Abstract : This paper briefly describes the melt conveying and spinning process of partial melt direct spinning, and explains the main control measures in production. It outlines the use of Siemens PLCs and frequency converters to achieve process control, alarms, and interlocks, and points out the advantages and disadvantages of this scheme. Keywords : Polyester staple fiber; Booster pump; PLC; Frequency converter In the partial melt direct spinning of staple fiber, how to control the speed of the booster pump to ensure stable pressure before the spinning metering pump and guarantee normal and continuous spinning production has always been a problem that plagues equipment manufacturers and users, especially during the start-up of a partial melt direct spinning production line. Jinan Zhenghao Chemical Fiber, in the process of using Shanghai No. 2 Textile Machinery's first 70,000 t/a staple fiber spinning complete set of equipment, has successfully solved this problem by applying the unique functions and advanced control concepts of Siemens S7400 PLC and MICR. 440 frequency converter, achieving success in actual production. [b]1 Process Overview[/b] The Jinan Zhenghao 70,000 t/a polyester staple filament production line is a supporting project for the first domestically produced 160,000 t/a polyester production line. It utilizes spinning equipment from Shanghai No. 2 Textile Machinery, making it the first domestically produced production line. Its process is as follows: Melt discharge pump → melt distribution valve → melt booster pump → melt distribution pipe → spinning metering pump → spinning polyester unit. The melt from the polyester spinning unit is discharged through the melt discharge pump, distributed by the distribution valve, with one portion sent to the pelletizer to produce polyester chips, and the other portion sent to the spinning unit. After being pressurized by the booster pump, it is distributed through the melt distribution pipe to the 32 spinning metering pumps for spinning. Stable staple filament production requires maintaining a constant melt pressure before the spinning metering pump. Factors affecting this pressure include the metering pump speed, the number of spinning positions, the booster pump speed, and the melt viscosity and temperature. The speed of the metering pump is determined by the production capacity of the short filament and is essentially a constant. The viscosity and temperature of the melt are determined by the product being produced and are also relatively stable. The number of spinning positions is determined by the condition of the components and spinnerets, which must be replaced periodically. Therefore, ensuring stable pressure before the metering pump relies solely on the booster pump for regulation, and the effectiveness of this pressure regulation is also affected by the amount of melt supplied by the polyester unit. In previously introduced production lines, the amount of melt sent to the pelletizer was adjusted to maintain a relatively constant melt volume before the spinning booster pump, ensuring that the pressure before the metering pump remained constant after adjusting the booster pump speed. All of these controls were performed by the polyester unit. However, Jinan Zhenghao's domestically produced production line is different. The amount of melt supplied to the spinning unit is controlled by the polyester unit through the opening of the melt distribution valve, and the speed of the booster pump is controlled by the spinning unit. Its control block diagram is shown in Figure 1. [b][align=center]For details, please click: Application of PLC and Frequency Converter in Partial Melt Spinning Production Process[/align][/b]