Technical Discussion on How to Construct Loop Flanges
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For the construction of the deacidification and ammonia evaporation project, the main pipes and valves are made of titanium; slip-on flanges are used, and the gaskets are also made of titanium, while the flanges themselves are made of carbon steel. Teflon gaskets are used between the gaskets during connection. My question is: Can the flange and the gasket be in direct contact? Is it still necessary to use shims for isolation? How to add it? According to research, different metal types should not come into contact with each other; the image shows a valve in the on-site training warehouse.
During the construction of the loop flange, especially when there is contact between different types of metals (such as titanium and carbon steel), it is indeed necessary to consider the issue of electrochemical corrosion between these metals. Direct contact between titanium and carbon steel can cause galvanic corrosion in certain environments; therefore, it is generally recommended to use isolation measures. For the configuration you mentioned, the body of the loop flange is made of carbon steel, while the gasket ring is made of titanium; in this case, it is recommended to use a spacer gasket between the gasket ring and the flange. PTFE gaskets are an excellent choice, as they not only effectively prevent direct contact between two metals but also possess good chemical and temperature resistance, making them suitable for various chemical processing environments. The construction steps are briefly described as follows: 1. Ensure that the connection surfaces of the flanges and pipes are clean and free of contaminants. 2. Place the titanium gasket ring on the connection surface of the flange or pipe. 3. Place a PTFE gasket on the titanium gasket ring to prevent direct contact between the carbon steel swage flange and the titanium gasket ring. 4. Install the other part of the flange or pipe, and ensure that the gasket is in the correct position. 5. Tighten the flange bolts alternately and evenly according to the specified torque to ensure the sealing and stability of the connection. By following the above steps, corrosion issues resulting from direct contact between different metals can be effectively avoided, while ensuring the reliability of the connection and the long-term stable operation of the system. .
Regarding slip flanges, digging through old posts from 10 years ago: https://bbs.hcbbs.com/thread-1292666-1-1.html
Different metals are not suitable for being in contact with each other, which is strange. If they really aren’t suitable for contact, then wouldn’t the tubes always be made of titanium? What about the space between the flange’s inner hole and the pipe?
I’ve never seen an isolation material used between the flange and the gasket; isn’t painting sufficient?