In the high-temperature and high-pressure steam system of thermal power plants, the J61Y-320 high-pressure butt-welding stop valve has become a core component to ensure safe operation of 540℃ steam conditions with its innovative sealing technology and material system. This article will deeply analyze the anti-leakage mechanism of the valve under extreme working conditions from four dimensions: material selection, sealing structure, welding process, and maintenance design.

I. Pressure self-tightening sealing structure

The J61Y-320 high-pressure butt-welding stop valve adopts a mid-cavity pressure self-tightening sealing design, and its sealing performance is positively correlated with the medium pressure. When the system pressure reaches 32MPa, the sealing pressure ratio of the valve body and the valve cover increases by 40%, effectively compensating for the gap change caused by thermal expansion. The valve seat and the valve disc sealing surface are welded with Stellite cobalt-based cemented carbide, the thickness of the weld layer is ≥3mm, the hardness reaches HRC45-50, and the leakage rate is still maintained at ≤0.01% under 540℃ conditions.

Sealing structure innovations:

1. Double cone seal: The valve disc and the valve seat are matched with a 60° cone, the contact area is increased by 35% compared with the flat seal, and the sealing pressure ratio is increased to 220N/mm2

2. Elastic compensation ring: An Inconel 718 alloy spring is set at the bottom of the valve seat to compensate for the thermal deformation of 0.3mm

3. Secondary sealing system: Flexible graphite + 316L stainless steel wire braided packing is set at the neck of the valve stem to form a double sealing defense line

II. High temperature resistant material system

The valve body of the stop valve J61Y-320 is made of chromium-molybdenum-vanadium steel (such as 15Cr1Mo1V), which is tempered and surface nitrided. The depth of the nitrided layer is 0.3mm, the friction coefficient is reduced to 0.12, and the anti-scratch life is increased by 5 times. Key material parameters are as follows:

Material Processing Technology:

- Vacuum Quenching: The valve stem is quenched in a vacuum environment at 1050℃, with a hardness of HRC 35-40

- Plasma Spraying: The sealing surface is treated with a high velocity flame spraying (HVOF) process, with a porosity of ≤0.5%

- Stress Relief: Post-weld Heat Treatment (PWHT) is kept at 650℃ for 2h to eliminate 95% of welding residual stress

III. Welding Process and Connection Technology

The stop valve J61Y-320 adopts ASME B16.25 standard butt welding connection, groove angle 37.5°±2.5°, blunt edge thickness 1.6mm, ensure weld penetration ≥8mm. Key control points of welding process include preheating treatment: preheating to 200-250℃ before welding can reduce the risk of hydrogen-induced cracking. The interlayer temperature is controlled within 300℃, and E9018-B3 welding rod is used for multi-layer and multi-pass welding. After welding, 100% radiographic flaw detection (RT) and penetration testing (PT) non-destructive testing are carried out in accordance with ASME B31.1 standard.

Welding joint performance:

- Tensile strength: ≥620MPa

- Impact energy (-29℃): ≥54J

- Bending test: 180° without cracks

Through the four-dimensional innovation of materials-structure-process-operation and maintenance, the J61Y-320 high-pressure butt-welded stop valve has achieved an excellent performance of annual average leakage <5ppm under 540℃ steam conditions, setting a new benchmark for the safe and economical operation of thermal power plants. Its technical route has important reference significance for the design of high-temperature and high-pressure valves.

When looking for high-quality, reliable globe 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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