On 5 June 2025 a rigid plastic washing line left our workshop on a flatbed for Hebei province. The buyer is one of the larger rigid HDPE recyclers in China, and this was the second line they had bought from BKL-MACHINE. Repeat orders are the only endorsement in this business that costs the customer something, so it is worth writing down what was actually on the truck and why it was configured the way it was.
What Was Actually on the Truck
Seven items, in the order the material passes through them:
| Stage | What it does on this line |
|---|---|
| Belt conveyors | Feed between stages. High side walls, because drum sections tumble rather than lie flat. |
| Heavy-duty wet crusher | Reduces drum sections to 8–16 mm flake. Wet crushing, so the first rinse happens here and no dust leaves the machine. |
| Friction washer | Scrubs flake against flake at high rotor speed. Stainless internals, wear-resistant blades. |
| Two flotation tanks | Sink-float separation. HDPE and PP float; sand, grit and metal fragments sink and are screwed out of the bottom. |
| Centrifugal dryer | Spins flake down towards the moisture target. Octagonal screen, dynamically balanced rotor. |
| Buffer silo | Holds dried flake so bagging does not have to keep pace with the line minute by minute. |
| Spare parts | Wear items shipped with the line rather than ordered after the first failure. |
The output specification for this line family is flake at 8–16 mm with moisture below 1%. Both numbers are set by hardware choices upstream: the flake size by the crusher screen, the moisture by the dryer and the hot-air stage behind it. Neither is adjustable later by running the line differently.
Why a Drum Shredder Was Not Part of This Line
A drum shredder is the machine most people assume sits at the front of a drum recycling line, and on many lines it does. It did not on this one, and the reason is worth explaining because it is the single decision that most changes what a line costs.
On our rigid washing line the shredder is an optional front-end module. Its job is to pre-shred bulky feed so the crusher is not asked to swallow something it cannot bite, which raises the throughput of the whole line and reduces wear on the crusher rotor. Whether you need it comes down to one question: what shape is the material when it reaches your yard?
This buyer receives drums that have already been cut open and quartered upstream. Sections that size feed a heavy-duty wet crusher directly, so the shredder would have added capital cost, floor area and a motor to run without changing the output. Where drums arrive whole — 200-litre chemical drums, IBC cages, closed-head barrels — the crusher cannot take them and a shredder in front is not optional at all.
Two shredder types cover that case, and they behave very differently:
| Twin-shaft (DS series) | Single-shaft (SS series) | |
|---|---|---|
| Rotor speed | 8–15 rpm | 72 rpm |
| Throughput | 400–4,000 kg/h across the range | 200–1,500 kg/h on lumps |
| Feeding | Two counter-rotating rotors pull material in | Hydraulic ram pushes material onto the rotor |
| Suits | Whole drums, IBCs, thick-wall pipe, mixed hard scrap | More uniform feed where a consistent cut size matters |
The speed difference is the whole story. A twin-shaft turning at 8–15 rpm is a slow, high-torque machine that tears rather than cuts, which is what you want when a drum still has a steel bung ring or a stray bolt in it. Knife steel is specified per application — 9CrSi, D2 or tungsten carbide — and that choice matters more on drum feed than on almost anything else, because drums are the stream most likely to arrive with something in them that should not be there.
It Ran in Our Workshop Before It Left
The line was assembled and test run at our factory before any of it went on a truck. That step is easy to skip and expensive to skip. Once equipment is on site, a rotor that is out of balance or a tank section that does not line up stops being a workshop job and becomes an engineer with a plane ticket.
Two things are worth checking during a factory test on a rigid line specifically. The sink-float tanks only work if the flow across them is even, and flow is the one property that changes when a tank is bolted to a different floor. And the centrifugal dryer has a rotor spinning fast enough that balance is not something to discover later — the screen is octagonal and each vane carries a replaceable stainless block on its leading edge, both of which are there because this is the machine that wears fastest on the line.
What Happens on Site
Our engineer travelled with the line for installation guidance and commissioning. On a rigid washing line the commissioning work is mostly water: getting the flow through the flotation tanks right, setting the friction washer so it scrubs without shattering flake into fines, and confirming that what comes out of the dryer is actually under the moisture target rather than approximately under it.
