specfit

What is a Flange?

A flange is a category of gasket made to fix two sections of pipe together, or act as a removable plug at the end of a single pipe. All flanges are round disks with holes for bolts around the rim, but the commonalities end there. There is a variety of flanges to suit every purpose, from blocking high-pressure pipes to attaching two pipes of incompatible material. Also known as pipe flanges or flange gaskets, flanges are most often selected in place of other fittings to make cleaning and repairs more feasible.

flange, heavy duty with large bolts every 2 inches

Blind Flange

The simplest, most straight-forward flange in design, a blind flange is a solid disk used to block the end of a pipe. It’s anomalous in that most flanges are open in the center, allowing the contents of the pipe to move through it. Sometimes, there is a slight indent around the rim, creating a niche for the pipe to fall into. Blind flanges are also known as blank flanges, and referred to as flat face or raised face depending on the presence of an indent.

Weld Neck Flange

Named after the neck shape protruding from the center, a weld neck flange is designed for quick welding. The neck, which extends from the center, is thin and malleable in order to melt quickly. It’s generally butt-welded to the pipe before the disk portion of the flange is affixed to the rim with bolts.

Slip-on Flange

The one-piece version of the lap joint flange, the slip-in flange has a short length of pipe extruding from one end, creating a sleeve for a pipe to nestle into. The pipe is then fillet-welded both along the disk and the inner rim of the flange, adding extra support. 

Lap Joint Flange

The close cousin of the slip-on flange, the lap joint flange comes in two pieces: a disk with a hollow center and a neck piece which fits perfectly inside the hole. This second piece, called the stub-end, is secured to a pipe using a fillet weld.

Threaded Flange

The same shape as a slip-on flange, a threaded flange is a disk with extra material extruding from one end, plus threading to feed the pipe onto the flange. Unlike most flanges, they can be securely attached with or without welding, making them perfect for pipe sections that need regular cleaning. 

Socket Weld Flange

Following the basic design of the slip-on flange, the socket weld flange gets its name from the shoulder, or extended rim at the end of the stub-end. When installed, the pipe is nestled inside the socket of the flange and welded into place. The socket helps steady the pipe during the welding process, and add additional surface area for a successful weld.

Orifice Flange

An orifice flange is a specialized piece designed to house an orifice meter. The basic design is two weld neck flanges back to back, with a gap in the center for the meter. An orifice meter is an excellent tool for tracking the flow speed within a pipe, making this somewhat complex flange a worthy investment. 

Expander Flange

Designed to serve as both a gasket and a reducer, an expander flange is a weld neck flange with a hub that widens at the far end. The neck, working as a funnel, channels the contents into the small opening at the base of the flange, where it’s bolted to the next section of pipe. 
If we don’t have your flange in stock, we will make it to order. We are also glad to consult on the types of flanges and other pipe fittings needed for your project. Please contact us so we can get started building your custom fittings ASAP.