News

Home >> News

What Is the Cause of Cracking of Stainless Steel Elbow?

Jul. 13, 2020

1. Corrosive environment. In the tube heat exchanger tube, the main medium is titanium tetrachloride liquid, which also contains chlorides such as ferric chloride and sodium chloride. Since the casing heat exchanger has no purge and discharge device, air and water droplets enter during the long-term shutdown, which causes hydrolysis of titanium tetrachloride in the pipeline and blocks the pipeline. Chloride ions reduce the corrosion resistance of the material and cause corrosion to accelerate.

2. Material. The material of the casing heat exchanger tube is 1Cr18Ni9Ti, which is prone to stress corrosion under the environment of chloride ions, which is generally transcrystalline fracture.

3. Residual stress. The residual stress of the elbow is not eliminated. The stress comes from the residual stress generated during the manufacturing process and the working stress generated by the load. Under the action of internal pressure, thermal stress, welding residual stress, etc., the elbow of the casing heat exchanger has horizontal tensile stress conditions.

3. Residual stress. The residual stress of the elbow is not eliminated. The stress comes from the residual stress generated during the manufacturing process and the working stress generated by the load. Under the action of internal pressure, thermal stress, welding residual stress, etc., the elbow of the casing heat exchanger has horizontal tensile stress conditions.

45 Degree Elbow

45 Degree Elbow

Solution

1 Maintenance and management. In order to ensure the long-term operation of the double-pipe heat exchanger, it is necessary to strictly implement the rules and regulations of the heat exchanger, review the existing defects, grasp the development of defects in operation in time, and take appropriate measures to reduce the corrosion of the equipment.

2. Strictly abide by the operating procedures. The process operation and process conditions have a great influence on the corrosion of austenitic stainless steel elbows. Therefore, strictly control the medium composition, flow, medium temperature, pressure, pH value, and other process indicators, and the process conditions allow Add corrosion inhibitor within the range.

3. Stress control: through the stabilization treatment after solid solution, part of the stress can be eliminated and the crack resistance of the material can be improved. However, when considering this method of eliminating local stress, various problems that may be caused by sensitization should be well weighed.

4. Choose anti-stress corrosion materials. In recent years, a variety of stress corrosion-resistant stainless steels has been developed: high-purity austenitic chromium-nickel steel, high-silicon austenitic chromium-nickel steel, high-chromium iron steel, and iron-austenitic dual-phase steel. The stress corrosion resistance of dual-phase steel is better.

Stainless steel elbows and carbon steel elbows are mainly different in materials, and the chemical composition contained in them will keep the surface of the elbows from rust and corrosion for a long time.

How to do the maintenance of Stainless Steel Elbow China

1. Long-term storage of stainless steel elbows should be checked on time, and the exposed surface should be kept clean, cleaned of dirt, and stored neatly in a dry place with indoor air. It is strictly prohibited to stack or store in the open air. Always keep the stainless steel elbow dry and breathable, keep the device clean and tidy, and store it according to accurate storage methods.

2. During installation, the stainless steel elbow can be installed directly on the pipe according to the connection method, and the 45 Degree Elbow can be installed according to the position of use. Generally speaking, it can be installed in any position of the pipeline, but it needs to be easy to manipulate. Note that the medium flow direction of the stainless steel elbow should be upward from the bottom of the vertical valve disc. The stainless steel elbow can only be installed horizontally. When installing the stainless steel elbow, pay attention to sealing to prevent leakage, so as not to affect the normal operation of the pipeline.

3. Stainless steel elbow ball valves, globe valves, and gate valves are only allowed to be opened or closed, and the flow rate is not allowed to be adjusted to avoid corrosion of the sealing surface and accelerated wear. The gate valve and the upper thread stop valve are equipped with an inverted sealing device, and the top position of the handwheel is tightened to prevent the medium from leaking from the filling point.