{"id":2202,"date":"2026-10-19T01:53:28","date_gmt":"2026-10-19T05:53:28","guid":{"rendered":"https:\/\/slecotech.com\/?p=2202"},"modified":"2026-10-19T01:53:28","modified_gmt":"2026-10-19T05:53:28","slug":"plastic-drum-shredder-why-barrels-are-a-volume-problem-not-a-hardness-problem","status":"publish","type":"post","link":"https:\/\/slecotech.com\/es\/plastic-drum-shredder-why-barrels-are-a-volume-problem-not-a-hardness-problem\/","title":{"rendered":"Plastic Drum Shredder: Why Barrels Are a Volume Problem, Not a Hardness Problem"},"content":{"rendered":"
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A recycler in Poland called me about a shredder that was “underperforming.” They were feeding 200-litre HDPE drums and getting about a third of the throughput the brochure promised. They wanted to know if the motor was undersized.<\/p>\n

I asked two questions. How much does one of those drums weigh? He said about nine kilos. Second question: how many can you fit in the hopper at once? He said two, maybe three.<\/p>\n

There was the answer. Nine kilos per drum, three in the hopper \u2014 that is 27 kg of plastic in a machine sized to move hundreds of kilos an hour. The motor was fine. The machine was spending most of its time waiting for the next barrel to fall in.<\/p>\n

The short answer<\/h2>\n

Drums and barrels are not a hardness problem. They are a volume problem.<\/strong> A 200 L drum is mostly air. It fills the hopper, weighs almost nothing, and on impact it can bounce instead of being grabbed. So the number that matters is not kilograms per hour \u2014 it is how many drums you can get into the chamber per hour<\/strong>, and that is set by hopper size and feed opening, not motor power.<\/p>\n

Two things decide whether a machine can take whole barrels:<\/p>\n

    \n
  1. Hopper opening<\/strong> \u2014 can the barrel physically go in?<\/li>\n
  2. Feed width at the rotor<\/strong> \u2014 can the rotor actually grab it once it is in?<\/li>\n<\/ol>\n

    Most people check neither. They check kilowatts.<\/p>\n

    The drum is mostly air<\/h2>\n

    This is the part that misleads everyone.<\/p>\n\n\n\n\n\n\n\n\n
    Container<\/th>\nTypical size<\/th>\nEmpty weight<\/th>\nMaterial per unit volume<\/th>\n<\/tr>\n<\/thead>\n
    20\u201325 L jerrycan<\/td>\n~290 \u00d7 250 \u00d7 400 mm<\/td>\n1.2\u20131.5 kg<\/td>\nBajo<\/td>\n<\/tr>\n
    60 L drum<\/td>\n~\u00d8400 \u00d7 650 mm<\/td>\n3\u20134 kg<\/td>\nBajo<\/td>\n<\/tr>\n
    200 L HDPE drum<\/td>\n~\u00d8580 \u00d7 900 mm<\/td>\n8\u201310.5 kg<\/td>\nMuy bajo<\/td>\n<\/tr>\n
    1000 L IBC tote<\/td>\n1200 \u00d7 1000 \u00d7 1150 mm<\/td>\n55\u201365 kg<\/td>\nVery low (metal cage excepted)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    A 200 L drum has a wall thickness around 2\u20134 mm. Cut it open and flatten it and you have a sheet maybe 900 \u00d7 1800 mm \u2014 a few kilos of HDPE spread over a lot of area. The drum is a container, not a lump of plastic.<\/p>\n

    That is why the throughput in kg\/h looks so poor when someone tests your machine with barrels. The machine is doing exactly what it was built to do. You are feeding it air with a thin skin of plastic around it.<\/p>\n

    \n

    On hollow parts, the hopper is the bottleneck, not the rotor. Count containers per hour, not kilos.<\/p>\n<\/blockquote>\n

    Does the barrel actually fit? Two numbers to check<\/h2>\n

    This is where I see machines get bought wrong. There are two separate openings and both have to work.<\/p>\n

    1. Hopper opening<\/h3>\n

    The opening has to accept the barrel in whatever orientation it will actually land in. Our SC series hoppers are:<\/p>\n\n\n\n\n\n\n
    Modelo<\/th>\nHopper opening<\/th>\n<\/tr>\n<\/thead>\n
    SC600<\/td>\n800 \u00d7 500 mm<\/td>\n<\/tr>\n
    SC800<\/td>\n850 \u00d7 630 mm<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    A 200 L drum is about \u00d8580 mm. Against a 500 mm dimension on the SC600, it does not fit in either orientation \u2014 580 mm is bigger than 500 mm whether you stand it up or lay it down. On the SC800 the 630 mm dimension clears 580 mm, so a whole drum goes in.<\/p>\n

    2. Feed width at the rotor<\/h3>\n

    The rotor has a working width, and the usable intake is roughly rotor width minus 100 mm<\/strong>. From the S Series:<\/p>\n\n\n\n\n\n\n\n\n\n\n\n
    Modelo<\/th>\nRotor width<\/th>\nUsable intake<\/th>\n<\/tr>\n<\/thead>\n
    S600<\/td>\n600 mm<\/td>\n~500 mm<\/td>\n<\/tr>\n
    S800<\/td>\n820 mm<\/td>\n~720 mm<\/td>\n<\/tr>\n
    S1000<\/td>\n1030 mm<\/td>\n~930 mm<\/td>\n<\/tr>\n
    S1200<\/td>\n1230 mm<\/td>\n~1130 mm<\/td>\n<\/tr>\n
    S1400<\/td>\n1450 mm<\/td>\n~1350 mm<\/td>\n<\/tr>\n
    S1600<\/td>\n1650 mm<\/td>\n~1550 mm<\/td>\n<\/tr>\n
    S1800<\/td>\n1850 mm<\/td>\n~1750 mm<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    Same conclusion from the other direction. A \u00d8580 mm drum against an S600 with ~500 mm of usable intake will not be grabbed cleanly. Move to the S800 with ~720 mm and it drops straight in.<\/p>\n

