Failure Analysis for Evaporator Fin-Tubes of HRSG in CCGT

2020 ◽  
Author(s):  
Hong Xu
Keyword(s):  
Pitting Corrosion ◽  
Power Plants ◽  
Ph Value ◽  
Water Pressure ◽  
Carbon Steels ◽  
Combined Cycle ◽  
Normal Operation ◽  
Hydraulic Test ◽  
Commercial Operation ◽  
The Matrix

Abstract The finned evaporator tube of medium pressure evaporator leakage occurred after the no. 1 unit of a combined-cycle gas turbine (CCGT) power station was put into commercial operation for only 40 days (including 24 days of operation and 19 days of shutdown and standby). Cut off a section of failure pipe for a thorough inspection. Macro inspection found that severe corrosion occurred in some local areas of some pipe sections, which led to the obvious thinning of pipe wall thickness, leading to perforation and leakage. Metallographic test and scanning electron microscopy (SEM) showed that the metal materials around the leakage points was qualified and the microstructure was normal. The corrosion products around the leakage points were mainly iron oxide which were generated before the unit had been put into commercial operation. The root cause was that the pH value of water used in the hydraulic test during the commissioning of the unit was as low as 9.2, and after the completion of the hydraulic test, the filled water remained in the boiler for a month and a half before being drained. Researches indicated that if carbon steels were prolonged immersed in demineralized water with a lower pH value, it would inevitably occur severe local corrosion which was due to pitting induced by the activation of inclusions in the steel. After pitting corrosion induced by active inclusions, no obvious pitting corrosion occurred in the surrounding inclusions. Accompanied with the extending of corrosion spots that had been formed, the activation zone continued to expand. Along with the formation of surface rust spots, corrosion developed along the inclusion boundary to the depth of the matrix, and finally caused the perforating and leaking of the tubes. The inner pitting corrosion of fin-tube of evaporator in HRSG could be avoided as long as the relevant provisions of “Guidelines of chemical supervision for combined cycle power plants” (DL/T 1717-2017) were strictly implemented during normal operation of boiler, standby maintenance and water pressure test after overhaul.

Evaluation of Arabian Super Light and Arabian Extra Light Crude Oil for Use in Dry Low NOx (DLN) Combustion Systems

2019 ◽  
Author(s):  
Jeffrey Goldmeer ◽  
Paul Glaser ◽  
Bassam Mohammad
Keyword(s):  
Power Generation ◽  
Saudi Arabia ◽  
Natural Gas ◽  
Crude Oil ◽  
Gas Turbine ◽  
Power Plants ◽  
Combined Cycle ◽  
Kingdom Of Saudi Arabia ◽  
The Past ◽  
Commercial Operation

Abstract The Kingdom of Saudi Arabia has seen significant transformation in power generation in the past 10 years. There has been an increase in the number of F-class combined cycle power plants being developed and brought into commercial operation. There has also been a shift to the use of natural gas as primary fuel. At the same time, there has been an interest in switching the back-up fuel for new power plants from refined distillates to domestic crude oils. Both Arabian Super Light (ASL) and Arabian Extra Light (AXL) have been proposed for use in new F-class gas turbine combined cycle power plants. This paper provides details on the combustion evaluations of ASL and AXL, as well as the first field usage of ASL in a gas turbine.

Design Guidelines for the Safe Operation of Steam Surface Condenser Turbine Bypass on Combined Cycle Power Plants

2017 ◽  
Author(s):  
Darren M. Nightingale
Keyword(s):  
Power Plant ◽  
Power Plants ◽  
Design Guidelines ◽  
Combined Cycle ◽  
Normal Operation ◽  
Fundamental Aspect ◽  
Design Parameters ◽  
The Past ◽  
Surface Condenser ◽  
Start Ups

The ability to bypass steam, around the steam turbine and directly into a steam surface condenser, has been a fundamental aspect of the design of base loaded power plants for many years. The increased dependence on natural gas, and the subsequent increase in the number of combined cycle plants, has provided additional challenges for the condenser designer, and also the plant operator, with respect to safely accommodating steam bypass. However, the steam bypass requirements for modern combined cycle power plants differ significantly from those of traditionally base loaded plants, like fossil and nuclear. Higher cycle frequencies for steam bypass, faster start-ups, as well as increases in bypass steam temperatures and pressures, have all impacted the design criteria for the condenser. Indeed, for modern combined cycle plants, the bypass steam conditions are often higher than normal operation, such that the bypass requirements can very well dictate the overall design of the condenser. This, in turn, has resulted in an increase in the reported instances of operational problems, tube failures, condenser damage and plant shutdowns due to steam bypass related issues. Recorded issues and reported failures experienced by combined cycle power plants during steam bypass, have been traced to causes such as transient conditions during commissioning, faster start-ups, the poor design and location of steam bypass headers internal to the condenser, over-heating due to curtain spray deficiencies, excessive tube vibration and tube failures. Many of these issues are based on an inherent lack of understanding of the impact of the rigors of steam bypass on condenser internals. Furthermore, operation of steam bypass outside of the generally accepted design parameters often compounds these problems. This paper consolidates the learning and advances in the design of turbine bypass systems for steam surface condensers from the past 20, or so, years. It includes current design guidelines, as well as safe operational limitations, and general considerations for minimizing potential damage when operating steam bypass on a modern combined cycle power plant. Included is a Case Study of how an existing fossil power plant that was repowered, along with the existing steam surface condenser that was modified to accept the bypass steam, experienced excessive erosion and damage during the past 10+ years of operation. The condenser was recently reviewed once again, and additional modifications were implemented to take advantage of current improvements in steam bypass design. This drastically reduced further erosion and improved the condenser availability, reliability and longevity; thereby improving the plant efficiency.

