Modeling strength properties of inner pipe protective linings

Summary

Lately polymeric spray applied protective linings have been widely used for rehabilitation of old water supply pipelines. Investigations of physical and mechanical properties of Scotchkote™ 169HB polymeric lining spray applied on the inner surface of old water pipes were carried out. In the process of experimental studies Instron 3345 electromechanical tensile testing machine and Ansys software package of finite element analysis were used. In the process of testing a stress model of two-layer pipe structure based on steel pipeline and polymeric lining the following results were drawn: maximum tensile strength of lining 14.95 MPa; flexural yield stress 13.92 MPa; maximum breaking extension 25.57 mm (~ 13%). The strength properties of a steel pipeline with perforation damage were investigated in the process of trenchless rehabilitation with the use of Scotchkote™ 169HB inner lining within the operation range of 0–50 years at 20 °С. With hole diameter enlargement over time to 20 mm the system strength criterion has the value more than 1; herewith the two-layer structure will be age-resistant while providing for the required strength properties for 50 year operation. If the hole diameter is more than 20 mm the strength criterion values less than 1 will be observed which does not ensure the required strength properties of the two-layer pipe structure. The relationships for calculating pipeline strength after the lining application as well as the model itself constructed in the system of Ansys finite element analysis are suggested. This will provide for predicting the behavior of «pipe + Scotchkote™ 169HB protective lining» two-layer structure for various pipeline operating conditions.

Key words

pipeline , trenchless renovation , polymeric lining , physical-mechanical property , computer modeling

Optimization of operation modes and improvement of operation conditions of surface runoff treatment facilities

Summary

Common drawbacks of packaged units for urban runoff treatment are considered. The task of the study was regulating and optimizing the operation modes of the existing facilities in order to improve the effluent quality to meet the standards. By the example of the unit that was most suitable for the generally accepted treatment process flow scheme the analysis of the operation of a laminar sedimentation tank module under design conditions was carried out. To determine the operation efficiency in the hydrodynamic mode physical experiments (by adding a chemically inactive tracer to wastewater being treated) and computer simulation were carried out. To upgrade the laminar sedimentation tank the chemical treatment stage was introduced into the process flow scheme. Adding coagulant provided for improving the treatment efficiency; however, the required concentrations of suspended solids in effluent downstream the sedimentation tank (10 mg/dm3) were not met. The efficiency of the sedimentation tank in hydrodynamic mode was improved by using stepped feed and distributed collection of wastewater in a modular unit as well as by using an air distribution system located in the lower central part of the laminar sedimentation tank module. This type of the design provided for coarse bubble aeration over the entire surface area of the chamber at the required mixing rate. The implemented design changes in the laminar sedimentation tank module resulted in the efficiency of urban runoff treatment before the further tertiary treatment meeting the regulatory requirements.

Key words

reagent treatment , lamella settler , computer modeling , urban runoff , packaged modular water treatment unit , hydrodynamic mode , air distribution system