    Both numbers point at the same answer, which is what makes it trustworthy.<\/strong> If you are feeding 200 L drums, the SC600 and S600 are the wrong size and the SC800 \/ S800 class is the starting point. If you are feeding IBC totes at 1200 \u00d7 1000 \u00d7 1150 mm, no standard single shaft shredder takes that whole \u2014 those get dismantled first.<\/p>\n

    The safety step people skip<\/h2>\n

    Sealed drums can hold pressure, liquid, or both. Putting one into a shredding chamber is how people get hurt, and it is also how you destroy a set of knives.<\/p>\n

    Before a drum goes anywhere near a rotor:<\/p>\n

      \n
    1. Check what was in it.<\/strong> Not what the label says \u2014 what is actually in there. Pharmaceutical, agrochemical and solvent residues are the ones that bite.<\/li>\n
    2. Drain it.<\/strong> Completely. Residual liquid turns your shred into hazardous waste and ruins the regrind.<\/li>\n
    3. Vent or open it.<\/strong> A sealed container that gets crushed by a rotor at 73 rpm with tens of kilowatts behind it will let go. Cut or puncture it first.<\/li>\n
    4. Strip the metal.<\/strong> IBC cages, drum lid clamp rings, and steel handles. Steel in a shredder does not get shredded \u2014 it takes a chunk out of your rotor knives.<\/li>\n<\/ol>\n

      That fourth one is the expensive one. A lid clamp ring is cheap to remove by hand and very expensive to remove from a rotor.<\/p>\n

      I should also say plainly: if the contents are unknown and you cannot verify them, do not shred it. There is no throughput target that justifies guessing.<\/p>\n

      Why barrels bounce, and what the pusher is for<\/h2>\n

      A solid lump gets bitten by the rotor on the first pass. A hollow drum often does not. It lands, the rotor hits it, and because there is nothing behind the wall to resist, the whole drum skitters across the top of the rotor instead of being drawn down.<\/p>\n

      This is exactly what the hydraulic pusher on a single shaft shredder exists to solve. It is not a convenience feature. On hollow parts it is the thing that makes the machine work at all.<\/p>\n

      Our S Series carries a hydraulic unit at 5.5 kW up to 7.5 kW depending on model, and that is what drives the pusher. When someone tells me their shredder “won’t take drums,” the pusher cycle and its pressure setting is the first thing I look at \u2014 before the motor, before the blades.<\/p>\n

      Related: hollow parts are also the loudest thing you can feed. A sealed drum failing inside the chamber is an impact event, not a cut, and those push a machine from 75\u201385 dB(A) up past 100 dB(A). If you are running drums, read the noise and dust article<\/a> \u2014 the hopper lid and lined discharge matter more on this material than on any other.<\/p>\n

      Single shaft or double shaft for drums?<\/h2>\n

      Both work, and they suit different operations.<\/p>\n\n\n\n\n\n\n\n\n\n
      <\/th>\nSingle shaft + pusher<\/th>\nDouble shaft<\/th>\n<\/tr>\n<\/thead>\n
      How it takes a drum<\/td>\nPusher forces it onto the rotor<\/td>\nTwo rotors grab and pull it through<\/td>\n<\/tr>\n
      Resultado<\/td>\nMore uniform, sized by screen<\/td>\nCoarser, more variable<\/td>\n<\/tr>\n
      Best for<\/td>\nBarrels you want to size for a crusher or wash line<\/td>\nVery bulky, mixed, or contaminated feed<\/td>\n<\/tr>\n
      Hollow-part behaviour<\/td>\nNeeds pusher pressure set right<\/td>\nGrabs hollow parts more naturally<\/td>\n<\/tr>\n
      Downstream<\/td>\nFeeds a crusher cleanly<\/td>\nOften needs a second stage<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

      If you already have, or plan to buy, a crusher for the second stage, the single shaft is the cleaner choice \u2014 the screen gives you a predictable ceiling and the crusher does the sizing. If the feed is mixed bulky scrap where drums are one item among many, a double shaft is more forgiving. We wrote that comparison properly in the single vs double shaft article<\/a> and in the double shaft guide<\/a>.<\/p>\n

      What comes out, and why it jams your next machine<\/h2>\n

      Drums shred into curved, springy pieces. They do not pack down. They bridge.<\/p>\n

      Two consequences worth planning for:<\/p>\n

        \n
      1. Bulk density is poor.<\/strong> A bin of shredded drum weighs far less than the same bin of shredded purgings. If your downstream is a conveyor or a metering feeder sized by weight, it will run starved.<\/li>\n
      2. Pieces bridge in hoppers and chutes.<\/strong> Curved fragments interlock and form arches over an outlet. This is the most common cause of “my crusher keeps starving” on a drum line.<\/li>\n<\/ol>\n

        The fix on both is to get the material through a second sizing stage rather than trying to handle it as-is. That is where screen choice matters \u2014 on hollow parts, running a screen that is too small just re-cuts material that is already small enough, which is the whole argument in the shredder screen size article<\/a>.<\/p>\n

        How to estimate throughput on barrels<\/h2>\n

        Do not start from the brochure kg\/h figure. Start from the container.<\/p>\n

        Containers per hour \u2248 (chamber intakes per hour) \u00d7 (containers per intake)<\/strong><\/p>\n