The scraper assembly 20MG.33.11.07 is a core stone coal discharge component matched with the drive disc of ZGM series roller-and-bowl medium-speed coal mills. It is installed inside the primary air chamber and on the drive disc, rotating synchronously with the drive disc, and serves as a critical wear-prone spare part in the pulverizing system. When raw coal is pulverized inside the mill, hard impurities mixed in coal such as gangue, iron blocks and hard sandstone that cannot be ground fail to be lifted by the primary hot air. These impurities pass through the nozzle ring and settle at the bottom of the primary air chamber. The scraper assembly continuously sweeps accumulated stone coal at the bottom and pushes debris to the stone coal discharge port into the stone coal hopper to realize continuous slag removal.
If the scraper assembly malfunctions, stone coal will keep accumulating inside the air chamber, disturbing the flow field of primary air. This leads to increased ventilation resistance and reduced capacity of the coal mill. In severe cases, it may trigger spontaneous combustion of stone coal, scraper jamming and excessive mill vibration, threatening the safe and stable operation of the whole pulverizing system.
Product Features
The scraper assembly 20MG.33.11.07 adopts a split assembly structure, mainly consisting of wear-resistant scraper plates, brackets and fastening connectors. The wear surface is made of high-hardness wear-resistant alloy material with outstanding wear resistance. It can withstand friction and impact from stone coal and hard particles for a long time, slow down the wear rate and extend the maintenance and replacement cycle.
The bracket features sufficient structural rigidity and strong resistance to impact and deformation, and is not prone to bending or fracture under continuous alternating loads and material impact. An adjustable clearance structure is designed for this product. The assembly clearance between the scraper and the air chamber bottom plate can be adjusted via fastening bolts. The standard operating clearance is controlled within 6–10 mm. After the wear plate is worn, there is no need to replace the whole assembly on site. The slag scraping performance can be restored simply by adjusting the clearance, which offers high maintenance flexibility.
The whole assembly is fastened by bolts for easy installation and disassembly during major and minor maintenance, facilitating overhaul work in power plants. Meanwhile, this scraper model adapts to the harsh working conditions inside the coal mill with high temperature and heavy dust. The material has good heat resistance, can withstand the high temperature brought by primary air, and is not susceptible to high-temperature softening or material failure, meeting the demand for long-term continuous operation of generating units.
Application Scope
The scraper assembly 20MG.33.11.07 is mainly matched with ZGM series medium-speed roller coal mills of thermal power plants, widely used in the boiler pulverizing system of coal-fired power generating units. It is a standard spare part for coal mills of mainstream units such as 300 MW and 600 MW units. It acts as a core replacement part of the stone coal discharge unit during daily operation, unit overhaul and coal mill technical transformation projects of power plants.
Besides the thermal power industry, it is also applicable to medium-speed coal mills of the same model in self-owned power plants, coal chemical industry and coal injection systems of iron and steel enterprises, providing slag removal guarantee for coal pulverizing equipment. This scraper is only compatible with the mounting interface of the corresponding drive disc. It needs to cooperate with the nozzle ring, stone coal discharge valve, primary air chamber liner and other components to complete the whole process of raw coal impurity removal, grinding and powder conveying, so as to ensure stable pulverizing under load of the coal mill.
Precautions for Use
Before installation, carefully check whether cracks or chipping exist on the wear surface of the scraper plate, whether the bracket is deformed, and whether the matching bolts and anti-loosening parts are complete and intact. During assembly, strictly control the clearance between the scraper and the bottom plate. Too small a clearance will cause scraping against the liner plate, resulting in scraper fracture and liner damage; too large a clearance leads to incomplete slag scraping and stone coal accumulation.
Fasten the fixing bolts evenly according to the specified torque and install anti-loosening gaskets to prevent bolts from loosening and the scraper from falling off due to operating vibration. The scraper shaft shall not be welded dead to ensure a certain movable margin of the scraper and avoid jamming and damage.
During unit operation, regular inspection is required to monitor coal mill vibration and stone coal discharge volume, and regularly measure the wear loss of the scraper. Adjust or replace the wear plate in a timely manner when wear exceeds the standard or the clearance goes beyond the allowable range. If coal quality deteriorates and gangue content rises during operation, increase the inspection frequency to prevent rapid wear and failure of the scraper.
When replacing the scraper, inspect the wear condition of the liner plate at the bottom of the primary air chamber at the same time. Uneven deformation of the liner plate will accelerate scraper wear. Spare parts shall be stored in a dry and ventilated warehouse with dust-proof and rust-proof measures, and the wear surface shall be protected from collision and scratching.
The scraper assembly is a wear-prone component. During maintenance, thoroughly clean the accumulated stone coal and debris inside the air chamber before reassembly to prevent foreign matters from jamming the scraper after assembly. Once scraper jamming or abnormal noise is found during operation, reduce the coal mill output in a timely manner, and shut down the coal mill for internal inspection if necessary to avoid fault expansion and damage to the transmission parts of the coal mill.
DFYLSYC-2026-11-04-A
