Titanium tube production and installation process
Acetic acid pipeline of chemical plant is the most important process pipeline of chemical plant. The original design of acetic acid pipeline of a chemical plant was made of acid-resistant stainless steel (316L). After several years of operation, the corrosion of acetic acid pipeline in oxidation section was serious.The leaked acetic acid gradually corrodes the nearby steel structure and equipment, seriously pollutes the environment and poses a serious threat to personal safety.
Through the analysis of the causes of pipeline corrosion, it is found that the concentration of acetic acid in the chemical plant is as high as 99.5%. After the acetic acid molecules in the acetic acid pipeline are heated, the temperature rises and the activity increases.There are also some pipelines, although the acetic acid concentration is low, but because of a small amount of hydrobromic acid (HBr), still caused serious corrosion to the pipeline, the pipe wall thinning phenomenon is serious, to the chemical plant safety production formed a potential accident.Therefore, since 1997, the 316L acid-resistant stainless steel tube of the chemical plant was gradually replaced with titanium tube. Within more than 4 years after the replacement, the operation effect was very good, which created good conditions for the safe, stable, long, full and excellent operation of the chemical plant.This paper mainly describes the production, installation and technical essentials of titanium tube.
After the arrival of the titanium pipe, the owner, the construction person in charge, the constructor, the quality inspector and the welding technician shall be organized to inspect the material, specification, quantity, quality and quality certificates of the pipe valve parts.The pipe must have the factory certificate and quality certificate of the manufacturer.Besides, the outer diameter and wall thickness should be measured root by root. The outer diameter, wall thickness and ellipticity must meet the requirements of the code.The inner and outer surface should be smooth and clean, without pinhole, crack, folding, over-corrosion and other defects.
Titanium tubes should be placed according to the same requirements during transportation.In hoisting process, appropriate use nylon or synthetic fiber sling.If wire rope and shackle are used, they shall not be in direct contact with pipelines. Rubber or asbestos products shall be used for isolation.
Under the good material of titanium pipe, smaller diameter, the best on the lathe machine groove, lathe speed should be slow, and pay attention to cooling.Larger caliber (DN100 or above), should use polishing machine grinding groove.Operation speed should be slow, several times to complete, and pay attention to cooling.When approaching the requirements, remove the contaminated layer with a fine tooth file until the groove requirements are met.Groove surface should be smooth, no cracks, heavy skin phenomenon, and thoroughly remove burr, slag and oxide.The groove Angle should meet the requirements of the welding process. After the groove processing is finished, pickling and cleaning shall be carried out within 50mm on both sides of the groove.Then cover it with plastic and make a sign.When grinding is used, the operation should be carried out in other places that meet the requirements.Groove processing to meet the requirements, and then move to prefabricated special site.
In the construction of titanium pipe, there are often some small holes such as discharge, discharge, meter source parts, etc. It is difficult to open holes with conventional methods.Before welding the titanium tube, draw the size of the hole and the exact position of the hole on the corresponding titanium tube.Car bed along the edge of the hole center line drill a lot of holes, the denser the better.After drilling, tap the center arc plate of the hole with a copper hammer to detach it, and then process the hole to meet the requirements with special tools such as round file with fine teeth.
All the welded surfaces and the base material surface of each side of the welded parts must be cleaned before welding. At least 50nrn range of non-inductive wire brush should be used to remove impurities. The surface of the titanium tube with oxide layer should be cleaned with oxide film, and then the base material should be cleaned with acetone.The welding wire must be cleaned in the same way. The finished welding parts and wire should be welded immediately. If the time of standing for more than 2h, the above cleaning process should be repeated.At the same time, the operator must wear clean gloves in the welding process, the welding environment should be clean, the wind direction is appropriate, reduce the dust in the air, to protect both sides of the groove and the clean welding wire.