Scrap Standards for Hooks, Sheaves, Drums and Wire Ropes of Tower Cranes
Tower crane is a kind of lifting machinery with an upright tower and a rotating boom. The tower crane is mainly composed of metal structure, working mechanism and control system parts. The basic components of the metal structure of the tower crane include: chassis, tower body, turntable, tower cap, lifting arm, balance arm and other parts.
1. Metal structure
Chassis
The structural form of the tower crane chassis structure is determined by the tower crane’s structural form (up rotation and down rotation), traveling mode (track type or tire type), and installation method relative to the building (attached and self-elevating). Light-duty, quick-installation tower cranes with lower slews mostly use flat frame chassis, while medium or heavy slew tower cranes often use jellyfish-type chassis. When the upper slewing tower crane is required to be used as a temporary storage yard or as a pedestrian passage in the center of the track, a gantry-type chassis can be used. The chassis of self-elevating tower cranes mostly adopts a flat frame and diagonal brace chassis. The tire-type tower crane adopts a box-beam structure.
Tower body
Tower structure forms can be divided into two categories: fixed height type and variable height type. Light-duty rotating tower cranes with small hook heights generally adopt a fixed-height tower structure, while other tower cranes mostly have variable tower heights. The variable-height tower structure can be divided into five different forms: folding tower, telescopic tower, lower-high tower, middle-high tower and upper-high tower.
Tower cap
Tower cap structures come in various forms, including vertical, forward-inclined and backward-inclined. Like the tower body, the main chord is made of seamless steel pipe, round steel, angle steel or welded square steel pipe, and the web rod is made of seamless steel pipe or angle steel.
Lifting arm
The lifting arm is a trolley luffing arm, which generally adopts an equilateral triangle cross-section.
The pitch luffing jib mostly adopts a rectangular cross-section lattice structure, which is composed of angle steel or steel pipes. The sections are connected by pins, flanges or cover bolts. The boom structural steel material is 16Mn or Q235.
Balance arm
The balance arm of the upper slewing tower crane mostly adopts a plane frame structure, the main beam is made of channel steel or I-beam, and the connecting beam and web rod are made of seamless steel pipe or angle steel. The balance arm of heavy-duty self-elevating tower cranes often adopts a triangular cross-section lattice structure.
2.Working organization
Tower cranes are generally equipped with a hoisting mechanism, a luffing mechanism, a slewing mechanism and a traveling mechanism. These four mechanisms are the most basic working mechanisms of the tower crane.
Lifting mechanism
Most of the lifting mechanisms of tower cranes are driven by electric motors. Common driving methods are: 1) slip ring motor drive; 2) dual motor drive (high-speed motor and low-speed motor, or load operation motor and empty hook lowering motor).
Luffing structure
The luffing mechanism of the boom luffing tower crane is used to complete the pitch change of the boom.
Horizontal arm trolley luffing tower crane: The construction principle of the trolley traction mechanism is the same as that of the hoisting mechanism. The transmission method used is a pole-changing motor → a small tooth difference reducer or a cylindrical gear reducer or a bevel gear reducer → a steel rope drum.
Slewing mechanism
The currently commonly used driving methods for tower crane slewing mechanisms are: slip ring motor → hydraulic coupling → small tooth difference planetary reducer → open pinion → large ring gear (ring gear of the slewing bearing device).
Light and medium-sized tower cranes are equipped with only one slewing mechanism, heavy-duty tower cranes are generally equipped with 2 slewing mechanisms, and super-heavy-duty tower cranes are equipped with 3 or 4 slewing mechanisms depending on the lifting capacity and rotating mass.
Cart traveling mechanism
Light and medium-sized tower cranes use 4-wheel traveling mechanisms, heavy-duty tower cranes use 8-wheel or 12-wheel traveling mechanisms, and super-heavy-duty tower cranes use 12 to 16-wheel traveling mechanisms.
Hooks, sheaves, drums and wire ropes
Hooks, pulleys, drums and wire ropes are important accessories for tower cranes. During selection and use, inspections should be carried out according to specifications. If scrap standards are reached, they should be scrapped in time.
Scrap standards for hooks
The hook should be scrapped if any of the following conditions occurs:
(1) Use a 20x magnifying glass to observe if there are cracks and breaks on the surface;
(2) There is permanent deformation of dangerous sections such as the hook tail and threaded parts and the hook bars;
(3) The cross-section wear of the lanyard exceeds 10% of the original height;
(4) The wear amount of the mandrel exceeds 5% of its diameter;
(5) The opening is increased by 15% compared to the original size.
Scrap standards for sheaves and drums
According to relevant regulations, items should be scrapped when one of the following conditions is found:
(1) Cracks or rim damage;
(2) The drum wall wear amount reaches 10% of the original wall thickness;
(2) The wear amount of the wall thickness of the sheave rope groove reaches 20% of the original wall thickness;
(3) The wear amount at the bottom of the sheave groove exceeds 25% of the corresponding wire rope diameter.
Scrap standards for wire ropes
The scrapping of wire ropes should be strictly carried out in accordance with the standards. Wire ropes must be scrapped and replaced when the following conditions occur:
(1) The phenomenon of wire rope breakage is serious;
(2) Local accumulation of broken wires;
(3) When the steel wire is severely worn or corroded and the diameter of the steel wire is reduced to 40% of its diameter, it should be scrapped immediately;
(4) When the wire rope loses its normal condition and is severely deformed, it must be scrapped immediately.
During work, the temperature of each component of the crane has its own normal range. If it falls below or exceeds this range, it will accelerate the wear of the parts, cause the lubricating oil to deteriorate, cause changes in material properties, etc. If the cause of the crane cannot be found for a while, the machine must not be allowed to work without treatment. In daily work, pay attention to check the working condition of the cooling system.
Glory Rail is based on rail systems. At the same time, we expanded the research, development, and production of crane hooks, sheaves,wheels and drums. Provide different types of these accessories products for various cranes and port machinery equipment.