Gas Turbine & Combined Cycle Plants

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Johnathan Harris
6 years ago
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1 Gas Turbine & Combined Cycle Plants

Introduction With a worldwide reputation for excellence, DEKOMTE de Temple manufactures fabric and stainless steel expansion joints for all applications within a gas turbine power station, and offers

Gas turbine power stations subject the exhaust duct and HRSG casing to extreme stress and fatigue, with the expansion joint being the focus point of the systemic issues.

Base Load Operational Plants Base load stations can obtain acceptable performance from a basic design, due to the reduced stresses and fatigue caused by fewer start-ups and shutdowns.

2 Introduction With a worldwide reputation for excellence, DEKOMTE de Temple manufactures fabric and stainless steel expansion joints for all applications within a gas turbine power station, and offers varying technical standards to suit the technical requirements, maintenance cycles, and budgets for each joint. Gas turbine power stations subject the exhaust duct and HRSG casing to extreme stress and fatigue, with the expansion joint being the focus point of the systemic issues. Both fabric and metal expansion joints are used in many positions around the plant. Base Load Operational Plants Base load stations can obtain acceptable performance from a basic design, due to the reduced stresses and fatigue caused by fewer start-ups and shutdowns. Good construction techniques and fabrication quality are essential to bring simpler solutions to the required reliability. Stations originally designed for base load are now being asked to run cyclically. Cycling Operational Plants Conversely, cycling plants are subject to increased maintenance when using basic duct and joint constructions that were not designed for the increased stresses and fatigue. DEKOMTE s designs and constructions offer technically based guarantees and a lifespan of up to years, depending on the site s operating conditions. The biggest challenges occur in high-cycling plants. Steel frame designs should minimize the temperature gradient across frame to minimize stress and fatigue. Design of the flow plate is made in such a way that the axial, lateral and possible angular movements are considered to make sure that no points are fixed and stressed during the movements. DEKOMTE has proven designs for cycling operational plants with installations in a vast number of power stations around the world, as OEM equipment and as retrofitted systems. DEKOMTE offers improvements in the construction of the fabric joint and insulating bolster to allow use of the latest materials and production processes. The tailored joints are built on custom molds giving higher joint flexibility and greater plant availability. The clamping area and the bolts are designed in such a way that there is no overheating, allowing the application of constant pressure during operation. CONTENTS 4 GT Exhaust / HRSG Inlet GT Exhaust / HRSG Inlet 8 HRSG Outlet (Hot Casing) (Cold Casing)

3 DEKOMTE is accredited to RAL GZ 79, the world-class quality standard for fabric expansion joints, ensuring that a detailed and thorough technical approach is maintained in all products offered, and the highest quality is ensured in the delivered solutions. a b c d e GT Inlet GT Outlet (hot casing) HRSG Inlet (cold casing) HRSG Outlet Penetration Seals e d c a b e 0 Penetration Seals Pumpable Insulation and 4 Inspection, Monitoring, and Casing Repairs Installation

GT Exhaust / HRSG Inlet (Hot Casing) Gas turbine power stations subject the exhaust duct and HRSG casing to extreme stress and fatigue, with the expansion joint

Base load stations can obtain acceptable performance from a basic design, due to the reduced stresses and fatigue caused by fewer start-ups and shutdowns.

comparison of possible design solutions. The design is broken into key elements to establish independent technical criteria for each one.

