Plug valve bolts removal

Figure 5-8 The wrong bolts are removed from a plug valve and a massive leak develops. Courtesy of the Institution of Chemical Engineers.

The plug, cage, seat ring, and associated seals are laiovvn as the trim, A kev feature of globe valves is that thev allow maintenance of the trim via a removable bonnet without removing the valve bodv from the line. Bonnets are tvpicallv bolted on but rnav be threaded in smaller sizes. 

Before any work inside the column commences, it is essential to take steps for preventing small parts such as nuts eind bolts from finding their way into downstream equipment, such as pumps, heat exchangers, and control valves. In one case (145), a column bottom pump frequently lost suction because a leftover piece of rope ladder reached its inlet and lodged there. Temporary plugs in the column base and some drawoffs can effectively prevent such incidents. It is important to positively ensure that these plugs are removed prior to startup. 

---