1. The iron shell modification and maintenance of glass-lined pressure vessels should be conducted by units with the corresponding modification and maintenance license. Specific requirements should be implemented in accordance with Section 5 of the TSGR0004-2009 "Safety Supervision Regulations for Fixed Pressure Vessels."
2 Repair of Local Ceramic Burst in Glass Lined Reactor Equipment
2.1 Local glass patching of fused quartz equipment during the local porcelain bursting on fused quartz reactors. The common principle is to cover the damaged porcelain surface with a corrosion-resistant overlay. This repair layer should meet the following requirements: it should not affect the reaction of the medium inside the equipment and comply with the reaction process requirements. Methods include: corrosion-resistant metal packing, corrosion-resistant metal sheet repair, paint repair, Teflon sleeve repair, and thermal spray ceramic powder repair, among others. If entry into the fused quartz tank for repair is necessary, the following must be done:
Comprehensively clean the reaction vessel to prevent the harmful gases and remaining materials from the decomposition of the material from posing risks to human health.
(2) Close all incoming material valves and disconnect the valves from the incoming material pipes, adding blind plates to prevent material from entering the tank during the filling process.
(3) Disconnect the power to the motor that drives the stirrer and assign a dedicated person to supervise, or remove the V-belt to prevent any accidental re-energization that could cause the stirrer to rotate and injure personnel inside the tank.
(4) Measure flammability and toxicity levels, and replace the air inside the tank to prevent residual hazards from affecting human health. In case of necessity, enter the tank while wearing a gas mask and ensure forced ventilation.
All personnel entering the tank during the 5-step construction process must be under constant supervision. Tank entry personnel must wear safety belts, and in case of any adverse symptoms, supervisors must immediately pull the tank entry personnel out.
Ensure you wear protective goggles and avoid the front of the repair area during sanding to prevent the glass frit from shattering and damaging your eyes and face.
(7) Prior to repair, any perforations or corrosion pits in the pot wall must be welded. Operators performing the repair on the iron mold must possess the relevant qualifications for welding pressure vessels.
(8) During welding, protect the porcelain surface outside the welding area to prevent slag from burning the porcelain. In the welding process, interrupt the welding periodically. Immediately stop welding if the iron base body temperature is too high, and wait for the welding area to cool down before resuming. This is to prevent the porcelain layer from cracking due to excessive temperature. After welding, use an angle grinder to smooth the repaired area. Meanwhile, conduct a hydrostatic test according to the technical parameters specified in the completion drawing. The repair area is considered合格 if there is no leakage. After the welding repair, the equipment should be left undisturbed for one day to relieve welding stress.
2.2 Corrosion-Resistant Metal Filling Method: When there are microscopic pores in the glass-lined equipment's surface, it is often possible to use corrosion-resistant metals like gold and tantalum to make plugs that can be directly inserted into the small holes. The advantages of this repair method are: due to the sufficient stability of corrosion-resistant metals against certain media, the lifespan is longer if used appropriately. Disadvantages include: high cost, limited repair area, suitable only for small hole repairs, complex construction techniques, and if the repair technique is not up to par, the plug may easily fall out and cause leakage. Additionally, some media are not suitable, such as gold with aqua regia, bromic acid, iodic acid, and nitric acid mixtures, alkaline cyanides and sulfides, and instability against chlorine, bromine, and iodine. Tantalum is used to repair equipment that is not resistant to fuming sulfuric acid, and if there are lead, zirconium, and stainless steel parts in the equipment, it can also cause corrosion of tantalum. Moreover, alkalis can promote the embrittlement of tantalum, and as temperatures rise, its erosion rate increases. Currently, the corrosion-resistant metal filling method is rarely used for on-site repairs.
2.3 Corrosion-Resistant Metal Sheet Repair Method: Primarily, use metal sheets that can withstand corrosion in the medium to cover the locally damaged areas of the porcelain surface, then securely fasten them with screws made from the same metal. Specific methods are illustrated in Figure 1. Corrosion-resistant metal materials include S31608 (06Cr17Ni12NO2), S31603 (022Cr17Ni12MO2), and S31668 (06Cr17Ni12MO2Ti).
2.4 Coating Repair Method: This method involves applying a corrosion-resistant coating over the damaged surface. Its features include simplicity and the ability to repair various shapes of porcelain surfaces with good corrosion resistance. Drawbacks: The quality of application significantly affects the service life, and different coatings should be chosen for different media. The following are the repair requirements for several types of coatings:
Bellzona: Import repair coatings, product name BELZONA 1311 (Ceramic R-Metal) is used for repairing metal systems damaged by chemical substances (suitable for patching local porcelain bursting on enamel equipment). The manufacturer, BELZONA DNC1311, combines high molecular weight reactive polymers with silicon steel alloys to form a repair system composed of two raw materials. This system, designed for special purposes, is used to repair damaged metals and offers anti-chemical corrosion protection. The material is not machinable and can only be ground. After complete curing during the repair process, it can be used in environments with carbonic acid, 10% hydrobromic acid, 10% nitric acid, 5% phosphoric acid, etc. Specific operations during use should follow the Bellzona product manual.
(2) Inorganic Paint Repair: This involves a mixture of binder fillers and a certain amount of hardening accelerators, primarily using acid-resistant mortar. Its characteristics include resistance to concentrated and dilute inorganic acids (except hydrofluoric acid), organic acids, fatty acids, aqua regia, mixed acids, as well as organic solvents like alcohols, ketones, and fats. It also withstands aqueous solutions of halogen (except F) acids and neutral salts, but is not resistant to alkaline or alternating acid-base media. The binder component of acid-resistant mortar: water glass with fillers such as acid-resistant ash, basalt powder, diatomite, quartz powder, ceramic powder, and barium sulfate, etc. When water glass is mixed into mortar, its proportion is about 27-30% of the total material weight, while for thin slurry, it is 40-50%.
(3) Organic Paint Repair: Utilizes various resins as binders, mixed with a certain amount of filler. Its characteristics: It can be used in places where inorganic coatings cannot be applied, such as in media where toxic substances are prohibited. For example, in alkaline solutions, organic coatings remain very stable. However, phenolic cement, furan resin cement, and epoxy cement are widely used both domestically and internationally.
(4) Paint Repair: Currently, Bellzon 1311 is commonly used, while inorganic and organic coatings are rarely used due to higher requirements for raw material technology and construction techniques, as well as their specific application areas. The general procedure for applying inorganic and organic coatings is: rust removal, sandblasting the iron base and damaged glass-lining to ensure a strong bond between the coating and the衬物 surface. The layers should be applied sequentially, with the coating area of the mortar overlapping the edge width of the glass-tiled surface being greater than 10mm. Acid Treatment: After the mortar coating dries, it is treated with acid to form a silica gel film on the surface. Coating Surface: After the coating application and treatment are completed, cover it with resin to prevent acid penetration.
