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How to machine damaged RTJ flanges


Above: Watch the video showing set up process of the MM600e flange facing machine 

Ring Type Joint flanges are typically used in high pressure and/or high temperature applications and differ from other flanges as angled faces are cut into the flange faces to accept steel ring gaskets, to create a metal to metal seal.
When an RTJ flange is damaged before installation or is in need of maintenance, this can be carried out using a flange facing machine. Read on and watch the video to get an insight into the steps needed to return the RTJ flange to its original condition. 


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Dimensional Survey


The first step is to carry out a existing dimensional survey of the existing RTJ to be machined, including the depth of the groove. This can be done using the Mirage Machines RTJ measuring kit.  Dimensions should be recorded for reference, as the machining operation is to return the RTJ groove back to its original dimensions, removing any incurred operational damage.


Machining the flange

  1. Set the machine to the flange face and concentric to the RTJ groove. Tolerance ± 0.002".

  2. The critical dimension of the RTJ groove is the groove pitch diameter "P", equal amounts to be removed from the groove angle faces to maintain the centre line position.

  3. Dependant on the damaged face (inner or the outer face can be machined first). Machine the inner RTJ groove face until the damage is removed.

  4. Machine the outer RTJ groove face removing the equal amount of material as removed from the inner face.

  5. As the groove has now been oversized (groove width "F") the top face of the RTJ flange has to be machined to recover the RTJ inner and outer dimensions as recorded within the dimensional survey.

  6. Machine the top face and monitor the RTJ inner and outer dimensions using the RTJ measuring kit. Continue until the dimensional survey dimensions are achieved.

  7. The groove depth "E" is now too shallow. With the tool post rotated to the appropriate angle for the inner and outer flank, machine to match the 23° angle on both inner and outer flanks.

  8. Dependant on the material removal the bolt hole to the raised face dimension may require machining to recover the relief. Caution to be used as bolt hole material removal can affect the flange strength required for re-torquing/tensioning the RTJ joint. Only machine if required and with technical advice.

To find out more, download The Complete Guide to Managing Flanges or if you have a potential project needing this product right now  please click here to get in touch.

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