Mortar Lining as a Protective Layer for Ductile Iron Pipes
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RESEARCH PAPER
Mortar Lining as a Protective Layer for Ductile Iron Pipes Wojciech Da˛browski1,2
•
Fusheng Li2
Received: 30 March 2019 / Revised: 27 October 2020 / Accepted: 5 November 2020 The Author(s) 2020
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. Keywords Cement mortar lining Friction to flow Ductile iron pipes Smooth pipes
1 Introduction In most cases, ductile iron pipes require both external and internal protection against corrosion. The most prominent disagreements are concerned with the external protection. 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, consequently, avoiding mechanical failures; an annealing process is applied in the pipe production
& Wojciech Da˛browski [email protected] Fusheng Li [email protected] 1
Environmental and Power Engineering Department, Cracow University of Technology, 31-135 Krakow, Poland
2
River Basin Research Center, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
foundries. After this process, the wall surface of the pipes is covered by corrosion products being recognised by DIPRA as an efficient protective layer, which should not be removed by sandblasting because of a danger of creating blistering or slivering of the pipe’s surface that may not be totally covere
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