The turbomachinery industry is using augmented, virtual, and mixed realities to create immersive, immediate, and interactive environments that are transforming not only a user’s view of the real world, but the industry’s approach to safety, productivity, design and manufacturing, repairs and maintenance, employee training, customer presentations, and more.

With virtual reality (VR), the user is immersed in a digital environment while augmented reality (AR) overlays virtual objects on top of a real-world environment. Mixed reality (XR) is an extension of AR that blends physical and digital worlds.

Gone are the days when VR and AR were questioned for their functionality and credibility—these are reliable and imaginative tools on the shop floor, in the training room, in the field, and beyond. As Patrick M. Kessler, Global Communications and Digital Marketing Manager at Atlas Copco Gas and Process, pointed out, these immersive technologies are no longer seen as something futuristic or intimidating. “We have found solid business cases for using 3D technologies, where previously it was often seen as pure entertainment,” he said.

Ellie Smith, Product Manager of Augmented Reality at Howden, a Chart Industries Company, echoed Kessler's view: “We are now fully convinced that AR has a place in the way we work and are working hard to embed it as part of our everyday processes. We started our journey with AR five years ago running pilot projects, working on specific standalone challenges to understand how AR tools can work for our business and what problems they can solve for us,” she said. “We’re now at a stage where we’re confident in the technology. We’re beginning to scale up our usage, embed-ding it into our everyday processes for internal use and offering our AR services to more of our customers.”

Remote collaboration is the most popular AR application, according to Inderpreet Shoker, Director of Research at ARC Advisory Group.“ VR is touted as the next-gen solution for taking operator training to the next level. It can create effective training programs with large field of view and complete immersion to help train new workers quickly and efficiently.” She said that research supports the use of AR, indicating that hands-on training programs are more effective compared to presentations and books.

Interaction with XR. Credit: Atlas Copco Gas and Process

New digital tools and technologies in this space are breaking into the market and further enhancing features, software, graphics, and speed. Meta offers three versions of its VR headset, Meta Quest, with varying forms of graphics, performance, and ergonomics. Microsoft’s XR headset, HoloLens, comes in four offerings, including an industrial edition that is “designed and tested to support regulated environments such as hazardous locations.” According to Microsoft, in manufacturing, HoloLens 2 reduces downtime, increases efficiency by 90%, reduces travel time by 40%, and boosts employee learning of complex tasks.

“The emergence of Meta Quest in VR and Microsoft HoloLens 2 in XR has been historic,” said Kodai Tsushima, xR Application Development Section, Strategic Technologies Research Department at Ebara Corp., parent company of Elliott Group.

“Meta Quest has succeeded in promoting the widespread use of VR with its concept of affordability and PC-free experience. HoloLens 2 projects information into space hands-free and enables scanning of spatial shapes, meeting almost all the requirements of XR in the manufacturing industry. Moreover, with the improvement in PC graphics processing speed, simulations of previously impossible physical phenomena are now possible, and the technology continues to break barriers.”

As Shoker pointed out, AR has opened the door to more dynamic remote collaboration via smart glasses, phones, tablets, etc., “allowing users to connect with remote experts through video calls and receive guidance in real-time using diagrams, markers, instructions, and annotations in the user’s live field of view,” she said. “Many advanced applications also allow users to view critical tasks as well as asset information within their field of view. With digitally created content—including digital twins of assets and equipment—overlaid on a live video stream, AR can provide virtual hands-on assistance.”

Howden uses AR to enhance worker health and safety by helping onsite engineers maintain an awareness of their surroundings. “We can take our AR experiences out of the classroom and into the working environment,” Smith said. “This gives the information we’re showing a contextual grounding—we’re not just looking at data or work instructions in isolation; we’re able to show how that fits into the real working environment.”


The industry is not limiting its use of these technologies, as they are present in the training room, on the shop floor, in the field, and beyond.

For example, Siemens Energy’s collaboration with Microsoft and other partners to create an ecosystem of applications and services that can be integrated into HoloLens 2—”an untethered, self-contained holographic headset that offers the option to include XR applications and information in the physical environment while working heads-up and hands-free,” said Marion Mirold, Head of XR Center of Competence at Siemens Energy. This integration provides XR use cases in-shop and in the field among all project phases.

Augmented reality glasses; credit: Siemens Energy

Another example is the role of AR and VR as a way to enhance employee training and development. “At Atlas Copco Gas and Process, we harness the power of AR/VR, immersing our employees in virtual scenarios that closely resemble real-life situations,” Kessler said. “This hands-on training helps improve employee skills. For example, it is possible to use our virtual models to perform task-site simulations. This allows for potential errors or shortcomings in the field to be identified and rectified immediately.”

The use of virtual and augmented environments also creates another layer of detection in the manufacturing process, as well as increases customer response times, optimizes maintenance and troubleshooting, and guides workers/engineers step-by-step.

Even if the 3D design theory is correct, mistakes can still be overlooked, “during reviews, discovery of problems not seen in the design theory, and difficulties in assembly that can lead to manufacturing problems,” explained Tsushima. “By using VR, it is possible to review designs in life-size (or any desired scale) without the need for prototyping. This enables verification from various angles and helps catch manufacturing problems.”

MAN Energy Solutions’ smart glasses, PrimeServ EyeTech, facilitate remote inspections, support, and quality checks. They provide wearers with a heads-up display that overlays relevant information into their field of view so users can access real-time data, instructions, and visual aids while keeping their hands free to perform tasks.

“The primary goal behind developing these smart glasses was to reduce reaction time and travel costs, ensuring fast assistance whenever needed,” said Roland Kabitzke, Manager of Learning & Development at MAN Energy Solutions.

Continual developments and refinements are made to the smart glasses while a close partnership with the service provider ensures improvements.

“The next step in our journey is integrating the solution into our existing systems, which will lower the barrier for usage,” Kabitzke said. “Once our PrimeServ EyeTech is integrated into Outlook, creating an invitation for a remote inspection call will be easier and faster. Users will be able to send a calendar invite with just one click. Additionally, integrating it with our ticketing system will enable us to connect all footage—pictures, videos, annotations, etc.—to a defined service case,  streamlining the troubleshooting and documentation process.”

