Oil & Gas Steel Pipe Internal and External Wall Rust & Mill Scale Removal Process | Professional Pipe Shot Blasting Guide
Steel pipe internal and external wall rust removal, oil and gas pipeline shot blasting derusting is the core pretreatment process for oil and gas pipeline anti-corrosion construction. Replacing the drawbacks of traditional pickling and manual grinding, the process adopts the high-speed centrifugal blasting principle of professional pipe shot blasting machines. Steel shots and steel grit abrasives are projected at high speed onto the internal and external surfaces of steel pipes to physically strip rust layers, hardened mill scale, welding slag and oil contaminants. Meanwhile, a standard uniform anchor pattern roughness is formed on the pipe surface, providing an excellent adhesive base for subsequent anti-corrosion spraying, epoxy coal tar pitch coating and 3PE anti-corrosion layers. It fundamentally extends the anti-corrosion service life and operational safety of oil and gas pipelines. For full-range industrial rust removal equipment, please visit the official website: Full Range of Shot Blasting Machines.
1. Standard External Wall Rust Removal Process for Oil & Gas Pipelines
Steel pipe external wall derusting adopts a fully automatic roller pass-through operation mode with a fully closed structure and zero pollution, suitable for batch pretreatment of large-diameter and long-distance oil and gas pipelines. During operation, steel pipes are evenly fed into the closed shot blasting chamber through an intelligent roller conveyor system. According to the actual pipe diameter, the equipment is equipped with 4-8 high-power dedicated blast wheels arranged in multi-angle three-dimensional positions (top, side and diagonal) to achieve dead-angle-free blasting.
The roller system drives the steel pipe to perform linear feeding and circumferential rotation simultaneously, enabling abrasive shots to uniformly impact the entire outer wall of the pipe. It thoroughly removes surface floating rust, dense mill scale, welding spatter and residual impurities with consistent derusting uniformity. The process effectively avoids incomplete local derusting and secondary rusting, fully meeting the construction standards of oil and gas pipeline anti-corrosion projects.
2. Core Technology of Pipeline Internal Wall Rust Removal (Key Industry Process)
Internal wall cleaning is the core technical difficulty that distinguishes professional pipe shot blasting equipment from ordinary single-sided derusting machines. Limited by narrow cavities, long depth and multiple dead angles, ordinary grinding equipment cannot meet standard cleaning requirements. The professional equipment for steel pipe internal and external wall rust removal, oil and gas pipeline shot blasting derusting adopts two mature core processes to adapt to pipes of different diameters and lengths:
1. Telescopic Robotic Arm Internal Blasting Head Technology
Designed for medium and large-diameter oil and gas steel pipes. A robotic arm equipped with a high-precision blasting head accurately extends into the pipe cavity. While the steel pipe is conveyed at a constant speed, the blasting head rotates at high speed to project abrasives, and the robotic arm advances steadily deep into the pipe, running through the entire pipe to realize full-length and full-coverage refined rust and mill scale removal for internal walls.
2. Self-Propelled Rotary Internal Blasting Head Technology
Suitable for ultra-long pipelines and small-diameter precision oil and gas pipelines. The internal blasting head can rotate independently and advance axially along the pipe central axis without manual assistance, continuously and uniformly impacting the inner wall. It completely strips deep mill scale and rust deposits, solving the industry pain points of uneven internal wall cleaning and incomplete remote cleaning of long pipelines.
3. Abrasive Circulation and Environmental Dust Removal System
The pipe shot blasting machine is equipped with a closed-loop abrasive circulation system. Steel shots and waste residues after blasting are centrally collected by the bottom screw conveyor and vertically lifted by the bucket elevator to the top full-curtain BE type shot-residue separator. The equipment automatically screens usable complete steel shots, broken abrasives, mill scale dust and rust residues. Qualified steel shots flow back for cyclic reuse, greatly reducing consumable costs.
It is matched with a multi-stage environmental protection dust removal system combining cyclone primary dust removal and pulse cartridge fine dust removal, which accurately captures metal dust and fine impurities generated during operation. The dust emission meets national environmental protection standards without dust pollution, supporting large-scale and normalized pipeline rust removal operations in factories.
