**Detailed Valve Pressure Testing Principles?**
Valve pressure testing is a critical process to ensure the integrity and safety of valves in various applications. Under normal conditions, valves are not subjected to strength tests unless they have been repaired or show signs of corrosion on the body or cover. For safety valves, specific tests such as set pressure and backseat pressure must be conducted according to the manufacturer's instructions and relevant standards.
When installing valves, both strength and tightness tests should be performed. For low-pressure valves, 20% of them are inspected, and if any are foundä¸åˆæ ¼, a full 100% inspection is required. Medium and high-pressure valves, however, must undergo 100% testing to ensure their reliability. During the test, the valve should be positioned in a way that allows for easy visual inspection.
If a valve is welded, it may be tested using tapered seals or O-rings if a blind flange test is not feasible. During hydraulic testing, air trapped inside the valve should be removed as much as possible to prevent inaccurate results. The pressure during the test should be increased gradually, avoiding sudden or abrupt pressurization.
The duration of the strength and sealability tests is typically 2–3 minutes, with important or special valves requiring up to 5 minutes. Smaller diameter valves may require shorter test times, while larger ones need more time. If there are doubts about the results, the test duration can be extended. During the strength test, no sweating or leakage should occur on the valve body or cover. In the sealing test, most general valves are tested once, but safety valves and high-pressure valves should be tested twice.
Small leaks are acceptable for low-pressure, large-diameter, or non-critical valves, but for common valves, power plant valves, marine valves, and others, strict leakage requirements must be followed. Throttle valves are not tested for closure sealing, but strength and sealing tests at the packing and gaskets should still be conducted.
During the test, the closing force of the valve should be applied by hand with normal physical strength. Tools like levers (except torque wrenches) should not be used. If the handwheel is larger than 320 mm, two people may work together to close it. Valves with an upper seal should have the upper seal removed for the seal test. After sealing, check for leaks. When using gas for testing, inspect the stuffing box for water. The upper seal should not be in a tight position during the packing test.
For valves with a drive mechanism, the drive device can be used to close the valve for leak testing. Manual devices should also be used to close the valve for the sealing test. Bypass valves installed after the main valve should be tested along with the main valve, and the main valve’s closing member should be opened when necessary.
When testing cast iron valves for strength, gently tap the valve body and cover with a copper hammer to detect any potential leaks. Except for plug valves, which may allow sealing surfaces to be oiled, other valves should not have oil applied to their sealing surfaces.
During pressure testing, the pressure on the blind plate should not be too high to avoid deforming the valve, especially for cast iron valves, which can be damaged if over-tightened. After completing the pressure test, the water inside the valve should be drained and cleaned thoroughly, and a detailed test record should be made.
Island Light
Island Light is a type of Pendant Light commonly used over the central island in a kitchen or over a long table in a dining room. It typically has multiple bulbs to provide sufficient light to illuminate the entire area. Island Lights come in a wide variety of designs, ranging from traditional pendant styles to modern, industrial, or artistic designs. Island Lights not only provide light but can also serve as a decorative element in a room.
Chandelier Light is a commonly used lighting decoration on the island of a restaurant, which can not only meet the lighting function, but also serve as the main focal point decoration of the restaurant. The Island Light is made of a variety of materials, such as crystal, glass, metal, etc., and has a variety of design styles, which can be matched according to your preferences and the overall style of the restaurant. As a rule of thumb, a gap of 72 cm to 90 cm between the edge of the Lighting Fixture and the surface of the island is optimal. Small islands (1.2 to 1.5 m long) are usually suitable for two medium-sized Island Light or a large Island Light. As for the larger islands, three medium-sized or two larger Island Light can be handled.
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