Owing to complex petrochemical device as well as toxic and harmful media, it's quite vital to ensure the quality of pipeline construction and project quality control. Welding connections and flange connection are commonly used. Leakage accidents caused by flange interfaces has been increasing over 18% in recent years because of a large number of flange bolts and complicated working conditions.
一、Main Causes of Flange Leakage
1. The damage of sealing surfaces such as flanges and gaskets.
2. The wrong materials of gaskets or bolts.
3. Flange deflection.
4. Improper tightening.
5. Insufficient tightening load.
6. Excessive fastening load.
The ideal solution should combine excellent corrosion protection with simple construction procedures, easy access to bolts during maintenance and should be suitable for flanges of various sizes and shapes.
1. Maintainance Coating
It's usually an epoxy or polyurethane coating, which is a hard coating that bonds directly to the substrate. There are many corners and edges in the flange, and due to the thinning of the edges, it's difficult for traditional paint to effectively cover the edges. Even if a thickened coating protects the edge, it also seals the fastener, making it impossible to remove for subsequent repairs as well as the painting can be damaged while manipulating the bolts.
2. Mechanical Solutions
We mainly use protective covers and clamps to seal the flange and its seal surface, which normally made of stainless steel, plastic and other materials equipped with rubber sealing strips.
3. Tape or Semi-solid Anti-corrosion Tape
Tape in rolls are warpped around the surface of substrate, protecting the firm tightness such as mineral grease tape, waxy or elastic polymer wrapping tape. But it’s hard to reseal and restore the original protection after removing the package.
4. Thermoplastic Packing
It refers to a waxy soluble polymer that is heated at high temperature by hot melt equipment and then sprayed onto the surface of the substrate. Its advantage is that it can be reused, but it requires hot processing, professional equipment, and is not easy to open and seal later.
5. New Peelable Sealing Film System
Use corrosion inhibitors as primers to provide complete corrosion protection. Meanwhile, the coating itself has strong adhesion and can remove all moisture from the system.
Pipeline and flange management is systematic project that requires comprehensive consideration of many factors like flange group, sealing surface, gasket, bolts, torque valve control, process operating condition and beyond. Through strict process control, material management and proper installation, the potential risk of flange leakage can be effectively avoided.
