Page 216 - Root Cause Failure Analysis
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204 Root Cause Failure Analysis
Figure 17-2 Non-rising-stem gate valve (source unknown).
Valves with rising stems (see Figure 17-3) are used when it is important to know by
immediate inspection if the valve is open or closed or when the threads exposed to the
fluid could become damaged by fluid contamination. In this valve, the stem rises out
of the valve bonnet when the valve is opened.
Butte fly
The butterfly valve has a disk-shaped element that rotates about a central shaft or
stem. When the valve is closed, the disk face is across the pipe and blocks the flow.
Depending on the type of butterfly valve, the seat may consist of a bonded resilient
Figure 17-3 Rising stem gate valve.
