A pipe flange is a protruding rim, edge, collar, or rib used as a mechanical connector for piping applications. Pipe flanges can join one pipe section to another pipe section, inline components, and other plumbing equipment. Where solvent cementing is impossible, pipe flanges can be used to dismantle piping systems, do mobile and temporary installations, and make transitions between dissimilar materials.
They are ideal for high-pressure piping applications. For instance, stainless steel ANSI b 16 5 belong to a standard which is considered a maximum pressure class. As such, any plumber should be precise with piping flange dimensions specifications.
The dimensions must fit the equipment or pipe for which it is designed. When buying pipe flanges, consider the material used to make the pipe fitting because it directly relates to how well the fitting will be joined to pipes. It also determines what type and amount of pressure the pipe can withstand.
- Types of flanges
The type of flange to be used depends on: how it connects to the pipe itself and the type of face. One advantage of flanges is that it can be dismantled conveniently, thus facilitating maintenance operations. Types of pipe flange connections include:
- Threaded flange
- Slip-on welding flange
- Lapped flange
- Blind flange
- Welding neck flange
- Socket welding flange
Other special types of flanges include:
- Nipo flange
- Weld flange
- Elbow flange
- Latro flange
- Swivel flange
- Expanding flange
- Reducing flange
- Threaded flanges
These are suitable for piping systems for low pressure. They work best with galvanized steel pipes and connections that are not ideal for temperature fluctuations and welding connections that requiring more than 2600 or below -450 require threaded flanges.
Threaded flanges should not be used with pipes susceptible to crevice corrosion, cyclic loading, and severe erosion.
Threaded flanges are connected by screwing the pipe onto the flange. They have no seam welds. They are available in various sizes up to 4 inches. They are a prerequisite in explosive piping connections such as gas stations and industrial plants. This is because of the safety associated with them.
- Welding neck flange (“WN”)
The main feature of a welding neck flange is a long tapered axis welded with a pipe. It is stiff and has good strength. Welding neck flange is typically used in high or low-temperature applications and high-pressure utility. It is also ideal where there’s an unrestricted flow of liquid content conveyed by the piping system.
The tampering axis allows for smooth and equal distribution of mechanical tension between the pipe and weld neck flange. The hub also facilitates successful radiographic inspections for possible welding defects and leakages.
The piping flange dimensions should match that of the connecting pipe. A single full penetration, a firmly fixed welding neck flange is connected to a pipe to form a v-shaped butt weld in a single maximum penetration.
- Slip-on welding flange
A slip-on flange is designed to glide over the piping edge and then welded to fix the connection. A slip-on flange bore size should be large than the outside diameter of the joining pipe. It helps the tube to slide inside the flange and be joined by a fillet weld.
Slip-on welding flange is ideal for an application that has less medium quality. It is, therefore, used for low-pressure circulating water and non-purifying compressed air. They have a relatively easy alignment and have low installation costs.
- Socket weld flange
Socket weld flange is different from other types that require two welds. It is joined to pipes using a single fillet weld applied on the outer diameter of the flange.
To make a flange connection with a socket weld flange, insert the pipe in the flange’s socket till it touches the bottom of the flange. Once there, lift it by approximately 1.6mm and weld to secure the connection. This space should be left to permit accurate positioning of the pipe inside the socket once the solidification of the weld set.
Socket weld flanges are ideal for high-pressure and small-size piping that conveys non-corrosive fluids. This is because socket flanges are susceptible to corrosion in the gap area between the socket’s shoulder and the pipe’s edge. Because of a single fillet weld, socket weld flanges have higher fatigue strength, while the static stability is similar to slip-on flanges.
- Lapped flange
Lap joint flange has a flat face and cannot be used alone. It requires piping that is filled with stub ends or with a lapped pipe. They rotate around the pipe, allowing easy alignment and a series of bolt drillings even after the welds are complete. This feature makes lap joint flange best suited in systems that need frequent dismantling of the flanges and pipe.
Lapped flanges resemble slip-on flanges but for the curved radius at the crossing of the face to allow a lapped joint stub end. This flange glides over the piping and locks on the back of the stub end. The pressure of the bolts attaches the two.
The combination of lap joint and stub ends lapped joint flange cost-effective for nicked alloy and stainless steel alloy because the lap joint is made of carbon steel, which is lower than the material making the stub end. The duality of the flange has two strengths:
- The cost of a flanged joint is considerably reduced because the quantity of high-grade material is minimized.
- The bolting requirement is simplified because the lapped flange rotates around the pipe, facilitates the bolt’s alignment.
- Blind flange
Blind flange is the only flange without a center hold to seal the ends of the valves pipeline and block the flow of the fluid flow. Blind flanges are made to withstand high tension due to the system pressure and the bolting forces applied.
They are frequently used for flow pressure sampling, such as gaining access to a pipeline. They are easily unbolted, allowing an operator to execute the flow inside the piping’s terminal end. For this same feature, blind flanges are used as maintenance hole for pressure carriers.
Interestingly, blind flanges are amongst the easiest to manufacture but attract a premium costing per unit compared to other types of flanges.