4 GT Exhaust / HRSG Inlet (Hot Casing) Gas turbine power stations subject the exhaust duct and HRSG casing to extreme stress and fatigue, with the expansion joint being the focus point and relief. Many problems with the complete design become evident in this area. Base load stations can obtain acceptable performance from a basic design, due to the reduced stresses and fatigue caused by fewer start-ups and shutdowns. Conversely, cycling plants are subject to increased maintenance when using basic duct and joint constructions that were not designed for the increased stresses and fatigue. The use of a competent third-party design authority (such as DEKOMTE), to verify and compare each of the solutions offered can establish a consistent basis for the comparison of possible design solutions. The design is broken into key elements to establish independent technical criteria for each one. The expansion joint also represents a system that requires a complete analysis of the total scope using the latest technology. In DEKOMTE s experience, the only reliable way to carry out a technical analysis is using FEA (Finite Element Analysis) and CFD (Computational Fluid Dynamics) programs, taking extreme care to ensure the correct boundary conditions and calculation parameters are used in these processes. 4

Key elements of the design are: Steel Frame Design This is the most critical aspect of hot casing solutions.

Durable multi-layer compositions with high temperature membranes and outer protection protect the gas-tight seal from stress and damage.

turbulence and insulation degradation. bolting and clamping to meet the required site pressure.

compression and damage caused by the movements.

5 Key elements of the design are: Steel Frame Design This is the most critical aspect of hot casing solutions. The temperature gradient created on the frame during transient operating conditions of the gas turbine creates high fatigue stresses that may result in cracking and gas leakage with cycling. 4 Fabric Formed fabrics that prevent creasing, crumpling and folding through all movement are important for cycling and longer life. Durable multi-layer compositions with high temperature membranes and outer protection protect the gas-tight seal from stress and damage. Flow Plate Bolting / Clamping Detail Smooth cross section changes in the duct are important A gas-tight seal is achieved with proper design of the to reduce turbulence and insulation degradation. bolting and clamping to meet the required site pressure. Internal Bolster Fully encapsulated and formed insulating bolsters (or pillows) protect the joints from the inside, and segmented sections can reduce compression and damage caused by the movements. Duct Connection Both welded and bolted flange systems are available with consideration given to thermal fatigue, distortion and remaining gas-tight. 7 Adjacent Insulation and Cladding The expansion joint system is further protected from excess external radiated temperatures by tightly integrating adjacent insulation and cladding insulation Other details to consider when looking at the joint design are the duct condition, stiffeners, supports, and moving points, ensuring that they work as a system with the correct movements.

GT Exhaust / HRSG Inlet (Cold Casing) Expansion joints that are installed within a section of duct with internal lining, known as cold casing duct arrangements, experience lower stresses than hot

DEKOMTE recommends a review of the connection and internal lining of the joints to ensure that no heat path becomes a weak element of the design.

6 GT Exhaust / HRSG Inlet (Cold Casing) Expansion joints that are installed within a section of duct with internal lining, known as cold casing duct arrangements, experience lower stresses than hot casing arrangements. Protecting the expansion joint frame and bolster from the highest gas temperatures will increase the joint s life and reliability. DEKOMTE recommends a review of the connection and internal lining of the joints to ensure that no heat path becomes a weak element of the design. The design is broken into key elements to establish independent technical criteria for each one. The expansion joint also represents a system that requires a complete analysis of the total scope using the latest technology. In DEKOMTE s experience, the only reliable way to carry out a technical analysis is using FEA (Finite Element Analysis) and CFD (Computational Fluid Dynamics) programs, taking extreme care to ensure the correct boundary conditions and calculation parameters are used in these processes. 9 o F 7 o F 9 o F o F o F

Key elements of the design are: Steel Frame Design As a cold casing system, the steel frame design is not

4 Flow Plate Smooth cross section changes in the duct are important to reduce turbulence and insulation

The liner plate should cover over the complete expansion joint space, allowing flexibility by floating/

A liner that is seamless over the adjacent flanged connections protects the casing and interface to the

Internal Bolster Fully encapsulated and formed insulating bolsters (or pillows) protect the joints from

Fabric Formed fabrics that prevent creasing, crumpling and folding through all movement are important for

Durable multi-layer compositions with high temperature membranes and outer protection protect the

