A barred tee is a tee or any fitting with a branch used in pipelines that is pigged and has a restriction bar welded internally preventing the pig from traveling down a branch connection. The bars are installed so they are flush with the inside diameter of the pipeline to keep the pig from hanging up when it passes through. The bars should be of a similar or identical material as the parent material.
Bars are placed on the internal side of a tee or really any branch connection big enough to sidetrack a pig while traveling down a pipeline. The size of the bars on the tee should be small enough so that they do not restrict the flow from the branch connection. However, they should be large enough to prevent breakage based on the flow rate through the branch connection of the tee.
Tee vs Barred Tee
- Straight Tee - A straight tee has the same branch size as the pipe. These are used for making 90 degree branching from the main run of pipe.
- Reducing Tee - Reducing tees have a single 90 degree branch from the main run of pipe. The branch is smaller than the main run.
- Barred Tee - The bars are installed so they are flush with the inside diameter of the pipeline to keep the pig from hanging up when it passes through.
Barred Tee Design Requirements
- The applications of these tees can be in used above ground or subsea pipelines.
- The bar plates prevent the pig from changing direction or becoming jammed at the branch outlet.
- The bar plates must be of good quantity, thickness, and spacing for the pig to maintain a smooth flow through the pipe with no interference from the branch.
- A rule of thumb is that the opening in the branch pipeline after guided bars does not exceed 40% of the main pipeline area.
- The branch connection bars size must be small enough not to limit flow while being large enough not to restrict the flow pressure.
- The bar plates must be machined to match the branch curve and sharp edges, spatters must be eliminated.
- The smoothness of the pigging procedure is critical for protecting the pig’s sensor from harm.
- The bar plates should be evenly spaced.
- A bridge plate should be installed in the middle of larger tee, sizes 14 inches and higher, to support the bar stiffness when hit by the pig.
- The material of the bar plates is generally the same as the material of the tee.
Barred Tee Buying
Barred Tee Standards
- ASME B16.9 - Factory-Made Wrought Buttwelding Fittings
- MSS SP-75 - High Test Wrought Butt Welding Fittings