What Is a Paper Machine?

Paper machine is a collective name for a complete set of equipment that links pulp to form a web, including headboxes, nets, presses, dryers, calenders, paper reels, and drive units, as well as steam and water. , Vacuum, lubrication, heat recovery and other auxiliary systems.

Paper machine

Paper machine is a collective name for a complete set of equipment that links pulp to form a web, including headboxes, nets, presses, dryers, calenders, paper reels, and drive units, as well as steam and water. , Vacuum, lubrication, heat recovery and other auxiliary systems.

Chinese name

Paper machine

Founder

Cai Lun

Initial age

Eastern Han Dynasty

Types of

mechanical

Will meet the requirements of papermaking

In 1798, the Frenchman NL Robber first proposed the idea of a paper machine and obtained the government's

According to the type of paper former used, the paper machines are divided into long net, round wire, pinch net and long round net, etc .; there are also cultural paper machines (including

according to

When the equipment or system loses the prescribed function or reduces the efficiency for some reason during use, it is called equipment failure. There are two main types of paper machine shutdown failures: inherent productive failures and equipment failures.
(I) Productive inherent fault shutdown characteristics and rules This type of shutdown is mainly work to ensure product quality and meet production process requirements, especially the production of high-end cultural paper is more prominent. The main reasons for shutdown are: first, brushing work, wet The water filtering and dewatering elements (or materials) at the end of the function decline after a certain period of use, and the dewatering and filtering do not reach the initial effect, which requires regular cleaning. The second is to replace the main process equipment, such as copper mesh and wool cloth, which need to be replaced regularly after reaching the end of their useful life; press rubber rollers, stone rollers are subject to contact and wear caused by paper and scrapers, and the medium and high roller surface changes, which will affect product quality and require regular repairs.
(II) Features and analysis of equipment failure and downtime Due to the particularity and complexity of the paper machine production process, equipment failure has the following characteristics:

1. There are many equipment failure points, and equipment failure and shutdown often occur;

2. Some parts have a short service life, and the frequency of replacing spare parts is high;

3. The gap between the failure cycle and the time taken for maintenance is large and difficult to manage. There are many reasons for paper machine equipment failures. The main causes of equipment failures are:
1. Abrasion: Cause one: Long-term contact with worn parts and equipment such as pulp pumps, pulp mills, sanders, vacuum box panels, press rolls, and calender rolls due to long-term contact with copper mesh, wool cloth or pulp and molding paper; Reason two, parts that move relatively frequently between parts, such as scrapers, steam inlets, air cylinders, vacuum rollers, vacuum pumps, etc.
2. Lubrication: Mechanical rotation is inseparable from bearings. Paper machines with rotating rollers are the main types. There are many types and numbers of rollers. There are hundreds of various types of bearings. Therefore, lubrication management is very important, especially affected by water, high temperature, Under the influence of heavy load, the lubricating oil (fat) is easy to lose, evaporate, and aging, so that the lubrication effect is destroyed, causing bearing damage and shaft head wear. Therefore, regular inspections and refueling are essential.
3. Fatigue: Heavy load and continuous running machinery are prone to fatigue damage. On the paper machine, because some parts are restricted by the mechanical structure and operating principle, the design strength of parts (such as net case shake spring plate, electromagnetic clutch suction cup, coupling anti-overload pin, etc.) should not be too large to avoid damage. The solution is to take measures such as maintenance and technical transformation. ^[1]

Leakage of transmission gearbox:

After the paper machine is installed and running for a period of time, various meshing points of the gear box leak to different degrees, forming an oil accumulation area at the base plate of the paper machine. This situation is analyzed and summarized due to the following reasons :

(1) Due to the non-uniform distribution of the center of mass of the dryer (the weight of the single cylinder of the dryer is about 5 tons), and the dryer is heated by steam, during the operation of the equipment, high-pressure steam forms condensate in the dryer. Causes unfavorable drainage of condensate in the dryer

A centrifugal force is formed inside the cylinder. When the dryer releases this force, it can only move to both ends of the cylinder, causing a certain frequency of vibration at the gear meshing place. Generally, modern multi-cylinder paper machines are composed of 55-80 cylinders, which generate such vibrations together during operation, causing leakage at various meshing positions. This is the main cause of leakage;

(2) Because the dryer is heated by saturated steam, the steam temperature is 120 ° C-130 ° C. The metal frame can absorb heat up to 150 in the closed steam hood, and the thermal expansion and contraction can make the gap of the fitting position of some parts too large (such as the joint of the dryer and the gear box), forming a leak;

(3) Apply sealant between the meshing surfaces of the parts of the gearbox. Prolonged high-temperature vibration will cause the seal to fail and leak;

(4) The gear box is a casting, and it must be aged during the production process. If the aging time is short, the internal stress of the gear box is not completely eliminated, and the installed gear box will continue to deform during operation, resulting in leakage;

(5) In the process of installation or maintenance, the materials of bearing gland, gear gland, and gear half shaft are different, and the coefficient of thermal expansion during operation is different. Therefore, the expansion gap is required to be greater than a certain standard during installation. During the actual operation and installation of the gearbox, due to improper maintenance and installation technology, the expansion gap is less than the standard value, which will cause the gearbox to withstand the strong expansion force of the gearbox's internal components during operation, causing deformation and leakage;

(6) In order to ensure the sealing effect of the joint surface of the gearbox, the cold and hot tightening bolt elongation of each bolt is also clearly defined. However, in the actual maintenance work, if the bolts are not tightened in accordance with the requirements, the joint surface will be deformed and leaked.

Advantages and feasibility analysis of on-site repair of polymer composites

On-site repair is an emerging maintenance mode. The principle is to repair the site using polymer composite repair technology without dismantling the damaged equipment or components. The intermolecular force formed by the polymer infiltration of the repairing composite material forms excellent adhesion to the repairing parts, which meets the requirements of the equipment to withstand various composite forces during operation. For such repair materials, Fu Shilan polymer composites have the most reliable performance.

On-site repair accuracy is guaranteed through several links: the repair location is firm and reliable, and the metal surface is clean ,dry.