7 Key elements of the design are: Steel Frame Design As a cold casing system, the steel frame design is not subjected to the thermal stresses, as long as the frame can remain cold. 4 Flow Plate Smooth cross section changes in the duct are important to reduce turbulence and insulation degradation. The liner plate should cover over the complete expansion joint space, allowing flexibility by floating/ sliding sections. A liner that is seamless over the adjacent flanged connections protects the casing and interface to the expansion joint frame. Internal Bolster Fully encapsulated and formed insulating bolsters (or pillows) protect the joints from the inside, and segmented sections can reduce compression and damage caused by the movements. Fabric Formed fabrics that prevent creasing, crumpling and folding through all movement are important for cycling and longer life. Durable multi-layer compositions with high temperature membranes and outer protection protect the gas-tight seal from stress and damage. Bolting / Clamping Detail A gas-tight seal is achieved with proper design of the bolting and clamping to meet the required site pressure. Duct Connection Both welded and bolted flange systems are available with consideration given to thermal fatigue, distortion and remaining gas-tight. 4 4 Other details to consider when looking at the joint design are the duct condition, stiffeners, supports, and moving points, ensuring that they work as a system with the correct movements. 7

HRSG Outlet The HRSG outlet is a cool condition operating expansion joint, where the temperature conditions are typically a maximum temperature of 0 o F, which are favorable to a simple material and

The movements are also not significant due to the low temperature, and the main function is isolating the structure of the duct, HRSG, and stack to allow civil structural tolerances, vibration

8 HRSG Outlet The HRSG outlet is a cool condition operating expansion joint, where the temperature conditions are typically a maximum temperature of 0 o F, which are favorable to a simple material and thin layered expansion joint. The movements are also not significant due to the low temperature, and the main function is isolating the structure of the duct, HRSG, and stack to allow civil structural tolerances, vibration elimination, and flexibility from dynamic weather loading. DEKOMTE recommends the use of a ¼ reinforced rubber expansion joint or a multi-layer PTFE expansion joint with rubber sealing area as the best solutions, as these address the main issues: Weather tightness Water sealing Environmental degradation DEKOMTE recommends the retrofit addition of water barriers, drains, and flow plate systems. These give the security of a cleaner, longer functioning expansion joint by eliminating the build-up of water, deposits, and debris from the inner joint space. Careful consideration of the material selection will help a joint at the stack connection reach an expected life of 0 years. Short-term cost savings can result in high maintenance costs on an expansion joint where the cost of access is prohibitive. The effect of these aspects include heavy corrosion on the roof section caused by weather ingress into the duct through the joint flanges, and also on the bottom, caused by water leakage out through the flange from inside the unit. 8

Key elements of the design are: Steel Frame Design The use

prevents condensation, water and debris from pooling in the

Fabric Materials that are stable for the environmental and

Fabric compositions that include water sealing materials

Other details to consider when looking at the joint design

9 Key elements of the design are: Steel Frame Design The use of the correct material, coating, and drain design reduces corrosion and extends the life. Flow Plate A protective flow plate and water barrier prevents condensation, water and debris from pooling in the expansion joint space. Fabric Materials that are stable for the environmental and plant conditions will maximize the maintenance life cycle. Fabric compositions that include water sealing materials along with gas-tightness will extend the life of the joint. Other details to consider when looking at the joint design are the duct condition, stiffeners, supports, and moving points, ensuring that they work as a system with the correct movements. 9

Leaking packing glands and mechanical seals have a detrimental impact on casings and adjacent equipment not only do they require more regular maintenance, but they can necessitate additional