The Effect and Remedy of Nozzle Loads on Boiler Feed Pumps

2004 ◽  
Author(s):  
Alan P. Flory ◽  
William C. Livoti
Keyword(s):  
Power Plants ◽  
Base Plate ◽  
Combined Cycle ◽  
Real Cost ◽  
Start Up ◽  
Commercial Operation ◽  
Current Design ◽  
Ring Section ◽  
Section Type ◽  
Motor Vibration

Many frequently encountered start-up and operational problems in current design combined cycle power plants can be traced to pipe strain and nozzle loads placed upon pumps. This is most dramatic when the boiler feed pump is affected. Many of the symptoms are significant and can include misalignment, dynamic (changing) alignment, pump or motor vibration, bearing problems, mechanical seal failures and seizure of equipment on start-up and shutdown. While these are all nuisance items that can plague plant shake-down and commissioning, some can generate huge costs and plant unscheduled outages. More profoundly, these symptoms are often all present, making accurate diagnosis of the true cause very difficult. The real cost of these problems can be seen in plants missing commercial operation dates. Some of the piping issues that can cause these symptoms will be discussed, items including hydraulic aspects of the piping design, straight runs, horizontal runs, venting, location of minimum flow valve, and pipe hanger location. Also, the use of pre-fabricated pipe and spool pieces will be discussed. A short discussion will also be presented on how these piping issues impact various designs of pumps, such as barrel pumps, horizontal split case and ring section type pumps. This will also include some comments on pump mounting issues such as base-plate installation, the use of pin & key blocks and pedestal design. All of the discussions will be summarized and then presented with several recommendations for piping repair, operational changes, and material reinforcement. Optional pump features will be presented, indicating what items can be used to improve operation and reliability when abnormal nozzle loads are expected, including comments on internal clearances, wear part metallurgy and bearing upgrades. These recommendations will be compared against several field experiences for confirmation, with some focus on nozzle load data vs. design, and operation prior to and after strain removal. This combination of field results and engineering analysis of this topic should prove quite useful to the engineer attempting to diagnose any symptoms found in the field. Often times several symptoms may be present, making diagnosis difficult and it is only the methodical steps of symptom elimination that will get the new power plant on the way to commercial operation.

Update on Mitsubishi G Series Gas Turbines With Over 78,000 Hours Fleet Operation

2003 ◽  
Author(s):  
V. Kallianpur ◽  
D. Stacy ◽  
Y. Fukuizumi ◽  
H. Arimura ◽  
S. Uchida
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Operating Time ◽  
Operating Experience ◽  
Combined Cycle ◽  
Air Cooling ◽  
Commercial Operation ◽  
Advanced Stages ◽  
Steam Cooling

Seven G gas turbines from Mitsubishi are in commercial operational at various combined cycle power plants since the first Mitsubishi G gas turbine was inroduced in 1997. The combined operating time on the fleet exceeds over 78,000 actual hours. Additional power plants using Mitsubishi G-series gas turbines are in advanced stages of commissioning in the U.S.A., and are expected to be in commercial operation in 2003. This paper describes operating experience of the Mitsubishi G-series gas turbines, which apply steam-cooling instead of air-cooling to cool the combustor liners. The paper discusses design enhancements that were made to the lead M501G gas turbine at Mitsubishi’s in-house combined cycle power plant facility. It also addresses the effectiveness of those enhancements from the standpoint of hot parts durability and reliability at other power plants that are in commercial operation using Mitsubishi G gas turbines.

