{"id":394,"date":"2026-11-06T21:32:00","date_gmt":"2026-11-06T13:32:00","guid":{"rendered":"https:\/\/kerkepm.com\/knowledge\/pelletizing-methods-compared\/"},"modified":"2026-11-08T20:42:57","modified_gmt":"2026-11-08T12:42:57","slug":"pelletizing-methods-compared","status":"publish","type":"page","link":"https:\/\/kerkepm.com\/es\/knowledge\/pelletizing-methods-compared\/","title":{"rendered":"Seven Pelletizing Methods Compared"},"content":{"rendered":"<div class=\"k3\">\n<div class=\"wrap\"><div class=\"crumbs\"><a href=\"\/\">Home<\/a><span>\/<\/span><a href=\"\/knowledge\/\">Knowledge<\/a><span>\/<\/span>Seven Pelletizing Methods Compared<\/div><\/div><div class=\"wrap\"><div class=\"hero\">\n<p class=\"kicker\">Process \u00b7 8 min read<\/p>\n<h1>Seven Pelletizing Methods Compared: Strand, Water Ring, Underwater, Hot Face<\/h1>\n<p class=\"dek\">The pelletizer is chosen by the polymer, not by the budget. This table compares all seven methods we build on the criteria that actually decide the purchase: filler ceiling, water contact, pellet shape and fines. A reference pelletizing methods compared page from Kerke.<\/p>\n<div class=\"byline\"><div><b>Updated<\/b> 6 November 2026<\/div><div><b>Reviewed by<\/b> Kerke process team<\/div>\n<div><b>Basis<\/b> commissioning records, parameter table<\/div><\/div>\n<\/div><\/div>\n<div class=\"wrap\"><div class=\"grid\"><main>\n\n<p class=\"lead\">A pelletizing mistake shows up months later as dust in the customer's bag, moisture in their dryer or tails in their mould. Choose by polymer first, filler level second, pellet shape third.<\/p>\n\n<nav class=\"wp-block-rank-math-toc-block k3-toc\" aria-label=\"On this page\"><b>On this page:<\/b><a href=\"#rm-s1\">The comparison<\/a><a href=\"#rm-s2\">Why water contact is the deciding column<\/a><a href=\"#rm-s3\">What each option costs you downstream<\/a><a href=\"#rm-s4\">How we choose for a customer<\/a><a href=\"#rm-s5\">FAQ<\/a><\/nav><h2 class=\"sec\" id=\"table\" id=\"rm-s1\">The comparison<\/h2>\n<div class=\"tw\"><table>\n<caption><b>Table 1.<\/b> Seven pelletizing methods by application window.<\/caption>\n<thead><tr><th scope=\"col\">Method<\/th><th scope=\"col\">Filler ceiling<\/th><th scope=\"col\">Water contact<\/th><th scope=\"col\">Pellet shape<\/th><th scope=\"col\">Best for<\/th><\/tr><\/thead>\n<tbody>\n<tr><td>Water-cooled strand<\/td><td class=\"num\">\u2264 50%<\/td><td>Full immersion<\/td><td>Uniform cylinder<\/td><td>PET, PA, engineering plastics, low-filled masterbatch<\/td><\/tr>\n<tr><td>Air-cooled strand<\/td><td class=\"num\">\u2264 60%<\/td><td>None<\/td><td>Uniform cylinder<\/td><td>PVC, biodegradable, materials that must stay dry<\/td><\/tr>\n<tr><td>Water strand (special for PET)<\/td><td class=\"num\">\u2014<\/td><td>Full immersion<\/td><td>Cylinder, low dust<\/td><td>PET bottle flake and sheet grade, IV-critical<\/td><\/tr>\n<tr><td>Water ring hot face<\/td><td class=\"num\">70\u201385%<\/td><td>Spray + ring<\/td><td>Lens \/ half-round<\/td><td>Filler masterbatch, carbon black<\/td><\/tr>\n<tr><td>Air-cooled hot face<\/td><td class=\"num\">85\u201390%<\/td><td>None<\/td><td>Irregular, low bulk density<\/td><td>PVC, HFFR, WPC, high filler<\/td><\/tr>\n<tr><td>Underwater<\/td><td class=\"num\">\u2264 70%<\/td><td>Full chamber<\/td><td>Round, dense<\/td><td>TPE\/TPU, EPP beads, hot melt<\/td><\/tr>\n<tr><td>Spray \/ mist<\/td><td class=\"num\">\u2264 60%<\/td><td>Light<\/td><td>Round<\/td><td>Sticky or low-melting products<\/td><\/tr>\n<\/tbody><\/table><\/div>\n\n<h2 class=\"sec\" id=\"why\" id=\"rm-s2\">Why water contact is the deciding column<\/h2>\n<p>Water is a cooling medium and a contaminant at the same time. For PET, moisture hydrolyses the chain and destroys IV. For PVC, water plus residual heat means hydrolysis of the stabiliser system and corrosion in the bag. For PLA, water at 60 \u00b0C starts the same hydrolysis the product is designed for in a compost heap.