10 Penetration Seals Penetration seals are the most challenging expansion joints in a combined cycle power plant. The high levels of movement of these small joints in this environment demand the best technical solutions and highest quality of products to survive. Leaking packing glands and mechanical seals have a detrimental impact on casings and adjacent equipment not only do they require more regular maintenance, but they can necessitate additional maintenance and repairs to the surrounding area, that in the longer term make them an expensive and unreliable solution. DEKOMTE solutions are gas-tight and ensure no loss of flue gas or heat to the environment. DEKOMTE offers both metallic bellows and fabric expansion joints for this application, and the choice is normally established by the HRSG OEM. Metallic bellows offer the lowest initial cost and are therefore favored for the first installation. In high movement areas and for retrofit, fabric joints offer the best solutions and flexibility in the most compact design. Retrofitting metallic bellows is uncommon due to the necessity to either: Deliver the bellows in split halves resulting in: - welding the bellow on site, which is notoriously difficult and leaves areas prone to corrosion and failure - limiting construction to a single layer bellow, which is stiffer than multi-layer solutions Deliver the completed bellows resulting in: - A bellow more flexible than a split halve bellow - Cutting the steam nozzle to slide over the completed bellow - Complete NDT on the nozzle - Coded welding to re-attach the nozzle - Complete the pre-weld and post-weld heat treatment In almost every case, the bellow failed due to movement-induced issues, therefore installing the same or less flexible solution is not going to deliver reliability. DEKOMTE has developed the most reliable fabric solutions for penetration seals, both as an OEM installation with cost optimization being a key function of design, through to retrofit where longevity, durability and reliability are the keys to the design. 0

Key elements of the design are: Steel Frame Design Casing collars can align the joints by resetting the pipe concentricity to the casing position.

4 Bolting / Clamping Detail A gas-tight seal is achieved with proper design of the bolting and clamping to meet the required site pressure.

Internal Bolster Fully encapsulated and formed insulating bolsters (or pillows) protect the joints from the inside, and segmented sections can

Fabric Formed fabrics that prevent creasing, crumpling and folding through all movement are important for cycling and longer life.

Casing Insulation and Nozzle Liner The insulation around a nozzle in the casing is subject to highly turbulent gas flow, which invariably pits

DEKOMTE can avoid this by installing encapsulated casing bolsters and redesigned nozzle liner plate sections.

11 Key elements of the design are: Steel Frame Design Casing collars can align the joints by resetting the pipe concentricity to the casing position. Pipe collars can manage temperatures in the seals and offer space for integration of piping insulation to protect the seal from the inside. 4 Bolting / Clamping Detail A gas-tight seal is achieved with proper design of the bolting and clamping to meet the required site pressure. When possible to attach to the pipes, bolted flanges can eliminate the maintenance required of a circumferential clamp. Internal Bolster Fully encapsulated and formed insulating bolsters (or pillows) protect the joints from the inside, and segmented sections can reduce compression and damage caused by the movements. Fabric Formed fabrics that prevent creasing, crumpling and folding through all movement are important for cycling and longer life. Durable multi-layer compositions with high temperature membranes and outer protection protect the gas-tight seal from stress and damage. Casing Insulation and Nozzle Liner The insulation around a nozzle in the casing is subject to highly turbulent gas flow, which invariably pits and pulls the insulation into the gas stream. DEKOMTE can avoid this by installing encapsulated casing bolsters and redesigned nozzle liner plate sections. Ensuring casing temperature is maintained will ensure the further reliability of the penetration seal. Pipe Insulation Tight integration of the insulation to the expansion joint pipe collar prevents damage from excess external radiated temperature. 4 4 Other details to consider when looking at the joint design are the duct condition, stiffeners, supports, and moving points, ensuring that they work as a system with the correct movements.

Pumpable Insulation and Casing Repairs In cold casing duct systems with liner plates securing the insulation in place, the condition of the insulation is paramount to ensure that the casing stays in

If the liner plate system and attachments are in sound mechanical condition, then repairing the insulation can be intrusive and expensive.