Smart glasses play a crucial role in enhancing AR experiences. They provide an immersive platform where customers can access additional content such as live annotations, pictures, drawings, or screen shares. By overlaying digital information into the user’s field of view, smart glasses integrate virtual and real-world elements naturally and intuitively.

Shoker said that many OEMs provide AR collaboration tools to end users as a part of their maintenance services. “In many cases, using these tools, remote workers can fix issues themselves with remote guidance from an SME,” she said. These tools can speed up troubleshooting in the field and address issues more efficiently.

The team at Howden uses AR to visualize the next step in an assembly process—”overlaying the locations of piping and instrumentation in a more intuitive way than traditional 2D diagrams,” Smith said. Further, the company’s field service engineers can follow AR work instructions to guide them through each step of a process.

“Our AR-enabled remote support tool, Howden Virtual Expert, supports customers remotely by seeing what they see to help us respond faster to their needs,” Smith said. “AR remote assistance allows us to provide advice to our engineers in the field to achieve a first-time fix and reduce travel costs associated with a site visit by only sending one engineer with the expertise of many provided virtually. AR Work Instructions enables training regardless of location, reduces training time and costs, and enables better reporting and accountability as we capture data about servicing.”

Kessler said that Atlas Copco Gas and Process uses AR/VR similarly, as its service personnel can use these tools to access real-time equipment data and visual instructions during their tasks.

“This instant access to information makes it easier to optimize maintenance and commissioning processes while troubleshooting problems more efficiently,” he explained. “Ultimately, this helps reduce downtime and operating costs.”

AR also benefits customers by allowing companies to present their products and services using 3D models, animations, and more to bring their portfolio to life—and clients don’t even have to leave the office. “Today, we can bring our customers on tours of our different products in remote, inaccessible environments from the comfort of their own offices,” Smith said. “They can engage with the products and get information the way they prefer, by interacting with the content intuitively.”

Further, these technologies offer a perspective to customers that wasn’t easily accessible before. “With large and complex rotating equipment such as ours, it is challenging to look ‘under the hood’ of the actual turbomachinery, especially when it is running,” Kessler pointed out. 

“These 3D technologies enable the customer to take a deep dive into our solutions to understand and experience turbomachinery in a realistic, application-type setting. Our 3D equipment is typically placed inside a photorealistic version of a plant, making the experience even more immersive and relatable for our customer.”

Of course, every technology comes with limitations; however, the confines of these virtual and augmented realities may surprise you. Let’s start with the basics.

Often clients and employees have little to no experience with VR and AR, so it may take an adjustment period. “Generally, there needs to be a certain comfort level and willingness on the user’s end to literally take that leap and immerse themselves in 3D environments,” Kessler said.

In Howden’s case, it mostly uses mobile devices and tablets for its AR because they are familiar technologies, as there is a learning curve with headsets—they require end users to interact with the content in ways that are different from a traditional mouse and keyboard. For example, voice commands—which, even with noise canceling and directional mics, aren’t always practical in noisy environments—and hand gestures.

“Improved hand tracking has helped a lot in the latest HoloLens, but it can still feel quite unnatural,” Smith said. “Personally, I’d like to see a move toward bi-manual gestures, i.e., locking buttons and menus to locations on the hand or arm, and using the other hand to ‘click’—HoloLens does this for its start button, and it feels easier and more intuitive than grappling with virtual buttons floating in space because it gives us that tactile feedback we are used to.”

Plus, headsets are for situational use and cannot be worn all day, but even though they are “more capable compared to smartphones and tablets and can be operated with voice commands or head or hand gestures,” as Shoker pointed out, “most in today’s workforce are not familiar with these newer ways to input data and commands, so it may take more time for the workforce to get used to this technology.”

TeamViewer Frontline is an enterprise productivity platform with fully integrated AR solutions. It works with the latest wearable computing technology and mobile devices to streamline manual work processes in any industry. 

“We augment manufacturing processes with Frontline xMake, providing a ‘make-by-vision’ AR solution that ensures faster assembly by replacing paper manuals with instructions in the user’s field of view and built-in quality assurance based on sophisticated cameras and sensor integrations,” said Lisa Gruber, Senior Product Marketing Manager, TeamViewer. “By taking xMake to the third dimension with our Frontline Spatial Editor, new staff can be onboarded immersively by creating individualized XR trainings.”

The solutions’ interface can be configured according to language and specific process requirements. Inspection and maintenance are digitized with Frontline xInspect, and virtual troubleshooting is supported by Frontline xAssist. All the components in the Frontline platform can be managed from the central Frontline Command Center: one hub to coordinate the workforce, manage tasks and devices, and instantly troubleshoot by connecting to the workforce via remote assistance.

TeamViewer streamlines onboarding, training, and operational work processes; increases productivity; reduces errors and inspection times; and simplifies daily tasks for frontline workers by connecting them to information and data in a visual format.

Using TeamViewer, DHL increased productivity by 15%, reduced the error rate to 0.1%, and saved 50 -70% of onboarding time; Coca-Cola HBC increased picking performance by 6 - 8% and accuracy to 99.99%; GlobalFoundries saved 25% of its time in the picking process after only one month and increased inventory accuracy by one-third, as picking errors became non-existent and the new process eliminated ~100,000 sheets of printed paper per year. Airbus experienced faster inspection processes, cutting the time of completion by 40% while making the inspection processes fully paperless and reducing manual input errors simultaneously.

Beyond the comfort and familiarity with these environments, there are situations in which a physical presence is required when using VR and XR, which can be a barrier in some cases. Additionally, Smith pointed out other basic challenges such as a solid internet connection when working offshore, in a mine, or in very remote areas and a need for more devices that are ruggedized and/or rated for use in hazardous areas.

Further, some limitations depend on the end devices, as Tsushima pointed out, such as head-mounted displays and smart glasses rather than hardware or PCs. “For example, while 3D graphics representation and physics simulation have undergone significant changes in the past five years, HoloLens2 cannot process all of them,” Tsushima said.

In terms of functionality, AR headsets need to pack a lot into one lightweight package: display equipment, high-end graphics processing, batteries, etc. “With current technology, meeting these size and weight constraints means that battery life is limited, and your head warms after wearing a headset for a while, especially loading in large high complexity models,” Smith said. “So, there’s still a need for smaller, lighter-weight components to meet the kind of performance we need.”

