We have some corroded weld joints in one of our pipelines.
The extent of corrosion is that the actual weld thickness is lesser than the base metal thickness at many of the welds.
This condition can cause bending stresses in the weld joints which is a concern to be dealt with.
Is there any method for assessment of actual bending stresses imposed on the piping in this condition?
Bending Stresses on Piping
Re: Bending Stresses on Piping
Yes you are right, bending stresses would effect the pipeline mechanical integrity but it depends on the extent of metal loss at the welds and the supports near or far away from the welds.
The basic thing to look for is the actual metal thickness at welds and the remedy you have adopted for continuous operation.
Is pipeline welds running without any repair or you have adopted one like weld box-up or weld overlay?
The basic thing to look for is the actual metal thickness at welds and the remedy you have adopted for continuous operation.
Is pipeline welds running without any repair or you have adopted one like weld box-up or weld overlay?
Re: Bending Stresses on Piping
The actual thickness at the welds in being monitored and now it is just close to the required against the operating pressure / temperature conditions.
We have not carried out any repairs on the welds as of yet. May be in coming month, we would be planning for boxing up few of the problematic welds with thicknesses going down than the required.
Now my concern is that even after carrying out the repair (box-up or weld overlay), is there a method to estimate the actual bending stresses at the internally thin portion (welds) of the piping?
We have not carried out any repairs on the welds as of yet. May be in coming month, we would be planning for boxing up few of the problematic welds with thicknesses going down than the required.
Now my concern is that even after carrying out the repair (box-up or weld overlay), is there a method to estimate the actual bending stresses at the internally thin portion (welds) of the piping?
Re: Bending Stresses on Piping
The calculation of bending stresses on piping can be easily evaluated considering the type of supports attached to the pipe, the span in between the supports and the section modulus of the pipe considering total weight (dead, dynamic due to fluid).
Distribute the whole weight over the piping span in between the supports and then see what stress comes out be at the weld joints (section modulus will be based on the actual dimensions - reduced weld thickness).
However, an elemental analysis would be more helpful to determine the actual stress at the weld joint.
In my opinion, if the weld thickness is not significantly lower than the required thickness, do not worry about the bending stresses at this time and plan for an early re-welding / repair of these welds.
Distribute the whole weight over the piping span in between the supports and then see what stress comes out be at the weld joints (section modulus will be based on the actual dimensions - reduced weld thickness).
However, an elemental analysis would be more helpful to determine the actual stress at the weld joint.
In my opinion, if the weld thickness is not significantly lower than the required thickness, do not worry about the bending stresses at this time and plan for an early re-welding / repair of these welds.
Re: Bending Stresses on Piping
Thanks all for the inputs.