Repair and Refurbishment
Die Plate Repair and Refurbishment for Underwater Pelletizers
JINFENG repairs worn and damaged pelletizing die plates of any make, from JINFENG plates to imported plates on Coperion, JSW, Kobe Steel, and DLRPM lines. Each repair starts with an inspection of the hard face, die holes, heating channels, and remaining thickness, and ends with dimensional, pressure, and flaw-detection checks before the plate goes back into service.
Repair scope
- Cleaning and inspection
- Hard face regrinding
- Hard face replacement
- Heating-channel repair
- Pressure and leak testing
- Flaw detection and final inspection
Typical lead time: about one month for regrinding and minor repairs; three to eight months when the hard face is replaced.
Repairs for Die Plates of Any Make
JINFENG has repaired a large number of die plates for polyolefin producers, including plates originally supplied with the extrusion line and plates from other die plate makers. Because JINFENG also designs and manufactures new die plates for 200,000 to 600,000 t/a PP and PE lines, the same machining, vacuum brazing, and inspection equipment is used for repairs.
See the die plate reference list for the equipment platforms JINFENG has supplied die plates for.
When a Die Plate Needs Repair
A die plate is usually sent for assessment when one or more of these appear during operation or at a shutdown:
- Pellet tails, fines, or uneven pellet size that knife changes do not correct
- Grooves, high spots, chipping, or cracks on the hard face
- Knife wear increasing faster than normal
- Frozen or blocked die holes, or uneven die temperature
- Leaks or blockage in the heating channels
- Knife-to-plate contact after an overhaul or incorrect knife setting
Photos of the full die face and close-ups of damaged areas are usually enough for a first opinion on whether regrinding or hard face replacement is likely.
Repair Scope
- Incoming inspection and cleaning. The plate is cleaned and checked for hard face wear and damage, die-hole condition, remaining thickness, structural condition, and heating-channel condition.
- Hard face regrinding. Where enough hard face remains, the face is reground flat on 1.2 m or 1.8 m circular-table grinders held to 0.005 mm parallelism.
- Hard face replacement. When the hard face is worn through or cracked, it is removed and a new one is vacuum brazed in a 1.5 m or 1.7 m vacuum furnace, in JINFENG's TiC-NiCr cermet or the material the customer specifies.
- Heating-channel repair. Leaking or blocked heating channels are repaired, then pressure and leak tested.
- Final inspection. Dimensional and flatness checks, with hard face flaw detection and temperature-uniformity testing as required, and an inspection report. Third-party ultrasonic testing can be arranged on request.
Repair Time
- About one month for regrinding and repairs that do not require a new hard face.
- Three to eight months when the hard face is replaced, depending on plate size, hard face material, and heating-channel condition.
Because hard face replacement takes several months, many plants keep a spare die plate in service while the worn plate is being repaired. JINFENG can also quote a new die plate if that is faster or more economical than repair.
How Many Times Can a Die Plate Be Repaired?
There is no fixed number of repairs. Each regrind removes material from the hard face, so the limit depends on how deep the wear is and how much hard face and plate thickness remain. JINFENG measures these at inspection and advises whether another regrind is possible, whether the hard face should be replaced, or whether a new plate is the better option.
Repair Process for Overseas Plants
- Send photos, the drawing or main dimensions, and a description of the problem to JINFENG for a preliminary assessment.
- The die plate is shipped to JINFENG in Shenyang, China, for repair.
- JINFENG inspects the plate, confirms the repair scope and lead time, and carries out the repair.
- After final inspection, the repaired die plate is exported back to your plant with its inspection report.
For plants in China, minor hard face damage can sometimes be repaired on site. At a 200,000 t/a PP line, a knife shaft seal installed in the wrong position after an overhaul caused knife-to-plate contact and left 50 high spots on the hard face; JINFENG technicians restored the surface in about five hours so the line could restart.
Testing After Repair
Repaired die plates are inspected and tested before they leave the plant. Heating channels are pressure and leak tested after repair, and the inspection scope can include hard face flaw detection and a hard face temperature-uniformity test, which helps reduce the risk of frozen holes after start-up. Results are recorded in the inspection report.
See Quality Control for JINFENG's inspection equipment.
Cutter Hub Reconditioning
Worn pelletizer cutter hubs can be reconditioned together with the die plate and are checked and supplied with a test report after reconditioning. New complete pelletizing knives can be supplied for the reconditioned hub.
Information to Send for a Repair Assessment
- Photos of the complete die face and close-ups of worn or damaged areas
- Die plate drawing, or main dimensions and number of die holes
- Extrusion line maker, model, and capacity
- Polymer and operating conditions
- Operating history and previous repairs or regrinds, if known
- Description of the problem: pellet quality, knife wear, frozen holes, or heating-channel leaks
- Required inspection documents
Frequently Asked Questions
Do you repair die plates made by other manufacturers?
Yes. JINFENG repairs die plates from original equipment suppliers and other die plate makers as well as its own, including plates for Coperion, JSW, Kobe Steel, and DLRPM lines. Every repair starts with an inspection of the actual plate.
How long does a die plate repair take?
A repair without hard face replacement usually takes about one month. When the hard face has to be replaced, allow three to eight months, depending on the plate size, the hard face material, and the condition of the heating channels.
How many times can a die plate be repaired?
There is no fixed number. It depends on how far the hard face is worn and how much thickness remains after previous regrinding. JINFENG measures the remaining thickness during inspection and tells you whether regrinding is still possible or the hard face should be replaced.
Can you repair a die plate from a plant outside China?
Yes. The die plate is shipped to JINFENG in Shenyang for repair and then exported back to your plant. Send photos and dimensions first so the likely repair scope can be discussed before shipment.
Request a Die Plate Repair Assessment
Send photos, dimensions, and a description of the problem. JINFENG will advise whether regrinding, hard face replacement, or a new die plate is the right option.
Contact: [email protected] WhatsApp: +86 133 0983 7263