At one point, cost was a major barrier, but today it’s not as much of a setback. Over the past several years the cost of hardware, including headsets, has decreased significantly, and, oftentimes, the initial upfront costs are quickly offset by the rate of return.

“The hardware, development, and service costs are very low compared to the savings that can be achieved,” Mirold said. “In many cases, a single successful use of the device can pay off the investment. And little training is required to use the device and the applications.”

Kessler pointed out that the cost of customizing your 3D experience—i.e., the cost of creating and developing a fully immersive digital universe tailored to your specific environment with your tools and products—
is still a sizeable investment. “At the same time, it has provided an even greater return.” He explained that its digital environment was created in a game engine, meaning it can pull multiple outputs ranging from AR to VR, and even singular 3D visualizations.

Beyond hardware, another cost consideration is software. “For us, because of the size of our company, the scale we operate at, and because we want to decentralize the creation of AR experiences to let product and process experts drive content—rather than AR or software experts—it made sense to invest in enterprise-level AR software, mostly SaaS-based and ‘click-and-drag’ style development interfaces,” Smith said. “It comes with some pretty significant costs, but the payoff is it allows us to develop and deploy solutions quickly, and with more input from our business experts because it’s easier for more people to get involved. Software cost doesn’t have to be a barrier to AR, especially for businesses just dipping their toe in the water with a quick proof of concept, but as you scale up, those enterprise features tend to become more important.”

All that said, Kessler doesn’t see any limitations. In fact, a limitless environment is the point of 3D technologies: “removing all limitations in the real world and immersing yourself in another one,” he said.

Mirold agreed: “Every day new use cases are being identified in the different branches of the organization. When the cybersecurity aspects are covered and the data transfer is ensured, even in tough conditions and at very remote locations, the use cases are nearly unlimited.”

As cliché as it may sound, the sky is the limit with these technologies. Currently, the industry continues to invest in AR/VR and look for new ways to integrate it into its economies, and that trend
will continue.

“There will be new processes and applications in plants, and they will require new and, in many cases, more complex equipment technologies,” Kessler said. “Therefore, 3D technologies will not only have significant potential in these fields, but they can also be an essential tool and driver, from internal training to external marketing and other fields.”

Tsushima believes the use of AR and VR will become indispensable. “For example, in design, VR will be used for design reviews, allowing manufacturing to take place without prototyping. In assembly, logistics, and maintenance, AR and XR will be used to support workers. Furthermore, while human judgment is currently relied upon, in the not-so-distant future AI will also be utilized in these areas.”

Again, these tools enable high-quality training with 3D visualizations and interactive training sessions that enhance worker learning in a way that wasn’t possible before. It’s already taken training to the next level, and that can translate into other areas of the workplace. Additionally, AR can support the industry as it struggles to replenish skilled workforces and as folks retire or leave the industry.

“With remote augmented communication and augmented operations, AR can help the industry better address the impending skills gap challenge by capturing and leveraging SMEs using AR technology,” Shoker said. “AR work instructions are a really simple way to capture expert knowledge,” Smith said. “Which may or may not exist in written documentation, and pass it on to our newer, less experienced team members to embed the knowledge in the organization rather than in individuals.” 

The future of VR/AR/XR is vast. “We’re now past the point of AR being some new-fangled gimmick,” Smith said. “We’ve seen the benefits proven over again. The industry is ready, the underlying tech platforms are ready, and I think we’re going to see an acceleration in AR and VR being adopted across the whole supply chain.” 

Augmented and virtual realities increase safety, enable remote support, enhance operator training, and support the design process.

The Immersive Worlds of AR & VR in the Turbomachinery Industry

Camfil: Pulse Filter Technology, TurboPulse

Camfil Power Systems introduced TurboPulse filters, featuring a square inner cage design and aerodynamic TubroVanes that redirect pulse energy and optimize airflow distribution. TurboPulse can fit into filter houses designed for conical cylindrical filters and offers 25% greater dust retention, a 20% lower initial pressure drop, and a 30% pressure drop recovery after each pulse. It is corrosion-proof and 100% incinerable; the inner cage is made of plastic with a high compressive strength. The design has been pulse-endurance tested for over 250,000 pulses. The filters are also designed to save maintenance hours by more than 25% by reducing installation time.

The TurboPulse filter with square inner cage design. Credit: Camfil Power Systems

Concepts NREC: Updates Engineering Design System

Concepts NREC updated its Agile Engineering Design System to v2023.2. Engineers can explore cycles for potential carbon emissions reduction in all applications, including the use of hydrogen in combustion and fuel cell applications. The MAX-PAC CAM software works in tandem with its current version of AxCent to optimize moving from design to production. Additionally, MAX-PAC includes new hole-drilling capabilities. 

Riverhawk updated its hydraulic clamp hub to comply with API STD 671, so it is an alternative design to traditional shaft-end connections. The hydraulic clamp hub uses a clamping force on the hub and has been used as a replacement hub on shafts for similar applications, including generators, pumps, and refrigeration systems.

A mounted hydraulic clamp hub. Credit: Riverhawk Company

FS-Elliott: P400HPR Centrifugal Air Compressor

FS-Elliott introduced the P400HPR centrifugal air compressor, featuring more aero stages to support higher discharge pressures up to 250 psig. The P400HPR has three stages of compression and is suitable for heat of compression applications. The compressor's aero design reduces the amount of energy used. 

P400HPR centrifugal air compressor. Credit: FS-Elliott

The latest turbomachinery industry innovations.

New Products: Fall 2023

’s November/December 2023 issue features a collection of the latest news and new products from the turbomachinery industry, a how-to guide on selecting lube oil for turbomachines, and a case study on the effects of undissolved air in lube oil. This issue’s cover story is a deep dive into the immersive worlds of augmented (AR) and virtual reality (VR) and how these 3D tools enhance safety, support, training, and much more. In addition to our show report from Turbomachinery & Pump Symposia 2023 (TPS) and an in-tandem Q&A with FS-Elliott—who speaks on its takeaways from the show and offers insights into centrifugal air compressors—the Myth Busters tackle part II of their column on 

Reciprocating vs Centrifugal Compressors for Carbon Capture and Sequestration.

