In large power plant boiler systems, superheater outlet block valves bear the dual missions of steam channel control and system safety protection. As a key equipment under high temperature and high pressure conditions, the design of the safety shut-off mechanism of the SD61H-P54.5150V block valve is directly related to the safety and reliability of unit operation.

1. Coupling of structural design and safety function

The SD61H-P54.5150V block valve adopts a pressure self-tightening sealing structure, and the design of welding connection at both ends of the valve body eliminates the leakage risk of traditional flange connection. The stainless steel layer on the surface of the valve seat is welded, and the flat O-ring sealing assembly is used to form a three-level sealing system: the primary seal is achieved by the flat contact between the plug plate and the valve seat; the secondary seal compensates for the thermal expansion difference through the elastic deformation of the O-ring; the final seal relies on the self-enhancement effect of the system pressure on the sealing surface.

A removable plugging plate assembly is set inside the SD61H-P54.5150V valve body. Its innovation lies in the decoupling of the isolation function from the flow function. During the hydraulic test, the plugging plate is installed to form a complete seal, and the test pressure can reach 1.5 times the design pressure; during normal operation, it is replaced with a guide sleeve to keep the steam flow field in the optimal fluid mechanics. This dual-mode design not only meets the pressure test requirements of the GB/T 30832 standard, but also avoids the throttling loss caused by the permanent blind plate.

2. Dynamic pressure response mechanism

The safety shut-off function of the plugging valve SD61H-P54.5150V is achieved through the synergy of the pressure sensing system and the mechanical actuator. When the superheater outlet pressure exceeds the set threshold, the pressure sensor triggers a two-stage response: first, the worm gear drive mechanism is started to complete the rapid locking of 90% of the stroke within 15 seconds, and then the micron-level sealing surface is tightened by adjusting the compensation bolts on the upper end of the support plate to ensure that the zero leakage standard can still be achieved under 540℃ working conditions.

This mechanism forms complementary protection with the system safety valve: the safety valve is responsible for steam release during overpressure, and the plugging valve realizes physical isolation of the pipeline. The action sequence of the two has been accurately calculated. When the pressure reaches 1.05 times the working pressure, the safety valve takes priority. If the pressure continues to rise to 1.08 times the working pressure, the plugging valve will start the complete shutdown procedure, forming a double safety guarantee.

3. Installation, maintenance and life management

The installation process of the plugging valve SD61H-P54.5150V strictly follows the ANSIB16.25 standard, and the design of the welding transition section eliminates the stress of the connection of dissimilar materials. It is particularly important to note that the direction of the arrow mark on the valve body must be consistent with the steam flow direction. Incorrect installation will cause the wear rate of the sealing surface on one side to increase by more than 3 times.

The maintenance cycle adopts the state inspection mode. By regularly extracting O-ring samples for compression permanent deformation testing, combined with the valve seat surface hardness test data, the timing of component replacement is scientifically determined.

Compared with conventional gate valves, the safety shutoff mechanism of this type of block valve has three advantages: first, the design without transmission device eliminates the risk of mechanical jamming; second, the modular structure reduces maintenance time by 70%; third, the pressure self-tightening seal automatically enhances the sealing effect when the system pressure fluctuates to achieve passive force protection.

The safety shutoff mechanism of the SD61H-P54.5150V block valve reflects the balance between safety and economy in the design of modern power station equipment. Its technical value lies not only in providing reliable overpressure protection, but more importantly, it establishes a complete safety chain from fault prevention, process control to accident isolation.

When looking for high-quality, reliable boiler valves, YOYIK is undoubtedly a choice worth considering. The company specializes in providing a variety of power equipment including steam turbine accessories, and has won wide acclaim for its high-quality products and services. For more information or inquiries, please contact the customer service below:
E-mail: sales@yoyik.com
Tel: +86-838-2226655
Whatsapp: +86-13618105229

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