A common practice in process services is to use manual globe valves with hand wheels for regulating flow. These valves are relatively simple, rising stem devices that use a screwed stem to drive a disk into a seat horizontal to the flowing stream. For the most part, this practice has been effective. However, significant instances have occurred where these valves failed, particularly when they are used as maintenance bypass valves around control valves. Standard manual globe valves should be used with caution.