Repair and maintenance of artificial hot press

- Mar 16, 2020-

1. Piston maintenance and replacement of the seal ring The wear or incorrect installation of the rubber seal ring is the direct cause of oil leakage in the cylinder; the damage to the surface of the piston or the incorrect position is the indirect cause. With a good piston surface, a properly installed rubber seal will last more than 6 months.

The main cause of piston surface damage is sand and other impurities in the oil. Once the piston surface is scratched, the scar will rapidly expand and deepen under the intense grinding of the leaked high-pressure oil. During the pressurization process, the acidic wastewater extruded from the wet plate has a corrosive effect on the piston surface. This is particularly serious when the hard protective layer on the surface of the piston is flawed. In addition, the fine fibers in the extruded wastewater can easily be squeezed between the seal ring and the piston, affecting the sealing effect.

Hydraulic oil should be kept clean, and the oil pool should be sealed. The filter of the suction pipe of the oil pump should be kept intact, and if damaged, it should be replaced in time. During maintenance, the sediment in the oil tank should be removed, and the oil should be clarified or filtered before being used (the emulsion should be completely replaced). This is also very important to protect the oil pump and precision valves.

The water spray pipe around the piston flushes the piston to protect it from acidic wastewater and keep it clean. It also plays a role in reducing the temperature of the piston in areas with high temperatures.

Piston eccentric wear is also one of the reasons for surface abrasion and seal wear or squeezing. It is caused by the inconsistent thickness of the wet slab and the eccentric load when the press is pressurized. The precision of the fit between the piston and the cylinder liner is D (dc4). Excessive clearance will also cause partial wear.

Cylinders that often leak oil should be lifted out of the piston to check the surface condition during the inspection, especially the part of the seal position at the highest pressure, which should be replaced when the damage is serious. If there is eccentric wear, you need to check the accuracy of the piston and the cylinder liner and take measures to prevent eccentric load in the production process.

When replacing the sealing ring, pay attention to safety and prevent the introduction of dirt, and the "jacks" at the four corners of the supporting pallet (lower beam) should be firmly supported before the operation. First, lift the lower bushing pressure ring (the pressure ring of the large-diameter piston is too heavy and can be lifted with a small manual hoist), take out the seal rings one by one with a wire hook, replace them with new ones, and then tighten the pressure ring. To prevent the seal from "flanging", the replaced seal must be carefully inspected and the cause of damage analyzed to take preventive measures.

The specifications, structure, and appearance of rubber seals are selected in accordance with the standards specified in the drawings and cannot be changed at will.

2. Sealing ring of steam elbow tube Many steam tube rotating unions of hot presses use asbestos packing sealing device. At high temperature, asbestos packing is easy to harden and steam leakage occurs. The ball joint and Teflon sealing ring with good sealing performance are effective. The sealing ring can generally be used for about 1 year. There are also polytetrafluoroethylene plastics impregnated with asbestos thread, which are compacted and used in the original stuffing box. The effect is also good, but it is not convenient to use.

When replacing the sealing ring, the ring behind the ball needs to be cut at an oblique angle of 45 ° to be fitted, but it does not affect the sealing effect.

3. Maintenance of the hot press plate The upper and lower lining plates of the hot press plate protect the surface of the hot press plate. The upper lining board more directly affects the quality of the fiberboard surface. Fibers and other dirt are often easily caught between the lining board and the hot-pressing board. The lining board should be removed regularly to remove the dirt. The upper lining board is usually changed once a week to polish the surface and ensure the quality of the finished board.

When installing the backing plate, be sure to pad the fiberboard before pressing it up. Damaged or different sized slabs cannot be fed into the hot press. It is not allowed to directly press the fiberboard without a lining board. If the machine is stopped for a long time, the steam condensate in the hot press board must be removed in time to avoid internal corrosion.

The local (or all) of the hot press plate of the hot press is not hot, indicating that there is a blockage in the internal channel or a "short circuit" phenomenon in the channel. It is usually caused by the original fixed "plug" in the hot platen channel being disengaged or moved, but it is also caused by severe corrosion. If a large amount of steam is exhausted, the temperature rise in this part cannot be returned to normal, and a special deep-hole drill is required to open the channel to check and remove the obstacle before continuing to use it.

If local steam leakage is found on the hot pressing plate of the hot press, it can be repaired and smoothed by electric welding. After welding, the water pressure should be tested, and the pressure is 1.2--1.4 times the steam pressure. If it is a leak caused by severe internal corrosion, it should be replaced.