Comparison Between American and European Methods For Admitting Bypass Steam Into a Steam Surface Condenser: Advantages and Disadvantages of Each Practice

Abstract

Combined cycle plants are in operation in every part of the globe. The majority of the combined cycle plants have been designed by architect engineering companies in the USA or in Europe. The US standards for plant design are different from those in Europe. In spite of the differences, both design practices achieve the common goal of efficient and reliable electrical power generation. The method for admission of bypass steam into a condenser in the U.S. is substantially different from that in Europe. In the US practice, bypass steam entering the condenser is at relatively high pressures and is superheated. In the European practice, the bypass steam entering the condenser is at relatively low pressures and is wet. Each practice serves the common purpose of condensing bypass steam in the condenser and each practice has its own disadvantages and disadvantages. Tube failures are encountered in each practice. These tube failures are caused by droplets in the (moist) high velocity bypass steam. Low condenser pressures, improper design / control / operation of pressure reducing desuperheating valve (PRD valve), and improper drainage of bypass header lines are some of the major reasons that cause an environment favorable for tube failures. This paper examines the US and European methods for admitting bypass steam into a condenser. The advantages and disadvantages of each practice are discussed. For each practice, the performance in bypass mode for varying condenser pressures, bypass steam flow rates, support plate spacing, and moisture pockets quality are evaluated. Both actual and critical steam velocities are calculated. Condenser operating points prone to flow-induced vibration and associated tube failures are predicted.