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HRSGs Designed with Custom Expansion Joint Technology from an Experienced Manufacturer Lead to Greater Operational Efficiency

When it comes to equipping a sophisticated machine like a Heat Recovery Steam Generator with damage-mitigating expansion joints, a sophisticated, experienced manufacturer matters.

Professionals know that Custom Industrial Expansion Joints are critical for the energy efficiency, operational efficiency, and cost efficiency of Heat Recovery Steam Generators (HRSGs) due to their strong ability to mitigate damage caused by extreme temperature changes and other damage incurred over time.

Expansion joints from un-established or inexperienced manufacturers who fail to produce expansion joints specific to the application and tailored for the project can cause significant downtime and loss of efficiency due to damage over time.

An HRSG is not only an intricate machine with sophisticated components, but it is by its nature highly susceptible to damage from temperature-induced expansion and contraction. With sub-optimal expansion joints, over time, the repeated expansion and contraction due to extreme heating and cooling will damage components such as the economizer, evaporator, superheater and water preheater and the structures that connect them.

To mitigate the inevitable temperature-induced damage, a Heat Recovery Steam Generator design should include Custom Industrial Expansion Joints such as Metal Bellows Expansion Joints or Fabric Expansion Joints from an experienced manufacturer. These will give the HRSG maximum structural flexibility to better withstand expansion and contraction. Ultimately, Custom Industrial Expansion Joints from an experienced manufacturer will reduce maintenance and operational costs and boost efficiency.

A Heat Recovery Steam Generator design with sub-optimal Custom Industrial Expansion Joints invites inherent structural rigidity, which exacerbates the damage the temperature-induced expansion and contraction. Without Metal Bellows Expansion Joints or Custom Industrial Expansion Joints from an experienced manufacturer, however, the structure will not have maximum flexibility to expand and contract as the temperature changes and the structure will deteriorate. The same can be said for other structural damage over time such as damage from pressure, movement and vibration.

Flexcom has close to 25 years of experience manufacturing Industrial Expansion Joints and chooses the best configuration and materials for a given application. The expansion joints are custom, and Flexcom engineers work with the customer to ensure the joints meet the customer specifications and the machine as a whole – the specifications that will allow maximum flexibility within the design of the HRSG and therefore the most uptime and efficiency.

Second-rate Custom Industrial Expansion Joints will ultimately result in a loss of energy efficiency that, in turn, will result in a loss of operational and cost efficiency. Even small cracks or separations in a Heat Recovery Steam Generator’s components or ducts will allow heat to escape.

In an operation that aims to leverage heat for steam, the loss of heat is the loss of output. When heat escapes, either the output (and the value that can be derived from it) is diminished or the operator must increase costs to generate more heat to replace what is lost. In the plainest terms: without Industrial Expansion Joints from an experienced, custom manufacturer, either output goes down or input goes up.

The HRSG owner or operator may repair damage, but also at a cost. Moderate-to-severe damage may require not just the hard cost of the repair but also the opportunity cost of downtime during which the Heat Recovery Steam Generator is producing nothing at all. The most severe damage, meanwhile, may become a steep liability for safety reasons.

Whether a Vertical HRSG or a Horizontal HRSG, the more sophisticated the Heat Recovery Steam Generator, the greater the need for an experienced, Custom Industrial Expansion Joint manufacturer. Single-pressure HRSGs feature one steam drum and a constant pressure. Double-pressure HSRGs and Triple-pressure HSRGs, however, bring additional steam drums and varied pressure, meaning more pieces subject to extreme temperature change. Similarly, a Heat Recover Steam Generator that relies upon duct firing for supplement heating during peak periods also adds greater sophistication and concern for damage, as well as a greater need for optimal expansion joints.

A Once-Through Steam Generator (OTSG), while simplified in many ways due to reduced variables and structural components, also benefits greatly from Custom Industrial Expansion Joints. The OTSG design relies upon sections being allowed to expand or contract based on the temperature, and Custom Industrial Expansion Joints such as Metal Bellows Expansion Joints or Fabric Expansion Joints are an ideal choice to provide the structural flexibility to allow this to happen.

By reducing damage caused by the extreme heating and cooling inherent in Heat Recovery Steam Generators, Custom Industrial Expansion Joints from an experienced manufacturer improve the energy, operational and cost efficiency in HSRGs. By enabling the maximum structural flexibility for pieces to expand and contract due to temperature, damage is reduced resulting in greater energy efficiency and greater retention of heat. 

Operational efficiency is enhanced as the flexible structure avoids repairs and liability for greater uptime. And cost efficiency is enhanced due to reduced maintenance and repair costs, reduced need for increased input, and less reduction in valuable output.

Expansion Joint Challenges In Gas Turbine Exhaust Applications

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Designing an effective custom expansion joint for a GTX (Gas Turbine Exhaust) application requires strict attention to a number of unique engineering problems. Typically installed in the vital space between the turbine duct and exhaust duct, a GTX expansion joint represents a single point of failure – if the joint fails, the plant ceases to operate as the turbine must be shut down. Therefore, when FlexCom engineers are tasked to design a custom expansion joint for a gas turbine exhaust system, we expect to face certain challenges common to most gas turbine applications, but unique compared to other industrial facilities.

Heat stress poses an intense issue to gas turbines, since the thermal state of a GTX system fluctuates severely during the course of turbine operation – particularly as the turbine starts. A gas turbine initiates from a cold state to extreme heat very quickly, subjecting an expansion joint installed on the exhaust outlet flanges to thermal shock. If the joint is not adequately protected against these rapid shifts in thermal stress, the heat will damage the joint and ultimately cause it to fail.