Amin Almasi lays out considerations when selecting a lube oil, such as oxidative and thermal stability, viscosity, interactions with oil additives, etc., in his Turbo Tips column,

 Lube Oil Types & Selections for Turbomachines. 

The Myth Busters Klaus Brun and Rainer Kurz close out their two-part column on reciprocating versus centrifugal compressors in CO

 capture and storage applications. They discuss the challenges reciprocating presents, such as pulsation control, leakage, and mechanical reliability.

, includes reporting on compressing and pumping hydrogen, troubleshooting aero-performance issues, and turbomachinery in LNG production plants, including compressing LNG, cryogenic pumps and expanders, turbine and motor components, and materials. Running in tandem with our show report is a Q&A with FS-Elliott. Dominic Sarachine, Product Manager at FS-Elliott, discusses the company’s takeaways from TPS 2023 and offers insights into air compressors and centrifugal compressor control systems.

Siemens Energy presents a case study on the impact of undissolved air on the heat transfer properties of lube oil: Lube oil’s ability to cool affects the efficacy and reliability of turbocompressors, and undissolved air can have a significant effect on its heat transfer behavior.

The Immersive Worlds of AR & VR in the Turbomachinery Industry, 

shows how the industry is using these 3D technologies in everyday processes and beyond to increase safety, enable remote support, enhance operator training, support the design process, and so much more.

The November/December 2023 issue features augmented and virtual reality coverage, reporting from TPS 2023, a Q&A on air compressors, and more. 

Turbomachinery International: November/December 2023

The most serious issue for many large turbomachines, e.g., large pumps, turbocompressors, turbines, and others, is a cut-off of the lube oil flow. This could lead to a catastrophic failure of oil-lubricated bearings, such as hydrodynamic bearings, within a few seconds. It is important to understand how lube oil systems react to temporary faults, such as those that can stop the oil pump.

At least two full-sized lubrication oil pumps (one operating, another standby) should be employed in any critical turbomachinery with lubricated bearings. The lube oil pump changeover or switch-over (starting the standby pump) in various emergencies is an important topic for any piece of turbomachinery. Starting the standby pump is necessary when lube oil (header) pressure falls. A fast response time is essential, and although there are other solutions and configurations for a decrease in pressure, the direct pressure signal to fast start-up of the standby oil pump is the simplest and most cost-effective solution. Of course, in some cases, even this may not be sufficient and other provisions may be needed. 

A common cause of unscheduled downtime is the lube oil system’s inability to ride through transient events such as a 1- to 6-second loss of electrical power in the network. For some hydrodynamic bearings, even a 2- to 3-second interruption in lube oil flow during a transient situation could cause damage. When an electrical fault happens in the electrical network connected to the operating oil pump, the flow of oil could be lost for the duration of the fault. The question is can the turbomachinery tolerate such a situation?

Another concern when the oil pump fails is the time needed to start up the standby oil pump, which can be an electrical-driven pump connected to an alternative electrical network, a steam turbine-driven oil pump, etc. Can the turbomachinery continue operating properly during this transition? The same applies to many control and/or hydraulic oil systems. An oil accumulator can be used, if needed, to deal with these types of situations.

An oil accumulator—or a set of accumulators—maintains the oil pressure while the standby oil pump accelerates from an idle condition to an operating speed during a 1- to 6-second loss of electric power, for example, or during other transient situations. The oil pressure should always be above the equipment’s minimum-specified oil-supply pressure. The conservative sizing of the oil accumulator is necessary because:  

Over time, the situation may get worse, and some margin is needed. For example, an electrical-driven pump can degrade over time, which could decrease the available voltage to the electric motor of the standby oil pump. This voltage drop can impose serious limitations on the start-up time needed for the pump.

To deal with inaccuracies and uncertainties in the theoretical assumptions and analytical calculations. 

A bladder-type accumulator is recommended. Accumulators are usually constructed from a 300-series stainless-steel shell and often have a “nitrile” bladder, which forms a barrier between the inert gas (nearly always nitrogen) and the oil. Oil accumulators are usually installed vertically. Nitrogen is the best inert gas for this application because of its availability and chemical and physical properties. Air should not be used because of its corrosive or explosive properties. As a rough indication, the inert gas pre-charge is usually maintained around 80%-85% of the working pressure of the oil system. The high flexibility of the bladder causes the response time to be quick, which is an important factor considering the fast pressure drop in an oil system during an emergency or transient case. A properly selected large accumulator with sufficient pressure capability and a suitable differential pressure (between the oil accumulator and the oil consumption point) offers a fast response time. An oil accumulator should provide the oil flow fast enough and maintain the oil flow for the necessary period at sufficient pressure.

Standard methods and calculation procedures for commonly used water or process accumulators cannot be applied to an oil accumulator. A specific set of requirements and considerations is needed for oil accumulators in lube/control/hydraulic oil services, different from what’s needed for water or process services. An oil accumulator should push oil to the system once the minimum pressure (the low-pressure alarm + a margin) is reached. The required oil should hold up while the mid pressure (the pressure between the maximum and the minimum) is retained. This can result in two to four times more volume for the oil accumulator compared to a conventional water (or process) accumulator.

Amin Almasi is a Chartered Professional Engineer in Australia and the U.K. (M.Sc. and B.Sc. in mechanical engineering). He is a senior consultant specializing in rotating equipment, condition monitoring and reliability.

Guidelines and technical notes for dealing with lube oil, control, and hydraulic oil systems in turbomachinery.

Turbo Tips: How Transient Faults Affect Turbomachinery Lube Oil Systems

In this episode of the TurboTime podcast, Dr. Mike Shepard, Vice President of Aerospace and Defense at 3D Systems, discusses additive manufacturing, including its background as a fabrication technique in the turbomachinery industry, the role of data, as well as the various types of additive manufacturing. Dr. Shepard also addresses the advantages and disadvantages of this 3D printing technology, including size constraints, dimensional tolerance, etc., and advancements he sees happening in the near future.