<\/p>\n<p>So the sequence of questions is: does the polymer tolerate water (PET tolerates it if dried afterwards; PVC does not) \u2192 does the filler level allow a strand (above 50% the strand embrittles) \u2192 does the application need a specific pellet shape (bead products need round, dense pellets).<\/p>\n\n<h2 class=\"sec\" id=\"cost\" id=\"rm-s3\">What each option costs you downstream<\/h2>\n<ul>\n<li><strong>Strand lines<\/strong> are the cheapest to buy and the most labour-intensive to run: a broken strand stops the line and the operator rethreads it.<\/li>\n<li><strong>Water ring<\/strong> removes the strand handling problem but adds 8\u201312% surface moisture, so a centrifuge and a fluid-bed dryer are part of the price.<\/li>\n<li><strong>Air-cooled hot face<\/strong> needs no dryer at all, which is why PVC lines use it even though the pellet shape is irregular.<\/li>\n<li><strong>Underwater<\/strong> gives the best pellet quality and the highest cost per kg\/h; the water circuit must be temperature-controlled to \u00b12 \u00b0C.<\/li>\n<\/ul>\n\n<h2 class=\"sec\" id=\"trial\" id=\"rm-s4\">How we choose for a customer<\/h2>\n<p>We run the material on the lab line with the pelletizer we think is right, then send pellets plus a note on fines percentage, bulk density and moisture. If the pellet does not feed in your downstream machine, the trial has failed early and cheaply \u2014 which is the point of doing it before the order.<\/p>\n\n<h2 class=\"sec\" id=\"faq\" id=\"rm-s5\">FAQ<\/h2>\n<details open><summary>Water ring or underwater for TPE?<\/summary><p>Underwater. TPE and TPU need round, dense pellets and the water chamber holds temperature more evenly than a ring. Water ring gives lens-shaped pellets that bridge in some feeders.<\/p><\/details><details><summary>Why does my strand break at 60% filler?<\/summary><p>There is not enough polymer left to hold the strand together through the bath. Above roughly 50% move to water ring, above 82% to air-cooled hot face.<\/p><\/details><details><summary>Can one line run two pelletizing methods?<\/summary><p>Yes, if the die and discharge are designed for it. The pelletizer is a module; the die plate and the water circuit are what need to be swapped.<\/p><\/details>\n<div class=\"method\"><h2 id=\"rm-s6\">Where these numbers come from<\/h2>\n<p>Values are drawn from the Kerke parameter table, commissioning records and service reports from lines in the field. Temperature windows and consumption figures are typical ranges \u2014 confirm on your own material before they become a production setpoint.<\/p><\/div>\n<div class=\"related\"><h2 id=\"rm-s7\">Related reading<\/h2><div class=\"rel-grid\"><a class=\"rel\" href=\"\/knowledge\/twin-screw-extruder-startup\/\"><span>Knowledge<\/span>Twin Screw Extruder Startup: The 9-Step Sequence That Protects the Screw<\/a><a class=\"rel\" href=\"\/knowledge\/twin-screw-extruder-troubleshooting\/\"><span>Knowledge<\/span>Twin Screw Extruder Troubleshooting: Nine Symptoms, Nine Causes<\/a><\/div><\/div>\n<div class=\"cta\"><div><b>Tell us your material \u2014 we will tell you the line<\/b><p>Send 25\u201350 kg and we run it on our lab extruder: pellets, running video and a capacity report back in 3\u20137 days.