Perfect repair of large size gate valve
The waste valves replaced from the working site are corroded by various media, fluid pressure, and affected by different temperatures. The parts including the valve body are affected by different degrees and different locations and cause valve malfunction. The drop cannot even be used. However, the used old valves that have been ineffective at the “validation” are not worthless and have no remediation value. They cannot be repaired and used, as long as they use the principles of metal structure, dynamics, fluidics, corrosion protection, welding, and heat treatment. Knowledge, the provision of essential maintenance equipment and the establishment of an experienced professional team, can fully implement deep-level, high-grade, high-quality repair and refurbishment of used valves.
The quality problem and situation for gate valve
In Jun 2017, there were 4 pcs wedge gate valve PN25 dn500 WZ41H-PN2.5MPa in the water supply circulation system of Sichuan Jiuda Group vacuum salt making equipment. The nominal diameter DN500mm gate valve was replaced by a large amount of leakage and sent to our maintenance (only one for example) .
After the dismantling check, a large area of erosion corrosion occurred on the valve body, the gate plate and the sealing surface at the lower part of the valve inlet. The valve body has 120mm2 of corrosion, the depth is 20mm, the gate plate has 300mm2 corrosion, the depth is about 22mm, the sealing surface It is completely eroded.
The valve body and gate plate A216 (WCB) of the valve, this type of carbon steel harden tends to be harder, welding is easy to produce cold cracks in the weld, welding performance is poor.