"The adoption of additive manufacturing has really been growing in the turbomachinery industry,” Dr. Shepard said. “I'd say that's true in a couple of different ways—not just in the new-build environment where you're getting new construction and new designs, but it's also really important in the refit and aftermarket environment—parts, etc. And there are a lot of different reasons, right? You get design flexibility more than traditional methods. However, it's not going to replace things like CNC, but it's going to powerfully complement them. You also get very complicated geometries, which are possible now. And it's easy to incorporate extra complexity like cooling channels for fluid flow. You can also utilize it to combine a bunch of parts into one, which is super advantageous. We've seen examples where people were able to go from 200 components sometimes into one, and you can also iterate very quickly. So, these are the types of advantages that designers really love, On the back end, in the aftermarket/spare parts, it can potentially cut down on your lead time. I think a lot of the people who are listening to the podcast have probably had that experience—where you're waiting a year for a part sometimes, right? So with the additive manufacturing technologies that we have now, you can sometimes get that core metal part in a few days. So that kind of design flexibility and really tightening up your supply chain means that people are driven to pick up additive manufacturing technologies."

Shepard closed out the show with a forecast on the future of additive manufacturing technology: "I think we're going to see a lot of improvements in terms of the throughput of the processes and the economy of the processes. I'm really excited about the work that people are doing in metallurgy; there are these new computational methods you can use to discover new alloys, and you’ll see this more and more."

In this episode of the TurboTime podcast, Dr. Mike Shepard, VP of Aerospace and Defense at 3D Systems, talks about additive manufacturing. 

TurboTime Podcast: Additive Manufacturing with 3D Systems

With the transition toward a more sustainable energy economy, the old debate between reciprocating versus centrifugal compressors —and which one is better—has reared its ugly head again. For conventional hydrocarbon compression applications, this discussion has been raging for at least 50 years. But over the last 10 years or so most industry experts have arrived at some kind of peace agreement and a common acceptance that there are some applications where one or the other makes more sense. This has not yet happened in the new energy economy where this debate has just started. Since this is a complex subject, we will discuss it in a two-part myth with part one focusing primarily on applications and design, and part two will outline the fundamental challenges of each compressor type. 

When talking about alternative energy sources, the primary gases of concern are green or blue hydrogen and CO

 for carbon sequestration. Both hydrogen and CO

 are physically very different from each other and from natural gas—which is still the most widely used energy source. Whereas the widespread use of hydrogen for major energy production applications is forecast to occur in maybe 10-20 years, the implementation of carbon capture and sequestration in power plants is happening right now. Therefore, we will focus this article on what type of machine is best for CO

 compression. We can have a similar debate about hydrogen later … maybe in a few years from now. 

Reciprocating and centrifugal compressors are fundamentally very different machines. They use different compression principles and function mechanically differently. A reciprocating compressor uses a piston inside of a cylinder with suction and discharge valves for a positive displacement volumetric gas compression process. These compressors are well-suited for lowflow capacity requirements, high-pressure ratio applications, and can handle varying process gas compositions. However, reciprocating compressors are relatively bulky, less reliable, require more maintenance, and can produce higher levels of pulsations, vibrations, and noise. 

A centrifugal compressor uses rotating impellers and stationary diffusers in a fixed-volume gas compression process. Compression is accomplished by dynamically adding work to the gas. These compressors are ideal for medium-to-high flow capacity applications, are more compact, require less maintenance, and provide a smoother operation with reduced vibration and noise levels. Centrifugal compressors excel in handling large volumes of gas, making them ideally suitable for large-scale industrial processes. 

So, what are the applications of a typical carbon capture and sequestration application? In the United States, over 70% of the CO

 from stationary sources is emitted by fossil-fueled electric power plants. In many developing industrial nations, this percentage is much higher. Thus, the primary and initial target—the low-hanging fruits—for industrial-scale decarbonization using capture and sequestration are large fossil-fueled power plants. These power plants are mostly fueled by natural gas or coal. There are different options for carbon separation in fossil-fueled plants, including pre-combustion hydrogen production or post-combustion flue gas cleanup. In both cases, the CO

 will be produced at relatively low pressures, usually below 30 psia. After separation, the CO

 needs to be compressed to supercritical pipeline transport pressures to around 2,000-2,200 psia, and then injected into a geological formation for permanent storage at similarly high pressures. The advantage of transporting CO

 at supercritical pressures is that it has a high density (similar to that of liquid water) and very low viscosity, allowing for efficient pipeline transport. Operating in the dense phase also significantly reduces the power demand for the pumping or compression stations along a CO

 pipeline, although applications where existing natural gas pipelines are to be used will operate at much lower, typically subcritical, pressures. Thus, for the new sustainable energy economy, the most common compression applications are:

(1a) pipeline injection from near atmospheric to 2,000+ psia

(1b) pipeline injection from near atmospheric to 600 psia

(2) pipeline recompression or re-pumping with typical pressure ratios        around 1.5, and 

(3) geological injection compression or pumping from the pipeline at pressures that depend on the final geological storage pressure, which can vary widely but can be well above 2500 psia.

As a side note, from an aerodynamic design perspective, there is not much of a difference between a compressor and a pump when they operate at high pressures above 1080 psia in the dense phase. Here the fluid is not very compressible, and any work input does not result in significant density and temperature changes. The primary difference is that pumps are usually designed to operate at the synchronous speed of an electric motor while compressors often run at much higher speeds using a gearbox of high-speed drivers. Consequently, to achieve a similar head, pumps usually require more stages than compressors, but because of their construction, they are usually less expensive.

The reality is that centrifugal compressors can also produce high-pressure ratios for fluids that have physical properties associated with low specific heat and a high molecular weight, i.e., most heavy gases.

Back to the discussion of what is the best compressor for a sustainable energy economy: Reciprocating compressor manufacturers (and their supporters) claim that their machines are good for hydrogen compression. There is some truth to that for low-flow applications since reciprocating compressors using piston compression can achieve high-pressure ratios with relatively few stages. Similarly, they claim that, since most CO

 capture applications require very high-pressure ratios, reciprocating compressors are equally superior in this area. However, this argument is false and based on a fundamental misunderstanding of compression thermodynamics. 

