Tilt Measurement

Tilt or inclination measurement of pipe lines is mainly used to find depressions or backfalls in the pipe. Inclination measurement provides a diagram that is able to visualize the inclination course within a pipe section. The inclination diagram is calculated exclusively on the basis of the raw data gathered by the CCTV camera. Its purpose is to clearly show any relevant difference to the ideal inclination course of the pipe.
The tilt measurement process cannot define the height difference between the start and end point of the section, these values would normally be measured using a dumpy level.

Principle

The tilt measurement instrument consists of an electronic spirit level, this spirit level provides continuous tilt values in digital form while the camera tractor is moving or the counter is counting.
The axle distance of the vehicle wheels or the support points of the wheels correspond to the length of the spirit level. During the CCTV pipe inspection the spirit level is moved through the pipe and tilt values are collected continuously.
The captured values are averaged over a length of 10cm i.e. a tilt value is being calculated for every 10cm portion.
The end result is a record consisting of lengths and corresponding tilt values. This record represents the inclination of the pipe. The inclination of the whole pipe is averaged across all the captured tilt values. This principle remains similar across different software and hardware brands but may differ in some areas.

Inclination graph

Accuracy

The support points of the spirit level depend on the condition of the camera system in the pipe and are, therefore, affected by its design.
The following items can cause measuring inaccuracies:

• Condition and design of the camera system
• Accuracy of calibration
• Condition of the wheels (worn, different diameters)
• Speed of the camera vehicle
• Consistency of speed when reversing
• Wheel and axle distance (length of the spirit level)
• Direction of examination
• Condition of the pipe, sand deposits or obstructions

Resources:

• Ibak Helmut Hunger GmbH & Co. KG
• Ipek GmbH