Pipe Inspection Methodology

Piping systems are used in various residential and commercial applications. Pipes are used to transport material from one location to another or acting as a housing to protect communication or power cables. These pipes come in a variety of shapes, sizes and materials. They consist of straight runs installed vertically, horizontally and a combination of both. Within these runs, you may find various elbows, tees, reducers and other inter-connect components that help redirect the piping from one location to another.

When a piping system fail, it's often due to blockage caused by a foreign object or from the formation of corrosion of the inner pipe wall lining. In some situations, a failure in the pipe wall has created a penetration where foreign objects enter into the piping system or where the internal material escapes. In either cases, identifying and locating the blockage or breach can be a simple to impossible task for the maintenance personnel.

Inspecting pipes can be performed as part of a pre-service or in-service program. Piping materials, sizes, and configurations can dictate the type of inspection technology utilized. For this discussion, we will attempt to outline the more generic and leave specific applications to another document in the Prometheus collection.

Visual examination is the first and most straightforward non-destructive examination method when inspecting piping.

Technologies that are available include manual push systems for shorter runs to more advanced robotics for longer and complicated piping configurations. Which system is preferred and is the best for my piping application?

Well that depends on a number of underlying factors pertaining to pipe size and configuration.

Manual Systems

For short run applications (<200ft[70m] and diameters <2in[50mm]) a manual push system can be simple and straightforward. These technologies include camera head units attached to fiberglass push rod systems where the operator "pushes" the system. For very small applications such as instrumentation lines (0.50in[10mm]) borescopes or fiberscopes can be employed. Their operating distances are usually less than 15ft[5m] and are limited in control.

For longer run applications such as a storm sewer or where both ends of the piping system can be opened at the same time, a camera head unit can be attached a jetter nozzle unit and the water propulsion from the jetter head propels it to the end location. Once the jetter has reached a certain distance, the inspection can be performed as the unit is pulled back to the original access point.
Robotic Systems

For longer and more advanced applications, robotic systems are ideal due to their flexibility. These systems can be tethered or untethered. See our section under tethered or untethered for a more detailed discussion on the pros and cons of this type of remote application and how it can benefit your situation.

Robot inspection systems encompass an inspection camera, with a fixed or pan and tilt, delivered by some drive system. These drive systems consist of:


Just like manual systems, their exist pros and cons to each type of design. For horizontal and limited angular pipe runs, wheel, crawler and walking type systems do well and are often faster in operation. For vertical type runs, the other design types offer a positive engagement within the pipe walls that allow the robot system to maintain its' position as it travels from one location to another without the ill effects of gravity.

Hurdles

A common hurdle facing all inspection applications is the ability to leave the intended piping system intact without introducing another foreign object, the inspection device in the system. For most applications, the use of a tethered system in an event a device failure is encountered allows the operator the flexibility to manually pull the system out of the piping system. In addition to emergency retrieval, the operator's ability to navigate or avoid obstructions found within the pipes is also important in preventing failures. The ability to travel-to is just as important as the ability to travel-from.

These include difficult to reach areas such as multiple elbows. For tethered systems, the presence or navigation of multiple elbows can pose several potential problems. Power and traction are two limiting factors when utilizing drive-type systems to combat friction encountered by cable drag. The inspection device must have enough power and traction to drag its' cable along the pipe. Whereas in elbows, the friction encountered for each elbow is exponential and often a pipe crawler dragging its' cable beyond 3-4 elbows in a single run is virtually impossible. To combat this, designers and manufacturers have resorted to non-tethered applications or simply avoiding them altogether by creating access ports beyond the elbow areas.

Related items

RedScope Enterprises, Inc. © 2017. All rights reserved.

RedScope is a nondestructive technology service provider, supporting asset and component owners with traditional and innovative technologies in their maintenance programs.