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Flange types

Flange types

AUTHOR : _ _ Date : 3/7/2013 11:58:11 PM



According to ASME B16.5, the most used flange types: Welding Neck, Slip On, Socket Weld,Lap Joint, Threaded and Blind flange
. Here below you will find a short description and definition of each type, completed with an detailed image.


  WELDING NECK FLANGE


Welding Neck Flanges are easy to recognize at the long tapered hub, that goes gradually over to the wall thickness from a pipe or fitting.


The long tapered hub provides an important reinforcement for use in several applications involving high pressure, sub-zero and / or elevated temperatures. The smooth transition from flange thickness to pipe or fitting wall thickness effected by the taper is extremely beneficial, under conditions of repeated bending, caused by line expansion or other variable forces.


These flanges
are bored to match the inside diameter of the mating pipe or fitting, so there will be no restriction of product flow. This prevents turbulence at the joint and reduces erosion. They also provide excellent stress distribution through the tapered hub and are easily radiographed for flaw detection.

 
This flange type will be welded to a pipe or
fitting  with a single full penetration, V weld (Buttweld).


1.weld neck flange 2. butt weld 3. pipe or fitting

 

•  SLIP ON FLANGE


The calculated strength from
a Slip On flange under internal pressure is of the order of two-thirds that of welding neck flanges, and their life under fatigue is about one-third that of the latter. The connection with the pipe is done with 2 fillet welds, as well at the outside as also at the inside of the flange

The X measure on the image, are approximately:
Wall thickness of pipe + 3 mm. 

This space is necessary, to do not damage the flange face, during the welding process.



1. slip on flange  2. filled weld outside 3. filled weld inside 4. pipe


 


Socket Weld Flangeswere initially developed for use on small-size high pressure piping. Their static strength is equal to Slip On Flanges, but their fatigue strength 50% greater than double-welded Slip On flanges. The connection with the pipe is done with 1 fillet weld, at the outside of the flange. But before welding, a space must be created between flange or fitting and pipe.

ASME B31.1 1998 127.3 Preparation for Welding (E)
Socket Weld  Assembly says:
In assembly of the joint before welding, the pipe or tube shall be inserted into
the socket to the maximum depth and then withdrawn approximately 1/16" (1.6 mm) away from contact between the end of the pipe and the shoulder of the socket.

The purpose for the bottoming clearance in a
socket weld is usually to reduce the residual stress at the root of the weld that could occur during solidification of the weld metal. The image shows you the X measure for the expansion gap.
The disadvantage of this flange is right the gap, that must be made. By corrosive products, and mainly in stainless steel pipe systems, the crack between pipe and flange can give corrosion problems. In some processes this flange is also not allowed. You will find a lot of information about forms of corrosion on the internet.
 
Also for this flange counts, that principle always firstly a pipe must be welded and then just a fitting.


1. socket weld flange  2. filled weld  3. pipe  X=expansion gap

 
 

Lap Joint Flanges have all the same common dimensions as any other flange named on this page however it does not have a raised face, they used in conjunction with a "Lap Joint Stub End". These flanges are nearly identical to a Slip On flange with the exception of a radius at the intersection of the flange face and the bore to accommodate the flanged portion of the stub end.

Their pressure-holding ability is little, if any, better than that of
Slip On flanges and the fatigue life for the assembly is only one tenth that of welding neck flanges.

They may be used at all pressures and are available in a full size range. These
flanges slip over the pipe, and are not welded or otherwise fastened to it. Bolting pressure is transmitted to the gasket by the pressure of the flange against the back of the pipe lap (Stub End).

Lap Joint flanges
have certain special advantages:
1. Freedom to swivel around the pipe facilitates the lining up of opposing
flange bolt holes.
2. Lack of contact with the fluid in the pipe often permits the use of inexpensive
carbon steel flangeswith corrosion resistant pipe.

3. In systems which erode or corrode quickly, the flanges may be salvaged for re-use.



 

1. lap joint flange 2. stub end 3. butt weld 4. pipe or fitting


•  
STUB END

A Stub End always will be used with a
Lap Joint flange, as a backing flange. This flange connections are applied, in low-pressure and non critical applications, and is a cheap method of flanging.

In a stainless steel pipe system, for example, a
carbon steel flange can be applied, because they are not come in contact with the product in the pipe.

Stub Ends
are available in almost all pipe diameters. Dimensions and dimensional tolerances are defined in the ASME B.16.9 standard. Light-weight corrosion resistant
Stub Ends (fittings) are defined in MSS SP43.

•  THREADED FLANGE

Threaded Flanges are used for special circumstances with their main advantage being that they can be attached to the pipe without welding. Sometimes a seal weld is also used in conjunction with the threaded connection. Although still available in most sizes and pressure ratings, screwed fittings today are used almost exclusively in smaller pipe sizes.

A
threaded flange or fitting  is not suitable for a pipe system with thin wall thickness, because cutting thread on a pipe is not possible. Thus, thicker wall thickness must be chosen...what is thicker ?

ASME B31.3 Piping Guide says:
Where steel pipe is
threaded  and used for steam service above 250 psi or for water service above 100 psi with water temperatures above 220° F, the pipe shall be seamless and have a thickness at least equal to schedule 80 of ASME B36.10.




1. threaded flange 2. thread 3. pipe or fitting 


• BLIND FLANGE

Blind Flanges are manufactured without a bore and used to blank off the ends of piping, valves and pressure vessel openings. From the standpoint of internal pressure and bolt loading, blind flanges, particularly in the larger sizes, are the most highly stressed flange types.

However, most of these stresses are bending types near the center, and since there is no standard inside diameter, these
flanges are suitable for higher pressure temperature applications.


1. blind flange 2. stub bolt 3. gasket 4. other flange
 


• Check all kinds of pipe fittings

1. Elbow:
45 degree elbow
45D CS butt weld elbow    45D SS butt weld elbow   45D socket weld elbow   45D threaded elbow
90 degree elbow  
90D CS butt weld elbow    90D SS butt weld elbow   90D socket weld elbow
   90D threaded elbow     street elbow
180 degree elbow  
180D CS butt weld elbow      180D SS butt weld elbow

2. Tee:
CS butt weld straight tee   CS butt weld reducing tee   SS butt weld straight tee  SS butt weld reducing tee  socket weld tee   threaded tee
   Lateral tee:
CS butt weld lateral tee   SS butt weld lateral tee   socket weld lateral tee   threaded lateral tee

3. Cross:
CS butt weld straight cross   CS butt weld reducing cross   SS butt weld straight cross   SS butt weld reducing cross   socket weld cross   threaded cross

4. Reducer:
CS concentric reducer   CS eccentric reducer  SS concentric reducer   SS eccentric reducer

5. Cap:
CS butt weld cap   SS butt weld cap   socket weld cap   threaded cap

6. Stub end:
CS stub end   SS stub end

7. Coupling:
socket weld full coupling   socket weld half coupling   threaded full coupling   threaded half coupling

8. Union:
socket weld union   threaded union

9. Socket insert:
A  B

10. Plug:
hex head plug   square head plug   round head plug

11. Bushing:
hex head bushing   flush bushing 

12. Nipple: 
TBE   PBE   TOE&POE   hex nipple

13. Swaged nipple:
concentric swage nipple   eccentric swage nipple

14. Flange:
Orifice flange   lap joint flange   threaded flange   socket weld flange   weld neck flange   blind flange   slip on flange   long weld neck flange   plate flange   large diameter flange   spectacle blind   square flange   

15. Outolet:
weldolet   socketolet   threadolet  laterolet  coupolet  elolet   nipoflange   nipolet
 




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