As U.S. infrastructure rapidly ages, organizations have shifted focus to assets that are often out of sight and out of mind – buried linear assets. These pipes and tunnels are among some of the oldest structures in our nation, dating back to the 1800s, and have fallen into disrepair due to neglect, increased or unintended use, and many other variables. Many system owners have implemented routine condition assessments using CCTV and defect rating systems to determine the deterioration and deficiencies of these pipes. These improved inspection methods, specifically those for large diameter pipe, offer clearer data and solutions.
Not all pipes are alike
One of the key distinctions for linear assets is diameter (pipe size). Estimates place 75% or more of the pipes in a conveyance system to be 12 inches or less, resulting in an abundance of pipe to be reasonably accessible and capable of inspection with standard equipment. But what about remaining 25% of systems? What exactly is a large-diameter pipe, and how do you inspect it?
Large diameter pipe has been classified as anything greater than 15 inches in diameter. For many system owners, the classification of large-diameter pipe can vary. For example, not every system requires 60 inch pipes, but in some metropolitan areas, 60 inch pipe may not be adequate. Typically, these larger lines are classified as trunk or interceptor pipes. These linear assets are designed to convey flow from smaller lines that feed it, to one central location. As the pipes get bigger, they are required to maintain more hydraulic capacity. This often results in higher and faster flows, as well as other hazardous conditions, such as sediment buildup and hydrogen sulfide gas (H2S). Performing an assessment on the condition requires nothing but the strongest and most capable machinery for navigating and collecting this inspection information.
RedZone’s Responder to the rescue
Enter Responder. Weighing in at over 700lbs, this hydraulic-tracked, independently-steered, robotic crawler was designed for handling varying conditions and is capable of inspecting 36 inch to 240 inch diameter pipes, and larger. Due to the incredibly capable cable and winch system, it can successfully traverse 4,000 linear feet of distance in one deployment. This ensures reduced traffic control and public disruption from inspection activities.
Equipped with a 1080p HD lens, Responder allows for a full 360-degree view of the interior of the pipeline, complete with pan/tilt/zoom navigation. While CCTV is the backbone of inspection, it can’t provide the full picture, like Responder can.
Multi-sensor inspection for healthier pipes
As noted earlier, we are typically inspecting lines that have flow. CCTV inspections beneath wastewater don’t provide the clearest image quality available. Above the flow, the unit can zoom for long distances, but may not offer a clear enough image to ascertain how much material has deteriorated from the pipe walls. Responder’s multi-sensor inspection (MSI) provides quantifiable results utilizing sonar, LiDAR, and gas detection.
Sonar
Sonar uses audio pulses below the flow to detect the echo, or return of that audio, off of a surface. The time taken from emitting the pulse to receiving the echo provides a distance measurement. When these readings are analyzed and compared to the expected diameter of the pipeline, debris measurements such as depth and volume, can be calculated. This not only informs hydraulic capacity loss, but also cleaning regimen, including how much debris may need to be removed prior to a rehabilitation project.
LiDAR
The LiDAR sensor works via a time-of-flight principle (ToF), and similar to sonar, measures the return of a light pulse off of a surface. This produces detailed, high-accuracy, three-dimensional (3D) scans of the interior wall of the pipe, and allows for comprehensive reporting of the internal condition. Cross-sections of the laser return are compared to the expected diameter. This enables Responder to gather corrosion (where the cross-section is larger than the expected diameter) or buildup (where the cross-section is smaller than the expected diameter) measurements. Additionally, in flexible materials this can be used to measure the ovality of the pipeline.
Analyzing the Data
From the Responder’s 3D scans, full-detail models of the entire pipe, from access point to access point, can be constructed and utilized for determining alignment. Because these pipes are below ground, it can be difficult to determine where a pipe might bend or curve in relation to above-ground infrastructure, such as streets or buildings. In rehabilitation design, this alignment can be used for measuring the curvature of the bends. It can also be used for sliplining and mandrel testing.
Sliplining is a common method for extending the useful life of a linear asset. The design process involves not only determining the current internal diameter (cross-section) of the host pipe, but what lengths of the new pipe can fit around the bends. Typically this is done by dragging or pushing a mandrel (a manufactured piece of steel, measured to a specific diameter to simulate replacement pipe) through the host pipe. By performing this step virtually, via LiDAR scans, countless dollars can be saved and the potential for damage to the host pipe is significantly decreased.
Large diameter pipelines are not only complicated infrastructure, but can be complicated to assess. The expertise and advanced technology of the Responder unit can streamline the work, meet the needs of a system owner, and remove some of the undue stress and burden of asset management.
Read more about Responder and how RedZone Robotics is using this robot to inspect large diameter pipe.
