Views: 3 Author: Site Editor Publish Time: 2022-02-14 Origin: Site
Modern paper machine can be said to be a behemoth with a high degree of integration. Its width can reach 10m, height can reach 20m, and length can even reach 150m. Each papermaking machine includes at least four main parts: forming part or wire part, press part, drying part, rewinding part, usually the three parts of pulp flow conveying part and forming part press part in front of the paper machine are called as three parts. The wet part, the drying part, the calendering part, and the rewinding part in the back are called the dry part. Different types of papermaking machines produce newsprint, coated paper, whiteboard paper, kraft cardboard and other paper types. Modern paper machines have more than 1,500 different bearings, which are subjected to harsh conditions such as water, heat, steam, pulp, etc., and each part has special lubrication requirements depending on the mining and operating speed of the equipment. The fierce competition in the papermaking industry also puts forward higher requirements for the reliability and production efficiency of papermaking machinery. The correct selection and application of lubricating oil and grease have an important impact on the life of papermaking machinery bearings and papermaking machinery.
Requirements for the performance of lubricating oil and grease for each part of the paper machine:
Proper lubrication is very necessary for all papermaking machinery, where lubricating oil and grease play a role in removing heat, reducing friction and wear, and preventing bearing surface corrosion. The life of the bearing is affected by its material, heat treatment process and other factors, but almost half of the bearing failure is caused by unsuitable lubrication, so strengthen the monitoring of operating temperature, the analysis of the leakage phenomenon of the lubrication system, unconventional noise and vibration The analysis of the paper machine can identify the problems existing in the lubrication system of the paper machine as soon as possible and avoid the damage of the bearing.
(1) Requirements for grease for bearing lubrication in wet part
Wet end requirements for bearing lubricating grease include: very good water resistance, good sealing effect, very good corrosion resistance, good lubricating film formation, good rubber compatibility, and compatibility with various metals good oxidative stability, good cleanliness, good lubricating performance (its composition should be adapted to a variety of bearing types), good centralized lubrication delivery (no oil separation under pressure, good pumpability) .
The biggest hazard for parts lubricated by grease is poor grease supply capacity, dilution of grease by moisture, and corrosion of bearings and other components by moisture. The lubrication interval is about two weeks. The new grease enters the bearing outer ring through the lubrication groove or lubrication hole, and a certain amount of the old grease is replaced. Note that the bearings must be stopped when relubricating.
Since water will penetrate and deposit when the bearing is shut down for cleaning, causing corrosion, it is best to completely re-lubricate the bearing part when the machine is shut down or when the shaft roll is stored for standby. Relubrication of new bearings is also required immediately after assembly to remove contamination from the assembly process. Mixing of different thickener types should be avoided.
(2) Performance requirements of cadres for bearing circulating lubricating oil
Due to the working environment, the bearings in the paper machine system are characterized by high temperature, high speed and high load, so the lubricating oil meets the requirements for use. The oil should be able to clean and bring possible contaminants of the system to the filter screen or oil tank for settlement. The large oil flow can make all parts fully lubricated, and the fast-flowing lubricating oil can take away the bearings generated during operation. heat to lower its operating temperature. The performance requirements of oil products for paper machine lubrication systems include: excellent oxidation stability (long-term high temperature use, no or less formation of residue deposits in the oil), good demulsification ability, good corrosion resistance, and many The metal has good adaptability and hydrolysis stability, high viscosity index, high viscosity pressure coefficient, good rubber compatibility, ability to keep clean, and good filterability.
(3) Key factors when choosing paper machine oil
As the papermaking machinery is developing towards a large-scale, continuous and automated level, the width and discharge speed of the paper machine have been greatly improved, and the rotational speed of the bearing has been greatly improved accordingly. More and more paper machine customers have begun to In the system, lubricating oil is selected instead of grease as the lubricating medium for bearings and gears in the system. Therefore, the following factors must be comprehensively considered in the selection of paper machine oil JF.
Hydrolytic stability: Moisture is the biggest hazard in the lubrication system of a paper machine. When the tiny cracks on the bearing surface come into contact with water, the fatigue rate of the bearing will increase, causing pitting corrosion, early failure and abnormal shutdown, resulting in huge losses. High-quality paper machine circulating lubricants must have excellent hydrolytic stability. Reasonable oil selection and first-class on-site system maintenance can help reduce water entry into bearing housings and prevent bearing fatigue and early failure.
Filterability: If the frequency of filter replacement is too high, it means that the filterability of the oil is poor and the system maintenance is poor. The PALL filterability test can provide a relatively reliable reference, and the test is divided into two types: dry method and wet method. In the dry test, the oil is heated to 63°C, and the oil is filtered at a rate of 20mL/min through a filter with a filter diameter of 3 microns. When the pressure difference reaches 25psi, the number of milliliters of oil that passes through is generally considered to be qualified. . In the wet phase test, the oil needs to be added with 1.0% distilled water, aged at 7°C for 24h, then placed at room temperature for 24h, and then the above PALL filtration test is performed.
Stable viscosity: Because the bearings in paper machines operate at high temperatures for a long time, it is important to ensure that the oil maintains a stable viscosity during transportation and operation. The design of the delubrication system should be able to heat the cooling device, maintain a relatively constant working temperature of the system, and ensure the viscosity of the oil. It is more critical that the oil should have good oxidation stability and thermal stability.
Deposition control ability: When the oil is aged, a series of oxidative decomposition reactions will occur to form by-products, which will affect the performance of the oil. These by-products will increase the viscosity of the oil and block the filter screen. When they deposit on moving parts such as bearings, they can increase contact pressure, damage equipment, and even cause downtime, so oils must be formulated with good deposit control.
Maintenance of paper machine lubrication system:
A paper machine is a huge and continuous mechanical equipment. Intense industry competition requires high operational reliability of the equipment, and abnormal downtime should be minimized. Lubricants used for bearings, gears, etc. in equipment must be well managed. According to the requirements in the manual of the paper machine, make a complete statistics of the lubricating oil required by all the equipment, including the lubrication point, the lubrication method, the variety and viscosity level of the lubricating oil, etc., to facilitate the oil inventory management.
The inspection items for the circulating lubrication system circuit include: daily monitoring of lubricating oil and bearing temperature, vibration analysis of bearings, oil appearance inspection of oil distributor and oil level visual pipe, physical and chemical data analysis of oil in use, Bearing relubrication intervals, cleanliness of equipment, seals to prevent water and other contaminants from being soaked in, regular discharge of water in oil tanks, and testing of water content in oil, etc.
In a word, the reasonable storage, selection and monitoring of the oil in the lubrication circulation system of the paper machine, and the reasonable design and maintenance of the lubrication system ensure that a reasonable amount of the best lubricating oil is supplied to the lubrication point of the equipment within a suitable time, which can ensure the equipment Improve the operation performance, prolong the service life of the equipment, reduce the operating cost, and increase the production efficiency and reliability of the equipment.