What the recycler needs ready before the truck arrives is unglamorous and worth stating plainly: a floor slab sized for the line, three-phase power at the installed rating, a water supply and a drain, and space to stack incoming drums where a loader can reach them. The floor area and power figures for this line family scale with capacity:
| Capacity | Installed power | Floor area | Operators | Water |
|---|---|---|---|---|
| 200–300 kg/h | 100 kW | 300 m² | 2–3 | 4–5 m³/h |
| 400–500 kg/h | 115 kW | 400 m² | 2–3 | 4–5 m³/h |
| 800–1,000 kg/h | 125 kW | 500 m² | 3–5 | 6–8 m³/h |
| 1,300–1,500 kg/h | 180 kW | 600 m² | 3–5 | 8–10 m³/h |
| 1,800–2,000 kg/h | 250 kW | 800 m² | 3–5 | 10–15 m³/h |
Installed power divided by rated throughput. This is connected load, not measured draw — actual consumption runs lower, because not every motor sits at full load at the same time. The figure to notice is labour: it rises from two to three people once, at the 800 kg/h step, and then does not rise again. A rigid line at 2,000 kg/h runs on the same crew as one at 1,300. That is the clearest argument for sizing up that this table contains, and it is the opposite of what happens on a PET bottle line, where the sorting belt keeps adding people.
The Second Line, Not the First
This buyer had run a BKL-MACHINE line before ordering this one. That matters more than any specification in this article, because a second order is placed by someone who has already lived with the wear rates, the spare parts lead time and the answer they got the first time something went wrong at two in the morning.
It also changes the commissioning conversation. A first-time buyer needs to be taught the line. A repeat buyer already knows how a friction washer sounds when it is being fed too fast, and the site work turns into a much shorter set of questions about what is different this time.
If you are working out what a drum stream needs before you buy anything, the process side is set out in more detail in our guide to HDPE recycling from drums to pellets, and the selection logic for the front-end machine is in how to choose a recycling shredder by material. If you would rather describe your feed and have us come back with a configuration, send us the details of your waste stream — the shape it arrives in tells us more than the tonnage does.
Frequently Asked Questions
How long does it take to install and commission a rigid washing line?
It depends far more on site readiness than on the line. Where the slab, three-phase supply, water and drain are already in place, mechanical installation and pipework are the bulk of the work and commissioning follows immediately. Where the building work is still running, the line waits. We send an engineer for the whole sequence rather than for a fixed number of days, because the variable is never the equipment.
What does a recycler need to prepare on site before the line arrives?
A floor slab sized for the capacity tier you ordered — 300 m² at 200–300 kg/h, up to 800 m² at 1,800–2,000 kg/h — three-phase power at the installed rating for that tier, a water supply and drain able to handle 4–15 m³/h depending on size, and a stacking area for incoming drums that a loader can work in. Power and water are the two that most often hold a start-up back.
Can a drum shredder handle drums that still have residue inside?
Mechanically, a twin-shaft shredder running at 8–15 rpm will take a drum with residue in it. Whether it should is a different question and is not ours to answer: residue is a chemical handling matter for the recycler and their regulator, not an equipment specification. What we do specify is knife steel, and drums are the stream where that choice earns its money, because they are the most likely to arrive with a bung ring or a fastener still attached.
Does every drum line need a shredder in front of the crusher?
No. If drums are cut and quartered before they reach the washing line, a heavy-duty wet crusher takes them directly and the shredder is cost you do not need. If drums arrive whole, the crusher cannot feed and the shredder is mandatory. It is worth answering this question before requesting quotations, because it moves both the price and the floor area.
How is a line tested before it leaves the factory?
It is assembled and run in our workshop. The point is to find balance and alignment problems while they are still workshop problems. The two stages that repay the most attention are the flotation tanks, where separation depends on even flow, and the centrifugal dryer, where a rotor spinning at speed has to be balanced before it ships rather than after.
What spare parts ship with a washing line?
Wear items travel with the line rather than being ordered after the first stoppage. On a rigid line the parts that wear are predictable — crusher blades, friction washer blades, and the replaceable stainless blocks on the dryer vane tops — and every one of them is a part you would otherwise be waiting on with the line stopped.
