Abstract: Based on the axiomatic theory of systems, this paper identifies problems existing in the sealing of closed valves and solves these problems using inventive theory. Keywords: Closed valve, TRIZ, AD 1 Overview In engineering design, many problems are encountered, which can be divided into two categories: large problems and small problems. A product is a system, which may contain many subsystems. Large problems affect changes in the entire system, while small problems affect changes in subsystems. According to incomplete surveys, 75% of problems in the engineering field are small problems, which can be solved using modern technology. Solving small problems is crucial for an enterprise to maintain a leading position in the market. This paper takes a closed butterfly valve used in the ventilation and exhaust system of civil defense projects as an example, introducing the method of identifying small problems provided by the axiomatic theory of systems (Axiomatic Design—AD) and the method of solving small problems provided by inventive theory (Russian Teoriya Resheniya Izobretatelskikh Zadatch—TRIZ). 2. Butterfly Valve Performance Butterfly valves have advantages such as simple structure, small size, light weight, low material consumption, small installation dimensions, low driving torque, easy operation, and rapid execution. They also have good flow regulation function and sealing characteristics. The manually operated sealed butterfly valve introduced in this article is shown in Figure 1. When the valve is opened, first loosen the locking device, the butterfly plate springs up, and the shaft rotates counterclockwise, simultaneously driving the flapper frame and the butterfly plate to move. The butterfly plate leaves the oil-resistant rubber sealing gasket, and is rotated to the maximum open state with a wrench. When the valve is closed, the shaft rotates clockwise, simultaneously driving the flapper frame and the butterfly plate to move. The butterfly plate presses the oil-resistant rubber sealing ring, causing it to deform and achieve a sealing effect. To prevent the shaft from reversing, a locking device is used to ensure the continuity of the sealing effect. Two O-rings are used for sealing at the front end of the shaft hole. At the joint with the valve body, lead oil and asbestos board are used for sealing by bolts. However, in actual production, through water pressure testing, leakage often occurs at the oil-resistant rubber seal, resulting in unstable product performance and failure to meet technical requirements. For details, please click: Performance Study of Sealed Valves Based on TRIZ and AD Methods