JINFENGDie Plates & Pelletizer Knives

Technical Article

Pellet Tails in Underwater Pelletizing: Causes and Fixes

Pellets with tails come from strands that are not cut cleanly at the die face. They create fines and dust, cause bridging in silos and conveying, and are often the first sign that the knives or the die face need attention.

Published 2026-09-25 by JINFENG engineering, Shenyang Jinfeng Special Equipment Co., Ltd.

Main Causes

  • Knife edge condition. Chipped, torn, or worn knife edges leave uncut strand material.
  • Knife setting. An incorrect gap or contact between knives and die face, or knives not seated evenly on the cutter hub.
  • Die face condition. Grooves, high spots, or uneven wear on the hard face stop the knives from cutting evenly across all die holes.
  • Knife material for the grade. Some grades, such as high melt-index products, need a different knife or hard face material.
  • Process conditions. Melt temperature, throughput, cutter speed, and water temperature outside the range set for the grade. Follow the equipment manufacturer's settings.

Case: Chipped Imported Knives

At Shandong Yulong Petrochemical, imported polyethylene pelletizing knives chipped and tore at the edge and the line started producing pellets with tails. JINFENG took knives from stock, sent them with a technician by air the same day, and helped sharpen the knives until the line produced qualified pellets again.

Imported pelletizer knife with a chipped cutting edge marked in red Pellets with tails caused by chipped knives Clean round pellets after the knife problem was solved
Chipped knife edge (marked), pellets with tails, and pellets after the problem was solved.

What to Check First

  1. Inspect the knife edges for chipping and wear, and check that all knives are seated evenly on the hub.
  2. Check the knife-to-die-plate setting against the pelletizer manual.
  3. At the next shutdown, inspect the hard face for grooves, high spots, and uneven wear.
  4. Compare melt temperature, throughput, cutter speed, and water temperature with the settings for the grade.
  5. If tails persist after new knives, have the die face and knife material assessed.

Damage to the hard face from knife contact can sometimes be repaired quickly: at a 200,000 t/a PP line, JINFENG restored 50 high spots on a hard face on site in about five hours.

Frequently Asked Questions

What are pellet tails?

Thin strands or tails left on pellets when the strand is not cut cleanly at the die face. They cause fines, dust, and poor flow in downstream handling.

What is the most common cause?

Knife condition is usually checked first: chipped, worn, or incorrectly set knives do not cut the strand cleanly. A worn or uneven die face is the next thing to check.

Can a die plate cause pellet tails?

Yes. Grooves, high spots, or uneven wear on the hard face stop the knives from cutting evenly across the whole die face. Regrinding or replacing the hard face restores a flat cutting surface.

Need Replacement Knives or a Die Face Assessment?

Send photos of the knives, the die face, and the pellets, together with your line data.

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