Voices: Field Notes

Take The High Road With Low-Pressure Vessels

Insist that units meet standards even when unsure if they apply

By Dirk Willard, Contributing Editor
Dec 12, 2018

A silo collapsed at an acid regeneration plant near Chicago. This “silo” actually was a low-pressure vessel, according to American Society of Mechanical Engineers (ASME) code. It collapsed because the instrument that protected it failed. The instrument has been installed because the designers thought that a vessel operating near but not above 15 psig didn’t need to be built to withstand full vacuum. ASME Section VIII requires a stamp above 15-psig pressure. This same company also suffered a similar type of failure at a Spanish site; it involved a blocked-in drain line on a large fiberglass atmospheric tank and a hydrostatic test in +90°F temperatures.

Read More