Method of improvement of operational and technical conditions of a large cooling water system

Ryszard Zwierzchowski, Michal Pachocki

Increasing the energy efficiency of industrial installations is one of the European Union’s priorities for achieving energy policy goals. These goals can be achieved, among others, by applying the appropriate methodology for modernization of cooling water distribution pipelines and improving their operation. Water distribution in cooling systems of large industrial installations is associated with significant hydraulic losses due to large flows and spatial spread of these systems. The losses are unavoidable and have a decisive impact on the energy consumption for pumping. Thanks to optimal design solutions, implementation of the repair program and proper operation of cooling water transmission pipelines, it is possible to significantly reduce hydraulic losses and water leakage. This will translate into reduced energy consumption for pumping and, as a result, improved energy efficiency. Abovementioned goals can be achieved by replacing or renovating pipelines. This paper deals with determination of a method and schedule of modernization of cooling water piping systems on the basis of a case study – a large industrial plant. Firstly, evaluation of the existing condition is carried out. Data on flow rate and cooling water pressure in the system are collected and analyzed. A graphical and numerical database of the cooling water system is made, which maps the system in terms of system geometry (lengths, pipe diameters, ordinates) and flow and pressure streams. The hydraulic losses of the cooling water system are simulated. The results of simulation calculations of pressure losses in water distribution system are presented in the form of maps of water pressure distribution in pipelines. Calculations for the pipeline network are performed in the current state for two hydraulic load cases: maximum and average. An assessment of the failure rate is made on the basis of information about the place, time, cause and type of damage. Wall thickness of pipelines in selected locations is measured and samples are taken from pipes in places of failure. The reasons for water pipeline failures are diagnosed. On the basis of pre-modernization simulation, information on failure rate and forecasts of future water demand are obtained, it is proposed which pipeline sections and in what order should be modernized. Depending on the technical condition, pipeline diameter and location in the field, pipe replacement or renovation is recommended. For pipes to be replaced, new diameters, adjusted to the forecasted demand are calculated. For pipes qualified for renovation, different site hardened liners or full wall pipes are recommended depending on pipe condition. Renovation methods, despite the reduction of the internal cross-section, provide similar or lower hydraulic resistance values. After selecting the variants of modernization of distribution pipelines, hydraulic simulations are carried out in the post-modernization condition, taking into account the future demand for cooling water. The presented method can be applied to cooling water systems as well as other industrial water piping systems.

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