The reality is that centrifugal compressors can also produce high-pressure ratios for fluids that have physical properties associated with low specific heat and a high molecular weight, i.e., most heavy gases. This is especially true for CO

, which has a molecular weight of 44 and a specific heat of 0.8 kJ/kg K. A basic reading and simple analysis of Euler’s turbomachinery equation (which relates fluid angular momentum to head) and the isentropic relationships (which relate temperature differential - and thus head rise - to pressure ratio) demonstrates this. Here the physical relationship between pressure rise and head for centrifugal compressors shows that each rotating impeller stage can produce very high-pressure rise even at moderate impeller tip speeds. For example, a single-casing centrifugal compressor can easily compress CO

 fluid from 20 psia to 1,200 psia (well above its critical point) using only seven impellers running at normal tip speeds of 1,200 fps. This is a staggering pressure ratio of 60:1. Clearly, these impeller stages must have some intercooling to avoid excessive temperatures and to maintain high efficiency, but this is no different than what is required from all types of compressors, including reciprocating compressors.

On the other hand, centrifugal compressors have major operational advantages over reciprocating compressors in that they can handle much higher flows, are more reliable, require less maintenance, have nearly zero gas leakage, do not contaminate the process gas with lubrication oil, do not require pulsation control, are significantly quieter, have lower vibrations, have a wider operating range, are easier to scale, and provide for more concise and stable flow control. In the past, for lower-flow carbon sequestration applications, reciprocating compressors rather than centrifugal compressors were the traditional option. These were mostly electric motor-driven. However, as the industry is moving rapidly toward much higher CO

 capture flow rates, the limits of the practical use of reciprocating compressors are being reached. 

In part two of this Myth Busters article, we will discuss compression challenges and some of the lesser-understood disadvantages of reciprocating compressors for CO

The authors want to thank Karl Wygant and Rob Pelton, both at Elliott Turbo, for their contributions to this article.

Klaus Brun is the Director of R&D at Elliott Group. He is also the past Chair of the Board of Directors of the ASME International Gas Turbine Institute and the IGTI Oil & Gas applications committee. 

Rainer Kurz is the Manager of Gas Compressor Engineering at Solar Turbines Incorporated in San Diego, CA. He is an ASME Fellow since 2003 and the past chair of the IGTI Oil & Gas applications committee.

Any views or opinions presented in this article are solely those of the authors and do not necessarily represent those of Solar Turbines Incorporated, Elliott Group, or any of their affiliates.

Part one of this two-part myth on reciprocating versus centrifugal compressors addresses design and application differences.

Myth Busters: Part I: Reciprocating vs Centrifugal Compressors for Carbon Capture and Sequestration 

The U.S. Environmental Protection Agency (EPA) drafted a third set of greenhouse gas regulations using an explicit Congressional delegation of authority, but litigation is still expected. Although climate change has led to more weather extremes, decarbonization of the U.S. power sector remains a “two steps forward, one step back” exercise.

As the United States prepares to enter the third year of the Biden administration, with its priority to decarbonize the electric generation market, the challenges to decarbonization are so significant as to call to mind the Tennyson poem, “The Charge of the Light Brigade,” which chronicled the ill-fated attack launched by lightly armed British cavalry troops against better-armed Russian artillery forces during the Crimean War. As recounted by Tennyson, the British troops suffered a beating at the hands of the more numerous and better-equipped Russians:

Cannon to right of them, 
Cannon to left of them, 
Cannon in front of them Volleyed and thundered; 
Stormed at with shot and shell, 
Boldly they rode and well, Into the jaws of Death,
Into the mouth of hell
Rode the six hundred.

A seasoned dealmaker with 36 years of inside-the-Beltway experience as a U.S. senator, Joe Biden as President has notched impressive legislative victories to decarbonize the U.S. power industry. The Infrastructure Investment and Jobs Act, enacted in late 2021, and the 2022 Inflation Reduction Act, with $369 billion in federal support for renewable energy, will go a long way to reducing CO

U.S. Power Generation Capacity: Under Development with Construction Kick-off Scheduled During 2024-2028

In May 2023, the EPA issued its third set of draft regulations to reduce CO

emissions from current and future power plants. All significant accomplishments. But permanent? One wonders, given the forces that stand in opposition:

Congressional Republicans, furious about House Speaker Kevin McCarthy’s 11th-hour debt ceiling deal this past spring, are determined to claw back federal spending on renewable energy, among other items, under the rallying cry of fiscal austerity.

Coal-rich states such as Montana, Wyoming, West Virginia, Kentucky, and Utah have enacted various measures to impede the closure or sale of coal-fired generators in their states, prop up in-state coal mines, and preserve the flow of tax revenues into state coffers.

In the closing hours of the 2023 Texas state legislative calendar, lawmakers approved, and Governor Greg Abbott signed into law, a bill creating a $10 billion fund to support the construction of new gas-fired generation, as well as the modernization of existing gas-fired generators. Republican-elected officials and fossil-fuel interests staunchly oppose the EPA’s May 2023 draft Clean Air Act rule designed to limit CO

 emissions from power plants. Legal challenges are sure to come, perhaps even before the rule is finalized, and yet another trip to the U.S. Supreme Court appears likely. 

If such a legal challenge does make its way to the highest court in the land, the composition of the court seems unfavorable to those who seek to decarbonize the power sector. In 2022, the justices ruled 6-3 against an EPA effort to cut carbon emissions. Shortly after that decision, Congress closed the regulatory loophole that gave the justices such pause. Will the third time be the charm for this rule, or will the court find yet another reason to intervene?

These and other challenges to decarbonization emerged during 2023 and are expected to continue unfolding in 2024 and beyond to shape the U.S. new-build power business. The industry has an outlook that extends for decades, but small changes in the near term can lead to dramatically different outcomes in the long term.

That said, renewable energy continues to dominate the outlook for U.S. new-build power-generation projects scheduled to begin construction over the 2024-2028 period.

The transition to lower-emitting generation fuels has been underway for several years, but the 2022 Inflation Reduction Act’s direction of $369 billion of federal funds into renewable energy is expected to significantly strengthen a years-long trend of heightened investment in new non-emit-ting electric generation.

