Flanges play a crucial role in connecting pipes, valves, pumps, and other components to create a secure and leak-proof piping system. They are a vital part of pipeline infrastructure and stand as the second-most employed joining method, right after welding.
Flanges come in various types, each serving specific purposes based on their designs and applications. Let’s delve into the details of some common flange types.
1. Slip-on Flange : Slip-on flanges, aptly named, slip over pipes. These flanges are attached through two fillet welds—one inside the flange cavity and another outside. The bore size of a slip-on flange exceeds the outer diameter of the connecting pipe, requiring the pipe to move inside for a secure connection through fillet welding. Commonly used in fluid pipelines, slip-on flanges offer a straightforward joining solution.
2. Threaded Flanges : Similar to slip-on flanges, threaded flanges are bored to fit the inner diameter of a specific pipe. They save time and money, especially in piping systems with small diameters. Threaded flanges become the preferred choice in areas prone to explosions, where welding presents a safety hazard.
3. Weld Neck Flange : Weld neck flanges, also known as high-hub or tapered hub flanges, effectively manage pressure build-up. Featuring a neck that redistributes tension in the pipe, they are suitable for both high and low-temperature applications, resisting high pressure. The connected pipe’s diameter must match the flange’s dimension for a secure fit.
4. Socket Weld Flanges : Socket weld flanges connect to pipes through a single fillet weld executed outside the flange. After welding, the pipe is inserted into the socket with a small gap to ensure proper positioning. These flanges find application in compact, high-pressure pipe systems carrying non-corrosive liquids.
5. Blind Flange : Blind flanges, without a bore, seal pipe ends, valves, and pressure vessel openings, preventing fluid flow. These flanges withstand significant mechanical stress due to system pressure and bolting forces. They are commonly used to block off unused nozzles or for pressure checks in a plant.
6. Lap Joint Flange : Lap joint flanges, featuring a flat face, are used with a stub end. Unlike slip-on flanges, lap joint flanges have a radius where the flange face meets the bore. Bolts attach the flange to the stub end, allowing it to slide over the pipe. This economical option is advantageous for stainless steel or nickel alloy pipelines.
7. Long Neck Weld Flanges :
Long weld neck flanges, employed in high-pressure and temperature conditions, serve in the oil and gas industry. Similar to standard weld neck flanges, the extended neck functions as an extension bore. These flanges find use in anchoring water mains or gas sources in extensive pipe networks, such as those in manufacturing facilities or apartment buildings.
