Part 3: Technical Standards and Quality Assessment Criteria for Core Components of Electric Hoists
The overall performance, service life, and safety factor of an electric hoist depend entirely on the quality of its core components and the precision of their assembly. Most equipment failures in the industry stem from the use of non-standard or inferior parts, assembly errors, or the continued operation of components that have exceeded wear limits. In accordance with the industry-specific standard JB/T 9008-2021 for electric hoists, the seven core components—wire ropes, chains, brakes, gear reducers, motors, hooks, and limit devices—are subject to clearly defined standards regarding materials, performance parameters, wear thresholds, and criteria for scrapping. Strict control over component quality is fundamental to ensuring the safe and stable operation of electric hoists. This article systematically outlines the technical standards and quality assessment criteria for these core components, providing a professional basis for equipment procurement, acceptance inspection, maintenance, and decommissioning.
The wire rope is the primary load-bearing component of wire-rope electric hoists. National standards mandate the use of flexible galvanized wire ropes (specifications 6×37+NF or 6×19+NF) made from high-quality, high-carbon steel wire, characterized by high tensile strength, good flexibility, wear resistance, and resistance to wire breakage. Quality acceptance criteria require the rope to be free from rust, deformation, kinks, flattening, or severe wear, with a full, well-lubricated core. Scrapping criteria are clearly defined: the rope must be immediately discarded and replaced if it exhibits any of the following conditions—broken wires exceeding 10% of the total count within a single lay length, a reduction in wire diameter of more than 7% due to wear, severe rust, deformation, fatigue-induced kinking, or an exposed core. Continued use is strictly prohibited. Furthermore, the wire rope requires uniform and thorough lubrication; dry, unlubricated ropes accelerate wear and significantly reduce service life.
Alloy steel lifting chains serve as the primary load-bearing components for chain electric hoists. National standards require the use of Grade 80 high-strength alloy steel chains that have undergone quenching and tempering heat treatments to ensure compliance with tensile strength, toughness, and wear resistance requirements, maintaining a safety factor of at least 4:1 for single-strand configurations. Chain quality standards require that chain links show no deformation, cracks, or severe wear; welds must be free of fractures; and there must be no elongation. Mandatory scrapping thresholds include wear exceeding 10% of the original diameter, link elongation, surface fatigue cracks, or corrosion/cracking at weld points; reaching any of these limits necessitates immediate decommissioning to eliminate the risk of chain breakage and falling loads. Routine maintenance requires keeping the chain clean and lubricated—free from accumulated grease or dust-induced binding—to prevent jamming or chain skipping.
The braking system is a critical safety component of the electric hoist. It utilizes an electromagnetic power-off brake assembly comprising a coil, spring, brake pads, and a brake disc. National standards mandate a braking response time of ≤0.2 seconds, ensuring instantaneous locking upon power loss without slippage or load drift. Brake pads are made of wear-resistant, high-temperature asbestos composite material, offering heat resistance, friction durability, and stable braking performance. Quality inspection criteria dictate that pad wear must not exceed one-third of the original thickness, springs must retain adequate tension without fatigue-induced slackness, and coil insulation must be intact and free from burn damage. Issues such as excessive pad wear, spring slackness, coil aging, brake slippage, or load drift require immediate component replacement and brake clearance adjustment to ensure reliability.
The gearbox and motor constitute the core power transmission assembly. Electric hoists typically employ planetary or cycloidal pin-wheel gearboxes, characterized by high transmission precision, low noise, high torque, and low failure rates. Gearbox gears are forged from high-strength alloy steel, with tooth surfaces free from wear, chipping, or excessive backlash; lubricant levels must meet specifications, and the oil should be clear, free of impurities, and show no signs of emulsification or degradation. The hoisting and travel motors are specialized conical-rotor brake motors designed for lifting applications; they feature high starting torque, strong overload capacity, integrated braking, and an IP54 or higher protection rating. The motor windings show no signs of burnout, overheating, or abnormal noise, and insulation resistance meets required standards. The hook assembly must be manufactured using a forging process—cast hooks are strictly prohibited—and must be free from cracks or deformation, with any increase in the hook opening not exceeding 10% of the original dimension; the safety latch must operate flexibly and reliably. Safety components, such as travel limiters and overload protection devices, must be sensitive and precise in operation; only when all components meet the required standards can the safe and compliant operation of the electric hoist be ensured.
