Flanges

1. FLANGES

2. What is a flange? • A flange is a metal disc used to join pipes. A gasket is fixed between the two flanges to tighten up the seal. A flange is used to connect two pipes or valves or tubes to form a piping network. Flanges provide support and strength and prevent leakage. • Flanges are commonly welded or screwed into pipes or valves and are then joined with bolts. Flanges provide easy access to clean or inspect a piping system.

3. Flanges are made of different metal – Stainless Steel, Cast Iron, Ductile Iron, Carbon Steel, etc. As they are made from a variety of metals, flanges differ in their ‘pressure classes’.

4. Every flange is classified under a pressure class, depending on the capacity of the flange to withstand a particular amount of temperature. Also, the metal used in a flange can determine how much pressure it can withstand. • This means that different flanges can withstand different temperatures (or pressures.) If the temperature increases, the pressure rating of the flange decreases and vice versa.

5. Types of Flanges Different industries demand different types of flanges according to their usage and pressure classes. The most commonly used flanges are: weld-neck, slip-on, socket, lap-joint, threaded and blind flanges.

6. Weld-neck flanges Weld-Neck flanges are welded to the base of the pipe as the bore of the flange matches the bore of the pipe; thus allowing undisturbed product flow of the inner fluid. They provide supporting strength and stress distribution in high-pressure applications Pros: • Allow free flow of the product • Reduces turbulence and erosion at the joints • Allow radiography for flaw detection • Highly durable • Highly durable Cons: • They are quite expensive

7. Slip-On flanges Slip-on flanges have bores with a diameter slightly larger than the pipe; this helps it to slide/slip over the pipe. This flange is then welded inside and outside too, with fillet welding. Pros: • Cost-effective • They are thinner compared to other flanges • Easy to use in fabricated applications

8. Socket weld flanges These flanges are counter-bored i.e. the enlargement of the flat-bottomed, smaller coaxial hole. This permits good flow of the product through the pipe. Yet, a demerit of socket weld flange is the Pros: • Used in small-sized high-pressure pipes • Useful in high-pressure systems Cons: • A gap created between pipe and flange during the welding process may lead to corrosion.

9. Lap joint flange These flanges are used with a stub end, which is welded to the pipe. Therefore the stub end forms the face of the flange. They are designed in a way that they swing over the pipe without the need to be welded. Pros: • They do not corrode • Re-usable • Inexpensive • Easy assembly and disassembly for quick inspection.

10. Threaded flanges: The most noteworthy feature of these flanges is that they can be joined to a pipe without welding. The bore of these flanges have threads and can be fitted to pipes that have external threads. Pros: • Useful in low pressure applications • Beneficial in highly combustible industries where welding is dangerous. • Low priced • Fit best for small pipes

11. Blind flanges: These flanges are mostly used to seal the end or opening of a pipe, which is why they come without a bore. This comes in handy for inspection and pressure tests, as it allows quick access to the pipe. Pros: • They allows quick access to the pipe • This comes in handy for inspection and pressure tests.

12. To sum it all up, flanges offer great strength as well as flexibility to piping systems in industries like oil, gas, petrochemicals, chemicals, etc. To know more about flanges, visit http://www.rajendrasteel.com/