ASTM A860 BARRED TEE 6 INCH SCH STD BE S32705 SUPER DUPLEX
STAINLESS STEEL PIPE TEE
Tee or Tee connection in piping engineering is a very important
pipe fitting and is frequently used to combine or divide a flow.
Two types of Tee are available, Equal Tee and Reducing Tee.
However, in pigged pipelines, one special type of Tee is widely
used which is known as Barred Tee or Pigged Tee.
Tee vs Barred Tee
- Tee is a type of fittings that allows fluid to flow on its main
pipe and branch out. The branch can be designed equally the same
size as the main pipe (known as Equal Tee), or smaller size than
the main pipe (known as Reducing Tee).
- Barred Tee is a special type of Tee that base from a normal tee
(can be either equal tee or reducing tee) that at later stage, will
be added with bar plates inside the branch outlet (From inside it
looks like a steel cage) to restrict the pig from flowing from the
header pipe into the branch pipes.
Design Codes and Standards for Tee and Barred Tee
- The international standard dimension of tee will be covered under
ASME B16.9 or MSS-SP 75 (for DN16 and above). To know more about
Tee Connections.
- There is no international standard dimension for the barred tee. It
is custom made using the ASME B16.9/ MSS-SP 75 tee as a base.
However, many develop their barred tee based on Shell DEP
31.40.10.13-Gen or ISO 15590-2 standard.
- This design can be a guideline to assess Vendor’s design.
Design Considerations for Barred Tee
- The barred tee will be used when there is a requirement for
pigging. Thus, many of its applications can be found in the
pipeline or in the subsea field.
- The bar plates that welded internally at the branch are to avoid
the pig from changing direction or getting stuck at the branch
outlet.
- The design of the bar plates must be in sufficient quantity,
thickness and adequately spaced to ensure the smoothness for the
pig to run through the main pipe, and at the same time not
affecting the flow that was meant to flow through the branch.
Normal practice is to ensure that the opening in the branch
pipeline after guided bars is not more than 40% of the main
pipeline area.
- The size of the bars in the branch connection has to be small
enough not to restrict the flow but large enough to sustain the
pressure of the flow.
- To ensure the smoothness, the bar plates have to be a grind to suit
the branch curvature. Any sharp edges, spatters and burs are
required to be removed. This smoothness of the pigging process is
important to protect the sensor of the pig from damage.
- Refer to Shell DEP 31.40.10.13-Gen Figure 4 above; the quantity of
the bar plates start with two (2) pieces and increase as the ID of
the branch increase.
- The bar plates ideally will be equally spaced.
- For larger tee (size 14 inches and above), there will be a bridge
plate in the middle to support the bar stiffness when getting hit
by the pig.
- The material of the bar plates commonly used the same as the tee
material for weldability.
- Standard practice is to avoid welding of guide bars directly on the
high-stress concentrated areas of the extrusion neck. Bar ends must
be machined to fit the branch.
- Weld Repairs on Parent metal is prohibited.
Difference Between Tee and Barred Tee
So from the above discussion, we can summarize the following
differences:
Parameter | Tee | Barred Tee |
Definition | Standard Pipe Fitting | A special type of piping component |
Manufacturing | Generally by Extrusion or forging | Mostly Fabricated |
Use | Used in both piping and pipeline engineering | used in pipeline engineering near the pig launcher/receiver |
Design Code / Standard | ASME B 16.9/MSS SP 75 | Shell DEP 31.40.10.13-Gen or ISO 15590-2 |
Production Quantity | Large scale in bulk | Select small quantities (custom made) |
Cost | Cheaper | Costlier than normal Tee |