Valve procurement in today’s market environment is not just about specifying the type and pressure; it requires a comprehensive understanding of technical requirements to meet industry standards. However, due to the competitive nature of the valve manufacturing sector, many companies adopt unique design concepts and develop their own corporate standards, which can lead to inconsistencies. Therefore, it is essential for procurement teams to define detailed technical specifications and reach consensus with manufacturers, often including these details as an annex to the procurement contract.
1. General Requirements
1.1 Valve specifications and categories must align with the pipeline design documents.
1.2 The valve type should be marked according to national standard numbers. If using an enterprise standard, the model description should be clearly provided.
1.3 The working pressure of the valve must be equal to or greater than the pipeline pressure. Under normal conditions, the valve should withstand at least 1.1 times its rated pressure without leakage. In the open position, the body must endure double the rated pressure.
1.4 Manufacturing standards should follow national standards. If enterprise standards are used, they must be included in the procurement contract along with relevant documentation.
2. Valve Quality
2.1 The body material should primarily be ductile iron, with clear identification of grades and physical/chemical test results.
2.2 The stem material should ideally be stainless steel (2CR13), while large-diameter valves should use stainless steel embedded stems.
2.3 Nuts should be made from cast aluminum brass or bronze, with hardness and strength exceeding that of the stem.
2.4 Stem bushings must have lower hardness and strength than the stem, and should prevent electrochemical corrosion when exposed to water.
2.5 Sealing surfaces vary by valve type. For example, wedge gate valves require copper rings with specific fixing and grinding methods. Soft-seal gate valves need rubber lining with health and chemical testing data. Butterfly valves must specify sealing materials on both the body and disc, with emphasis on hygiene, aging resistance, and wear properties. NBR and EPDM rubbers should not contain recycled materials.
2.6 Packing materials must remain effective for several years without aging, ensuring long-term sealing. For frequently operated valves, the packing should maintain performance over time and allow for easy replacement under pressure conditions.
3. Transmission Gearbox
3.1 The gearbox body should follow the same anti-corrosion standards as the valve body.
3.2 It must be sealed and able to withstand a 3-meter water column soak.
3.3 The opening/closing limit device should be adjustable within the box and require special tools for access.
3.4 The transmission structure must ensure smooth rotation of the valve shaft without vertical movement. Components should be well-matched to avoid slippage or separation.
3.5 The gear box and valve shaft seal must be independent to prevent leaks, with anti-stringing measures if necessary.
3.6 The interior should be clean, with gears protected by grease.
4. Valve Operating Mechanism
4.1 The valve should close in a clockwise direction.
4.2 Manual operation should be smooth, with large-diameter valves requiring 200–600 turns for full operation.
4.3 The maximum torque should not exceed 240N-m to ensure ease of use.
4.4 The operating mechanism should have a square tenon, standardized in size, and positioned to allow ground-level operation. Valves with wheels are not suitable for underground systems.
4.5 The display plate should be clearly marked, with visible indicators and fixed securely.
4.6 If the valve is buried deeper than 1.5 meters, additional rods should be installed for accessibility and safety.
5. Valve Performance Testing
5.1 Batch-manufactured valves should undergo pressure testing, tightness checks, and flow resistance analysis by an authorized agency.
5.2 Factory tests should include pressure endurance and leakage checks, with metal-sealed butterfly valves meeting specific leakage criteria.
6. Anti-Corrosion Treatment
6.1 Internal and external surfaces should be sand-blasted and coated with non-toxic epoxy resin, with a minimum thickness of 0.3mm. Extra-large valves may require brushing or spraying.
6.2 All parts must be fully protected against corrosion and electrochemical reactions. Surface smoothness reduces water flow resistance.
6.3 Anti-corrosive materials must meet health and chemical standards, with proper testing reports.
7. Packaging and Transportation
7.1 Both sides of the valve should be sealed with light-blocking plates.
7.2 Small valves should be tied with straw and transported in containers.
7.3 Large valves should be packaged in sturdy wooden frames to prevent damage during transport.
8. Factory Instructions
The factory manual should include: valve specifications, model, working pressure, standards, materials, sealing components, operating direction, torque, manufacturer details, dimensions, flow coefficient, and maintenance instructions. It should also provide installation and safety guidelines.
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