Quality appraisal of straight-through globe valve

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straight-through globe valve is based on the core principle of precision matching of sealing surfaces and coordination of medium flow direction control. By optimizing the valve seat sealing force, valve stem lifting accuracy and pressure resistance strength, it achieves the synergy of zero leakage of the medium, high pressure difference stability and long sealing life. It is widely used in the field of fluid control in petrochemical, electric power, water treatment and heating systems. In high-temperature steam pipelines, it is used for precise flow regulation and emergency shutoff; in chemical industry installations, it meets the requirements for reliable sealing of highly corrosive media; in the field of nuclear power, it ensures the harsh working conditions of the primary loop. Compared with gate valves or ball valves, the straight-through globe valve has the characteristics of small flow resistance, self-cleaning sealing surface (one-way flow of medium) and convenient maintenance (the valve cover is removable). It is the core component of high-pressure and high-precision fluid control.

Zhongke Testing is a product quality appraisal service organization registered with the court. It can provide quality appraisal services for straight-through globe valves. It has a professional appraisal team and advanced instruments and equipment to provide fair and accurate appraisal results for the quality appraisal of straight-through globe valves.

As the safety requirements of industrial systems increase, related quality dispute cases have increased significantly. The judicial dispute focuses on:

1. Dispute over performance indicators: excessive sealing leakage rate and insufficient pressure strength;

2. Material defects: insufficient Cr content in Cr-Mo steel in the valve body and insufficient hardness of the cladding layer on the sealing surface;

3, process problems: coaxiality deviation between valve stem and valve seat, bellows seal welding failure;

4, contract performance dispute: core components (such as imported flexible graphite fillers, carbide sealing rings) do not comply with the technical agreement.

0 Such cases need to pass sealing performance testing, material composition analysis and dynamic opening and closing verification to clarify the quality responsibility.

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straight-through globe valve litigation quality appraisal mainly includes the following technical methods:

1. Appearance inspection: Check the overall appearance of the valve, including surface defects, rust, scratches, etc.

2. Dimensional measurement: Measure various dimensions of the valve, such as outer diameter, height, flange size, and compare them with drawings or technical requirements.

3. Disassembly and inspection: Disassemble the valve and check whether the internal components are complete and qualified. Focus on checking key components such as valve cores, valve seats, and seals.

4. Pressure test: Pressure test the valve to check for leaks. Water or oil is usually used as the test medium.

05. Functional test: Functionally test the valve to check whether it opens and closes normally and flexibly. The valve can be operated manually or electrically.

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A chemical factory of the applicant signed a "PN64 High Temperature Globe Valve Procurement Contract" with a valve manufacturer of the respondent, stipulating that the leakage rate under steam conditions is ≤0.005%. After being put into use, the valve seat leakage rate reached 0.08%. The manufacturer argued that it was caused by the medium containing particulate impurities.

Identification and analysis results:

Quality analysis expert group's relevant information on "straight-through globe valve", contract technical agreement, on-site inspection case materials, etc. The data were discussed and comprehensively technical analyzed, and the following quality analysis opinions were made:

The coaxiality deviation between the valve stem and the valve seat of the straight-through globe valve involved was 0.3mm (agreement ≤ 0.1mm), and the hardness of the sealing surface surfacing layer was HRC 40 (protocol ≥50); the Cr content of the valve body is only 0.7% (protocol 1.0-1.5%), and intergranular corrosion occurs at high temperatures.

The appraisal conclusion determined that process accuracy and material defects were the main causes of leakage.

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The quality appraisal report of the straight-through globe valve should include:

1, the purpose of the appraisal (such as leakage accident attribution, safety compliance verification) and reference standards;

2, the valve model involved, material certificate, production batch;

3, testing method and equipment list ( Such as helium mass spectrometer, hydraulic test bench);

4, correlation analysis of test data and failure (the impact of coaxiality deviation on sealing);

05,clear quality responsibility judgment conclusion and technical basis;

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26,signature of appraiser, pressure vessel engineer qualification certificate and official seal of the organization.

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