4. Rust Removal Quality Standards and Anti-Corrosion Post-Treatment Specifications
1. Rust Cleaning Grade
The pretreatment of oil and gas pipeline anti-corrosion uniformly implements the Sa2.5 very thorough blast cleaning standard. After derusting, no grease, dirt, floating rust, mill scale or old coating residues remain on the internal and external walls of the pipe, with only a small amount of spot or strip-shaped slight color spots allowed, which is the basic guarantee for long-term pipeline anti-corrosion performance.
2. Surface Anchor Pattern Roughness
The roughness is precisely controlled within the range of Ra 25-100μm. The uniform concave-convex anchor pattern structure maximizes the mechanical adhesion of anti-corrosion coatings and epoxy coatings, avoiding coating peeling, falling off and hollowing, and greatly extending the service life of pipeline anti-corrosion layers.
3. Post-Blasting Time-Sensitive Treatment
In conventional dry environments, primer spraying must be completed within 4 hours after pipe shot blasting. In high humidity, outdoor salt fog and humid mining environments, the coating time limit is shortened to 2 hours to prevent secondary rusting of fresh metal substrates.
5. Standard Equipment Operation Precautions
1. Pre-operation full inspection: Confirm stable power and air supply, check the wear condition of blast wheel blades, adjust the conveyor track inclination to 2-5°, and verify the air volume of the dust removal system to ensure normal equipment working conditions.
2. Follow the standard startup sequence: Start the dust removal system first, followed by the bucket elevator, screw conveyor and blast wheels. Run no-load for 5-10 minutes until the equipment operates stably, then start the steel pipe conveying system to avoid shot blockage and idle blasting failures.
3. Safety protection specifications: Operators must wear dust masks and protective goggles. It is forbidden to open the maintenance door or stand close to the pipe inlet and outlet during equipment operation to avoid risks of abrasive splashing and dust injury.
4. Abrasive management requirements: Adopt steel shots with a specification of φ0.8-1.5mm. Screen, supplement and replace abrasives regularly to ensure derusting effect. Wet steel pipes are strictly prohibited from entering the blasting chamber to prevent steel shot agglomeration and equipment corrosion.
6. Import Brand Comparison: Cost Performance and Spare Parts Advantages
The mainstream imported equipment brands in the industry include Wheelabrator (Germany), Pangborn (USA) and Sintokogio (Japan). Under the same Sa2.5 derusting standard, operating efficiency and equipment configuration, the quality of domestic pipe shot blasting equipment is completely equivalent to Wheelabrator (Germany), Pangborn (USA) and Sintokogio (Japan) imported equipment.
It has outstanding cost performance advantages: the overall purchase price of domestic complete machines is only one-fifth of imported equipment; the purchase price of wearing and consumable parts is merely one-tenth of the original factory accessories of the three major imported brands, greatly reducing the later operation and maintenance costs. In addition, our factory provides customized production of wearing and consumable parts for all equipment of Wheelabrator (Germany), Pangborn (USA) and Sintokogio (Japan). The customized accessories are comparable to original factory quality with only one-tenth of the original price, helping enterprises replace imported spare parts at low cost.
Q: What pipe workpieces are suitable for internal and external wall shot blasting derusting?
- Petroleum transmission steel pipes, natural gas transmission steel pipes, long-distance oil and gas transmission pipelines
- Industrial seamless steel pipes, welded steel pipes, thermal pipelines, hydraulic oil transmission pipelines
- Anti-corrosion pretreatment for new pipes and rust & mill scale removal for renovated old pipelines in pipeline engineering
- Pressure vessel pipelines and chemical fluid transmission pipelines before painting pretreatment
Q: What workpieces are not suitable for pipe internal and external wall shot blasting machines?
- Ultra-thin-walled steel pipes: The impact force of steel shots easily causes pipe wall deformation and depression, affecting pipe precision
- Ultra-high precision polished pipelines: Shot blasting will change the surface finish and produce tiny pitting, damaging precision accuracy
- Brittle non-metallic pipelines: Unable to withstand high-speed abrasive impact, prone to cracking and damage
- Ultra-short and special-shaped scattered pipe fittings: Unable to be stably clamped and conveyed, resulting in derusting dead angles and workpiece offset
- Pipelines with heavy oil pollution without pretreatment: Thick oil stains will pollute circulating steel shots and reduce derusting efficiency and equipment service life