Manual shut-off and gate valves can be operated manually via a handwheel, impact handwheel, or gear drive. Electric shut-off and gate valves are actuated by an electric device.
5.7.1 The stuffing box depth should be twice the stem diameter. When the stem diameter is 64mm or larger, the maximum depth shall be 110mm.
5.7.2 For pressure self-sealing valves, the packing material should be flexible graphite spiral wound gaskets without any joints to ensure a secure seal.
5.8 Handwheel: The handwheel used for valve operation must be turned clockwise, and it should be clearly marked with directional indicators.
5.9 Electric Device: Electric actuators installed on electric valves must comply with the requirements of the "DZ series valve electric device" standard.
5.10 Assembly Requirements:
5.10.1 All components, including purchased and outsourced parts, must have inspection certificates and proper identification marks.
5.10.2 Critical parts must be rechecked for size and surface roughness, and their assembly should be optimized for performance.
5.10.3 The surfaces that come into contact during assembly and the friction surfaces must not be damaged or worn, as this could affect the valve's functionality.
5.10.4 Before assembly, all components (including purchased and external parts) must be visually inspected for burrs, corrosion, or machining imperfections. They must pass spectral analysis before being assembled.
5.10.5 Fasteners must be securely tightened after assembly and must not be loose. Screws should be coated with heat-resistant Sikaflex grease before installation.
5.10.6 Manual valves should have smooth stem lifting action without any sticking or uneven resistance.
5.10.7 After installation, the electric actuator must be adjusted so that the travel switch aligns with the fully open and closed positions of the valve. The shut-off valve should have a torque protection device. When switching from electric to manual mode, the handwheel rotation should be even and consistent.
5.10.8 After assembly, when the gate valve is closed, the center of the gate should be higher than the center of the valve seat. For a single gate, the height difference should be two-thirds of the valve seat sealing surface width; for a double gate, it should be half of the sealing surface width.
5.11 Rust Prevention and Painting:
5.11.1 Rust removal and painting should be carried out after the hydrostatic test, ensuring that all internal water stains are removed.
5.11.2 The outer surface of the valve should be painted with anti-grease paint, except for non-processed areas.
5.11.3 Before painting, non-processed surfaces must be cleaned, then a layer of red lead primer applied, followed by a top coat of paint.
6 Test Methods
6.1 Material Testing: Valve material testing must follow the guidelines outlined in Article 5.2.2.
6.2 Hydrostatic Test: A full hydraulic pressure test must be conducted according to the provisions of Article 8.4, including shell strength test, sealing test, and inverted sealing test.
6.3 Type Testing:
6.3.1 Type testing is required under any of the following conditions: when a new design is introduced, when significant changes are made to the structure or materials, or when production is resumed after a long period of inactivity. This ensures that the valve meets all required performance and safety standards.
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