Clarifier Calculations

The New Zealand Pipe Inspection Manual 3rd Edition has been prepared in order to provide: • An overview of the tasks that can be completed using Closed Circuit Television (CCTV) and how these activities can be used to manage wastewater and stormwater assets. • A standardised set of codes for recording observations noted during CCTV inspections. • An outline of good practice procedures for carrying out CCTV inspections and for processing and analysing the information collected. • Standard Technical Specifications and Model Conditions of Contract for use when engaging CCTV contractors.

It is common practice worldwide for piping designers to route piping by considering mainly space, process and flow constraints (such as pressure drop) and other requirements arising from constructability, operability and reparability. Unfortunately, pipe stress analysis requirements are often not sufficiently considered while routing and supporting piping systems, especially in providing adequate flexibility to absorb expansion/contraction of pipes due to thermal loads. So, when “as designed” piping systems are handed-off to pipe stress engineers for detailed analysis, they soon realize that the systems are “stiff” and suggest routing changes to make the systems more flexible. The piping designers, in turn, make changes to routing and send the revised layout to the pipe stress engineers to check for compliance again. Such “back and forth” design iterations between layout and stress departments continue until a suitable layout and support scheme is arrived at, resulting in significant increase in project execution time, which, in turn, increases project costs. This delay in project execution is further worsened in recent years by increased operating pressures and temperatures in order to increase plant output; increased operating pressures increase pipe wall thicknesses, which, in turn, increase piping stiffnesses further. Such increased operating temperatures applied on “stiffer” systems increase pipe thermal stresses and support loads. So, it is all the more important to make the piping layout flexible at the time of routing.