At Combined Cycle Power Plants the Heat Recovery Steam Generator (HRSG) is an easily-overlooked, but key component, providing steam to the steam turbine and to attached process steam hosts. While base-loaded HRSGs tend to be the most reliable - cycled or two-shifted plants suffering from accelerated damage - the importance of allocating sufficient resources to maintenance of the HRSG is often only realised in hindsight.
If your plant suffers from frequent failures, installing additional thermocouples can prove to be invaluable when assessing the actual root cause of the failures.
Inspection is part of routine maintenance for any Heat Recovery Steam Generator (HRSG). Visual inspections are performed at regular intervals in accordance with the requirements of regulatory bodies and insurers. In the US statutory inspections are mandated typically every year although some jurisdictions allow justification for longer intervals. Additional inspections are sometimes performed to establish the baseline condition of the HRSG (often early in life, but not always) or to perform less frequent special inspections to confirm component integrity.
Thermohydraulic simulations can provide detailed heat recovery steam generator (HRSG) data to help determine the root cause of failures, predict the degree of wear from various mechanisms, and assess the overall thermal efficiency of the boilers. In this article, the results obtained from three case studies are presented to show the real-world benefits obtained through thermodynamic simulations.
We have solutions to your HRSG, Boiler and Power Piping Problems
Managing the Power Piping in CCGT Plants
Risk of failure and attendant personnel safety concerns are always present when operating highly-pressurized systems. Over the years, the occurrence of catastrophic events has driven improvements in construction codes and updated recommendations for O&M practices. As part of this trend, expanded requirements for operations and maintenance (O&M) were recently added to the ASME Code for Power Piping—ASME B31.1. The “Chapter VII Operation and Maintenance” was created in 2007 to prescribe guidelines that promoted early failure detection and overall safety. This was a fundamental change to the scope of B31.1, which up until then was strictly a design code; going forward, it now serves a dual purpose…
Read the full story by our colleague Robert Rosario, published online in Power Magazine here.
2018 CPS Piping Services for CCGT Plants
Tetra Engineering Group, Inc. has assisted many owners of natural gas-fired combined cycle plants with the development of effective Covered Piping Systems (CPS) Programs, Inspection Plans, Pipe Stress Analysis and Field NDT since the ASME adopted the new Code requirements for piping O&M in Section B31.1 Chapter VII in 2007.
Tetra has developed such programs for CCGT owners in the US, Canada, Mexico and the Middle East. They have been prepared for 'bubble' 2x1 design with F-class gas turbines as well as modern 1x1 fast-start units, plants with aeroderivative GTs and once-through steam generators as well as smaller units operated by municipal power companies, some of which are in cogeneration service.
Based on the latest B31.1 requirements, the CPS Program Plan is tailored to meet your requirements especially regarding the scheduling of NDT inspections over multiple outages to distribute costs and meet outage budget constraints
2018 Spring/Summer Training Schedule
Join us in Deer Park Utah, USA in May or Sophia-Antipolis, France in June for HRSG & Combined Cycle training. Don't miss our Early-bird discounts! See our training page for more details.
2018 Spring/Summer Training Schedule Announced
Tetra Engineering announces the 2018 spring/summer training schedule! Join us in Deer Park Utah, USA in May or Sophia-Antipolis, France in June for HRSG & Combined Cycle training. See our training page for more details.
Recent Projects: Increasing HRSG Thermal Efficiency
The Power Plant Simulator & Designer (PPS&D) provides state-of-the-art capabilities for modeling and simulating the operation of nearly any type of thermal power plant. Originally developed by KED GmbH in Germany for use by boiler OEMs in their detailed design work, PPS&D has since been used by numerous clients worldwide for simulating the operation of many types of boilers and thermal power plants.
Using this powerful tool, Tetra can model power plants and use simulations to assess the impact of modifications done to equipment, or operating conditions. Recently, Tetra used this method to evaluate the impact of lowering the approach temperature of the LP Economiser for one of our clients. In addition to ensuring safe operations, by looking at potential steaming in the economizer and the risk of Flow-Accelerated Corrosion (FAC), it was found that the overall HRSG efficiency could be increased by 1% leading to an increase in power output for the steam turbine of 1MW. The overall efficiency increase is estimated to lead to an increase in revenue by over 400.000 EURO/year.
Technical Tidbits from the HRSG Inspection Planning Guide
The inspection of drums is a key element in determining the general condition of the waterside pressure boundary of the HRSG components and the quality of the water treatment program. They are a “window” on what the inside of the water-filled or steam and water-filled tubes and headers in the various pressure circuits (HP, IP or LP) might look like. Basic inspection is visual, yet often complemented by UT, and PT/MT examinations.One of the key items of interest is surface passivation. The HP drum should typically have a dark grey adherent surface layer, characteristic of magnetite, below the maximum waterline. Above the maximum water line there may be some light red coloration, indicating a mix of magnetite and hematite. Yet surface color can deceive, drums with “abnormal” color may simply reflect a specific water chemistry and process condition history. The experience of the inspector comes into play in these cases, to decide whether what is observed is indicative of a real problem or simply reflects a harmless difference.
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