A blocked drain on a sequence valve will cause which of the following?

A blocked drain on a sequence valve will cause which of the following?

• A. No change in function
• B. Reverse flow to occur
• C. The valve to stay closed
• D. None of the above

Answer: (C)

A sequence valve is designed to hold back flow to the downstream circuit until the upstream pressure reaches a set point, and it relies on venting its control chamber to tank so it can reset and open when needed. If the drain is blocked, the control chamber cannot vent, so pressure on the pilot side cannot drop and the valve’s poppet remains pushed closed by the spring and the trapped pressure. As a result, downstream flow never commences, and the valve stays closed. The other possibilities don’t fit because a blocked drain doesn’t create reverse flow or indicate no change; it prevents the valve from opening by blocking its vent path.

A sequence valve is designed to hold back flow to the downstream circuit until the upstream pressure reaches a set point, and it relies on venting its control chamber to tank so it can reset and open when needed. If the drain is blocked, the control chamber cannot vent, so pressure on the pilot side cannot drop and the valve’s poppet remains pushed closed by the spring and the trapped pressure. As a result, downstream flow never commences, and the valve stays closed. The other possibilities don’t fit because a blocked drain doesn’t create reverse flow or indicate no change; it prevents the valve from opening by blocking its vent path.