Created on:2021-06-29 14:52

Maintenance of loading device of press section in paper machine maintenance

Maintenance of loading device of press section in paper machine maintenance

With the rapid development of paper industry, more and more hydraulic systems are used in the loading device of press section of paper machine. If the hydraulic system is not well maintained, it will cause system pollution, frequent failures will affect the paper machine shutdown, resulting in huge economic losses. Practice has proved that it is very effective to maintain the hydraulic system of the loading device in the press section of the paper machine from the following three aspects.

(l) Correct selection of hydraulic oil

According to the characteristics of relatively high ambient temperature (30 ~ 50 ℃) in papermaking workshop, the selection of l-hl32 and l-hl46 domestic hydraulic oil for general paper machines can meet the requirements; L-hm32 and l-hm46 hydraulic oil should be preferred for medium equipment paper machine hydraulic system; Shell, Mobil and 45 series hydraulic oil can be selected for hydraulic system with higher reliability requirements; Large high-speed paper machine, the best choice of elf, total series and other brands of hydraulic oil. The suppliers of these brands will send technical service engineers to test and comprehensively evaluate the hydraulic system, recommend the best brand of hydraulic oil for users to choose, and provide tracking service.

(2) Cleaning and filtration of hydraulic system

Before the paper machine hydraulic system is put into use, it must be cleaned carefully and comprehensively. According to the specification, first use 20% dilute sulfuric acid or dilute hydrochloric acid for pickling, use 10% soda water and water, and then rinse with clean water. In practical operation, all pipe joints can be disassembled first, and compressed air above 0.5MPa can be used to purge the pipe, and special pipe short-circuit control elements and executive elements can be made. L-hl32 hydraulic oil is used for circulating cleaning for 6-8h. Complex hydraulic system must be circulating for more than 24h. If conditions permit, cleaning oil can be used to clean thoroughly the impurities in the system, and then the oil tank and control elements can be cleaned. After cleaning, the oil tank can be filled with hydraulic oil for system pressure test.

The hydraulic system of paper machine will be polluted in varying degrees after it is put into operation for a period of time. The hydraulic system itself, oil tank, oil pipe, control element and executive element are impacted by the fluid or move relative to form internal wear, which will produce impurity pollution; Impurities in the environment enter into the oil and produce impurity pollution. The influence of impurity pollution on hydraulic system is the most obvious: 1) increase wear, produce leakage, and produce new impurity pollution, chain reaction; ② The response of the action is slow, which reduces the efficiency and affects the working accuracy; ③ The damping hole is blocked, even the oil pipe is blocked, resulting in the control failure of the hydraulic system. In addition, the wet production environment of paper workshop will also produce water pollution and air pollution. Water pollution will cause oil oxidation, additives precipitation and other phenomena, which will affect the function of hydraulic oil; Air pollution will produce vibration and noise, cavitation phenomenon, reduce the working life of hydraulic pump. Therefore, it is very important to select the filter system and filter elements. The hydraulic system of low-speed small paper machine only needs to install a net filter or a line gap filter on the oil suction pipeline of the hydraulic pump to meet the requirements, and the filtering accuracy is 0.05 ~ 0.10 mm; For the hydraulic system of the paper machine whose speed is over 300m / MIM, the line gap filter or paper core filter should be installed on the oil suction pipe of the hydraulic pump, and the line gap filter should be installed on the oil return pipe, with the filtering accuracy of 0.03-0.05mm; For the hydraulic system of paper machine with speed over 800m / min, stainless steel fiber filter must be installed on the pressure oil pipe and oil return pipe. In front of some key control valves (servo valve, proportional valve, etc.), stainless steel fiber filter should also be installed to ensure the filtering accuracy of 0.01 ~ 0.05mm. In addition to the reasonable use of the system filter, the circulating filtering outside the system is also necessary. The hydraulic oil in the system is filtered regularly (45-50 days) with a special filtering car. In addition to removing the impurity pollution, the more important thing is to reduce the water and air pollution in the hydraulic oil.

(3) Daily maintenance of hydraulic system

① Check the oil level of the oil tank every day, not lower than the minimum level, and pay attention to supplement the same brand of hydraulic oil; Check the temperature indication and make good use of the cooler. The oil temperature should be controlled at 35 ~ 45 ℃ and the maximum should not exceed 60 ℃; Keep the surface of the oil tank clean, wipe the dust on the surface of the tank with silk cloth, and clean the oil tank regularly. Generally, it is appropriate to clean the oil tank once every 80-90 days.

② Regularly clean the oil suction filter of hydraulic pump (20-30 days), and check the integrity of the filter. If it is damaged, it should be renewed immediately, and it should not be used reluctantly; Pay attention to the running noise of the hydraulic pump, clean the filter in time when it is abnormal, and discharge the air in the pressure pipeline.

③ Regularly clean the pressure control element and reversing element (30-40 days), clean them with gasoline and wipe them with silk cloth to keep the damping hole unblocked and the valve core moving flexibly; The pressure gauge should be in good condition, and the working pressure should not exceed 2 / 3 of the measuring range.

④ Check the fixing condition of oil pipe joint and pipe support frequently, and tighten them every other period of time (80-90 days).

⑤ The seal of hydraulic cylinder should be kept in good condition, especially for the part with water spray pipe. Once the abrasion is found, it should be replaced in time. For the hydraulic cylinder with pressure greater than 5MPa and frequent action, the seal must be replaced once every 8 ~ 10 months, and the whole set must be replaced.

⑥ The hydraulic oil should be changed once a year; If conditions permit, oil quality test can be carried out. If the pollution degree, water content, air content and additive content meet the specifications, it can continue to be used for no more than 18 months.

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