1.4 Reason Four
(1) Cause: Low working pressure and operating current of the roller press
(2) Impact Analysis:
The content of fine powder (<80um) produced by the material being pressed varies with the operating pressure of the roller press, which directly affects the system's output, quality, and power consumption indicators for grinding. Reasonably increasing the working pressure of the roller press can enhance the content of fine powder (<80um) in the extruded material. Apart from the previously discussed factor of finer incoming material, the following aspects also contribute to this phenomenon:
- · Small capacity of the stable flow weighing bin, low operating bin level, small amount of stored material, and intermittent feeding;
- · Short vertical distance between the stable flow weighing bin and the roller press, resulting in low material pressure;
- · Oversized feeding pipe between the stable flow weighing bin and the roller press, leading to low material pressure within the pipe;
- · Small opening ratio of the oblique insert plate for material flow control on the roller press.
(3) Solutions:
① The first three points are related to factors before the material enters the roller press. The following measures can be taken to maintain relatively stable material flow and pressure:
- Given the small capacity of the originally designed stable flow weighing bin, use downtime to expand its capacity (enlargement), typically not less than 30 tons. A larger bin capacity is beneficial for stabilizing the incoming material flow. The expansion requires an investment of 10,000 to 20,000 yuan for steel plates (usually 10mm to 12mm thick) and a small amount of welding materials, which can completely solve the problem. The inner wall and the material discharge area of the weighing bin should be wear-resistant treated.
- During production before the expansion of the weighing bin, maintain the operating material level at no less than 70%;
- The vertical height of the feeding pipe between the weighing bin and the roller press should generally be no less than 3.0 meters;
- If the feeding pipe of the roller press is too large, causing low material pressure within, it can be appropriately reduced in size to fill the pipe with material, increase material pressure, and stabilize the working pressure of the roller press;
- During normal operation of the roller press, the moving roller hydraulic components move horizontally and reciprocally in a smooth and regular manner; the operating currents of the two main motors should reach 60% to 80% of their rated current values (reaching 80% is less common, with 60% to 75% being more typical).
② The opening ratio of the oblique insert plate for material flow control on the roller press should be adjusted to maintain a roller gap ≥0.02D (D-roller diameter in mm) and ensure that the operating currents of the main motors reach 60% to 80% of their rated values, with stable working pressure (e.g., 7.5 MPa to 9.0 MPa). This parameter also directly affects the power output of the roller press. Depending on the material grinding characteristics and on-site operating parameters, the opening ratio of the oblique insert plate for material flow control is generally around 50% to 80%, varying among different enterprises.
(4) Case Study: A unit's 160-140 roller press originally had a vertical feeding pipe with dimensions of 1200mm×600mm. Due to intermittent material flow within the pipe, the site experienced significant dust, ineffective material pressure, and poor material extrusion effects. The specific surface area of the incoming material was 150 m2/kg to 160 m2/kg, and the operating working pressure was 7.5 MPa to 8.0 MPa. During a winter overhaul, an investment of 5,000 yuan was made to modify the feeding pipe, reducing its size to 600mm×600mm and replacing the feeding gate valve. After the modification, the material within the pipe flowed continuously, material pressure increased, enabling overfeeding of the roller press, eliminating dust emissions, and improving extrusion effects. The specific surface area of the incoming material rose to 170 m2/kg to 180 m2/kg, and the operating working pressure of the roller press reached 8.0 MPa to 9.0 MPa.
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