26. Piping Components
❑ Flanges – Welding Neck
This flange type is designed to be connected by a butt weld connection to the pipe or equipment requiring
a flanged joint. Welding neck provides good service under variety of temperature and pressure applications.
A weld neck flange must specify the pipe schedule for the bore. Due to the welding neck, it is a popular
choice on pressure vessels and for creating man-holes etc.
27. Piping Components
❑ Flanges – Lap Joint
Lap joint flange Stub End Lap joint Flange
with Stub End
Lap joint flange is also knows as Van Stone Flange. This type of flange consists of both a stub end and a
flange. The flange itself is not welded but rather the stub end is inserted / slips over the flange and is
welded to pipe. This arrangement helps in flange alignment in conditions where non-alignment may be an
issue. In a lap joint flange, the flange itself is not in contact with the fluid. The stub end is the piece which
gets welded to the pipe and is in contact with the fluid.
28. Piping Components
❑ Flanges – Socket Welded
Socket-weld pipe flanges are typically used on smaller sizes of high pressure pipes. These pipe flanges are
attached by inserting the pipe into the socket end and applying fillet weld around the top. This allows for a
smooth bore and better flow of the fluid or gas inside of the pipe.
29. Piping Components
❑ Flanges – Slip on
Slip on flange is designed to slip over the end of pipe. It allows for easy positioning before welding. Both
the inside and outside of the pipe is welded on the slip on flange. See picture on the right. The pipe is
generally inserted all the way, inside the slip on flange, leaving only the gap equivalent to wall thickness of
30. Piping Components
❑ Flanges – Threaded
Threaded flange is also called screwed flange or screwed-on flange. This type of flange is used where
welding is not an option. Threaded flange is most commonly used on low pressure applications
31. Piping Components
❑ Flanges – Blind
Blind flange is a solid flange with no bore or threaded hole and is used to close the end of pipe, fittings,
valves or equipment. Blind pipe flange is also used for pressure testing equipment
32. Piping Components
❑ Flanges – Spectacle Blind, Line Blind, Spacer
Spectacle and line blind flanges are similar to a blind flange but different because they fit between two
flanges. Spectacle blind gets their name from similarity to pair or eye glasses. Once side of spectacle blind
is fully closed for complete flow shut off, whereas the other end is open for full flow.
Spacer Line Blind Spectacle Blind
33. Piping Components
❑ Flanges Facing
The flange face is the surface area that hosts the gasket. The 6 available types of flange face are flat (FF),
raised (RF), ring joint (RTJ), lap joint, male and female (M&F), tongue and groove (T&G). Flanges with
different faces require different gaskets and shall never be mated to prevent leakage of the joint. RF and
FF flanges may have different types of “finish” (i.e. roughness on top the surface): smooth, stock and
34. Piping Components
❑ Flanges Facing - Raised Face (RF)
The Raised Face flange is the most common type used in process plant applications, and is easily to
identify. It is referred to as a raised face because the gasket surfaces are raised above the bolting circle
face. This face type allows the use of a wide combination of gasket designs, including flat ring sheet types
and metallic composites such as spiral wound and double jacketed types.
35. Piping Components
❑ Flanges Facing - Flat Face (FF)
The Flat Face flange has a gasket surface in the same plane as the bolting circle face. Applications using
flat face flanges are frequently those in which the mating flange or flanged fitting is made from a casting.
36. Piping Components
❑ Flanges Facing - Ring-Type Joint (RTJ)
The Ring Type Joint flanges are typically used in high pressure and/or high temperature services. They have
grooves cut into their faces which steel ring gaskets. The flanges seal when tightened bolts compress the
gasket between the flanges into the grooves, deforming (or Coining) the gasket to make intimate contact
inside the grooves, creating a metal to metal seal.
37. Piping Components
❑ Flanges Facing - Tongue-and-Groove (T&G)
The Tongue and Groove faces of this flanges must be matched. One flange face has a raised ring (Tongue)
machined onto the flange face while the mating flange has a matching depression (Groove) machined into
38. Piping Components
❑ Flanges Facing - Male-and-Female (M&F)
With this type the flanges also must be matched. One flange face has an area that extends beyond the
normal flange face (Male). The other flange or mating flange has a matching depression (Female) machined
into it's face.
39. Piping Components
❑ Flanges Facing Finish
ASME/ANSI defined specific roughness standards for the flanges, as the flange face finish plays a pivotal
role in gasket’s reliability and service life. According to the ASME/ANSI specifications, the serrated, spiral
serrated, and concentric flange face finish should have an average roughness of 125 µinch to 250 µinch (3.2
µm to 6.3 µm).