In industrial production, the 95-type oil press is a small-scale screw oil press that was successfully trial-produced in China in 1958. Through long-term production practice, it has been proven that this press not only has strong overall technical performance but also offers many advantages of small oil presses.

Before starting the 95-type oil press, lubricating oil should be added to all lubrication points, and the gearbox lubricant level should be checked and replenished. Rotate the oil press without a load to check for any abnormal sounds or faults. Then, loosen the cake clamp, increase the cake outlet gap, and prevent the pressing chamber from becoming blocked by excessive feeding. When starting, first start the motor to allow the equipment to run unloaded for a few minutes. After normal operation, begin feeding. Feed a small amount of material initially. When the pressing chamber temperature rises, feed normally while monitoring oil output, residue discharge, cake discharge, and load conditions. Generally, the most oil is discharged at the pressing bar section, with the least near the cake outlet. The 95-type oil press produces relatively little residue, typically 3%-5%. During normal operation, the cake slices are firm, with a smooth, oil-free surface and patterns on the back. The cake thickness is 1.0–1.3 mm. The current is about 16A.

Before stopping, loosen the cake clamp to increase the cake thickness to 2–3 mm, feed all remaining material from the steaming pan and hopper into the pressing chamber, so that the oil residue or cake crumbs in the pressing chamber do not form hard blocks, avoiding the trouble of having to disassemble the machine before being able to restart.

The ZX-10 screw oil press is an improved design based on the original 95-type screw oil press. Compared with the original 95-type oil press, this machine has a more rational structure, particularly improvements to the feeding section and the pressing chamber, which enhance process efficiency. This machine offers advantages such as simple operation, stable performance, low single-machine weight, smooth operation, no abnormal vibration or noise, and no gearbox leakage.

The structure of the ZX-10 screw oil press is shown in Figure 3-11. Apart from the frame and base, it can be roughly divided into five parts: the feeding mechanism, screw shaft, pressing cylinder, cake outlet adjustment mechanism, and transmission device.

When pressing peanuts with the ZX-10 screw oil press, there are two pressing methods: cold pressing and hot pressing. Cold pressing is suitable for small-scale, simple production and processing. To improve peanut oil yield, pressing is typically performed twice. Since peanuts have an oil content of 45%-50%, to ensure sufficient pressure during pressing, they are often pressed with the red skin. During production and processing, first run the oil press without load for several minutes to check whether the no-load current is normal (typically 3–5A). Also,o check for abnormal sounds in the gearbox and whether the bearing parts are overheating. After normal no-load operation, feeding can begin. At the beginning of pressing, the temperature in the pressing chamber is relatively low, so feeding should not be too aggressive to prevent blockage of the pressing chamber. As the temperature in the pressing chamber rises, the pressed material gradually forms cakes, and oil gradually comes out. At this time, adjust the pressing chamber, slowly reducing the cake thickness from thick to thin, and tighten the locking nut. The press then enters normal operation.

During normal operation, the press should maintain uniform feeding. At the same time, pay attention to observing the ammeter pointer, which should generally be 10–12A. If the pressure exceeds the rated value excessively, the press is overloaded. A sudden pressure increase indicates that the pressing chamber is blocked. Immediately stop feeding and resume only after returning to normal. If a drop in current is observed, it may be caused by damage to the pressing chamber due to compacted material in the hopper. In this case, use a bamboo piece to stir the material in the hopper to continue uniform feeding. Under normal conditions, the oil output positions are mostly concentrated at the pressing bar ring, and several pressing rings near the pressing bar ring also produce oil, with clear and bright oil color. If the moisture content of the fed material is too high or too low, it can easily cause uneven oil output or insufficient oil output. During normal operation, the cake is tile-shaped, with a smooth surface and many small cracks on the other side. The cake hardens quickly after falling, with no oil stains or burnt smell on the surface. The cake thickness is generally 1.5–2.0 mm. If the cake is soft and weak, appearing in large flakes, it indicates excessive moisture in the feed material. If the cake does not form properly, easily turns into powder, and has a burnt odor and color, it indicates insufficient moisture in the feed material. Under normal circumstances, there is very little residue output. If flaky residue flows out of the pressing bar ring, it indicates excessive moisture in the feed material.

After the material in the hopper is finished, loosen the cake outlet, feed in a small amount of oil residue or cake crumbs to dislodge the remaining material in the pressing chamber, then stop the machine. This prevents the material in the pressing chamber from solidifying and prevents incidents such as the main shaft twisting or the pressing shell bursting during the next startup. If a sudden power outage triggers an emergency stop, first disconnect the power, then manually rotate the machine to empty the material from the pressing chamber before restarting.

