Partial overstress occurs on the valve seat.

During valve opening and closing, part of the sealing surface separates from the ball, giving rise to localized stress concentration, which is most prominent near the upper and lower shafts. This causes severe wear and leads to premature valve leakage.

Definition of Balanced Spring:

Springs at the bottom of the valve seat are evenly distributed circumferentially.

Most manufacturers adopt balanced spring design for valve seats.

Stress concentration is most severe when the valve opens at 20 to 30 degrees.

Excessive local stress is the root cause of premature valve seat failure.

The non-uniform spring design reduces stress concentration and achieves longer service life.