In addition to heat, vibrations and mechanical movement add significant stresses to an operating GTX expansion joint. As turbines and connected ductwork assemblies increase in size, power and temperature output, so too do they produce greater levels of duct movement and overall metallic vibrations. 


The turbulent flow of exhaust gas through the joint additionally increases vibration – as well as “flutter”, rapid shifts in gas pressure that can damage an unprotected fabric joint. These mechanical stresses can cause significant damage to an inadequately designed joint in a relatively short amount of time.

For hot-to-hot configurations (one in which both flanges must operate at the exhaust gas temperature), we also recommend including an accumulation pillow in the custom joint design. A pillow will reduce the overall temperature of the joint, as well as limit vibration transmission to the turbine outlet flange and help absorb ductwork movement stresses in these very high temperature environments.

Custom design of a gas turbine exhaust (GTX) expansion joint requires a special level of engineering precision, as well as specialized expertise in compensating for the extreme stresses present in this type of exhaust ductwork. Don’t risk your gas turbine operation on a lesser quality product – call FlexCom offices today and let us show you how our custom designs deliver superior performance.

NV Energy Case Study

Customer: NV Energy • Las Vegas, NV

NVEnergyNV Energy, Inc. provides electricity and natural gas to more than two million customers throughout Nevada and parts of California. The company’s service area covers approximately 54,500 square miles.

Challenge

The Edward W. Clark Generating Station, dating back to 1954, is the oldest steam-generated power plant in Nevada. Today, it is a multi-technology natural gas-fueled power-generating complex that includes a total of 19 gas-fired Pratt & Whitney turbines with Selective Catalytic Reduction (SCR) exhaust systems. The station is located just a few miles from the Las Vegas Strip and supplies much of the power for the city.

FlexCom was tasked with developing custom fabric expansion joints that could address several challenges:

  • internal operating temperatures of more than 900°F;
  • sudden and powerful rise in temperature in a very short period of time, putting great stress on equipment, compensation joints and connected pipes;
  • particulate contamination in the exhaust flow;
  • noise pollution generated by high vibration plant operations;
  • keeping the joint’s external skin temperature to within Occupational Safety and Health Administration (OSHA) requirements.

Solution

Based on NV Energy’s specifications, FlexCom designed and built composite fabric expansion joints to address all design requirements:

  • Frames were made from A387 chrome molybdenum steel composite, a custom alloy that provides high temperature and thermal shock resistance;
  • ChemShield®, a composite material made from polytetrafluoroethylene (PTFE) thermoplastic film laminated to a PTFE-coated fiberglass cloth, provided excellent temperature and pressure tolerance and a surface that is inert to nearly all chemicals and solvents;
  • Ceramic fabric accumulation pillows ensured superior abrasion resistance and reduced exterior temperatures;
  • Vinyl joint covers further reduced exhaust noise and joint surface temperature.  

When you have a demanding application, turn to the professionals at FlexCom for all your custom industrial expansion joint needs.

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Air Liquide Case Study

Customer: Air Liquide Inc. • Houston, TX

AirLiquidejpgAir Liquide Inc., located in 80 countries, is a world leader in gases, technologies and services for industry and health. Air Liquide has more than 5,000 U.S. employees, over 200 locations including more than 140 industrial gas plants and approximately 2,000 miles of pipeline.

Challenge

Air Liquide’s Hydrogen Manufacturing Facilities in El Segundo, California and Pasadena, Texas, are the first of their kind to be built in the United States. Each is designed to create up to 90 million cubic feet of hydrogen per day, used to supply nearby oil refineries. Air Liquide turned to FlexCom for a variety of industrial expansion joints, in sizes up to 25 feet in diameter and capable of compensating for regular steam exhaust above 1000°F.

Solution

FlexCom designed and fabricated close to 80 percent of the industrial expansion joints in Air Liquide’s hydrogen plants in El Segundo and Pasadena, including flexible fabric expansion joints and composite fabric expansion joints.

  • Flexible fabric expansion joints provided a cost effective, low maintenance solution. These fabric-only joints are relatively lightweight and easy to install. They are constructed of ChemShield®, a Teflon®-coated, high strength fiberglass cloth that is laminated to a sheet of pure Teflon, providing necessary heat tolerance.
  • Composite fabric expansion joints were built for larger outlets, measuring 25-feet by 13-feet. With the same protective features of the flexible fabric expansion joints, the composite fabric expansion joints have heavy-duty stainless steel frames for additional structural integrity.

Turn to the professionals at FlexCom for all your custom industrial expansion joint needs. We provide cost-effective, reliable solutions for even the most challenging environments. 

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Custom Fabric Expansion Joints

FlexCom’s composite fabric expansion joints tolerate heat stresses and pressure loads and provide movement compensation. Our flexible fabric expansion joints are a lightweight, economical option for low pressure and moderate heat applications.

About Fabric Expansion Joints »

Metal Bellows

FlexCom’s custom metal bellows are made from high quality alloys and handle pressure up to 300 psi, temperature loads up to 2500°F and the transfer of liquids through joints and surrounding piping.

About Metal Bellows »

When Connections Matter, FlexCom Delivers

6864 Chrisphalt Drive • Bath, PA 18014 • 888-376-FLEX • 610-837-3812 • sales@flexcomonline.com