Pressure‑piping Installation

It mainly covers the following four key items:

1.1 Piping Materials Material quality is the prerequisite to guarantee pressure‑piping construction.

1.2 Piping Prefabrication Piping prefabrication is a critical procedure prior to piping installation. Its construction quality directly determines the quality of subsequent installation processes for pressure‑piping works.

1.3 Piping Welding Welding is the core operation in pressure‑piping installation. The welding quality exerts a significant influence on the stable operation of pressure piping.

1.4 Piping Erection Piping erection constitutes both the key and difficult part of the whole project. Special attention shall be paid to tightness performance during piping installation.

1.5 Summary All above‑mentioned steps are of vital importance. Any defect arising in any link may trigger operational failures of pressure piping and cause substantial losses to the enterprise.

Non‑destructive Testing of Pressure Piping

Non‑destructive inspection shall be performed on piping welds according to the prepared isometric drawings. Inspection methods, inspection scope and quality requirements shall comply with design specifications. Radiographic testing methods and quality classification standards shall conform to GB 50236.

Welds rejected by non‑destructive testing shall be repaired. Repair welding shall follow the same requirements as production welding. The number of repairs at the same location shall not exceed twice. Welds still failing inspection after more than two repairs shall be cut out and re‑welded.

After completion of piping installation and satisfactory system‑integrity check, purging shall be carried out. Upon acceptance of purging, temporary facilities shall be removed promptly to restore piping to its original condition. A full inspection of the piping system shall be performed, and the piping‑system purging record shall be filled out.

For piping installation, after fabrication of main pipes, welded joints of main pipes shall be fully exposed for pressure testing. The test pressure shall be based on the higher value between internal and external design pressure of the main pipe. Maintain pressure for 10 minutes; no leakage and no visible deformation are acceptable. Afterwards reduce pressure down to design pressure and hold for 30 minutes. The test is qualified if there is no pressure drop and no leakage.