Valve positioners play a crucial role in the control of valves across various industrial applications. When selecting the most appropriate valve positioner for a specific use, several key factors should be considered to ensure optimal performance and reliability. First, the ability to support "split-ranging" is essential. This feature allows the positioner to respond to a specific range of input signals (e.g., 4–12 mA or 0.02–0.06 MPaG), enabling a single signal to control multiple valves. This can significantly enhance system flexibility and efficiency.
Second, ease of adjusting zero and span settings is important. Ideally, these adjustments should be possible without opening the device’s housing, while also preventing unauthorized or accidental changes. Third, stability of zero and span under varying environmental conditions—such as temperature, vibration, and pressure—is critical. Frequent recalibration due to drift can lead to inefficiencies and increased maintenance costs.
Fourth, the accuracy of the positioner must be high. It should consistently position the valve trim accurately, regardless of travel direction or load variations. Fifth, the air quality requirements of the positioner are significant, especially for pneumatic or electro-pneumatic models. These devices must withstand dust, moisture, and oil present in real-world environments, as only a few air supply systems meet ISA standards.
Sixth, whether the calibration of zero and span is independent or interdependent matters. Interdependent adjustments can complicate the process and require more time and effort. Seventh, the presence of a "bypass" function can simplify actuator checks, such as benchset and seat load verification, by allowing direct signal application to the regulator. This can reduce unnecessary calibration steps and enable online maintenance without shutting down the system.
Eighth, the speed at which the positioner responds to input changes is vital. A faster response leads to quicker adjustment to setpoints and load variations, resulting in lower hysteresis and improved control quality. Ninth, frequency response is another important factor. Higher sensitivity to sinusoidal inputs generally means better control performance, but it should be measured using consistent testing methods rather than theoretical assumptions.
Tenth, the maximum rated supply pressure of the positioner should match the actuator's requirements. If the positioner cannot handle the required pressure, it may become a limiting factor. Eleventh, positioning resolution is critical for accurate valve control. Higher resolution reduces overshooting and stabilizes the control process.
Twelfth, the feasibility of positive and negative conversion is sometimes necessary, especially when changing the way a signal affects the valve. Thirteenth, the internal complexity of the positioner influences maintenance needs and spare parts inventory. More complex designs may require more trained personnel and higher maintenance costs.
Fourteenth, steady-state air consumption is an important parameter, particularly in plants where this factor could limit system performance. Finally, other considerations include the feedback linkage, durability, environmental resistance, and ease of installation.
In China, hydropower and pumping stations face significant challenges due to high sediment levels in rivers. For example, the Yellow River and its tributaries have led to severe erosion problems in many turbines and pumps. According to experts, over 132 large and medium-sized turbines have been affected, with total capacities exceeding 12 million kW. In addition, about 6.6 million kW of small and medium hydropower stations and 100,000 pumping units on the Yellow River suffer from sand erosion, leading to frequent maintenance and reduced operational efficiency. Components like turbine blades and pump impellers often degrade rapidly, requiring early replacement and increasing downtime. These issues highlight the importance of selecting robust and reliable valve positioners that can withstand harsh operating conditions.
Forging Parts
Forging
Equipment
Sawing Machine, Intermediate Frequency Furnace, Air Forging Hammer, Flat Grinding Machine, Friction Press Forging Machine, Filling Machine, Quenching Furnace, Blasting Machine, Punch Machine
Material & Standard
Carbon Steel, Steel Alloys, etc.
ASTM, AISI, GB, DIN, JIS, SAE, UNS, EN, JP
Application
Automotive Industry, Construction Machinery, Mining Machinery, Agricultural Machinery, Marine, Pipe and Fitting, Railway, etc.
Capability
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Weight
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0.5-40 kg(1.1-88 lbs)
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Dimensions
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Diameter/Diagonal 25-350 mm(1"-13.75")
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Roughness
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Ra12.5~50
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Tolerance
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EN10243-1 (GB/T12362)
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Secondary Operations
CNC Machining, Milling, Turning, Threading, Drilling, Rolling, Wire Cutting, High Precision Grinding, Re-Shape, Sand Blaster, etc.
Surface: Painting, Plating, Black Electro-Phoresis, Dacro Coating, Polishing, etc.
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J.B Machinery (Ningbo) Co., Ltd. , https://www.jbcastings.com