Mechanical peeling method of 3PE anti-corrosion coating
At present, in the process of gas pipeline maintenance, the peeling method of 3PE anti-corrosion coating is proposed based on the analysis of the structure and coating process of 3PE anti-corrosion coating [3-4]. The basic idea of peeling off the 3PE anti-corrosion coating of the steel pipe is to create external conditions (such as high temperature heating), destroy the adhesion of the composite structures of the 3PE anti-corrosion coating, and achieve the purpose of peeling the steel pipe.
In the coating process of 3PE anti-corrosion coating, the steel pipe needs to be heated to above 200 ℃. However, if the temperature is too high, the following problems will occur: the curing reaction of the epoxy powder is too fast, the powder is not sufficiently melted, and the film formation is poor, which will reduce the bonding ability with the surface of the steel pipe; before the adhesive is coated, the epoxy resin functional group is excessively consumed. , partially or even completely lose the chemical bonding ability with the adhesive; the sintered epoxy powder layer may be slightly coked, manifested as darkening and yellowing, resulting in unqualified coating peeling inspection. Therefore, when the external temperature is higher than 200 ℃, the 3PE anti-corrosion coating is easier to peel off.
After the gas pipeline is buried, the buried pipeline needs to be cut and modified due to the needs of municipal engineering; or when the gas leakage needs to be repaired, the anti-corrosion layer must be peeled off first, and then other pipeline operations can be carried out. At present, the stripping operation process of 3PE anti-corrosion coating of gas steel pipes is: construction preparation, pipeline pretreatment, heat treatment, stripping of 3PE anti-corrosion coating, and other construction work.
① Construction preparation
Construction preparations mainly include: construction personnel and facilities in place, emergency repair of pipelines, depressurization treatment, operation pit excavation, etc. The construction equipment for peeling off the 3PE anti-corrosion coating mainly includes acetylene gas cutting gun, flat shovel or hand hammer.
② Pipeline pretreatment
Pipeline pretreatment mainly includes: determining the pipe diameter, cleaning the outer surface of the pipe, etc.
③ Heat treatment
Use an acetylene gas torch to heat the pretreated pipe at high temperature. The flame temperature of gas cutting can reach 3000 ℃, and the 3PE anti-corrosion coating applied on the gas pipeline can be melted at above 200 ℃. The adhesion of the coating is destroyed.
④ Peeling of 3PE anti-corrosion coating
Since the adhesion of the heat-treated coating has been destroyed, a mechanical tool such as a flat spatula or a hand hammer can be used to peel the coating from the pipe.
⑤ Other construction work
After peeling off the 3PE anti-corrosion coating, the cutting and modification of the pipeline, welding and the coating of the new anti-corrosion coating should be carried out.
The currently used mechanical manual peeling method is slow and the peeling effect is average. Due to the limitations of construction equipment, the stripping work efficiency is not high, which directly affects the emergency repair efficiency of the gas pipeline. The limitations of construction equipment are mainly reflected in: a. The limitation of the spray flame area of the gas cutting gun leads to a small area of the coating melted by the gas cutting heating treatment; b. The limitation of the fit between tools such as flat shovels or hand hammers and the outer surface of the round pipe Lead to low coating peeling efficiency.
Through the construction site statistics, the peeling time of the 3PE anti-corrosion coating under different pipe diameters and the size of the part to be peeled off was obtained.
Post time: Oct-13-2022