If the drain on a sequence valve is blocked, the valve will most likely remain in which state?

If the drain on a sequence valve is blocked, the valve will most likely remain in which state?

• A. Open
• B. Closed
• C. Partially open
• D. Unknown

Answer: (B)

A sequence valve holds the downstream circuit closed until upstream pressure reaches a preset level, and it relies on a drain path to vent its internal chamber so it can respond and re-seat correctly. When the drain is blocked, the valve’s interior can’t vent leakage or the pilot area to tank. That trapped pressure and the bias of the spring keep the valve seated, so it cannot open to supply the downstream circuit. In other words, without a vent path, the valve stays closed even as pressure builds, so the most likely state is closed.

A sequence valve holds the downstream circuit closed until upstream pressure reaches a preset level, and it relies on a drain path to vent its internal chamber so it can respond and re-seat correctly. When the drain is blocked, the valve’s interior can’t vent leakage or the pilot area to tank. That trapped pressure and the bias of the spring keep the valve seated, so it cannot open to supply the downstream circuit. In other words, without a vent path, the valve stays closed even as pressure builds, so the most likely state is closed.