Double-screws Turning Machine

The double screws compost turning machine is a type of trough-style fermentation equipment that utilizes two rotating shafts equipped with helical blades to turn the material; within organic fertilizer trough-fermentation processes, it is classified as a model that offers particularly thorough turning capabilities. It operates by extending two screw shafts into the material layer; as they rotate, they lift material from the bottom and push it toward the discharge outlet. The shearing and kneading action of the helical blades on the material is far more intense than that of toothed rollers. Whether dealing with clumpy pig manure, wet and pasty sludge, or fibrous, tangled cow dung, the twin-screw mechanism effectively breaks up and blends the materials. The equipment travels back and forth along rails mounted on the fermentation trough, with adjustable turning depth and travel speed. For organic fertilizer processing projects that prioritize uniform fermentation and precise control over the material's residence time in the trough, the double screws compost turning machine offers excellent performance in thorough turning, even mixing, and accurate material displacement.

Working Principle of the Double Screws Compost Turning Machine

The double screws compost turning machine performs turning and displacement operations through the rotation of two parallel screw shafts combined with the movement of the entire machine. The equipment straddles the fermentation trough, with a travel motor driving the unit slowly forward along rails on both sides of the trough. Two screw shafts are mounted horizontally within the trough, featuring continuous helical blades welded onto them; a turning motor drives the rotation of both shafts via a gearbox and gear transmission system. The helical blades cut into the material layer from the bottom of the trough; the helical surfaces scoop up the material, turning it over during rotation while simultaneously generating axial thrust toward the discharge end. The two screw shafts can rotate in the same direction or in opposite directions depending on process requirements: same-direction rotation results in faster material displacement, while opposite-direction rotation subjects the material between the shafts to repeated shearing and kneading, yielding superior mixing results. Material lifted by the helical blades falls back into the trough at a point shifted forward from its original position. After a single pass of the machine, the material layers within the trough have been interchanged, and the entire mass has shifted slightly toward the discharge end.

What are the operational requirements for the double screws compost turning machine?

Turning frequency. For newly loaded material with high moisture content prone to caking, turn the pile once or twice daily during the first two to three days to facilitate moisture evaporation and oxygen replenishment. During the high-temperature phase—when decomposition is most active—turn the pile at least once a day; move cooler material from the edges and surface into the high-temperature core to ensure the entire batch undergoes temperatures of 50–70°C. Once the temperature drops and the material enters the maturation phase, turning every two to three days suffices, allowing the material to stabilize gradually with less intensive agitation.

Spiral shaft immersion depth: The spiral blades should extend deep into the trough without touching the concrete bottom; maintain a clearance of 3–5 cm between the blade edges and the trough floor. If the immersion is too shallow, bottom material won't be turned up, leading to blackening and foul odors over time; if too deep, the blades may strike the concrete, causing rapid blade wear and potential damage to the trough floor.

Coordinate travel speed with spiral shaft rotation speed. At a constant shaft speed, moving slowly results in finer turning, minimal material displacement, and longer retention time in the trough; moving quickly results in coarser turning, greater displacement, and shorter retention time. Move more slowly when handling fresh, high-moisture material to ensure thorough turning; increase speed during the maturation phase—when the material is looser—to boost operational efficiency.

Safety precautions: Personnel must not stand inside the trough or touch the rotating spiral shafts while the equipment is running. When the machine changes direction at the trough ends, verify that limit switches are functioning correctly to prevent derailment. Always cut the power and display warning signs before shutting down for maintenance or cleaning the spiral blades.

How should the double screws compost turning machine be maintained?

Daily maintenance: Before startup, check for loose or detached spiral blades, assess blade edge wear, and ensure both shafts rotate smoothly. After shutdown, clear away long fibers and adhered wet material from the blades; if material dries and cakes on, restarting becomes difficult and can damage the blades.

Weekly checks on lubrication and fasteners: Apply grease to the bearings at both ends of the spiral shafts weekly, cleaning the area around the grease nipple beforehand. Check the lubrication status of the drive gears connecting the two shafts weekly to ensure an oil film remains on the gear teeth. Tighten all connecting bolts on the machine weekly, paying special attention to the spiral blade mounting bolts and bearing housing bolts.

Perform in-depth maintenance once a month. Remove the spiral blades to inspect for wear; replace them if the outer edge has worn down by more than one-third of its original width, as blades that are too thin reduce turning efficiency and are prone to breakage. Check the coupling and gear mesh clearance monthly using a feeler gauge; adjust or replace components if the clearance exceeds limits.

Inspect the electrical control system wiring for loose connections and check the responsiveness of limit switches quarterly. Conduct a major overhaul annually: disassemble and inspect spiral shaft and travel wheel bearings, replacing worn parts; change the gearbox oil and inspect internal gears; and check the seals and cylinders of the hydraulic lifting system.

What is the investment cost for a double screws compost turning machine?

Equipment purchase costs vary based on trough width and configuration. Double screws compost turning machines are more expensive than simple turners designed for the same trough width due to their more complex drive systems. However, compared to hydraulic trough-type turners, the twin-screw model features a simpler structure with fewer hydraulic components, making the equipment generally more affordable.

Civil engineering investment. Concrete or brick fermentation troughs must be constructed, with rails laid at the bottom and wall heights matched to the material pile height. Civil engineering costs depend on trough length and the number of parallel troughs; a single trough 40 to 60 meters long typically meets daily processing needs. Costs increase proportionally when multiple troughs are built side-by-side.

Operating costs. The total power rating ranges from ten to over twenty kilowatts; with one or two turning cycles per day, electricity costs represent a small fraction of total processing expenses. The primary wear parts are the spiral blades; under normal use, a set is replaced every few months to a year, depending on material abrasiveness and the quality of operation and maintenance. Gearbox oil and bearings require periodic replacement at a low cost. The equipment can be operated by a single person, resulting in low labor costs.