According to data tracked by Industrial Info Resources, 94% of all new-build power generation projects scheduled to begin construction in the United States between January 2024 and December 2028 will be for renewable energy (see the

Figure 1: Planned New-Build Generation, Renewables vs. Gas

That spending is expected to extend the rush to renewables, but what’s different about the 2024-2028 period is the dramatic increase in the projected volume of new-build construction: Developers plan to build about 482 GW of new generation over the 2024-2028 period, up 22% from last year and at least double the amount of any five-year period in the last 14 years (

By and large, electric utilities have found that their customers like and prefer renewable energy, provided it is cost-competitive with electricity produced from other fuels.

Figure 2: Planned New-Build Capacity Additions Shoot Up

The COVID-19 pandemic, now apparently receding into the rear-view mirror, turned much of the discussion about the energy transition into a rueful recognition of the importance of supply chains. In 2023, electric utilities were forced to defer, or rebid, planned renewable energy additions, citing rising component prices and delayed delivery dates. Evergy, an electric utility serving customers in Missouri and Kansas, caught some negative publicity from members of the environmental community in mid-2023 after it went public with a revised schedule and mix of generating options that included building new gas-fired generation, per requirements of its grid operator, and keeping some operating coal generators open past their planned retirement dates. Other utilities have had to rejigger their clean-energy plans, some more publicly than others.

Ultimately, state utility regulatory commissions, along with grid operators, have the whip hand in deciding what gets built where and when. We expect that the shifting economics of generating electricity will force several public utility commissions (PUCs) to revisit decisions made in earlier integrated resource plan (IRP) dockets.

Texas already has decided: Going forward, natural gas will play a bigger role in the state’s electricity future. Lone Star State politicians were quick to blame—incorrectly, as it turned out—renewable energy for the rolling blackouts and multiple catastrophes triggered by Winter Storm Uri in early 2021. More objective analysis found that frozen natural gas lines and poorly winterized thermal power plants bore a more signifi-cant share of responsibility for that event.

Never letting the facts get in the way of a good story, Texas politicians and the state’s grid operator, ERCOT, have been advocating for an increase in dispatchable, i.e., gas-fired, generation to ensure the lights stay on during weather extremes. The state has weathered some white-knuckled summer peaks in recent years, so the call for more dispatchable generation wasn’t all home-state hoopla.

In mid-2023, Republican Texas Governor Greg Abbott signed into law a bill to create a $10 billion fund to support building new-build gas-fired generation and modernizing existing gas power plants.

Republican-led energy-producing states like Texas, Montana, and Wyoming, among others, effectively are working in partnership with U.S. Senator Joe Manchin (D-WVa), chairman of the powerful Energy and Natural Resources Committee, to preserve the role of fossil fuels in the nation’s electricity supply.

Natural gas is expected to hold a strong share of the electric fuels market for the near term, accounting for approximately 41% of electricity generated in 2023 and 40% in 2024, according to the July 2023 Short-Term Energy Outlook produced by the U.S. Energy Information Administration (EIA). Coal’s market share is expected to continue weakening in the near term, sinking from 20% in 2022 to an estimated 15% in 2023, before rising slightly to 16% in 2024. Nuclear’s share of the electric generating mix is expected to hold steady at about 19% over the 2022-2024 period, while solar and wind are expected to continue gaining market share.

New-build coal-fired generation has been a rounding error in recent years, and the 2024-2028 period is no exception. “Early retirement” continues to be the watchword for existing coal-fired generation, with nary a new-build project in sight.

About 133 GW of coal-fired capacity has been retired since 2010, and over the 2024-2028 period, Industrial Info Resources (IIR) expects another 51 GW of coal genera-tion to be retired (

Figure 3: Coal-Fired Unit Retirements: Historical and Projected

But there are about 146 in-plant capital projects, worth an estimated $16.5 billion, that are scheduled to kick off at coal-fired power plants across the United States over the next five years. This broad category of projects includes automation; carbon capture, utilization, and storage (CCUS); debottlenecking; decommissioning and demolition (D&D); efficiency upgrades; environmental remediation; life extensions; upgrades; and uprates.

The states with the largest dollar value of in-plant capital projects are Wyoming (five projects valued at about $2.7 billion); Illinois (eight projects worth approximately $2.4 billion); Texas (19 projects valued at $2.2 billion); and New Mexico (one project worth about $1.3 billion).

The $16.5 billion of planned in-plant capital projects includes CCUS projects. A sharply increased federal tax credit of as much as $85 per ton of CO

 removed has led companies to schedule billions of dollars of CCUS projects to be constructed at coal-fired power plants over the next five years. We are tracking six CCUS projects, valued at $7.4 billion, that are scheduled to be built at stations in Illinois, Texas, Wyoming (which has three projects), and New Mexico over the next five years. These projects are expected to be vying for expanded federal tax credits under section 45Q of the federal tax code. 

Also included in that $16.5 billion sum are approximately 58 coal combustion residuals (CCR) remediation projects that are scheduled to begin construction by the end of 2028. The total investment value
(TIV) of these projects is about $3.6 billion. The states with the greatest dollar value of projects for remediating CCR, also known as coal ash ponds, are Montana, Texas, Indiana, and Missouri.

Coal power plant decommissioning and dismantling (D&D) projects also are included in that $16.5 billion in-plant capital sum. The value of these D&D projects is about $2.3 billion. The states with the largest dollar value of D&D projects include Ohio, Michigan, Indiana, Texas, and South Carolina. 

The grim outlook for coal-fired generation in the United States mirrors the outlook for coal mining. The number of people engaged in coal mining has leveled out at about 41,000, down more than 75% over the last two generations, according to the St. Louis Federal Reserve Bank (

). And the amount of coal burned to generate electricity, after briefly surging in 2021 and 2022 as utilities restocked their fuel-depleted piles, is expected to fall in 2023 and 2024 (

Figure 4: Coal Mining Employment Flattens

King Coal’s woes are a result of many factors—regulatory, legislative, economic, and technological—but another significant contributor is the rise of so-called “respon-sible” investing, where bankers and investment managers at pension funds, mutual funds, and other sources of public and private capital use environmental, social, and governance (ESG) metrics to identify companies in which they want to invest—and those they don’t.

