Mortar Lining as a Protective Layer for Ductile Iron Pipes

Wojciech Dąbrowski,Fusheng Li

doi:10.1007/s40999-020-00585-6

Wojciech Dąbrowski, Fusheng Li

Open Access

https://doi.org/10.1007/s40999-020-00585-6

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Abstract

The objective of the study is to recognise whether epoxy resin or polyurethane internal linings of ductile iron (DI) pipes create visibly smaller head loss in flow than cement mortar linings. Some data reported by the Ductile Iron Pipes Research Association (DIPRA) was used in the calculations. Only the data from hydraulic tests performed no later than 30 years after the placing of the mortar lining were considered. The average values of the Hazen–Williams roughness coefficients C for each of the internal pipe diameters were calculated, and single experimental data neglected. Two different approaches were taken for interpreting the DIPRA experimental results and omitting the fact that the flow rates during these tests are unknown. The Hazen–Williams roughness coefficients C were used in both for computing the friction factor f from the Moody chart for three values of flow rate: being equal to the optimal value for a given diameter, and then by 50% larger and 50% smaller than this value. Next, the computed friction factors were compared with the values predicted from the Moody chart for smooth pipes. In the first approach, the friction factors f were computed using the Epanet2 software, and in the second approach, a general equation for calculating f from known C and flow parameters was applied. Both approaches resulted in friction factors f very close to those for smooth pipes for the whole range of Q. In conclusion, more smooth plastic linings of DI pipes do not result in a significantly more visible saving of energy for pumping.

Highlights

In most cases, ductile iron pipes require both external and internal protection against corrosion
In the U.S.A., an approach summarised in the report by the Ductile Iron Pipe Research Association (DIPRA) is based on the principle that bonding cover protection efficiency is doubtful and the cost created by this kind of lining is unreasonably high [1]
The Committee on a Review of the Bureau of Reclamation‘s Corrosion Prevention Standards for ductile iron pipe, constituted by the U.S [9], stated that limited data indicates that ductile iron pipes with polyethene encasement and cathodic protection are not able to serve reliably more than a 50-year life-time in highly corrosive soil (\ 2000 X-cm)

Summary

Introduction

Ductile iron pipes require both external and internal protection against corrosion. In the U.S.A., an approach summarised in the report by the Ductile Iron Pipe Research Association (DIPRA) is based on the principle that bonding cover protection efficiency is doubtful and the cost created by this kind of lining is unreasonably high [1]. To improve the ductile iron structure and, avoiding mechanical failures; an annealing process is applied in the pipe production. The Committee expresses the opinion that bonded dielectric coatings with cathodic protection may provide superior protection to the ductile iron pipe when compared to polyethene encasement with cathodic protection. In contrast to the data included in the DIPRA report [1], the Committee concluded that it was not able to identify any ductile iron pipe (DIP) corrosion

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