III. ZX-18 Type Screw Oil Press

The ZX-18 (200A-3) screw oil press (Figure 3-12) is currently a relatively good oil press. It offers advantages such as a compact structure, high processing capacity, simple operation, and durable main components. This machine is also equipped with a steaming pan for the press, which can adjust the temperature and moisture of the feed material to improve pressing results. When combined with the auxiliary steaming pan, this machine enables continuous production.

The structure of the ZX-18 (200A-3) screw oil press comprises six parts: feeding device, screw shaft, pressing cage, cake-adjustment mechanism, press steam pan, and transmission system.

The pressing shaft is the main working component of the ZX-18 (200A-3) screw oil press. As shown in Figure 3-13, the right end of the figure is the feeding end, and the left end is the cake outlet end. On the 1960 mm long pressing shaft, 7 pressing screws and 6 lining rings are installed, all connected by flat keys to form a left-hand screw shaft. The lining rings are arranged between each pressing screw, serving to connect the pressing screws. When the root circle diameters of the pressing screws are different, tapered lining rings are used for connection. There are knife edges for installing scrapers on the lining rings. The scrapers prevent the material from rotating with the screw shaft and ensure effective stirring. After sequentially installing the pressing screws and lining rings on the pressing shaft, together with the cast iron copper sliding bearing at the front end of the pressing shaft, they are locked with a left-hand special nut and a left-hand lock nut. The other end of the pressing shaft is connected to the output shaft of the gearbox via a coupling. Since the pressing shaft has left-hand threads, when viewed from the oil press’s feeding end, the shaft rotates clockwise.

Like the ZX-10 oil press, the ZX-18 screw oil press requires a process from startup to normal operation when pressing peanuts. The time required for this process is often longer than that of the ZX-10 oil press. When using a new oil press or resuming production after maintenance, perform the necessary checks. The main contents include:

• ① Clear any material in the steaming pan, close the bottom steaming pan discharge gate to prevent accumulated material from entering the pressing chamber and causing blockage.
• ② Loosen the cake clamp to maximize the cake outlet gap.
• ③ Check all transmission systems to ensure no errors (including gearbox oil level and belt tension).
• ④ Check whether all connecting parts are secure.
• ⑤ Manually rotate the large pulley to check for smooth and easy rotation, ensuring no impact sounds or other abnormal noises.
• ⑥ Start the motor and observe whether the direction of motion is correct. If correct, run without load for a period. If the load is high during no-load operation, it may be due to excessive transmission tension, poor gear engagement, improper pressing-cage assembly, insufficient lubrication, or motor issues. Check step by step. Only after normal no-load operation can material feeding for production begin.

During startup, the pressing chamber temperature rises from low to high. This process is called the “warm-up process.” Simultaneously: ① Drain condensate from the steaming pan, open the steam valve; ② Open the steaming pan feeding gate, close the discharge gate to store material in the steaming pan; ③ Feed a small amount of material to raise the pressing chamber temperature.

When starting to press raw peanuts, it is best to feed oil residue or cake crumbs to avoid clumping in the pressing chamber. Do not interrupt feeding after starting. The feeding amount should be about 1/3 of the normal feeding amount. When the temperature of the residue and broken cakes from the cake outlet rises (taking about 30 minutes), begin to increase the moisture content of the material to promote cake formation and oil output. At this time, adjust the cake clamp to achieve normal cake thickness. The above warm-up process takes about 60 minutes.

During normal peanut pressing operation, there must be sufficient pressure in the pressing chamber, and the power load should be stable. The normal ammeter reading is 25–28A. If the material moisture is too high, the pressure will decrease. If the moisture is too low, residue leakage will be excessive. If there is excessive impurity or cooling, the current will increase. Maintain normal feeding, prevent interruption, and always pay attention to the cake discharge situation. The discharged cake should be tile-shaped, slightly elastic and hard, making a crisp sound when broken, with a neat break, a smooth front side, fine cracks on the back, a fragrant aroma, and no oil stains on the surface.

During normal production, a large amount of oil is discharged at the second and third pressing cage plates. When the moisture content is too high, plasticity increases, cake formation occurs too early, the oil output position advances, the oil color is lighter, and foam increases significantly. If the material moisture is too low, even continuous feeding may not advance this part of the cake block, causing a sudden increase in pressure in the pressing chamber and potentially leading to a pressing chamber explosion when a certain threshold is reached.

If stones are mixed in during the process before pressing, or iron objects are mixed due to poor iron removal, or iron parts such as nuts are mixed due to local loosening of equipment or negligence during maintenance, they can also damage the pressing chamber when they enter with the material. To prevent such accidents, the iron-removal equipment used in the preceding processes should be regularly inspected for completeness. During maintenance, screws and nuts should be cleaned, counted, and matched. During trial operation, pay close attention to any abnormal sounds. During operation, observe whether the current is stable.