Pipe installation – reduce the risk!

Concrete pipe can be properly manufactured and well designed, yet the integrity of the pipeline can be affected when it is subject to in situ forces during and after installation.

The installation of reinforced concrete pipe requires the material to be placed in accordance to design specification and typical pipe laying techniques. If this is neglected the pipeline can be vulnerable over its recommended design and service life. Therefore, it is essential to monitor the condition of the pipes over their lifetime, using technologies such as closed circuit television (CCTV).

Once a pipe is in service it is not uncommon for the loading conditions above ground to change. An increase in load due to changes in design during construction can cause the strength of the pipe to be put under stress.

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Sound installation of reinforced concrete pipe, in conjunction with design in accordance with AS/NZS 4058 and AS/NZS 3725, will provide the asset owner a pipeline that may be in service for over 100 years.

Installed pipe inspection

Engineers, asset managers and asset owners should all be concerned with the ongoing monitoring of buried concrete pipes. Regardless of the care taken during the installation procedures, some issues may not show up until after the concrete pipe has been installed and put into service.

In order to assess the condition of pipelines, CCTV inspections and assessments are used by many asset managers to gain an insight to the state of their pipeline. The structural integrity of a concrete pipe, at any stage of its service life, can be regularly monitored using the economical method of maintenance. These regular checks can help identify whether deterioration has occurred, and if so, to what extent and whether it is increasing.

As CCTV inspections have become an important condition assessment tool in the industry, the Water Services Association of Australia (WSAA) recommends the use of the CCTV cameras for the inspection of all conduits in their respective pipe inspection manuals. CCTV contractors can provide a video record of the pipe, and log sheets that outline the condition of the asset. This information can then be assessed in accordance with the criteria given in the inspection manuals.

Whilst this allows asset managers to gain details to make informed decisions about the pipe, at present there is no qualitative way for CCTV cameras to record crack widths with any confidence. As hairline cracks with widths in accordance to AS/NZS 4058, or service cracks up to 0.5mm in width, do not affect the durability of a concrete pipe, engineering judgement is required to ensure constructions costs are kept to a minimum.

In recent times the use of laser profiling in pipes has provided asset managers with more detailed information to improve decision making on the assessment of the asset. In particular, laser profiling can detect deflection and changes of shape in a pipe, vitally important when inspecting flexible pipeline due to the intrinsic manner in which the soil surrounding the pipe must act as the structure. Any failure in this facet and the pipeline will deflect dramatically.

Pipeline assessment is an important part of any ongoing maintenance system. Correct use of the tools and the information they provide is necessary to implement this system. Most importantly, understanding how to assess the information and make informed decisions is critical.