Flanges are needed to attach piping assemblies to pressure vessels, valves, pumps or other items. Flanges are either forged or cast rings of steel, created to join two sections of piping together by use of bolting and gaskets. Flanges can provide integrity and strength to pipelines, and can also serve as quick access routes for inspection, modification, or cleaning of piping assemblies.

The most common types of RF & RTJ pipe flanges include (and not limited to):

  • Weld neck flanges are butt welded onto the end of a pipe, providing a flange that is suitable for high temperature and pressure.
  • Threaded flanges have an internal (female) thread, a threaded pipe is screwed into it. This is relatively easy to fit but not suitable for high pressure and temperature.
  • Socket-weld flanges have a plain hole with a shoulder at the bottom. The pipe is inserted into the hole to butt against the shoulder and is then welded into place with a fillet weld around the outside. This is used for small diameter pipes operating at low pressure.
  • Slip-on flanges also have a plain hole but without the shoulder. Fillet welds are applied to the pipe on both sides of the flange.
  • Lap joint flanges consist of two parts; a stubend and a backing flange. The stub end is butt-welded to the end of the pipe and includes a small flange without any holes. The backing flange can slide over the stubend and provides holes to bolt to another flange. This arrangement allows disassembly in confined spaces.
  • Blind flanges are a form of blanking plate that is bolted to another pipe flange to isolate a section of piping or terminate piping.


The ASME B16.5 specification covers flanges for piping applications up to 24 inches in diameter, whereas the ASME B16.47 specification covers pipe flanges above 24 inches (series A and B are available). *API Flanges also available upon request.


½” through 48”

Pressure Ratings (Class):

150, 300, 600, 900, 1500, 2500


All Carbon Steel Grades, Stainless Steel, Low Temp, Low Alloy, Chrome, Nickel