Tank Inspection Robot Product

Overview

A tank inspection robot (sometimes called a mag-crawler) is an autonomous tracked vehicle that climbs the interior walls of large industrial vessels—crude oil tanks, chemical storage, water reservoirs—to perform non-destructive evaluation (NDE). The robot adheres magnetically to ferrous steel surfaces via a bank of [[tank-inspection-robot-magnet-array|controllable electromagnets]], allowing it to navigate vertical walls, domed roofs, and even underside welds. It carries three sensor heads: an [[tank-inspection-robot-ut-probe|ultrasonic thickness probe]] that profiles corrosion and material loss, a [[tank-inspection-robot-camera-thermal|thermal camera]] detecting hot spots and delamination, and a [[tank-inspection-robot-camera-rgb|visual RGB camera]] documenting suspicious defects. All data is streamed topside via an armored [[tank-inspection-robot-umbilical|umbilical tether]] under full operator control, and logged onboard for post-mission analysis.

This approach eliminates expensive confined-space entry, human exposure to H₂S and other hazardous vapors, and subjective inspection bias; the robot produces quantified maps of wall thickness, corrosion morphology, and thermal signatures—critical for regulatory compliance and asset management.

Magnetic adhesion and locomotion

The [[tank-inspection-robot-chassis|crawler chassis]] is a compact tracked vehicle with two [[tank-inspection-robot-motor-drive|independent BLDC drive motors]] spinning left and right [[tank-inspection-robot-track-left|rubber tracks]]. The tracks are embedded with permanent [[neodymium-magnet|magnet bars]] to maximize the contact footprint. The robot also carries four controllable [[tank-inspection-robot-electromagnet-coil|electromagnet coils]] mounted on the belly; the [[tank-inspection-robot-magnet-driver|driver circuit]] modulates coil current in real time, increasing adhesion on smooth surfaces and reducing it on irregular welds or coatings to prevent stalling.

The [[hall-sensor|adhesion feedback sensors]] continuously measure the residual field, allowing the [[tank-inspection-robot-controller|onboard MCU]] to maintain safe contact force—high enough to climb vertical walls (>80 kN), but low enough to release smoothly when the operator powers down the electromagnets for exit. Typical adhesion setup is 100 kN on flat plate, 60 kN climbing vertical, 40 kN on ceiling (gravity-assisted).

Ultrasonic thickness measurement

The [[tank-inspection-robot-ut-probe|UT probe]] is the critical sensor for corrosion assessment. It comprises a phased-array [[tank-inspection-robot-ut-transducer|transducer]] operating at 5 MHz, producing a 1 cm² measurement footprint. The transducer emits a short pulse into the steel wall; the echo returns after reflecting from the back surface. By timing the echo delay, the [[tank-inspection-robot-ut-processor|ultrasonic processor]] calculates wall thickness to ±0.5 mm accuracy. On a corroded tank wall with localized loss, a grid of UT measurements (spaced 25–50 mm) reveals the corrosion pit morphology—depth, lateral extent, and pit-to-pit spacing. ASME and API standards then apply acceptance criteria (e.g., minimum remaining wall, Maximum allowable corrosion rate).

The robot automatically sequences UT scans as it crawls, creating a 2D thickness map of the weld zone, heat-affected zone, and parent plate—exactly what engineers need for fitness-for-service assessment.

Thermal and visual imaging

The [[tank-inspection-robot-camera-thermal|IR camera]] running in parallel detects anomalies invisible to ultrasound. A corrosion pit filled with stagnant liquid shows a different emissivity than intact steel, often appearing cooler (or warmer, depending on external tank surface conditions and sun exposure). A delamination or disbond under a coating will have a distinct thermal signature. The [[tank-inspection-robot-thermal-processor|radiometric processor]] generates a false-color thermal map, making hot/cold zones immediately obvious to the topside operator.

The [[tank-inspection-robot-camera-rgb|RGB camera]] with LED illumination captures high-resolution (12 MP) photos of suspect regions for post-mission expert review. A corroded area might show orange rust staining, or a weld might show cracks—visual confirmation that supplements the quantitative UT and thermal data.

ATEX compliance and safety

Tanks often contain explosive vapors (crude oil produces flammable hydrocarbons; chemical tanks may contain combustible vapors). The [[tank-inspection-robot-atex-housing|ATEX enclosure]] is a sealed aluminum container meeting EU Directive 2014/34/EU Category 3 (Zone 2: occasional/limited exposure to explosive mixtures). The housing is designed to:

1. Limit surface temperature to <135 °C even under motor stall.
2. Provide a flame-path gasket with a calibrated pressure relief valve (2.5 bar) so any internal arc is contained and cooled to sub-ignition conditions.
3. Permit safe replacement of the umbilical and transducer without venting the tank.

The [[tank-inspection-robot-controller|onboard MCU]] monitors motor current; if a motor stalls (stuck on a weld), the current spike triggers an automatic shutdown to prevent overheating.

Tether and topside operation

The [[tank-inspection-robot-umbilical|armored umbilical tether]] is a multi-conductor cable combining:

• Two heavy copper power conductors (2.5 mm² each) delivering 400 W at 48 V to the robot.
• Twisted-pair shielded signal lines (CAN and Ethernet) for command and telemetry.
• A braided stainless steel strength member rated for 500 kg break load.

Tether lengths range from 300–500 m for deep tanks. The [[tank-inspection-robot-winch|topside winch]] is a motorized reel with a [[tank-inspection-robot-slip-ring|slip ring]] coupling power and data across the rotating drum. A [[pressure-sensor|load cell]] continuously monitors tether tension; if it exceeds 200 kg (robot stuck on a weld), the [[tank-inspection-robot-winch-brake|spring brake]] automatically locks and an alarm sounds.

The operator controls the robot from a ruggedized topside panel, joystick-steering the crawler and triggering UT scans or thermal snapshots at key locations. The [[tank-inspection-robot-memory-card|onboard SD card]] simultaneously logs every scan and thermal frame; after extraction, the mission data is transferred to a PC for detailed analysis (pit-depth statistics, corrosion rate trends, regulatory compliance reports).

Typical mission profile

A 5,000 barrel crude tank (10 m diameter × 15 m height) requires inspection of ~500 m² of wall surface. The robot is lowered through the nozzle by the winch, crawls the bottom weld (highest risk for corrosion), then spirals upward, scanning the lower 2 m of wall where accumulated water accelerates loss. A 2-hour mission covers ~50–100 m of vertical wall, producing UT grids, thermal maps, and RGB photos. Three or four missions over a week complete the assessment without shutting down the tank or venting vapor.