【FAQ】 Maintenance of Roller Shells for Roller Extrusion Granulators

I. Daily Use and Maintenance

Q1: What cleaning and maintenance are required for the roller shells after each shutdown?

A: At the end of each production shift, the roller shell surfaces and mold cavities must be cleaned. Use a scraper or brush to remove adhered organic matter and fertilizer powder; do not forcibly pry off hardened clumps—soften them with a small amount of water before cleaning. After cleaning, keep the roller shells dry to prevent moisture from corroding the mold holes.

Q2: How can material adhesion to the rollers be reduced and the service life of the roller shells extended during the production process of a double roller press granulator?
A: ① Strictly control raw material moisture content (10%–25% for organic fertilizer; keep NPK fertilizer raw materials dry); ② Adjust the side scrapers to fit closely against the roller surface to remove adhered material in real-time; ③ Reduce hydraulic extrusion pressure for wet materials to prevent them from clogging the mold cavities; ④ Remove impurities from raw materials beforehand; strictly prevent stones or metal fragments from entering the extrusion rollers to avoid damaging the roller shell cavities.

Q3: How should roller shells be stored and maintained during prolonged periods of inactivity?

A: Thoroughly clean out any residual powder from the mold cavities and wipe away surface moisture; apply a thin layer of anti-rust oil to the roller shell surfaces; cover the machine to protect it from dust and store it in a dry, well-ventilated warehouse to prevent rust from moisture or corrosion of the mold cavities by dust.

II. Wear and Tear Issues

Q4: What is the typical service life of the roller shells?

A: Normal service life is 8–12 months when processing matured organic fertilizer; for NPK inorganic salt fertilizers (which are highly corrosive), the lifespan is 4–7 months; if raw materials contain high levels of sand or stone impurities, or if the machine operates under high pressure for extended periods, the service life may be reduced by half.

Q5: How can I tell if the roller shells are worn out and need replacement?

A: ① Mold cavity edges become worn flat or uneven in depth, resulting in many loose granules and increased powder fines; ② Significant size variation among granules in the same batch, and a sharp drop in the granulation rate; ③ Deep pits, scratches, or chipped sections appear on the roller surface, accompanied by abnormal noise during extrusion; ④ Frequent material adhesion where even scraper cleaning fails to ensure proper granule release.

Q6: Can roller shells be repaired and reused if they show localized wear? A: Minor, shallow scratches can be repaired via wear-resistant surfacing welding; however, repairing large-scale worn areas, chipped sections, or deep pits is not recommended. Such repairs often lead to inconsistent die-hole specifications and uneven material output, making the direct replacement of the roller shell more cost-effective.

III. Operational Protection

Q7: What actions cause rapid damage to the roller shell?

A: ① Running the rollers against each other without material (dry friction); ② Metal or stones entering the gap between rollers, cracking the die holes; ③ Excessive raw material moisture causing long-term clogging and corrosion of the roller surface; ④ Prolonged operation at maximum pressure (overloading); ⑤ Failure to clear material before shutdown, allowing it to harden in the die holes and corrode the roller shell.

Q8: What operational practices help protect the roller shell during production?

A: Feed material before starting the machine; never run the rollers in contact without material; ensure uniform feeding to prevent uneven wear caused by one-sided material intake; process dry and wet materials separately, reducing pressure for wet materials; regularly inspect the scraper and replace it promptly when worn to prevent material buildup and surface corrosion.

IV. Replacement, Installation, and Maintenance

Q9: What maintenance details should be noted when replacing the roller shell?

A: After removing the roller core, clean rust and powder residue from the main shaft surface; ensure a tight fit with no gaps when installing the new shell and tighten bolts evenly; align the roller shells and match die-hole positions to avoid misalignment and crushing damage; perform a low-speed test run without material after installation, ensuring smooth operation before feeding material.

Q10: Do maintenance methods differ based on the roller shell material?

A: Standard alloy steel shells have moderate rust resistance and require cleaning and rust prevention after every shift; highly wear-resistant alloy and tungsten carbide shells offer superior corrosion and wear resistance but are susceptible to impact damage from hard objects—therefore, in addition to routine cleaning, prioritize removing impurities from raw materials to prevent hard debris from entering the machine.

V. Maintenance and Troubleshooting for Common Issues

Q11: Will forcibly prying out clogged or caked material from the die holes damage the roller shell?

A: Yes, it can scratch the inner walls of the die holes and impair molding performance. Correct procedure: Soak the material buildup in warm water to soften it, then remove it using a brush and a soft scraper; the use of steel chisels or hammers to forcefully strike the roller shell is strictly prohibited.

Q12: How should surface rust on the roller shell be treated or repaired?

A: For light surface rust, use a wire brush to grind it off, clean the surface, and apply anti-rust oil; if deep corrosion has penetrated the die cavities, repair is not possible, and the roller shell must be replaced; maintain dry conditions during daily production to prevent rusting at the source.