Small steel pipe inner wall sandblasting machine

Small steel pipe inner wall sandblasting machine
Core precautions for the inner wall sandblasting process of small diameter steel pipes (DN200 and below, especially 30-200mm small diameters)
For small diameter steel pipes, the inner wall space is narrow, it is difficult to position the gun head centrally, and there are problems such as sand blockage / missed sanding / abrasive embedding. The entire process from selecting the inner wall sandblasting machine for small diameters, parameter control, operation norms, and risk avoidance needs to be strictly controlled:
1. Selection and pre-preparation of the inner wall sandblasting machine (core prerequisite, choosing the wrong equipment will lead to failure)
Special equipment matching
It is necessary to select a dedicated inner wall sandblasting gun for small diameters: select the corresponding model according to the pipe diameter, such as SY-50 for 35-75mm diameters, SY-100 for 50-200mm diameters.
Nozzle must be made of tungsten steel (the wear resistance is 3-5 times that of boron carbide), and a φ6-8mm small diameter nozzle is used for small diameter pipes to avoid the gun head getting stuck in the pipe.
Air source configuration: the air compressor's exhaust volume must be ≥ 6m³/min (single gun), and a three-stage oil-water separator (filter accuracy ≤ 0.1μm) must be equipped - water in the compressed air will cause the abrasive to clog and the gun head to be blocked, which is the most common failure source for small diameter sandblasting.
Workpiece and abrasive pre-treatment
Steel pipe pre-cleaning: first, manually remove large pieces of welding slag, oxide scale, and debris from the pipe to avoid blocking the gun head or scratching the inner wall during sandblasting.
Abrasive control: select 0.3-0.8mm fine-grained abrasive (steel balls / brown corundum are preferred, and large particles > 1mm are prohibited), the abrasive must be dried and sieved to remove dust and debris - the inner space of small diameter pipes is limited, and 100% large particles or damp abrasive will cause the gun head to be blocked.
2. Precise control of the inner wall sandblasting machine process parameters
Working pressure: 0.5-0.6MPa (actual pressure at the nozzle is 0.35-0.5MPa).
Gun head moving speed: 0.5-1m/min (uniform backward movement), too fast will cause strip-like missed sanding, too slow will cause local excessive sanding and pitting.
Gun angle: the angle between the sanding head and the inner wall of the pipe is 15-30°: too large an angle will cause excessive sanding on one side, too small an angle will cause blind areas for cleaning.
Steel pipe rotation speed (rotary operation): 10-20r/min, combined with the axial movement of the gun head, ensure 360° uniform coverage, avoid spiral-like missed sanding bands.
3. Operating norms for the inner wall sandblasting machine
Switching sequence (key to preventing sand blockage)
Start-up: first, stabilize the compressed air pressure → then open the sand valve (uniform output of abrasive);
Shutdown: first, close the sand valve → keep the air supply for 30 seconds → then stop the air: thoroughly blow out the residual abrasive, dust, and debris in the gun head, nozzle, and inner pipe to avoid the residual sand from clogging and blocking.
Gun head operation requirements
Do not pause halfway: the gun head remaining at the same position for more than 3 seconds will cause local excessive sanding and thin-walled pipe perforation.
Post-treatment must be done
Immediately after sandblasting: ① use 0.6MPa compressed air to fully blow the pipe; ② use an endoscope to inspect the pipe corners to confirm no residual sand before transferring to the coating process.
Four. Quality acceptance and common problem avoidance
Acceptance standards
Cleanliness: reach Sa2.5 level, no visible oxide scale, rust, or welding slag on the inner wall, uniform metal color exposure, no strip-like missed sanding;
Surface roughness: Ra25-50μm, no abrasive embedding, no pitting, no thin-walled deformation;
Cleanliness: no residual abrasive, dust in the pipe, does not affect subsequent coating or medium transportation.
Common problem avoidance: frequently occurring issues
Blocked gun: the root cause is damp abrasive / large particles / incorrect shutdown sequence, strictly follow abrasive drying and shutdown norms to avoid 99% of problems;
Missed sanding: too fast gun head movement during operation;
Abrasive Embedding: Excessive pressure and oversized abrasive particles. For thin-walled pipes, the pressure drops to 0.4-0.5 MPa, and the abrasive particles should not exceed 0.8mm.
Internal Wall Scratches: The nozzle sticks to the pipe wall, and there are foreign objects inside the pipe. Thorough pre-treatment is necessary to clean the pipe thoroughly and ensure the nozzle is centered.
V. Safety and Environmental Mandatory Requirements
Personnel Protection: Dust from small-diameter pipe sandblasting is highly likely to accumulate inside the pipe. Operators must wear positive pressure respirators and are strictly prohibited from using ordinary masks; standing directly in front of the pipe opening is forbidden to avoid sand particles rebounding and injuring people.
Environmental Control: A pipe internal ventilation and dust removal system must be equipped (with a wind volume of ≥ 5000 m³/h). A dust removal hose should be connected to the sandblasting end, and the other end should be sealed to prevent unorganized dust emission; abrasive particles should be collected centrally and must not be discarded randomly.
Equipment Safety: The pressure gauge and safety valve of the air compressor should be calibrated monthly, and the sandblasting hose should be inspected for wear regularly to avoid high-pressure burst and injury.