Influence of the thickness of the layer of internal deposits in pipelines of water supply and discharge systems on their remaining service life

Abstract

Introduction. The practical operation of water supply networks, made of steel and gray cast iron, has proven that deposits accumulate on the inner surface of pipes under certain conditions. Deposition depends on the quality of transported water and the water flow regime, same as in gravity sewerage networks. A sediment layer accumulates in the flume of pipes if the actual flow rate is smaller than the minimum standard one. A layer of deposits in metal water pipes changes the value of the actual inner diameter of pipes and rises the pressure loss due to resistance along the pipeline length, which contributes to an increase in the energy consumption by the pumping equipment and affects the pressure value at the end point of a network. A layer of sediment in the flume of a gravity drainage network also rises losses along its length, slows down the flow rate and may block the water flow in the network. The purpose of the study is to find dependence between the remaining service life of water supply and sewerage networks, having internal deposits, and the thickness of the layer of deposits on pipe walls.
 
 Materials and methods. The authors use the dependences, that they have already derived for the hydraulic analysis of metal water supply networks and gravity sewerage networks, having internal deposits.
 
 Results. The authors have identified dependence between the remaining service life of water supply pipelines and sewerage systems and the thickness of deposits on the inner walls of pipes. Examples, confirming such a relationship, are provided. They are substantiated by graphs showing dependence between the remaining service life and the thickness of the layer of deposits in pipelines. A hydraulic criterion is proposed for projecting the term of operation of water supply and sewerage networks with internal deposits.
 
 Conclusions. The authors have proven the need to use special tables to analyze the characteristics of pipes within the framework of a hydraulic analysis of water supply and sewerage networks, having internal deposits.

On the need to account changes in hydraulic performance of worn-out metal water pipes

“…Accounting for the actual hydraulic characteristics of worn-out metal water pipes is the basis for predicting the residual service life of pipelines with internal deposits and making a decision whether their reconstruction projects are required [9][10][11].…”

Efficiency coefficient of water supply and removal as an assessment factor of further operation

“…Приведенные выше причины изменения значений характеристик гидравлического потенциала труб способствуют также образованию слоя отложений на внутренней поверхности водопроводных труб или слоя отложений (осадка) в лотковой части труб водоотведения [4,5]. Каким критерием следует оценивать изменение значений гидравлических характеристик труб?…”