Piston care of hot press machine

Nursing methods for pistons of hot press machines:

The protection and replacement of pistons, as well as the wear or incorrect installation of rubber seals, are the direct causes of oil cylinder leakage; Surface damage or incorrect positioning of the piston is an indirect cause. When the piston surface is in good condition, the correctly installed rubber sealing ring can have a service life of more than 6 months. The main cause of piston surface damage is the presence of impurities such as sand in the oil. Once the surface of the piston is scratched, the scar will rapidly expand and deepen under the strong grinding of the leaking high-pressure oil. During the pressurization process, the acidic wastewater extruded from the wet plate has a corrosive effect on the surface of the piston. The higher the temperature, the greater the corrosion effect, especially when there are scars on the hard protective layer of the piston surface, which is particularly severe.

In addition, the small wood fibers in the extruded wastewater are also easily squeezed between the sealing ring and the piston, affecting the sealing effect. Hydraulic oil should be kept clean, and the oil tank should be covered and sealed. The filter screen of the oil pump suction pipe should be kept intact, and if it is damaged, it should be replaced in a timely manner. During maintenance, sediment in the pool should be removed, and the oil should be clarified or filtered before use (all emulsions should be replaced). This is also very important for protecting the oil pump and precision valves. The water spray pipe around the piston is used to flush the piston, prevent corrosion from acidic wastewater, and maintain cleanliness. In areas with high temperatures, it also plays a role in reducing the temperature of the piston. The occurrence of eccentric wear on the piston is also one of the reasons for surface abrasion and sealing ring wear or extrusion. It is caused by the uneven thickness of the wet plate blank on the left and right, which leads to eccentric load when the press is pressurized. The fitting accuracy between the piston and the cylinder liner is D (dc4), and excessive clearance can also cause eccentric wear. Oil cylinders that frequently experience oil leakage should be inspected by lifting the piston to check the surface condition, especially the sealing position at the highest pressure. If the damage is severe, it should be replaced.

If there is uneven wear, it is necessary to check the accuracy of the fit between the piston and the cylinder liner, and take measures in the production process to prevent uneven wear. When replacing the sealing ring, pay attention to safety and prevent the introduction of dirt. The "top rod" at the four corners of the support plate (lower crossbeam) should be firmly supported before operation. First, remove the lining pressure ring (the pressure ring of the large-diameter piston is too heavy and can be lifted with a small manual hoist), use wire hooks to take out the sealing rings one by one, replace them with new ones, and then tighten the pressure ring. To prevent the sealing ring from turning over. The replaced sealing ring should be carefully inspected and the cause of damage analyzed in order to take preventive measures. The specifications, structure, and shape of rubber sealing rings shall be selected according to the standards specified in the drawings and cannot be changed arbitrarily.

The sealing ring of the steam elbow tube in many hot press machines uses asbestos packing sealing devices for the steam tube rotating joints. At high temperatures, asbestos fillers are prone to hardening and gas leakage. The use of ball joints with good sealing performance and polytetrafluoroethylene sealing rings has a better effect, and the sealing rings can generally be used for about 1 year. Some asbestos wires have also been soaked in polytetrafluoroethylene plastic and compressed in the original packing box, which has good results but is not very convenient to use. When replacing the sealing ring, the ring behind the spherical shape needs to be cut at a 45 ° angle before it can be fitted, but it does not affect the sealing effect.

The maintenance of hot press plates includes the upper and lower lining plates, which protect the surface of the hot press plate. The upper lining plate directly affects the surface quality of the slab, and dirt such as wood bundles are often trapped between the lining plate and the hot pressing plate. The lining plate should be disassembled regularly to remove the dirt. The upper lining board is usually replaced once a week to polish the surface and ensure the quality of the finished board surface. When installing the lining board, it is necessary to cushion the wooden bundle before pressing it up. Damaged or unevenly sized slabs cannot be fed into the hot press machine. It is not allowed to directly press fiberboard without lining. If the shutdown lasts for a long time, it is necessary to promptly remove the steam condensation water inside the hot press plate to prevent internal corrosion. If the hot pressing plate is partially (or completely) not hot, it indicates that there is a blockage in the internal channel. Or there may be a "short circuit" phenomenon in the channel. Usually it is caused by the detachment or displacement of the original fixed "plug" in the hot press plate channel, but sometimes it is also caused by severe corrosion. If there is a large amount of exhaust and the temperature rise of that part still cannot be restored to normal, a dedicated deep hole drilling machine needs to open the channel for inspection, eliminate obstacles, and then continue to use. Local air leakage is found on the hot press plate, which can be repaired by electric welding. After welding, the water pressure should be tested to 1.2-1.4 times the steam pressure, and the welded area should be leveled. If the leakage is caused by severe internal corrosion, it should be replaced.