In the three years of our country's chemical technology won the National Technology Invention Award 18 items of science and technology progress award 29
In the current market economy, valve procurement requires clear specifications, types, and pressure ratings to meet the practical needs of projects. However, the market environment is still imperfect, as manufacturers often adopt similar designs with slight variations, leading to the development of their own corporate standards and product identities. Therefore, when procuring valves, it is essential to include detailed technical requirements in the contract and obtain manufacturer agreement, ensuring clarity and consistency.
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, relevant model descriptions must be 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 more than the actual pipeline pressure without leakage. When closed, each side of the valve should hold 1.1 times the rated pressure. When open, the body should endure twice the rated pressure.
1.4 Manufacturing standards should follow national standards. If enterprise standards are used, the procurement contract must include the corresponding documentation.
2. Valve Quality
2.1 The body material should be ductile iron, with specified grades and actual chemical and physical testing data provided.
2.2 Stem material should ideally be stainless steel (2CR13). For large-diameter valves, a stainless steel embedded stem is recommended.
2.3 Nut material should be cast aluminum brass or bronze, with higher hardness and strength than the stem.
2.4 Stem bushing material should have lower hardness and strength than the stem and avoid electrochemical corrosion when in contact with water.
2.5 Sealing surface materials vary by valve type. For wedge gate valves, copper rings and grinding methods should be described. Soft-seal gate valves require rubber lining with health and physical testing data. Butterfly valves must indicate sealing materials on both the body and disc, including hygiene, aging resistance, and wear resistance. Non-doped EPDM or natural rubber should be used.
2.6 Packing material should last for years without degradation, maintain long-term sealing, and allow for easy replacement under pressure.
3. Gearbox
3.1 Box material and anti-corrosion treatment should match the valve body’s principles.
3.2 The box should be sealed and able to withstand 3 meters of water column during soaking.
3.3 Limit devices should be inside the box and require special tools for adjustment.
3.4 The transmission mechanism should rotate the shaft without vertical movement, with smooth gear engagement.
3.5 The gearbox and valve shaft seal should not leak; if they do, anti-stringing measures must be in place.
3.6 The box should be clean, with gears protected by grease.
4. Operating Mechanism
4.1 Valve operation should close clockwise.
4.2 Opening and closing speed should be moderate, especially for large valves, which should not exceed 200-600 turns.
4.3 Maximum torque should not exceed 240N-m for ease of manual operation.
4.4 The operating end should be a square tenon, standardized, and positioned downward for ground-level access. Wheel-operated valves are unsuitable for underground pipelines.
4.5 The opening and closing scale should be clearly marked, using stainless steel or painted steel for visibility.
4.6 If the valve is buried deeper than 1.5m, additional rods should be installed for easy access and operation.
5. Performance Testing
5.1 Each batch of valves should be tested for opening/closing performance, tightness, and flow resistance.
5.2 Factory tests include internal pressure testing when open and leakage checks when closed, with metal-sealed butterfly valves meeting specific leakage criteria.
6. Corrosion Protection
6.1 The valve body and gearbox should be sand-blasted and coated with non-toxic epoxy resin (at least 0.3mm thick). Large valves may use brush or spray coatings.
6.2 All parts must be fully protected against corrosion and electrochemical reactions. Surface smoothness reduces flow resistance.
6.3 Corrosion-resistant materials must meet health and physical property standards, with test reports from authorized agencies.
7. Packaging and Transportation
7.1 Light-blocking plates should be installed on both sides of the valve.
7.2 Small valves should be tied with straw and transported in containers.
7.3 Large valves should be packed in wooden frames to prevent damage during transport.
8. Factory Manual
The factory manual should include: valve specifications, model, working pressure, manufacturing standards, material details, operating direction, revolutions, torque, manufacturer name, date, serial number, weight, dimensions, flow resistance coefficient, inspection data, and installation/maintenance instructions.
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