Casing pipe expansion joint installation FAQ

As refractory material for centerless induction furnace, it should have very good thermal shock stability and resistance to crack expansion. Obviously, it is not suitable to use the castables used in centered induction furnace as the lining of centerless furnace. According to the practical application of the centerless furnace lining at home and abroad, we set the main direction of attack on the casing pipe expansion joint. The casing pipe expansion joint is a kind of casing pipe expansion joint which contains almost no water and any liquid participant and can be warmed up and baked quickly by short time oscillation or pounding. It is a special kind of casing pipe expansion joint, sintering agent occurs when heated so that the working layer has extremely high strength, while the non-working layer still adheres to the un-sintered bulk structure.
In the process of application, when the operating layer of the hot surface cracks, the un-sintered liner layer can absorb part of the concentrated thermal stress, avoiding the extension of cracks and ensuring the safe operation of the furnace. The water source of backwash is drawn from the seawater chamber after the rotary screen as the main circulating water, and then is pumped and filtered by two stages to the specific part of the rotary screen to flush the dirt, with a planned flow rate of 2.3m/s. The casing pipe expansion joint is planned to use the casing pipe expansion joint with a nominal diameter of 150mm (wall thickness 7.11mm). Leakage site is located in the vertical section of the pipeline and the horizontal section of the elbow weld, the leakage point is reflected in the penetrating hole, the diameter of the hole is very small, but visible to the naked eye, the inner wall of the pipe corrosion is extended brown rust, determined as a typical stainless steel pitting corrosion.
 
The treatment method at that time was to remove the leaking pipe section and replace it with a new pipe section of the same material, and add a trap at the bottom of the new pipe section, with the aim of draining the water inside the pipe during the pipeline shutdown to avoid the recurrence of corrosion. Due to its high chromium and nickel content, it is one of the most corrosion-resistant stainless steels and has excellent mechanical properties. The letter "L" indicates low carbon to avoid the grain boundary accumulation of chromium carbide in the critical temperature planning (430 to 900°C), supplying particularly good corrosion resistance after welding.
 
Casing pipe expansion joint in the metal surface part of the local corrosion to the depth of the unfolding of small holes, other surfaces do not corrode or corrosion is very slightly, this shape becomes a small hole corrosion, referred to as pitting corrosion. Casing pipe expansion joint according to the mechanism is divided into chemical corrosion and electrochemical corrosion. Pitting corrosion is classified as part of the electrochemical corrosion. A kind of pitting corrosion is generated by the partial inflatable cell, similar to the crevice corrosion of metals. Another, more common type of pitting corrosion occurs on metals that have a passivation embodiment or are masked by highly corrosion-resistant oxides.