In the chemical supervision and process control of thermal power plants, the chemical sampling system is the core link to ensure the water quality, steam quality and safe operation of equipment. The system collects samples of boiler feed water, condensate, steam and other media, monitors the composition changes in real time, and provides data support for chemical dosing, desalination treatment and equipment maintenance. However, the accuracy of flow control during sampling directly affects the representativeness of the sample and the reliability of the analysis results.

In response to this demand, the needle type stop valve J21W-16P has become an indispensable key component in the chemical sampling system of thermal power plants with its unique structural design and precise adjustment ability. This article will deeply analyze its technical advantages in precise flow control from the aspects of design principle, control mechanism, system adaptability and reliability verification.

I. Structural design and precise control principle

1. Precision valve core and valve seat structure

The stop valve J21W-16P adopts a needle valve design, and its core components are a conical valve core and a precision ground valve seat. The conical surface of the valve core and the valve seat has a matching accuracy of up to micron level, and the micron level adjustment of the valve opening can be achieved by rotating the hand wheel. This structural design enables the valve to maintain a stable flow output within a very small opening range, which is particularly suitable for precise control of trace fluids (such as ppm-level component analysis) in chemical sampling systems. The linear motion characteristics of the conical valve core can ensure that the flow rate and the opening are approximately linear, avoiding the flow fluctuation caused by the opening and closing characteristics of the valve plate of traditional gate valves or ball valves.

2. Anti-pollution and self-cleaning function

The sampling medium of thermal power plants often contains trace particles or crystalline substances (such as calcium and magnesium ion precipitation), which can easily cause valve blockage or sealing failure. The valve core and valve seat of the needle-type stop valve J21W-16PJ21W-16P are made of high-hardness stainless steel or ceramic, and the surface is polished and hardened to form a smooth and wear-resistant contact surface. The conical design of the valve core can guide the fluid to flow along the axial direction, reduce the deposition of particles at the valve port, and at the same time, the extrusion effect during the opening and closing process can remove tiny impurities and ensure smooth passage. This self-cleaning mechanism significantly reduces the risk of sudden flow changes caused by medium contamination.

3. External thread straight-through flow channel design

The stop valve J21W-16P adopts external thread connection and straight-through flow channel layout. The fluid passage path is short and there is no dead angle, which avoids the turbulence and vortex phenomenon caused by the bend of the flow channel of traditional valves. The straight-through structure makes the flow velocity distribution more uniform, and with the precise adjustment of the valve core, the stable output of the flow can be achieved. In addition, the straight-through design reduces the residence time of the medium in the valve cavity and reduces the risk of internal corrosion of the valve body caused by high temperature or corrosive media.

II. Core technology of precise flow control

1. Fine-tuning mechanism and operational stability

The handwheel mechanism of the needle-type stop valve J21W-16P is equipped with a high-precision worm gear transmission system, which converts the handwheel rotation into the micron-level displacement of the valve core through a multi-stage reduction ratio. The operator can achieve fine adjustment of the flow rate by feel or scale marking, and the minimum adjustable opening can reach 0.1 mm. This design is particularly suitable for scenarios with strict flow accuracy requirements in chemical sampling systems, such as boiler feed water sampling, which needs to maintain a constant flow rate of 2-5 L/h to ensure the detection accuracy of the online analyzer.

2. Pressure compensation and flow stability

The cut-off valve J21W-16P has an integrated pressure balance ring and a buffer chamber structure, which can dynamically compensate for the impact of system pressure fluctuations on flow. When the pressure at the sampling point fluctuates due to changes in boiler load, the balance ring adjusts the valve core opening through fluid pressure feedback to maintain the stability of flow output. For example, in a steam sampling system, the pressure may cause flow changes due to steam pressure fluctuations, and the J21W-16P can control flow fluctuations within ±5% through a pressure compensation mechanism to ensure the continuity and consistency of sample collection.

3. Sealing reliability and zero leakage design

The chemical sampling system has extremely high requirements for sealing, and any leakage may cause sample contamination or environmental risks. The needle valve J21W-16P adopts a double-pass sealing structure: the valve stem and the valve cover are sealed with packing, and the valve core and the valve seat are sealed with metal to metal or soft and hard laminated seals. The packing is made of high-temperature and corrosion-resistant graphite composite materials, which can automatically compensate the sealing pressure with temperature changes; the valve seat sealing surface forms multiple sealing barriers through pre-tightening force and conical surface extrusion to ensure zero leakage under high differential pressure conditions. This design not only ensures the accuracy of flow control, but also avoids sample cross-contamination caused by medium leakage.

III. System adaptability and application advantages

1. Multi-scenario compatibility

The external thread connection method of the needle valve J21W-16P can quickly adapt to sampling pipelines of different diameters, and no additional flanges or joints are required, which simplifies the installation process. Its working pressure range and temperature tolerance cover the working conditions of conventional sampling media in thermal power plants, such as boiler feed water, steam condensate and chemical agents. In addition, the compact structure of the valve can be installed in sampling cabinets or pipeline corners with limited space, which improves the flexibility of system layout.

2. Collaborative control with online analyzers

In chemical sampling systems, stainless steel stop valve J21W-16P is often linked with online pH meters, conductivity meters or ion chromatographs. The precise flow output of the valve ensures the stability of the analyzer injection volume and avoids measurement errors caused by sudden changes in flow. For example, in the monitoring of condensate hydrogen conductivity, if the sampling flow fluctuates by more than 10%, the conductivity reading may deviate by ±5μS/cm; while the flow stability of J21W-16P can control such errors within ±1%, significantly improving the credibility of analytical data.

3. Convenient maintenance and long-term reliability

The modular design of stainless steel needle valve J21W-16P supports quick disassembly and cleaning. The valve core and valve seat can be replaced as a whole without complex calibration, and the maintenance cycle can be extended to several years. Its corrosion-resistant materials (such as 316L stainless steel) and anti-sulfide corrosion properties are suitable for working conditions containing chemical agents such as ammonia and hydrazine in thermal power plants, reducing seal failure or valve core wear caused by medium corrosion. Long-term operation data shows that the failure rate of J21W-16P in the chemical sampling system is more than 50% lower than that of traditional stop valves, and the maintenance cost is significantly reduced.

The external thread needle instrument stop valve J21W-16P has become an indispensable key component in the chemical sampling system of thermal power plants due to its precise structural design, stable flow control capability and excellent system adaptability. Its outstanding performance in anti-pollution, zero leakage and long life not only ensures the reliability of chemical analysis data, but also reduces system maintenance costs and operation risks.

When looking for high-quality, reliable needle type stop 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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