Sewer Inspection Crawler Product

Overview

Municipalities are required to know the condition of sewer mains they cannot walk through, and excavating to look is absurdly expensive. A sewer inspection crawler answers this: a small, sealed Tractor Unit is lowered through a manhole, drives along the pipe invert, and streams video from a Pan/Tilt Camera Head up its Tether Cable to an operator at the Control Unit on the surface. A survey of a few hundred meters of main takes an hour or two and produces a coded condition report that drives relining and replacement decisions.

The crawler must work submerged in an environment of grit, grease, hydrogen sulfide, and occasional surcharge flow. Everything about the design follows from that.

The tractor

The Pressure Housing is the central trick: rather than relying on seals alone to keep water out, the housing is charged with dry air or nitrogen to about 0.5 bar above ambient. Any seal imperfection leaks gas outward instead of letting sewage in, and the onboard Pressure Sensor warns the operator the moment housing pressure decays — before the electronics get wet. All shaft penetrations run through an Oil Seal and the housing joints carry an O-Ring Set.

Each side of the tractor is driven by a Drive Module: a Servo Motor through two Helical Gear Pair reduction stages in a sealed Gearbox Housing, with an Encoder for speed control. Skid steering between the two modules turns the vehicle in the pipe. The Wheel Sets are the operator's pipe-diameter adaptation: small rubber wheels for DN150, large studded or pneumatic wheels for DN600–DN800, all on quick-change hubs with a Fastener Set, chosen so the camera sits near the pipe centerline. A Inclinometer logs grade continuously; plotted against distance it reveals sags and bellies where debris and water pool.

Camera and lighting

The Camera Core pairs a low-light CMOS Image Sensor with a 10× zoom Lens Assembly, because the standard inspection method is to stop at each defect or lateral connection, pan and tilt onto it, and zoom in. The Pan Drive rotates the head a continuous 360° and the Tilt Drive elevates ±135°, both through self-locking worm gearing so the view holds without power. The optical port is a Sapphire Window — glass and polycarbonate scratch into uselessness within weeks in this service.

Illumination comes from the Lighting Module: two LED Array banks behind sealed Light Windows, dimmed by the LED Driver Board so a DN150 pipe is not blown out while a DN800 pipe is still adequately lit.

Tether and reel

The tether is power line, network, and recovery rope in one jacket. A Wire Bundle of power conductors and data pairs surrounds a Kevlar Strength Member rated for several kilonewtons, inside an abrasion-resistant Cable Jacket. When a crawler dies or wedges behind a dropped joint 200 m in, the recovery plan is simple: winch it out by the tether.

The Cable Reel manages up to 300 m of this cable. A Servo Motor drives the Reel Drum in tension-control mode, paying out as the crawler advances and keeping slack out of the pipe; the Level Wind traverses on a Ball Screw synced by Drive Belt to the drum so wraps lie evenly. An Encoder on the reel counts payout, which becomes the distance figure stamped on every defect observation. A Slip Ring carries power and video across the rotating joint to the console.

The console and the survey product

At the surface, the Controller Board digitizes the video on a Compute SoC Module, overlays distance, date, and grade, and records to removable storage, while its Microcontroller closes the loop between Control Joystick, crawler drive, and reel tension. The operator watches the LCD Panel and codes each observation — cracks, fractures, root intrusion, infiltration, displaced joints, protruding laterals — against EN 13508-2 in Europe or NASSCO PACP in North America. The deliverable is not the video; it is the coded, distance-referenced defect database that lets an engineer rank kilometres of network by structural and service condition and decide what gets relined this budget year.

Operationally, crews gas-test the manhole before deployment, jet-clean heavily silted lines first, and survey downstream-to-upstream where possible so flow carries stirred sediment away from the camera. A two-person crew typically inspects 300–500 m of main per day.