Troubleshooting Challenge: Eroded Construction Plug Causes Manifold Leak

A mill that produces oil-field pipe is required to hydrostatically test the pipe with water according to ASTM standards. They used a hydraulically driven water intensifier to fill and test the pipe at pressure to 2,500 psi. They decided to add a second intensifier that could achieve higher pressure, but at lower flow. Using both intensifiers at the same time let them fill the pipe quicker. Then when the water pressure reached 2,500, the new intensifier took over to apply pressure to 4,000 psi.

A manifold was designed to allow selecting one intensifier, the other, or both at the same time. The intensifiers could supply maximum flow of 125 gpm, but the return flow back to tank exceeded 300 gpm.

The system was installed and running for a couple of years until one of the SAE O-ring construction plugs began to leak. The maintenance crew tightened the plug, but leakage increased. After removing the plug to replace the O-ring, they found the plug had been damaged, as shown in the photo. The manifold threads were also damaged, so they decided to drill and tap four holes and installed a four-bolt, Code 62, flange with an O-ring and plug to cover the construction hole.