Design Tomorrows Combined Cycle Power Plant Using Previous Lessons Learned. Todays construction boom in the combined cyclecogeneration sector is great news for suppliers of gas turbines GTs, heat recovery steam generators HRSGs, and engineer procure construct EPC services. But before this boom advances from artists sketches Figure 1 to first fires, the designers of all those next generation combined cycles should pause to reflect on the lessons learned from the current generation of combined cycles. So Id like to share some lessons learned by the original and longest running user group in this sectorthe HRSG Users Group. Crysis 2 Trainer Free Download. Many of these lessonswhen first discovered by our group back in the early 1. They might still surprise you todayClear and authentic standard operating procedures SOP, GMP manuals, templates, training courses for Pharmaceutical quality, validation laboratory. FOREWORD This manual is intended to give an overview of the role of control valves in the behaviour of a process control loop. This overview consists the information. The combined cycle power plant construction boom is great for suppliers of combustion gas turbines, heat recovery steam generators HRSG, and EPC services. Lesson 1 Designers Should Not Rely Solely on the ASME Code. The EPC firms that built and commissioned todays plants diligently complied with the American Society of Mechanical Engineers ASME Boiler and Pressure Vessel Code. That was a necessary first step, because laws mandate the code in most parts of the world. Completing a power plants startup and commissioning usually means pushing the prime contractor to wrap up the remaining punch list items and getting the new. But it was only one step in what should have been a rigorous engineering effort to deliver reliable plants. You see, the ASME codes one and only purpose is to protect life and property from catastrophic failuresnotably, the explosions that killed steam pioneers way back in the 1. Thats all the code was intended to doto protect against fatal booms It was not intended to be an all inclusive design manual dictating the full range of engineering analyses required for power projects. For instance, the code did not dictate the following Completing a fatigue life calculation, which could have reduced the thermal fatigue damage occurring in the tight tube bends and tube to header welds of todays HRSGs. Steam Plant Calculation Manual' title='Steam Plant Calculation Manual' />Marko buli technical calculation and estimators manhour manual erection of process or chemical plants i. Conducting a computational fluid dynamics CFD analysis, which could have prevented the flow imbalances that are tearing up todays HRSG Economizers. Running a finite element analysis FEA on all vulnerable joints, which could have prevented the deformation and cracking so prevalent in todays HRSG superheater tubes. Lesson 2 Full Penetration Welds Arent Always Stronger Than Partial Pens. In todays HRSGs, plant designers often specified that the welds at tube to header connections had to be the full penetration type, which had been shown in lab tests to have greater endurance than partial penetration welds. In theory, using full pen welds was a good idea, but in the practical world of power plants, it did not guarantee that those tube to header connections would last any longer than if the designer had specified partial pens. Heres why Full pen welds are more difficult to perform correctly. And if theyre not performed correctly, then they can be weaker than a correctly performed partial pen weld. In other words, tube to header welding is a game of percentages. Should you play the long shot for the chance to win big or take the more reliable performer Those Who Cannot Remember the Past Are Condemned to Repeat It. Designers who know this George Santayana quote, and who learn from the lessons mentioned above, will create combined cycle projects chock full of cycling friendly features. Many of them will be innovative things that todays HRSG users havent yet imagined. But heres a list of features that todays users have thought of and have gone to great effort to retrofit into their existing plants An exhaust stack damper, and a front end closure upstream of the gas turbine inlet, to reduce the loss of decay heat immediately after shutdowns Figure 2. A steam sparging system to reduce the decay rate of high pressure HP drum pressure while the unit is in a prolonged shutdown. An automated nitrogen blanketing system for the prompt setting of layup conditions after each shutdown. A responsive water treatment system that wont introduce oxygenated water on every startup. Greater steam bypass capacity to accommodate transients and partial load operation. Large, automated steam drains to prevent condensate quench of superheater and reheater tubes during startup. Bypass Control Solutions. When a combined cycle plant is operating in steady state at full load, its an elegant marriage of the Brayton and Rankine cycles. Unfortunately, when its operating under transient or part load conditions, its not so elegant. During these conditions, the GT is producing so much exhaust heat at such rapid rates of temperature change that it can damage thick walled HRSG and steam turbine components, if its not controlled. Scrolling Text Software For Pc. One control solution is to install a bypass damper upstream of the HRSG to divert some of the GT exhaust gas around the HRSG and out to atmosphere, effectively allowing the plant to operate in simple cycle mode during transients. But this solution isnt practical because large, bulky dampers cant be modulated with enough precision, and because its too capital and maintenance intensive. A second control solution is to allow the HRSG to generate steam, but to vent that steam directly to atmosphere until all of the steam cycle metal is properly warmed. Download Lg Flash Tool. The downside of this sky vent method is that it wastes a lot of demineralized water, plus it produces objectionable noise and steam plumes. That leaves designers with the thirdand most commoncontrol solution for managing the imbalance between GT exhaust heat and steam system thermal limits The cascading steam bypass system. In this design, the HP superheated steam thats generated during transients gets bypassed around the steam turbines firstHPsection, via a pressure control valve PCV and an attemperator, into the reheater. After passing through the reheater, the steam is diverted again, around the steam turbines latter stagesthe intermediate pressure IP and low pressure LP sectionsbefore it ultimately gets dumped into the condenser, hence giving this system its nickname of the condenser dump system. The condenser dump system has proved to be practical, but not particularly durable. It must handle an immense amount of energy at harsh temperatures, pressures, and velocities, and it creates even harsher changes in temperature and flow when the pressure control and attemperation valves suddenly open. The end result has been a host of operations and maintenance O M problems in todays combined cycle plants. So whats a Designer of tomorrows combined cycles to do I suggest we learn from the condenser dump systems installed in Europe, South Africa, and Japan, where durability has been much better. The main difference between the condenser dump systems overseas and those installed here is that most North American systems were originally undersized. To size a condenser dump system, designers must evaluate the worst case transientwhich is a steam turbine trip from full load. In past calculations, designers assumed that the mass flow going through the dump system would be the same as what was going through the fully loaded steam turbine. Sounds logical, right Unfortunately, its wrongWhen the steam turbine trips, the HP bypass valve opens, which allows attemperating spray to be injected into the fluid stream. This attemperating spray increases the mass flow by as much as 2. And further down the line, spray from the secondthe hot reheatbypass adds yet more mass flow another 2. Gryphon International Engineering Services Inc. If we sum these additional fluid streams, we see that the total mass flow for the worst case transient is not 1.