What design feature should valves avoid regarding the valve stem?

The functionality of a valve stem is crucial in maintaining the integrity and safety of a valve system. One key design feature that should be avoided is the ability for the valve stem to be removed without disassembling the entire valve body. This design could lead to unsafe practices, where the valve could be inadvertently discharged or opened during maintenance or adjustment, potentially leading to leaks or catastrophic failure.

A secure design that requires the entire valve body to be disassembled for stem removal ensures that the valve remains closed and contained, thus preventing gas leaks or exposure to hazardous materials. This requirement enhances safety by ensuring that all components are properly engaged and reduces the risk of accidental disengagement or manipulation of the valve stem while the system is still under pressure.

In contrast, the other options highlight features that can enhance the functionality of valves under certain conditions, such as the ability to adjust safely while under pressure or withstand extreme environmental conditions. These attributes are generally preferred in valve design to ensure reliability and operational efficiency.