Threaded Flanges

Threaded flanges

Threaded flanges is one kind of flange that contact with pipe via threads. The advantage is no need of welding, and when the flange is out of shape, it has small additional moment of force on the pipeline. Its disadvantage is that the thickness of flange is thick, as a result of high cost. Threaded flange apply for connection of high pressure pipelines.
When producing, inside hole of flange is processed into pipe threads, then connect with threaded pipe. It is one kind of no-welding flange, and get features of easy installment and repair, so it can be used on circumstance of prohibition of welding or fires. Alloy steel flanges has enough strength, but not good for welding, so the threaded flange can be used. However when the temperature of pipeline fluctuate sharply or temperature above 260℃ or below -45℃, threaded flange is not suggested in case of any leakage.
Though threaded pipe flange is available in different dimensions, threaded fittings mostly is used in small diameters pipeline. (Below 4 inch normally.) On the other hand, it is not compatible with a pipe system in thin wall thickness, since there is no space for doing the threading. 

Threaded Flange Types

There are two types of threaded flanges. One is to seal the two pipe ends with a certain sealing surface and a lens pad. This type of flange is mostly used for ammonia production. But it has been used less recently, and the lens pad has been replaced by a metal ring. The other type is the same as a normal flange, sealed with two flange sealing faces.

Facing Types
There are two facing types for threaded flange, raised face flange and ring joint flange.
Raised Face Threaded Flange
When the gasket surface area is above the bolted line of the flange, the raised face flange is easily identified. It is compatible with a wide range of gaskets, from flat to semi-metallic and metallic types, either ring or full.
The main scope of a raised face flange design is to concentrate the pressure of the two mating flanges on a small surface and increase the strength of the seal.

The height of the raised face surface depends on the flange pressure level, for example, for pressure classes 150 and 300, the height is 1.6 mm or 1/12 inch, and for the 400 to 2500 level, the raised face height is about 6.4 mm, or 1/4 inch.
RTJ Threaded Flange
The ring joint flange has a circular groove to accommodate the ring joint gasket, which can be used when metal to metal seals are required. Especially in conditions for high pressure and high temperature.

Convenient Installation and Maintenance

The threaded flange is screwed to the threaded pipe by the thread, which is processed in the inner hole of the flange. So It does not need to be welded. Therefore, it became so convenient for installation and maintenance comparing with other flange types, such as slip on flange, socket weld flange etc.

Application in Special Circumstance

Threaded flanges are used where it is difficult to weld or cannot be welded, such as threaded flanges used to protect the galvanized layer of pipes. In addition, It should not be used on pipes with repeated temperature fluctuations or above 260 ℃ and below -45℃ as well.

Measurement

If threaded pipe flange can be measured accurately, following data ​shall be required:
O: Outside Diameter of flange
C: Thickness of flange
R: Diameter of raised face
X: Hub Diameter at base
Y: Length through hub
T: Minimum thread length
Q: Minimum diameter of bolt circle

Threaded Flanges Information Table

Alternative name TH Flange
Production Method Forged flange, Centrifugal Casting flange 1.Casting flange advantage is in low cost and making complex form, but get casting defects 2. Forged flange advantage inner structure even, with no blowhole and harmful material, but in low production efficiency and slight higher cost 3.Slicing flange size is under the width of jobbing sheet.
Standard ANSI B16.5, ANISI 16.47, JIS, DIN
Pressure ANSI Class 150-1500Lb
Size DN10-1200mm
Materials Carbon steel: ASTM A105(N), 20#, C22.8, ST37.2, A516 GR60/70, ASTM SA350 LF2
  Stainless steel: ASTM A182, F304/304L/316/316L
  Alloy steel: ASTM A182 F1/F5/F9/F11/F22/F91
Surface Treatment Anti-rust oil, yellow or black painting, hot dipped galvanized
Packing In wood crate, Packed in Seaworthy Carton for Export
Usage Apply for high pressure pipeline, with temperature not too high or too cold
Advantage 1. No need welding 2. When the flange out of shape it get little moment of force for pipeline 3. can be used on circumstance of prohibition of welding or fires 4. Alloy steel flanges not good for welding, so can be used as threaded flange
Alternative name TH Flange
Production Method Forged flange, Centrifugal Casting flange

1.Casting flange advantage is in low cost and making complex form, but get casting defects

2. Forged flange advantage inner structure even, with no blowhole and harmful material, but in low production efficiency and slight higher cost

3.Slicing flange size is under the width of jobbing sheet.

Standard ANSI B16.5, ANISI 16.47, JIS, DIN
Pressure ANSI Class 150-1500Lb
Size DN10-1200mm
Materials Carbon steel: ASTM A105(N), 20#, C22.8, ST37.2, A516 GR60/70, ASTM SA350 LF2
  Stainless steel: ASTM A182, F304/304L/316/316L
  Alloy steel: ASTM A182 F1/F5/F9/F11/F22/F91
Surface Treatment Anti-rust oil, yellow or black painting, hot dipped galvanized
Packing In wood crate, Packed in Seaworthy Carton for Export
Usage Apply for high pressure pipeline, with temperature not too high or too cold
Advantage 1. No need welding

2. When the flange out of shape it get little moment of force for pipeline

3. can be used on circumstance of prohibition of welding or fires

4. Alloy steel flanges not good for welding, so can be used as threaded flange