Which valve features a flexible valve body and moves parts isolated to contamination?

Which valve features a flexible valve body and moves parts isolated to contamination?

• A. Globe valve
• B. Diaphragm valve
• C. Ball valve
• D. Needle valve

Answer: (B)

The main idea here is isolation of the moving mechanism from the process fluid using a flexible barrier. A diaphragm valve uses a flexible diaphragm as the barrier between the fluid and the valve’s stem and actuation mechanism. When you adjust the valve, the diaphragm flexes to open or close, so the actual moving parts remain separated from the fluid. This makes it ideal for applications where contamination must be avoided or where the fluid is dirty, viscous, or chemically aggressive, because the diaphragm provides a replaceable, fluid-contact surface and keeps the sensitive parts clean. Other valve types rely on metal-to-metal or hard-contact elements for flow control—such as a plug or disc in contact with a seat, a ball, or a needle—and do not provide the same continuous barrier between the fluid and the actuator.

The main idea here is isolation of the moving mechanism from the process fluid using a flexible barrier. A diaphragm valve uses a flexible diaphragm as the barrier between the fluid and the valve’s stem and actuation mechanism. When you adjust the valve, the diaphragm flexes to open or close, so the actual moving parts remain separated from the fluid. This makes it ideal for applications where contamination must be avoided or where the fluid is dirty, viscous, or chemically aggressive, because the diaphragm provides a replaceable, fluid-contact surface and keeps the sensitive parts clean.

Other valve types rely on metal-to-metal or hard-contact elements for flow control—such as a plug or disc in contact with a seat, a ball, or a needle—and do not provide the same continuous barrier between the fluid and the actuator.