Procurement valve products need to consider the eight necessary technical factors

Valve procurement requires clear specifications, including type and pressure, to meet the demands of current market conditions. However, the procurement process is often complicated due to the lack of a standardized framework in today’s economy. Valve manufacturers, in their efforts to compete, often adopt similar design concepts but introduce unique innovations, leading to the development of individual corporate standards and product characteristics. As a result, it becomes essential for procurement contracts to include detailed technical requirements that both parties agree upon, serving as an annex to the contract. 1. General Requirements 1.1 The valve specification and category must align with the pipeline design documents. 1.2 The valve type should be marked according to national standard numbers. If an enterprise standard is used, the model description must be clearly specified. 1.3 The working pressure of the valve must be equal to or greater than the pipeline pressure. Under normal conditions, the valve should be able to withstand 1.1 times its rated pressure without leakage. In the open state, the valve body should be capable of withstanding twice the rated pressure. 1.4 The manufacturing standard should follow national standards. If an enterprise standard is used, the relevant documentation must be included in the procurement contract. 2. Valve Quality 2.1 The body material should primarily be ductile iron, with grades and actual physical and chemical test data provided. 2.2 The stem material should preferably be stainless steel (2CR13). For large-diameter valves, the stem should also be made of stainless steel. 2.3 The nut material should be cast aluminum brass or bronze, with higher hardness and strength than the stem. 2.4 The stem bushing material should have lower hardness and strength than the stem, and should not cause electrochemical corrosion when exposed to water. 2.5 Sealing surface materials vary depending on the valve type. For example: - Wedge gate valves should specify copper ring material, fixing methods, and grinding techniques. - Soft-seal gate valves require rubber lining with physical, chemical, and health test data. - Butterfly valves must clearly indicate sealing material on both the body and disc, along with physical and chemical properties, especially regarding hygiene, aging resistance, and wear. Non-recycled rubber, such as natural or EPDM, should be used. 2.6 Packing material should remain effective for several years without degradation, ensuring long-term sealing. It should also perform well under frequent operation and allow for easy replacement if needed. 3. Gearbox 3.1 The gearbox material and anti-corrosion treatment should match the valve body's standards. 3.2 The box should be sealed and capable of withstanding a 3-meter water column for testing. 3.3 The limit device adjustment nut should be located inside the box and require special tools for access. 3.4 The transmission mechanism should be designed to rotate the valve shaft only, avoiding vertical movement. Gears should operate smoothly without separation or sliding. 3.5 The gearbox and valve shaft seal must be independent to prevent leaks. If connected, reliable anti-leakage measures are required. 3.6 The box should be free of debris, with gears protected by grease. 4. Operating Mechanism 4.1 The valve should close in a clockwise direction. 4.2 Manual operation should not be too fast, with large-diameter valves requiring 200–600 turns. 4.3 The maximum torque for opening and closing should not exceed 240 N·m under normal conditions. 4.4 The operating end should be a square tenon, standardized, and positioned facing the ground for easy access. Valves with wheels are unsuitable for underground pipelines. 4.5 The opening and closing scale should be clearly marked on the gear cover or shell, facing the ground, with visible markings. The indicator plate should be made of stainless steel or painted steel, not aluminum. The needle should be sturdy and fixed with rivets after calibration. 4.6 If the valve is buried deep, the operating mechanism should be at least 1.5 meters above ground, with an extension rod for easy access. 5. Performance Testing 5.1 Each batch of valves must be tested by an authorized agency for: - Opening and closing under working pressure. - Number of continuous cycles under pressure. - Flow resistance coefficient in the pipeline. 5.2 Factory tests should include: - Open condition: valve body withstands twice the rated pressure. - Closed condition: both sides withstand 1.1 times the rated pressure without leakage. Metal-sealed butterfly valves must meet specific leakage limits. 6. Corrosion Protection 6.1 The valve body (including the gearbox) should undergo sand blasting and electrostatic spraying with non-toxic epoxy resin (minimum 0.3 mm thickness). Extra-large valves may use brushing or spraying with similar non-toxic paint. 6.2 All parts must be fully protected against corrosion to avoid electrochemical reactions and reduce flow resistance. 6.3 Corrosion-resistant coatings must meet health and chemical requirements, with corresponding test reports. 7. Packaging and Transportation 7.1 Both sides of the valve should be sealed with solid plates. 7.2 Small valves should be tied with straw and transported in containers. 7.3 Large valves should be packaged in simple wooden frames to prevent damage during transport. 8. Factory Manual The factory manual should include: valve specifications, model, working pressure, manufacturing standards, body and stem materials, sealing and packing materials, corrosion protection details, operating direction, number of revolutions, torque under working pressure, manufacturer name, date, serial number, weight, dimensions, flow resistance coefficient, effective cycle count, inspection data, and installation and maintenance instructions.

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