12 Pumpable Insulation and Casing Repairs In cold casing duct systems with liner plates securing the insulation in place, the condition of the insulation is paramount to ensure that the casing stays in good condition. The cold casing must stay cold and well-insulated. If the liner plate system and attachments are in sound mechanical condition, then repairing the insulation can be intrusive and expensive. DEKOMTE can repair missing insulation pockets and hot areas of casing by injecting liquid insulation from the outside, while the unit is running. Causes of insulation loss: No liner Liner plate damage Gas flow under liner (by distortion / gap in liners) Compacting of insulation Degradation of insulation (by vibration / moisture) Pumpable Internal Insulation The pumpable soluble fiber insulation is a mix of short fibers dispersed in high temperature binders that, upon drying, produces a strong insulation structure with low thermal conductivity. Applications: GT Casings GT Exhaust Diffuser Penetration Seals HRSG Casings Effects of insulation loss: Casing cracks leading to gas leakage Temperature-induced material fatigue All effects cause adjacent safety and environmental concerns

13 Insulation Technical Details Pumpable Material Low thermal conductivity (00 F btu) Use limit 00 F Melting point >70 F Wet density 70 lb/cu.ft Dry density 7 lb/cu.ft Low shrinkage Good adhesion Resistant to flue gas velocities up to ft/s Typical Casing Insulation Low thermal conductivity (00 F btu) Use limit 00 F Melting point >70 F Dry density lb/cu.ft No adhesion Resistant to flue gas velocities up to ft/s 4 o F 7 o F 8 o F o F Casing Repairs DEKOMTE also offers casing repairs, liner modifications, and new attachment solutions. These are aimed at maintaining casing temperatures for a longer life.

Inspection, Monitoring, and Installation Engineering support in the form of annual inspections or lifetime assessments can form a critical part of the maintenance planning of a power plant or

The integration of duct supports, stiffeners, and bracing sections into the expansion joint solution can result in a complete problem solving package, rather than contractually interfaced scopes.

14 Inspection, Monitoring, and Installation Engineering support in the form of annual inspections or lifetime assessments can form a critical part of the maintenance planning of a power plant or industrial manufacturing process. The integration of duct supports, stiffeners, and bracing sections into the expansion joint solution can result in a complete problem solving package, rather than contractually interfaced scopes. DEKOMTE manages the technical and commercial aspects of the various on-site disciplines and trades. DEKOMTE also supports and advises its customers on supply and installation appropriate to their requirements. The design of the expansion joint uses the latest materials and composition to optimize cost and technical function. We provide a quality package comprising creativity, design, practical experience and technical expertise to be able to offer the optimum selection of components and fully developed solutions. It is our primary objective to guarantee plant availability, even under the harshest conditions over many years. Following installation, the DEKOMTE Customer Service team is available at all times to answer your questions. Design Studies and Technical Support Design comparison, investigation, and modelling can be achieved using DEKOMTE s extensive database of empirical knowledge. DEKOMTE offers objective technical support at short notice for critical problems. 4

Engineering Services DEKOMTE pushes the boundaries of product development with the latest computer and industry best practice tools

The discerning use of FEA (Finite Element Analysis) and CFD (Computational Fluid Dynamics), together with D and D design, allows a

Formulation of specifications, tenders and design critique are also offered as an independent technical service.

a technical report for maintenance planning and plant improvement, establishing a baseline of the site s expansion joints and helping

15 Engineering Services DEKOMTE pushes the boundaries of product development with the latest computer and industry best practice tools and procedures. The discerning use of FEA (Finite Element Analysis) and CFD (Computational Fluid Dynamics), together with D and D design, allows a correlation of on-site empirical experience and theoretical models. Formulation of specifications, tenders and design critique are also offered as an independent technical service. Plant Survey DEKOMTE has experienced site engineers and designers who are able to review all expansion joints in a plant and produce a technical report for maintenance planning and plant improvement, establishing a baseline of the site s expansion joints and helping to build a plan to reduce total costs. Turnkey Installation The use of skilled design engineers, technicians, and service engineers, together with qualified on-site skilled labor means DEKOMTE offers a complete turnkey contracting solution for duct problems. Please contact us for further information and to discuss your specific requirements.

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