist ZZ: right twist of rope and right twist of strand.
D the same twist to the left: the left twist of the rope and the left twist of the strand.
E right mixed twist: the rope is twisted right, some strands are twisted left and some strands are twisted right.
F left mixed twist: the rope is left twisted, some strands are right twisted, and some strands are left twisted.
Folding is classified according to the contact state of the steel wire inside the steel strand.
According to the contact state between adjacent layers of steel wires in steel strand, it can be divided into three types: point contact, line contact or surface contact.
① Wire rope in point contact: the diameter of the steel wire in the strand is the same, and the twist angle of each layer of steel wire is the same, but the lay length is different, so the inner and outer steel wires cross each other and are in point contact.
② Line contact wire rope: The lay length of each layer of steel wire in the strand is different, and the inner and outer steel wires are in line contact with each other on a helix. Under the same service conditions, the service life of line contact wire rope is longer than that of point contact wire rope.
(3) Compacted steel wire rope, originally called surface contact steel wire rope. In the process of wire rope twisting, after forging and drawing, contact surfaces are formed between steel wires, including strand compaction, wire rope compaction and strand double compaction.
④ Sealed steel wire rope: the outer layer is made of special-shaped steel wire, including steel wire with T-shaped S-shaped Z-shaped cross-section structure, with smooth surface and good wear resistance. Compared with other types of steel wire rope with the same diameter, it has higher tensile strength and can withstand lateral pressure, but it has poor flexibility, complicated technology and high manufacturing cost, and is often used as a load-bearing cable, such as the cable on cable cranes and aerial ropeways.