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Confidential (Power Plant)
>$250K
136
0
2023
In the summer of 2023, Notch was awarded this project, which involved replacing two welded-in-place steam pressure-relief valves with new flanged pressure-relief valves, while maintaining the exact orientation of the existing outlet relief piping. The objective was to avoid reworking interconnected piping, minimizing both cost and downtime. A detailed site survey was performed to capture precise dimensions of the installed system. The scope included the removal of welded valves and installation of new flanged relief outlets during a scheduled plant outage. This would be accomplished by removing a section of the boiler steam outlet header and replacing with a new section using flanged steam outlets instead of welded.
Original welded-in-place valve connections prior to removal, showing the welded inlets, flanged outlet elbows and space limitations.
Key challenges included:
3D Modeling & Design:
Our field technicians and design drafters conducted a detailed site survey and used 3D CAD modeling to replicate the existing field conditions. This enabled the accurate placement of new bolted flanged valves without modifying the relief valve outlet piping.
– Pipe size and rating: 6″ SA-335-P22 Schedule 80 seamless pipe
– Flange details: SA-182-F11, 1500# S80 BORE RF Weld Neck Flanges
– Flanges not 2-holed; custom orientation required for proper alignment
– Bolt hole angles offset from 2-hole orientation required the following:
– Left flange: 9.12°
– Right flange: 6.46°
– Spools fabricated with flange angles pre-set in the shop
– Muffler outlet (8″) cut to fit on site
– Weld preps applied to both ends of the 6″ spool piece
– CAD outputs visually confirmed alignment before field installation
– Dimension noted as non-critical, giving flexibility during field fit-up
This level of preplanning ensured that the new valve spools matched the installed geometry precisely, eliminating the need for piping rework or field modification.
Per ASME B31.1 for P22 materials
Localized heat treatment applied at Weld-O-Lets and pipe weld connections
Hydrotest was performed in the shop (not possible in field)
The spool was capped and hydrotested to 981 psi
After hydrotesting the flanges were removed, and the spool was beveled for field welding in position
Radiographic testing (RT) of field welds post-installation