Leak Behavior of SCC Degraded SG Tubes at a Constant Pressure

2007 ◽  
Vol 345-346 ◽  
pp. 1345-1348 ◽  
Author(s):  
Seong Sik Hwang ◽  
Nam Gung Chan ◽  
Jang Yul Park ◽  
Man Kyo Jung ◽  
Hong Pyo Kim ◽  
...  
Keyword(s):  
Stress Corrosion ◽  
Power Plants ◽  
Room Temperature ◽  
Constant Pressure ◽  
Axial Stress ◽  
Water Pressure ◽  
Leak Rate ◽  
Normal Operation ◽  
Pressurized Water ◽  
Efficient Operation

A primary water stress corrosion cracking (SCC) and an outside diameter SCC have occurred in the steam generator (SG) tubes of nuclear power plants around the world. It is important to establish the repair criteria for the degraded tubes to assure a reactor integrity, and yet maintain the plugging ratio within the limits needed for an efficient operation. For assessment and management of the degradation, it became crucial to understand initial leak behaviors under a small pressure and leak rate evolution under a constant pressure of SCC flaws. Stress corrosion cracked tube specimens were prepared by using a room temperature cracking technique, and leak behaviors of these tubes were measured at room temperature. Water pressure inside the tube was increased slowly in a step like manner with a designated holding time. Water leak rates just after a ligament rupture were measured by collecting the leaked water in a plastic container for a designated time. A leak rate was calculated by dividing the amount of water by the time. Under 3.45 MPa, a small water droplet was formed, but it did not grow after a 10 minute holding period at a constant pressure of 3.45 MPa. A throughwall crack seemed to open at around 8.28 MPa (1200 psi). Some tubes with 100 % through wall cracks did not show a leakage at 10.8 MPa, which is a typical pressure difference of pressurized water reactors (PWRs) during a normal operation. The higher the pressure was applied, the larger the rates of increase with the time were. Axial cracks showed a lower leak pressure than that of the circumferential cracks, which might be from a higher hoop stress than the axial stress. A large open and long axial crack showed an increasing leak rate with the time at a constant pressure.

Large Eddy Simulation and CO Prediction of Reheat Burner Switch-Off Concept

2015 ◽  
Author(s):  
Rohit Kulkarni ◽  
Michael Duesing ◽  
Theodoros Ferreira-Providakis ◽  
Teresa Marchione
Keyword(s):  
Gas Turbines ◽  
Power Plants ◽  
Combined Cycle ◽  
Formation Mechanisms ◽  
Operational Flexibility ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Scale Field ◽  
Commercial Operation

The reduction of the Minimum Environmental Load (MEL) is a key requirement for increased operational flexibility of Combined Cycle Power Plants (CCPP). In reheat combustors, the MEL is in general limited by CO emissions. The sequential combustion system used in Alstom GT24/GT26 gas turbines [1, 2] offers a unique operation concept, namely Low Part Load operation concept with switched off SEV burner (LPL). This concept is able to significantly reduce CO and thus MEL. Details of the CO formation mechanisms for this concept are analyzed via unsteady CFD calculations. These results are used to predict CO emissions for the full engine. Results are validated against experiments on full engine scale. Field implementation of the LPL concept and validation experience collected during long term commercial operation is described in a separate paper [4].

Combined Cycle Gas Turbines With Electrically-Heated Thermal Energy Storage for Dispatchable Zero-Carbon Electricity

2021 ◽  
Author(s):  
Daniel Stack ◽  
Charles Forsberg
Keyword(s):  
Renewable Energy ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Gas Turbines ◽  
Power Plants ◽  
Lithium Ion ◽  
Combined Cycle ◽  
Normal Operation ◽  
Low Carbon

Abstract A low-carbon world needs a replacement for natural gas-fired power to provide variable heat and electricity. The coupling of simple or combined cycle gas turbines (CCGTs) with advanced electrically-heated thermal energy storage (E-TES) systems is an alternative approach to energy storage with cost advantages over batteries or hydrogen production. CCGTs with E-TES may use stored low-value electricity to run the power cycle in place of fossil fuels. This (1) saves money for the power plants by allowing them to switch heat sources based on price, and (2) reduces carbon emissions by making use of otherwise curtailed renewable energy. The development of electrically conductive firebricks enables temperatures approaching 2000°C, hotter than existing E-TES options, sufficient to run CCGTs. Levelized cost of storage (LCOS) calculations show that the use of CCGTs with novel E-TES increases the cost of energy by less than a factor of 2, compared to a factor of 9 increase when using lithium-ion batteries. Unlike batteries, the CCGT with E-TES, provides assured generating capacity by normal operation of the gas turbine. A case study of CCGT coupled with E-TES is included based on 2019 electricity prices in Southern California, which showed an 18% reduction in fuel consumption and $11M savings based purely on the arbitrage case. The arbitrage case is expected to improve dramatically over the decade as deployment of renewable energy in California increases.

