Manhole & Vertical Asset Inspection Systems

Manholes serve as the primary vertical junction nodes connecting underground pipe networks. Subjected to dynamic surface traffic loads, severe hydrogen sulfide (( H_2 S)) acid corrosion, and groundwater infiltration through brick chimney rings, vertical manhole structures require regular condition assessment. Modern remote manhole inspection technologies, ranging from high-magnification optical zoom pole cameras to automated 360-degree photogrammetric scanners, enable rapid, street-level structural evaluations while reducing confined-space entry hazards.

Reducing Confined Space Entry Hazards in Vertical Inspection

Traditional manhole inspection required personnel to physically descend vertical shafts wearing safety tripods, retrieval harnesses, and atmospheric gas monitors. Confined space entry is labor-intensive, hazardous, and logistically demanding due to toxic gas exposure (( H_2 S, CO, CH_4)), oxygen deficiency, and sudden storm surcharges. Remote manhole inspection systems can reduce or, for some assessment tasks, avoid the need for personnel to enter the confined space. Entry requirements and safety procedures still depend on the actual work scope, site conditions, and applicable occupational safety regulations.

The 2 Primary Vertical Inspection Technology Classes

1. High-Magnification Optical Zoom Pole Cameras (Level 1 MACP Screening)

• System Design: High-definition video camera head with 10x to 30x+ optical zoom lenses and high-lumen LED spotlights mounted on an ultra-light telescoping carbon fiber pole (extending 15 to 30+ feet).
• Operational Role: Rapid city-wide condition screening. A single operator standing safely at street level can inspect 40 to 80 manholes per day, visually evaluating cover frames, chimney brick adjustment rings, corbels, wall barrels, and benching channels.

2. 360-Degree Spherical Photogrammetric Scanners (Level 2 MACP Detailed Assessment)

• System Design: Automated capsule incorporating dual ultra-wide fisheye optical lenses (185° Field of View each) and integrated high-density laser rangefinders lowered smoothly on an automated motorized winch.
• Operational Deliverable: Specialized photogrammetric algorithms unroll spherical images into flat, geometrically unfolded 2D orthomosaic wall maps and dense 3D point clouds (accurate to ±1 mm), enabling quantitative engineering measurements of crack widths, joint offsets, and structural degradation for CIPP manhole lining design.

Direct Technology Comparison Matrix

Key Structural Defects Assessed in NASSCO MACP

Vertical manhole evaluations focus on critical structural and inflow points:

1. Chimney Inflow & Grade Ring Displacement: Infiltration entering between street castings and adjustment rings.
2. Biogenic Sulfuric Acid Corrosion: Concrete matrix loss and exposed structural rebar caused by hydrogen sulfide oxidation.
3. Invert Benching Scour & Blockages: Broken concrete troughs and heavy silt accumulation impeding hydraulic flow.