Flanges play a key role in piping systems by enabling easy assembly, disassembly and maintenance. However, the variety of pipe flanges types can be overwhelming. This guide helps determine the optimal flange for different applications.

Weld Neck Flanges

As the name suggests, weld neck flanges are welded directly onto pipe ends. They withstand high pressures and temperatures of up to 600°C. Weld necks are commonly used in refineries, boiler headers, heat exchangers.

They can withstand very high bolt stress due to reinforcement from pipe. However, welding requires skill and makes removal difficult. Weld necks are bulky and expensive too. Suitable for high pressure systems.

Slip-On Flanges

Slip-on flanges slide over pipe ends and are attached by welding a collar around the pipe flanges types joint. They face less issues of distortion compared to weld necks during welding.

Removal is easier with slip-ons as they do not require pipe cutting. However, stresses on bolts are less than weld necks. Maximum temperature and pressure ratings are also lower at around 300°C and 100 Psig.

Slip-ons are preferable for intermediate pressures and commonly used in steam lines, gas lines and pipe rack installations.

Socket Weld Flanges

Socket weld flanges have female tapered threads on their bodies. They screw onto male tapered pipe threads and are welded into place. No field welding is required unlike slip-ons.

They provide secure joints and are suitable for outdoor piping. However, maximum pressure and temperature limits are lower at 600 Psig and 200°C due to thread strength.

Socket welds are appropriate for compressed air, gas, chemicals and general industrial process systems.

Threaded Flanges

Threaded flanges contain male straight threads to directly screw onto other threaded components like valves, pumps or elbows.

Installation is simple without welding. But threaded joints cannot withstand high pressures or temperatures beyond 150°C and 250 Psig. They often leak and must be sealed with thread sealant.

Applications include low pressure air, water and compressed gas lines below 2 inches in diameter.

Lap Joint Flanges

Lap joint flanges have a projection that protrudes into the flange hole. To join, the projection of one flange fits into the hole of the other in a "lap" configuration and is bolted together.

They provide metal-to-metal compression seals without gaskets. However, corrosion prone and difficult to dismantle as projections must be cleanly sheared. Used in services like oil, chemical and gas pipelines.

Choosing the Right Pipe Flanges Types

Factors like pressure level, temperature, medium, installation location and maintenance determine flange selection. Consider application parameters and industry standards for optimum flange type suiting technical requirements as well as budget.