Manufacturing and Construction, Operation of Karita PFBC 360 MW Unit

2003 ◽  
Author(s):  
Junichi Koike ◽  
Shinobu Nakamura ◽  
Hajime Watanabe ◽  
Tsuyoshi Imaizumi
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Power Plants ◽  
Large Scale ◽  
Combined Cycle ◽  
Fluidized Bed Combustion ◽  
Commercial Unit ◽  
High Efficient ◽  
The World ◽  
Commercial Operation

Pressurized Fluidized Bed Combustion Combined Cycle Power Generation, namely, PFBC is the clean coal technology, utilizing gas turbine and steam turbine, which is high efficient and friendly to earth. In early 90’s, 70 MW class PFBCs had started demonstration and commercial operation all over the world. Kyushu Electric Power Company (KyEPCO) decided to apply this technology as the real commercial unit, the world largest capacity 360MW, and put into commercial operation in July 2001. To apply PFBC to the large-scale commercial plant, it is essential to demonstrate the higher efficiency than any other conventional coal firing units. In order to achieve this, the gas turbine with higher operation pressure and advanced supercritical steam condition for steam turbine were applied. The reduction by size and weight of the equipment is the vital must to realize large scale PFBC, as 360MW unit. To reduce the pressure vessel size, the unique design of hexagon furnace was applied to install it efficiently in smaller vessel. The plant has started commercial operation in July 2001 and has well demonstrated PFBC’s technology advantages as planned. It achieved the efficiency, 41.8% as net value based on HHV, which is the highest level among existing coal fired power plants. It also verifies smooth operation, 3%L/min of Load following capability, 3 hours of hot start-up, that is comparable to conventional pulverized coal fired unit.

scholarly journals Taking into account the efficiency of turbine plant flow path compartments in design calculations of their energy characteristics

Vestnik IGEU ◽  
2019 ◽  
pp. 62-68
Author(s):  
K.N. Bubnov ◽  
A.E. Barochkin ◽  
V.P. Zhukov ◽  
G.V. Ledukhovsky
Keyword(s):  
Mass Exchange ◽  
Power Plants ◽  
Thermal Power ◽  
Combined Cycle ◽  
Thermal Power Plants ◽  
Technological Systems ◽  
Energy Characteristics ◽  
Turbine Plant ◽  
The Matrix ◽  
Efficiency Indicators

Development of regulatory energy characteristics of TPP equipment is a mandatory and resource-intensive proce-dure. A mathematical model of the turbine plant (the turbine plant itself and its regenerative feed water heating system) was developed earlier based on the matrix formalization of calculations of the energy and mass exchange installations. The analysis of the modeling results has shown that the model adequately de-scribes the real characteristics of a turbine plant only at low bleeding load. At higher load, the accuracy of description is much lower and the model cannot be used for practical analysis of real equipment. All this means that the turbine model needs to be refined by introducing stage-dependent efficiency indicators for more accurate determination of the equipment energy characteristics and, based on them, developing of computer aided methods for optimizing regimes of technological systems and sub-systems of thermal power plants. Methods of mathematical programming were used to investigate the multi-flow heat and mass exchange systems and sub-systems of thermal power plants on the basis of heat and mass balance equations. The energy characteristics and efficiency indicators of TPP equipment were determined in accordance with the existing normative approach. The turbine plant model has been refined by the matrix formalization method by introducing stage-dependent efficiency indicators. Model solutions have been obtained and analysed in order to calculate energy characteristics of the combined cycle turbine plant. The calculaiton results have been compared with the energy characteristics of a turbine unit in operation. It has been shown that the proposed approach is reliable and reasonable. The obtained results can be used for increasing the validity degree of equipment energy characteristics calculation, creating computer simulators and software tools for optimizing modes of technological systems and subsystems of heat power plants.

Development of corrosion flaws for the production of realistic test specimens

2020 ◽  
Vol 64 (1) ◽  
pp. 23-28
Author(s):  
J. Hodač ◽  
Z. Fulín ◽  
P. Mareš ◽  
J. Veselá ◽  
O. Chocholatý
Keyword(s):  
Power Plants ◽  
Galvanic Corrosion ◽  
Water Solution ◽  
Erosive Wear ◽  
Corrosion Damage ◽  
Water Mist ◽  
Carbon Steels ◽  
Bending Stress ◽  
Solution Flow ◽  
Mechanical Bending

AbstractTo produce realistic test specimens with realistic flaws, it is necessary to develop appropriate procedure for corrosion flaw production. Tested specimens are made from steels commonly used in power plants, such as carbon steels, stainless steels and their dissimilar weldments. In this study, corrosion damage from NaCl water solution and NaCl water mist are compared. Specimens were tested with and without mechanical bending stress. The corrosion processes produced plane, pitting and galvanic corrosion. On dissimilar weldments galvanic corrosion was observed and resulted to the deepest corrosion damage. Deepest corrosion flaws were formed on welded samples. The corrosion rate was also affected by the solution flow in a contact with the specimens, which results in a corrosion-erosive wear. Produced flaws are suitable as natural crack initiators or as realistic corrosion flaws in test specimens.

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