PVCu Flanges Inch

A flange in a PVCu pressure pipe system is a flat, circular connection fixed to the end of a pipe that allows it to be bolted to another flanged component. The joint is sealed using a gasket placed between the two flange faces, with bolt sets tightened evenly around the circumference to create a pressure-tight seal. In PVCu systems, flanges can be formed using a stub flange and a backing ring, rather than being moulded as a single solid fitting. This allows strong, reliable connections while keeping the system modular and serviceable.

A standard PVCu solvent weld socket creates a permanent joint; a flanged connection can be unbolted and reassembled without cutting the pipework, making it far better suited to installations where maintenance, inspection, or future modification is likely. This makes flanges the preferred choice in many pressure pipe installations. Flanges are especially common when connecting pipework to valves, pumps, filters, or other equipment that may need to be removed or replaced during their service life.

Flanges also become more practical as pipe diameters increase, where solvent welding is harder to carry out accurately, and alignment becomes more critical. A flanged joint allows for controlled, even compression across a gasket, helping to maintain a reliable seal while tolerating minor misalignment and reducing stress on connected equipment. In addition, flanged connections do not require curing time, allowing systems to be assembled and pressure tested more quickly than solvent-welded joints, which must be left to set before use.

• Stub flanges are designed to be solvent-welded directly onto PVC pipe, forming the flanged end of a bolted joint when used in conjunction with a backing ring, gasket and bolt set. The stub flange itself provides the sealing face, while the backing ring delivers the mechanical strength required for bolting.

• Full face flanges are flanges with a flat, uniform contact surface that runs right across the whole face of the flange. They eliminate the need for stub flanges and backing rings as they perform both roles, meaning just two full face flanges and a gasket are needed to join 2 pipes. The flat face design means the gasket makes contact over a large, even area, helping create a reliable seal without focusing stress on a small portion of the flange.

• Blanking flanges are commonly used to terminate a pipeline or isolate sections for maintenance or testing. They are similar to full face flanges, but have no hole in the middle for a pipe to attach to, effectively sealing off the pipeline when used with a gasket.

It is important to match flange standards when connecting flanged components. The flange standard refers to the pattern of the bolt holes; mismatching standards will not align correctly and provide a suitable seal. Common flange standards in the UK are:

• EN 1092-1 (PN10/16): A European standard, very common for newer systems, identified as PN (Pressure Nominal) and then a number, which relates to the pressure rating of the flange.
• ASA/ANSI: An American standard, often used in the oil, gas and chemical industries. Identified as "ANSI 150", meaning the fitting is rated to 150 lbs.
• Table D/E: D/E is an older British standard still found in many industrial applications, but is not used in newer pipelines.

A flange size can be identified by the Pitch Circle Diameter (PCD). This is the diameter of a circle that passes through the centre of all of the bolt holes in a flange. It can also be referred to as the Bolt Circle Diameter (BCD).

• Ensure the correct gasket is used: When using full face flanges, ensure that the gasket you have matches the hole pattern of the flange.
• Even bolt tightening: Ensure all bolts are tightened evenly in a cross pattern, which prevents distortion of the gasket and helps provide a good seal.
• Don't overtighten: Excessive torque can damage the flanges or crush the gasket.