What is the significance of pipe deflection?
The significance and consequence of pipe deflection is misrepresented in many publications. Flexible pipe systems are designed to accommodate ground movement. Excessive deflection has the potential to impact on the pipeline in two basic areas the strain generated in the pipe wall and joint performance. Thermoplastics (such as PVC, Polyethylene and Polypropylene) are not strain limited materials (2)(3)(4)(5) . Hence from the perspective of deflection leading to excessive strain in the pipe wall – this is simply not a limiting case. Deflection is not a limiting functional parameter. The selection of a deflection limit is an arbitrary one. “Design long term deflections of 15% are accepted and this is based on the limits of joint performance specification.” (2). Deflections have little impact on the flow through pipelines for example a pipe deflected by 15% will only experience a 5% reduction in flow capability. The most recent developments in this area of specification ISO/DIS 21138-1 (6)