<\/p><\/div>\n<div class=\"acts\"><a href=\"\/get-a-quote\/\">Get a quote<\/a>\n<a class=\"alt\" href=\"\/get-a-quote\/#trial\">Send material for trial<\/a><\/div><\/div>\n<\/main>\n<aside><h5>On this page<\/h5><ol><li><a href=\"#table\">The comparison<\/a><\/li><li><a href=\"#why\">Why water contact is the deciding column<\/a><\/li><li><a href=\"#cost\">What each option costs you downstream<\/a><\/li><li><a href=\"#trial\">How we choose for a customer<\/a><\/li><li><a href=\"#faq\">FAQ<\/a><\/li><\/ol>\n<div class=\"sidecard\"><b>Question not covered?<\/b><p>Send the material, the machine model and the symptom. We answer with a parameter sheet, not a brochure.<\/p>\n<a class=\"btn\" href=\"\/get-a-quote\/\">Ask an engineer<\/a>\n<a class=\"btn ghost\" href=\"\/knowledge\/\">All articles<\/a><\/div><\/aside><\/div><\/div>\n<script type=\"application\/ld+json\">{\"@context\": \"https:\/\/schema.org\", \"@graph\": [{\"@type\": \"TechArticle\", \"headline\": \"Seven Pelletizing Methods Compared: Strand, Water Ring, Underwater, Hot Face\", \"description\": \"The pelletizer is chosen by the polymer, not by the budget. 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Water ring gives lens-shaped pellets that bridge in some feeders.\"}}, {\"@type\": \"Question\", \"name\": \"Why does my strand break at 60% filler?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"There is not enough polymer left to hold the strand together through the bath. Above roughly 50% move to water ring, above 82% to air-cooled hot face.\"}}, {\"@type\": \"Question\", \"name\": \"Can one line run two pelletizing methods?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"Yes, if the die and discharge are designed for it. The pelletizer is a module; the die plate and the water circuit are what need to be swapped.\"}}]}]}<\/script>\n<div class=\"wrap\"><section class=\"k3-more\" id=\"rm-more\"><h2>Pelletizing methods compared \u2014 the short version<\/h2><figure class=\"k3-fig\"><img decoding=\"async\" src=\"\/wp-content\/uploads\/2026\/11\/kte-65b-co-rotating-twin-screw-extruder-01-1200.webp\" alt=\"pelletizing methods compared\" loading=\"lazy\" width=\"1200\" height=\"675\"><figcaption>Kerke test line, Nanjing \u2014 where the figures on this page were measured<\/figcaption><\/figure><p>Note on Pelletizing methods compared: every figure on this page is a reference range measured on Kerke's own test line in Nanjing, not a catalogue maximum. If your material differs from the one in the table, send 25\u201350 kg and we will replace the range with a measured number.<\/p><p class=\"k3-rel\"><b>Related on this site:<\/b> <a href=\"\/machines\/co-rotating-twin-screw-extruder\/\">Twin screw extruder range<\/a> \u00b7 <a href=\"\/applications\/\">Extrusion lines by application<\/a> \u00b7 <a href=\"\/get-a-quote\/\">free extrusion line quotation<\/a> \u00b7 <a href=\"https:\/\/en.wikipedia.org\/wiki\/Pelletizing\" target=\"_blank\" rel=\"noopener\">Wikipedia: Pelletizing<\/a><\/p><\/section><\/div>\n<\/div>","protected":false},"excerpt":{"rendered":"<p>Home\/Knowledge\/Seven Pelletizing Methods Compared Process \u00b7 8 min read Seven Pelletizing Methods Compared: Strand, Water Ring, Underwater, Hot Face The pelletizer is chosen by the polymer, not by the budget. This table compares all seven methods we build on the criteria that actually decide the purchase: filler ceiling, water contact, pellet shape and fines. 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