The Logic of the Use of Valve Fittings in Metallurgical Equipment: From the Valve Seat to the Lower Shaft

In large-scale control systems in the metallurgical industry, the performance of ball valves and gate valve fittings directly affects the operational stability of furnace pipelines and cooling water systems. Too often, the problem in the field is not with the overall valve design, but with a few small and inconspicuous parts – such as seat sinking, lower shaft clearance deviation, or stuffing box fatigue aging. If this kind of problem accumulates, the rotation of the sphere is not in place, and the deviation of opening and closing will become a systemic failure.

In recent years, we have matched the oxygen main pipe and coke oven main line ball valve projects of several steel mills, and the common problems focus on the valve stem structure and spring seat life. The customer's original drawings used an integral sealed valve seat, but the spring thrust fails quickly under high-frequency opening and closing, and the sealing surface is difficult to fit. We have optimized the structure, changed to a split spring seat with two-way limit, and the wear resistance of the lower shaft and support ring has been improved a lot after nitriding treatment.

For a component like the lower shaft, the requirements are not complicated, but they must be aligned and resistant. If the ball and shaft are not aligned, even if the actuator performance is good, the opening and closing speed will be offset by the error. When we match, we basically require customers to provide both ball core and upper shaft structure for coaxiality control.

In this kind of supporting project, the 'structural small parts' such as brackets, bonnets, and stem nuts are often the key factors that determine the service life of the whole machine. They are not directly involved in sealing, but determine whether the opening and closing are smooth. Friends who do foreign trade may have encountered: when the customer testes, it is not to look at the appearance, but to disassemble the assembly drawings layer by layer to see whether the accuracy of these small parts is up to standard.

Therefore, even if a valve fitting, don't look at it small, the design and processing problems can be exposed during on-site assembly. When we do this kind of project, we will uniformly recommend that customers send drawings to confirm the plan, and proofing and assembly before batching, especially for structures that mesh with each other such as valve seats, spring seats, and valve stems.