Selecting a metal crusher with the wrong throughput capacity leads to either idle equipment sitting in your yard or a bottleneck that stacks up unprocessed scrap. This guide compares the key mechanical specifications that determine real-world output so your procurement team can size the machine correctly.
Throughput: Nominal Ratings vs. Actual Yard Output
Manufacturers typically state capacity in tons per hour (t/h), but these figures are measured under controlled conditions with a uniform feed material. In a real scrap yard, mixed loads of thin sheet, heavy plate, and turnings will reduce effective throughput by 20 to 35 percent. A crusher rated at 15 t/h may deliver 10 to 12 t/h when processing mixed light ferrous scrap. Always ask the supplier whether their stated capacity refers to theoretical maximum or sustained operating throughput, and request the feed material specification used during testing.
Single-Shaft vs. Twin-Shaft: Matching Design to Material Mix
Single-Shaft Crushers
Single-shaft designs use a rotating drum with knives or hammers against a stationary anvil. They work well for lighter, more uniform scrap such as aluminum profiles, copper wire bundles, and thin steel sheet. Typical configurations range from 55 kW to 160 kW motors with rotor diameters of 600 mm to 1000 mm. Throughput generally falls between 3 and 12 t/h depending on material density and screen mesh size.
Twin-Shaft Crushers
Twin-shaft designs counter-rotate two cutting drums, generating higher torque at lower RPM. This makes them suitable for dense and irregular inputs: engine blocks, gear housings, bundled structural steel, and mixed non-ferrous loads. Motor ratings start at 110 kW and go up to 400 kW or more. Rotor diameters range from 800 mm to 1400 mm. Sustained throughput typically runs from 10 to 40 t/h, with some heavy-duty models reaching 60 t/h on light ferrous feed.
Three Specifications That Determine Real Capacity
- Rotor diameter: Larger rotors (1000 mm and above) draw material in more aggressively, reducing stall frequency when processing bulky items. This directly affects uptime and therefore daily tonnage.
- Motor kW: Power rating must be matched to the density of your most common feed material. A 75 kW motor handling engine blocks will trip repeatedly. As a rule of thumb, plan for 8 to 12 kW per ton of hourly throughput for medium ferrous scrap.
- Screen mesh opening: The discharge screen controls final particle size. A 40 mm mesh produces denser, more uniform output suitable for downstream smelting, but cuts throughput by 15 to 25 percent compared to a 60 mm mesh on the same machine.
Sizing Your Crusher to Daily Yard Volume
Start by calculating your average daily incoming scrap tonnage, not peak volume. If your yard receives 80 tons of mixed ferrous scrap per day and operates a single 8-hour shift, you need a sustained throughput of 10 t/h. Accounting for the 20 to 35 percent derate mentioned earlier, the crusher nameplate rating should be 13 to 15 t/h. A twin-shaft unit in the 132 kW to 160 kW range with a 900 mm to 1000 mm rotor typically meets this requirement. Also factor in screen change time (20 to 40 minutes per change) and knife maintenance intervals, which for twin-shaft cutters running mixed ferrous scrap usually fall every 120 to 200 operating hours.
Tiangong offers both single-shaft and twin-shaft metal crusher models. Share your typical feed material composition and daily tonnage with our engineering team, and we can recommend a configuration with the rotor diameter, motor size, and screen mesh that fits your processing line.