Main Steam Flow Nozzle Installed Backwards

[91RepairGuy]

During shearwave testing a weld-in stainless steel flow nozzle in a 12" S160 P91 main steam line we identified a defect in the pipe upstream of the flow nozzle (which was installed backwards). The defect could not be charachterized with the shearwave equipment, but it appeared to be approx 2/10" deep, not in a straight line and continuous half way around the pipe on the bottom side. At 1725 psi and 1004F, do you think it warrants further investigation? What might be the cause of the defect?

 

[Ron]

At that pressure and temperature, of course it warrants more investigation! With the nozzle installed backward, you might be getting some inordinate fretting, or other dynamic consideration for which the pipe and nozzle were not designed. This could lead to a failure of the pipe, which depending on the use and surroundings of the pipe, could be catastrophic.

 

[metengr]

If I were you, I would use a videoprobe and evaluate the condition of the pipe ID surface upstream and downstream of the nozzle to determine what is happening. A flow nozzle installed backwards could be causing a number of problems. This should be corrected ASAP.

 

[paddingtongreen]

I have difficulty in imagining a defect that cannot be characterized, how do you know it is a defect?

p.s. I always wanted to make a trip to the site when they did the "blow down" of those main steam lines, never did make it though.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[91RepairGuy]

Michael, our consulting engineer was using shearwave UT equipment. The transducers used for the shearwave test identified the suspect defect but were not able to positively identify if it was steam cut, crack, etc.

 

[EdStainless]

Did he have a ref std with an ID groove cut in it?
There is no way to use UT to identify the cause, only the size of the indication.

Video probe is your best bet now.

Fix this soon.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[91RepairGuy]

A reference block, per Section V, was not manufactured to replicate the disimilar weld being tested. They did have a section of a failed flow nozzle and pipe from another plant. The UT tech picked up the defect but could not identify it. With the weld-in flow nozzle installed backwards, and the damage on the bottom half of the pipe, I wonder if this may be liquid drop impingement defect - the main steam has been known to contain water prior to start-up. The geometry of the flow nozzle, if installed backwards, would allow the steam to deadhead on the ID of the pipe and the OD of the flow nozzle. If installed correctly, it is a smooth transition that would not disrupt the steam flow. I'm also concerned about flow nozzle damage. Any recommendations on how to convince the Owner to further investigate the defect?