(1) The use temperature is high, and it can be used for a long time at 1300 °C. The non-metallic materials have strong acid and alkali corrosion resistance, and there will be no oxidation of metal anchors at high temperatures, and the phenomenon of refractory spalling caused by welding; (2) The thermal conductivity is similar to that of the refractory material, which reduces the stress caused by the difference in volume change between different materials; (3) The thermal bridge effect is reduced because the ceramic anchors replace the metal anchors, which reduces the overall thermal conductivity, thus saving energy The effect is also significantly enhanced. By actually measuring the temperature of each section of the grate cooler, the average reduction is 10 °C. Ceramic Anchor,Ceramic Ring,Ceramic Cup,Welded Ceramic Ring Puyu kiln technology (jiangsu) CO.,LTD , https://www.anchorpy.com
Valve Problems and Selection in Water Supply Network (Part Two)
It should be noted that due to varying thicknesses of different body parts, casting a ball can be challenging. Appropriate measures must be taken to ensure the quality of the castings. Currently, there are still some issues with the casting bodies, such as the physical and chemical properties of ductile iron being loosely controlled by most manufacturers, except for a few. Additionally, sand casting is widely used, and many require mechanical processing for molding. It is recommended that all manufacturers establish a strict quality control system. For small and medium-sized valves, the lost foam molding method is suggested. Large-caliber valves should be made using resin sand, and effective measures must be in place to eliminate internal stress, promoting shot blasting and sand removal. Casting defects or welding should not be used to fix issues; instead, measures must be taken to address stress from welding repairs, followed by more rigorous testing and clear communication to users.
During inspections, it was found that many valve manufacturers outsource casting parts to complement their production. The acquisition of outsourced components and their assembly is also a common operational mode. However, the quality of these outsourced parts must be strictly controlled. Unfortunately, some companies purchase low-quality components, perform minimal modifications, and sell them at high prices, which needs to be stopped.
For stems, 2CR13 stainless steel is recommended. For stem nuts, cast aluminum brass or bronze is suggested, with the nut's hardness and strength greater than that of the stem. Regarding the opening and closing torque of the valve, it should be under 240 N·m at working pressure to allow manual operation. Manufacturers are encouraged to optimize the valve structure design, improve component concentricity, and enhance the finish of moving parts to reduce resistance. Simply increasing gear ratios is not ideal. In this regard, updating machining equipment, such as computer-controlled machine tools and machining centers, is commendable, as seen in some factories in Tianjin.
Valve stem packing often causes leakage, especially in large-diameter valves where maintenance is difficult and costly. Improving the durability of the packing material is essential—materials should resist aging and minimize wear. A Shanghai company uses three small aprons and a plastic cover for DN100-2600mm valves, ensuring long-term performance without leakage if concentricity and surface finish are maintained. This simple design reduces torque and is worth adopting.
Gearboxes for large-diameter valves must have an opening/closing limit device inside the housing, a compact and sturdy structure, and a rational transmission design to prevent movement during operation. They should also be sealed to avoid water ingress. Some manufacturers integrate the packing housing and gearbox, which can lead to contamination if leakage occurs, and this needs improvement.
Valves in water supply networks are typically buried, making the use of raised stem valves unsuitable. Operators on the ground need clear, marked openings and closings, with the direction specified (clockwise). Marking plates should be visible from above, cast into the valve, and made of phosphor-based paint for visibility. Aluminum materials should be avoided, and pointers and scales should be locked after installation.
Regarding valve performance and testing, key points include flexible and lightweight opening/closing under working pressure, tight closure at 1.1 times working pressure, and proper flow resistance testing. Valves must be tested by qualified units, and flow resistance coefficients should be determined. The valve body’s pressure capacity should match the pipeline, and many manufacturers lack the necessary testing equipment.
Anti-corrosion lining is crucial for valves, especially those transporting drinking water. Non-toxic, corrosion-resistant materials should be used, and electrostatic spraying of non-toxic epoxy resin is ideal. Many manufacturers still use harmful paints, which do not meet health standards.
Valve manuals should include technical data such as specifications, model, pressure, materials, sealing materials, torque, and instructions. When purchasing valves, buyers should compare multiple manufacturers, prefer those with ISO9001 certification, and consider product quality and cost-effectiveness. Proper packaging, storage, and inspection before installation are essential to avoid damage and ensure reliability.
Valve assembly should facilitate installation and disassembly, with appropriate flanges and connectors. Valves should not be placed on construction sites prematurely, as exposure to weather can cause damage. Proper storage and regular inspections are necessary. Good operational management includes maintaining technical records, regular inspections, and ensuring valve well conditions are optimal. Valve wells should be well-maintained, with proper ventilation and safety measures to protect workers.
Overall, a comprehensive approach involving quality control, proper manufacturing, reliable testing, and effective management is essential to ensure the long-term performance and safety of valves in water supply systems.