Shield machines are core heavy-duty equipment for underground tunneling in tunnel construction, undertaking tunneling tasks for urban subways, river-crossing tunnels, utility tunnels and other major underground projects. The whole machine features sophisticated structure and highly integrated electro-hydraulic systems. The hydraulic system serves as the "power heart" of the shield machine, powering all key actuators including thrust cylinders, articulated cylinders, cutterhead drive motors, segment erectors and posture adjustment mechanisms. The stability of the hydraulic system, cleanliness of hydraulic oil and reliability of components directly determine tunneling efficiency, construction safety and overall service life of the shield machine.

Engineering data and equipment failure statistics show that more than 90% of common hydraulic faults such as sluggish movement, clogged proportional and servo valves, abnormal oil temperature, oil seal leakage and insufficient thrust stem from substandard cleanliness inside hydraulic pipes. Contaminants remaining on pipe inner walls enter the hydraulic circulation loop. Therefore, pipe cleaning is an indispensable quality control procedure throughout the full lifecycle of shield machines, including manufacturing, factory commissioning, on-site maintenance and overhaul.

Most hydraulic pipes for shield machines are made of high-strength precision seamless steel tubes with highly complex layouts, featuring numerous 90° elbows, curved bends, tee branches, reducers and staggered long & short pipelines. During cutting, bending, welding, pipe end grinding and pre-assembly, pipe inner walls continuously accumulate metal iron filings, high-temperature oxide scale, welding slag, rolling anti-rust oil and processing dust. Many tiny contaminants are invisible to the naked eye and stick firmly to the pipe surface. After assembly and oil filling, these impurities circulate continuously with hydraulic oil, invading high-precision hydraulic components such as servo valves, proportional valves, hydraulic pumps and motors. This leads to spool wear, blocked orifices and hydraulic jamming. In mild cases, control accuracy decreases and tunneling posture drifts. In severe cases, sudden shutdowns occur, leaving the tunnel face exposed and triggering major safety risks, accompanied by high costs for valve replacement, on-site disassembly and project delays.

For a long time, shield equipment manufacturers and tunnel maintenance teams have been plagued by inherent drawbacks of conventional pipe cleaning processes. Traditional cleaning methods include water circulation flushing, chemical oil washing, manual wire brushing and ordinary compressed air purging, all of which perform poorly on complex shield machine pipelines:

1. Water flushing: Limited fluid shear force fails to strip cured oil sludge and hardened oxide scale. Water and fine debris easily get trapped in elbows and tees. Residual moisture causes pipe rust and generates new metal contaminants.
2. Chemical cleaning: While effective for degreasing, cleaning agents corrode tube walls and leave hard-to-eliminate residues that re-contaminate hydraulic oil. Waste liquid treatment brings high costs and heavy environmental pressure, failing to meet cleanliness standards for heavy-duty high-end equipment.
3. Manual brushing: Only works for short straight pipes. Brushes cannot pass through long multi-bend pipelines, resulting in ultra-low efficiency and inconsistent quality relying entirely on worker experience, with no standardized control.
4. Ordinary air blowing: Only blows away loose dust, unable to scrape off stubborn oil sludge and scale, so the cleaning result cannot meet factory inspection requirements for shield machines.

As manufacturing standards for shield machinery keep upgrading and hydraulic cleanliness requirements become stricter, traditional rough cleaning can no longer satisfy precision hydraulic system control. The industry urgently demands a dry, residue-free, verifiable and standardized pipe cleaning solution. The Aoboshi AM-2 FKIT tube cleaning gun kit, equipped with high-density foam projectiles and an intelligent projectile counting & collecting device, is tailor-made for hydraulic pipe cleaning on shield machines, large construction machinery and high-end fluid equipment. It effectively solves industry pain points including incomplete cleaning, dead zone residue, uncontrollable quality, low efficiency and secondary pollution, and has become the preferred choice for prefabricated pipe pretreatment, factory acceptance cleaning and on-site maintenance of shield machine pipelines.

The AM-2 FKIT kit adopts dry pneumatic physical cleaning, using regular workshop compressed air as power. No extra water or power supply is required, and no chemical agents are added during the whole process, making it eco-friendly and ideal for mass pipe processing in manufacturing workshops. The core cleaning medium is customized high-density polyurethane foam projectiles with strong elasticity, excellent wear resistance and high toughness, so they rarely break during operation. The outer diameter of each projectile is precisely sized slightly larger than the pipe inner diameter. Driven by compressed air, the projectile moves forward while tightly clinging to the tube wall. Through combined physical squeezing, friction and scraping, it peels off and encapsulates heavy oil sludge, iron filings, welding slag and oxide scale in one pass, carrying all debris out of the pipe outlet.

Compared with traditional cleaning, the biggest advantage of foam projectiles is full-coverage cleaning without dead zones. Faced with 90° elbows, curved bends, tees and reducers commonly found on shield machine hydraulic lines, the flexible foam projectile navigates smoothly without jamming, delivering 360° deep cleaning across the entire pipe and solving the long-standing difficulty of cleaning irregular bent pipelines. Operation is simple and does not require certified technicians. Operators can work independently after short training, greatly cutting labor costs and long-term training expenses.

To tackle the biggest pain point of conventional cleaning — unverifiable results, undetected missed cleaning and non-traceable quality — this kit is fitted with a dedicated projectile collection counter to standardize workflows, visualize results and record all cleaning data. Every time a foam projectile is successfully fired, the counter automatically records the quantity for single pipes and whole batches. Operators can cross-check against the construction list to avoid human errors such as missed cleaning, incomplete cleaning and repeated cleaning. Every pipe’s cleaning record is traceable, fully complying with factory inspection and project acceptance standards for shield machines.

This dry physical cleaning method leaves no residual water or chemical agents inside pipes after operation. All contaminants are collected together with foam projectiles. Pipes can be immediately sealed to prevent workshop dust from re-entering and causing secondary pollution, maintaining long-term pipe cleanliness. Unlike water washing, this process fundamentally eliminates pipe rust and hydraulic oil emulsification caused by water ingress, stabilizing hydraulic system performance and reducing post-commissioning failure rates and maintenance costs for shield machines.

The whole set adopts a lightweight portable case design for flexible transportation. It can be deployed in production workshops for batch prefabricated pipe cleaning, or transported to tunnel construction sites for pipe decontamination during shield machine overhaul and equipment refurbishment, delivering strong adaptability across multiple working scenarios.

Against the backdrop of intelligent manufacturing for shield equipment, pipe cleanliness has become a critical indicator of manufacturing precision and product quality. Many manufacturers focus heavily on mainframes, cutterheads and main drives yet overlook hydraulic pipe cleaning, which repeatedly leads to hydraulic system failures. Featuring dry physical cleaning, zero residue, full coverage and verifiable counting, the Aoboshi AM-2 FKIT cleaning kit makes up for the shortcomings of traditional processes and helps manufacturers standardize, streamline and upgrade pipe cleaning procedures. It meets strict cleanliness requirements for new machine delivery as well as periodic maintenance and overhaul decontamination on construction sites, economically avoiding hydraulic jamming, unplanned downtime and rework losses caused by pipe contaminants.

At present, the AM-2 FKIT pipe cleaning solution has been widely adopted in shield machine manufacturing, construction machinery, rail transit, ship hydraulic systems, nuclear fluid pipelines and high-precision equipment production. With reliable cleaning performance, high operation efficiency and standardized quality verification, this dry foam projectile pipe cleaning technology has become a mainstream solution for high-precision hydraulic pipe cleaning, safeguarding the safe, stable and long-term operation of large underground engineering equipment.