Appearance Color and Permissible Deviations of Large-Diameter Flanges
Large-diameter flanges are widely used in various industries such as mechanical, chemical, wind power, and wastewater treatment. They are highly popular among users. Large-diameter flanges are produced using two main manufacturing processes: rolling and forging. Extremely large flanges are typically produced through rolling. The materials used for large-diameter flanges include carbon steel, stainless steel, and alloy steel.
The color of large-diameter flanges is not related to their quality; it is simply the color of the rust-preventative oil used on their surface, not the color of the product's material itself. However, the product's manufacturing date can sometimes be judged by the color of the flange's surface. If the product has been stored for a long time, the rust-preventative oil may penetrate the product, causing it to appear aged with an older color. However, this does not imply that the product's quality is compromised. In fact, some older products manufactured in the past may have better quality than some of the current products. As with many other industries, the quality of current products is often not as good as in the past because profit is now the primary focus, leading to a compromise in product quality. It is hoped that manufacturers and users in the flange industry will collaborate to improve this unsatisfactory situation.
Regarding the permissible positional deviation of bolt holes in large-diameter flanges, there is a scale of tolerance. While there can be some deviation, it must not affect the installation and use of the product. In practical production, smaller flanges have smaller deviations in the position of the bolt holes, while larger flanges may have larger deviations. The reason for these deviations exceeding the standard is that, in certain specific situations with tight deadlines, multiple flanges are often stacked together to be drilled simultaneously. In such cases, the drill bits are more likely to miss their mark. It is known that if holes are drilled one by one, the deviation would not exceed the standard. However, when several flanges are stacked together, the hole positions can easily shift.
The most common types of large-diameter flanges are slip-on flanges and weld neck flanges. Threaded flanges are not generally considered large-diameter flanges. In practical production and sales, slip-on flanges account for a significant proportion. Slip-on large-diameter flanges and weld neck large-diameter flanges have different structures and application ranges, each with distinct features and advantages. Therefore, it is necessary to ensure that flanges serve a vital role according to their intended use. Large-diameter slip-on flanges have relatively poor rigidity and are suitable for low-pressure applications (P ≤ 4 MPa). Weld neck flanges, also known as high-neck flanges, have good rigidity and are suitable for high-pressure and high-temperature situations.
Flanges can be categorized into three types of sealing surfaces: flat sealing surface (suitable for low-pressure, non-toxic media), raised-face sealing surface (suitable for low to medium pressure), and groove sealing surface (suitable for flammable, explosive, toxic media, and high-pressure applications).
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