Advanced methods of the Moscow water distribution network reconstruction

Summary

A review of the advanced trenchless technologies of pipeline repair is presented. The main methods of damaged pipe rehabilitation with the use of polyethylene U-liner, spraying on cement-sand coatings, synthetic tubes impregnated with special polymerizing compounds are considered. The methods based on installing polyethylene, steel or cast iron pipes in the existing pipeline subject to reconstruction: «pipe in pipe without bursting» and «pipe in pipe with bursting» (pipe bursting) are discussed; their advantages and disadvantages are considered in relation to the conditions of usage in the dense city infrastructure.

Key words

polyethylene , pipeline , trenchless reconstruction , steel , cast iron , cement-sand coating , polymer liner

Method of formation of centrifugal cement-sand coating
in steel water pipes

Summary

The results of the experimental studies of determining the optimal composition of cement-sand coating and the procedure of its formation on the interior face of water pipes are presented. The internal cohesion of cement-sand mixture depending on its water content was studied; based on the research results the water-cement ratio and the optimal speed of pipe spinning in the process of coating formation were selected. Different cement-containing compositions resistant to dulling and ensuring adequate protective anticorrosive coating were tested. The process operations of the centrifugal coating formation based on the mixtures with flexible consistency are proposed; the method implementation is theoretically substantiated. The executed studies showed that introducing complexed mineral-chemical additive (in the amount of approximately 3% of the cement mass) into cement-sand mixture provided for improving significantly the operational properties of the coating, almost doubling the strength and waterproofing capacity, and reducing the water demand of the mixture. This additive is not toxic; it does not change the toxico-hygienic characteristics of the final product; and the mortar stone does not release substances hazardous to health.

Key words

cement-sand coating , protection of steel pipes against corrosion , internal adhesion of cement mixtures , centrifugal coating molding , composition of cement-sand composition