2026/06/18
The gap between the roller shells of a double roller press granulator directly determines the granulation quality, finished product hardness, and the volume of material recycled. The adjustment process involves three steps: coarse adjustment while the machine is stopped, no-load calibration, and fine-tuning under load; attention must also be paid to the parallelism of the left and right rollers and the alignment of the grooves. Proper operation minimizes roller shell wear and reduces the rate of fines (powder) generation.
Perform the initial coarse adjustment after the fertilizer produciton machine has been shut down and disconnected from power. Loosen the locking bolts on the bearing housings; adjustment screws and graduated scales are provided at both ends of the equipment. Rotate the screws synchronously on the left and right sides to control the distance between the two roller shells. The standard gap setting is 0.1–0.3 mm for conventional compound fertilizer raw materials, while materials with high organic matter or coarse fiber content require a setting of 0.3–0.5 mm. If the gap is too small, the roller shells rub against each other, causing rapid groove wear and increasing the load, which can lead to machine stalling or tripped breakers. If the gap is too large, the material is not compressed firmly, resulting in loose granules and excessive dust. During adjustment, ensure the number of turns for the screws on both sides is identical to prevent uneven tightness (one end tight, the other loose), which causes lopsided extrusion and inconsistent granule sizes.
After coarse adjustment, calibrate the alignment and parallelism of the roller shells. Check whether the grooves on the two rollers align correctly; misalignment causes flattened granules and uneven groove wear. If the grooves are offset, loosen the bearing on one side to make a minor adjustment, ensuring the male and female molds mesh perfectly. Use a feeler gauge to measure the gap at various points along the rollers, keeping the difference within 0.05 mm to prevent uneven wear or localized depressions. Once calibrated, tighten the bearing housing locking nuts evenly to prevent the gap from shifting during production.
After a no-load test run confirms the absence of abnormal friction noises, proceed to fine-tuning under load. Feed a small, steady amount of material and observe the output; if granules are flat, thin, and fragile, or if there is a large amount of recycled material, synchronously reduce the gap using the adjustment screws. If the roller shells overheat, the motor current spikes, or metallic grinding sounds occur, stop the machine immediately and increase the gap. Gap settings require adjustment based on the raw material: increase the gap for high-moisture organic fertilizers, while reducing it for dry, pure chemical fertilizers to enhance granule strength.
Routine maintenance helps extend the service life of the roller shells. Pre-process raw materials to remove impurities, as stones and hard objects can cause dents in the roller shells and compromise gap precision. Regularly clear material buildup from the roller shell grooves, as accumulations effectively narrow the working gap. Re-verify the gap and parallelism after every maintenance session; during continuous production, check the scale settings every two weeks to prevent gap drift caused by screw thread slippage, thereby ensuring consistent granulation quality and reducing roller shell replacement costs.
