Swaging


Metro Boiler Tube Co., Inc currently has the ability to provide boiler tube swaging in house with our two Mitchell Swagers. These swagers have the ability to control and maintain the finished wall thickness with the application of one of our many inverse draw mandrels.

The Swaging Process

‚ÄčTube Swaging is a fabrication process where a tube or pipe end is forced through a die or series of dies with hydraulics to increase or decrease the OD (Outside Diameter) of the tubing or pipe. This Process is a "cold" without the use of heat. This process compacts the material causing work hardening making a heat treating / annealing process necessary to meet the material specifications. The swaging process will also cause the wall thickness to increase effectively decreasing the ID (inside diameter) of the tube / Pipe. When The wall thickness and/or ID (Inside Diameter) of the tube is critical such as when you must purchase tooling for rolling the tube ends into a drum an Inverse draw mandrel can be used to maintain the ID of the Tube / Pipe. Inverse draw mandrels provide a smooth and consistent ID and wall thickness.

Material Hardness Requirements

MaterialP NumberMaximum Hardness
SA 178 AP177 HRB
SA 178 CP175 HRB
SA 178 DP177 HRB
SA 192P175 HRB
SA 210 A1P179 HRB
SA 210 CP189 HRB
SA 209 T1P380 HRB
SA 209 T1aP381 HRB
SA 209 T1BP377 HRB
SA 213 T2P385 HRB
SA 213 T9P5B89 HRB
SA 213 T11P485 HRB
SA 213 T22P5A85 HRB
SA213 T91P15E100 HRB
SA213 StainlessP890 HRB

As a general rule the hardness is returned to the origianal tube hardness as they were received from the mill.


Bent Swaged Boiler Tubes

Metro boiler tube co., Inc provides in house swaging, bending, and welding of your complete boiler bank generating tubes. We have over a half a million feet of the most common sizes and specs of boiler tubing in our inventory allowing for a quick turnaround.

When placing an inquiry we will need the following information:

  • Tube OD (Dim E)
  • MW (Minimum Wall Thickness)
  • Material Spec
  • Swage OD (Dim A)
  • Swage ID (Dim D) Or Swage Wall Thickness (Dim F)
  • Blade Length (Dim B)
  • Overall Length

Note: For tubes swaged on both ends please provide dimensions A,B,(D or F) for both "Top" And "Bottom" Ends Note: When providing Dim D (wall thickness) Please note an actual wall thickness is required not a min wall.

Swage Tube inspection

As a shop standard 10% of all swaging will be checked and documented by our Quality Control Department For Swage OD, Swage ID, Wall Thickness, Swage Length, And Hardness. ‚ÄčAll surfaces shall be checked for burrs and smooth contours inside and out. Upon request our quality inspection can be increased up to 100%.

Swaging Standard Tolerances

  • Swage OD: (+/-) 0.012"
  • Swage ID: (+/-) 0.010" (Inverse Draw Only)
  • Deviation From Concentricity: .0625" Max

Tube Cleaning

All Inverse Drawn swages will have sponges blown through them to remove any excess lubrication each time an end is swaged. If needed the tubes will be steam cleaned to remove any remaining oil and debris.

Polished Swaged Ends

Swaged boiler tube ends can be polished to remove scale and ease in the process of sticking them through the drums. Polished end will have a light coating of oil and 4" vinyl caps would be recommended to prevent corrosion in transit.