As a standard core component of corrugated paperboard production lines, preheating cylinders are typically made of seamless steel pipes with high-precision polishing and wear-resistant treatment. They utilize steam for constant temperature heating, and their core function is to uniformly preheat the corrugated base paper and core paper, precisely controlling the paper's moisture content. The moisture content of the base paper is a critical parameter in corrugated board forming. Excessive moisture content leads to weak adhesion and warping after gluing, increasing energy consumption in subsequent drying stages; conversely, insufficient moisture content increases paper brittleness, making the corrugated board prone to cracking and collapse during corrugation, directly reducing the physical properties of the cardboard. The preheating cylinder is involved in all stages of corrugation forming, gluing, and drying; its operating status and procedures directly determine the bonding strength, flatness, and bursting strength of the corrugated board.
In actual operation of corrugated paperboard production lines, the maintenance of preheating cylinders needs to focus on three core dimensions: temperature control, pressure regulation, and surface cleaning.
Temperature Control. Operators need to fine-tune temperature parameters in real time based on the basis weight and material (kraft paper, corrugated core paper): higher basis weight paper requires longer preheating time and the temperature can be slightly increased, while thinner paper requires a lower temperature to avoid excessive dehydration and embrittlement. Simultaneously, when the production line is running in tandem, the preheating cylinder temperature must match the production line speed. During high-speed production, the cylinder surface temperature should be appropriately increased to ensure sufficient moisture control of the paper as it rapidly passes through the preheating cylinder, avoiding moisture content fluctuations caused by speed and temperature mismatch.
Pressure and contact angle adjustment. The pressure of the preheating cylinder's pressure rollers needs to be evenly adjusted according to the paper thickness to ensure full adhesion between the paper and the cylinder surface, without wrinkles or misalignment, avoiding localized underheating or overheating. Some high-end corrugated paperboard production lines are equipped with preheating cylinders with adaptive angle adjustment functions, which can adjust the wrap angle according to the paper width, increasing the contact area between the paper and the cylinder surface, further improving preheating uniformity, and solving the industry-common problem of inconsistent moisture content between the edges and center of wide-width cardboard.
Surface cleaning and regular maintenance. During the production process, paper dust and scraps from the raw paper easily adhere to the cylinder surface. Over time, this accumulation forms an insulating layer, reducing heat transfer efficiency and leading to a decrease in preheating effect. Therefore, after production, specialized cleaning tools must be used to remove impurities from the cylinder surface. Sharp tools must not be used to scrape the cylinder surface to avoid damaging the polished layer. The steam pipes and drain valves of the preheating cylinder must be inspected monthly to ensure smooth steam circulation, prevent condensation buildup, and maintain a constant cylinder surface temperature. Furthermore, the roundness and temperature uniformity of the cylinder surface should be checked regularly. If the deviation exceeds ±5℃, timely maintenance and calibration should be performed to prevent decreased equipment precision from affecting the quality of the paperboard.