Figure 5: Coal Use at Electric Generators Expected to Decrease in 2023, 2024

Institutional investors with more than $120 trillion of assets under management have adopted the U.N. Principles of Responsible Investing (PRI), which don’t permit investing in or lending to companies in the coal business (

Because each trend spawns a counter-trend, there has been some recent push-back against ESG, or “responsible” investing: 18 states have enacted or proposed legislation restricting the state from doing business with companies that use ESG investing criteria, arguing that those criteria mask a political agenda. 

Figure 6: Surge in Cumulative Investments in “Responsible” Companies and Funds

During 2023, coal generators in a variety of states, including Michigan, Utah, Pennsylvania, Tennessee, West Virginia, and Texas, either were closed or announced premature retirement decisions. Asset owners claimed a variety of reasons for the decisions, but, broadly speaking, there were two reasons: 1) renewable generation, even allowing for its recent price increases, is still more economical than operating existing coal plants; and 2) state and federal environmental regulations and laws made it uneconomic to continue operating those plants.

A countervailing trend to coal unit retirements is the delay in planned retirements due to delays in interconnecting renewables to the grid, supply chain bottlenecks, and permitting delays. In the face of rising electric demand and continued uncertainties surrounding new-build projects, an operating power plant—even one that burns coal—is worth more than projects that remain on the drawing board.

Natural gas generation is feeling the fossil-fuel “splatter” effect that has hobbled coal-fired generation. Even though natural gas only emits about half the CO

 as coal when burned for generation, gas-fired generation still contributes to global climate change.

After a decade when developers made a “dash to gas,” that bloom is off the rose. Only about 4.7% of all new-build generation scheduled to begin construction over the next five years will use gas as a fuel. By contrast, as shown in 

, five years ago that percentage was 41%. A decade ago, that percentage was a still respectable 36%. Gas’ share of the electric fuel market should rise over the next five years, as Texas begins disbursing its $10 billion to support dispatchable generation. But for now, the new-build gas market remains a shadow of its former self.

The regions with the largest share of planned new-build gas generation are the Mid-Atlantic (15.6%) and the Great Lakes (13.6%). At the other end of the spectrum, the regions that plan to build the least amount of gas generation over the 2024-2028 period are New England (0.1%), the Rocky Mountains (0.3%), the Southeast (0.7%), and the Midwest (1.6%). All told, IIR expects about 19 GW of new-build gas generation to be built over the next five years.

By contrast, about $19.1 billion of new-build natural gas-fired generation projects that were scheduled to kick off during 2024-2028 have been canceled or placed on hold, according to IIR’s data. The states with the greatest dollar value of project delays or cancellations are Texas (nine projects valued at $6.6 billion), Michigan (six projects valued at $ 2.5 billion), West Virginia (two projects valued at $1.4 billion), and Florida (six projects valued at $1.1 billion). 

As large as these numbers are, they pale in comparison with the prior five-year period (2019-2023) when developers canceled or placed on hold 224 proposed new-build natural gas-fired projects valued at $80 billion. For that period, the greatest dollar value of cancellations and project delays were Texas (41 projects valued at $18.2 billion), Pennsylvania (25 projects valued at $7.7 billion), Virginia (seven projects valued at $4.9 billion), Ohio (eight projects valued at $4.5 billion), and New Jersey (seven projects valued at $4 billion). 

The wave of proposed gas plant cancellations and deferments doesn’t reflect the sharp political divide between blue and red states. Deep-red states like Texas, Florida, Indiana, and Ohio are among the leaders in gas-fired project cancellations or deferments, alongside deep-blue states like California, New Jersey, New York, and Pennsylvania.

Whatever the drivers—remember Tip O’Neill’s famous quip that all politics is local—the dash to gas has slowed dramatically. What could revive it? Widespread generation-related power outages. Perhaps Texas had solid reasons—beyond supporting the home team—to create a $10 billion fund to build or modernize gas-fired generation. 

As the United States sweltered under an unrelenting heat dome during the summer of 2023, fingers were crossed that power plants that were being run hard and long would hold up.

Developers who canceled or placed proposed gas-fired power projects on hold cited the shifting economics of electricity generation, driven by technology advances and regulatory or legislative mandates to build non-emitting generation. For example, New York’s plan to fight climate change envisions 70% of all electricity coming from non-emitting generation. California’s renewable portfolio standard (RPS) requires 60% of electricity to come from renewables by 2030 and 100% by 2045. 

The Golden State recently reported that RPS-eligible resources accounted for more than 37% of electricity delivered to custom-ers in 2021. But there are signs that the Golden State may be rethinking its stance on gas, at least for the near term. In a mid-year 2023 article, “California just can’t kick its coastal gas plant addiction,” the 

“Three natural gas-fired power plants in Huntington Beach, Long Beach and Oxnard were supposed to shut down in 2020, under a regulation designed to protect marine life. But (in 2020) officials voted to let the polluting generators keep churning out power another three years, just a few weeks after California experienced its first rolling blackouts since the early-2000s energy crisis. Now regulators are gearing up to approve another three-year extension, which would allow the plants to run through 2026. It’s only the latest illustration of the difficult balancing act California faces in its quest to phase out planet-warming fossil fuels and show the rest of the world that addressing the climate crisis is possible.”

The hand of environmental regulators in the state was forced after several summers of wildfires and power outages led to unpopular public safety power shutoffs (PSPS), where investor-owned utilities were given permission to preemptively shut off power in certain areas under red-flag conditions: high heat, low humidity, and high winds. Those conditions, coupled with failing utility equipment, have sparked extremely destructive wildfires in recent years. But even the PSPS could not stop rolling blackouts in certain areas during the blazing hot summer of 2022.

The state’s environmental regulators, forced to choose between people without power during broiling summers or fish that could be harmed by warmer water from gas-fired power plants, opted for people over fish.

The decision also was shaped by the state’s deepening “duck curve,” in which there is a surplus of renewable power during off-peak periods, like mid-day during the summers, and a shortfall during summer afternoons. Dispatchable gas-fired generation to the rescue! At least, for the short term.

California has not greenlighted a new-build gas power plant. Instead, it is trying to get a few more years of service out of the gas-powered generators on the coast, until battery energy storage becomes large enough, reliable enough, and economically viable so that it can replace gas generation. Gradually, gas generation will fade in California.

But gas is proposed as the fuel to power several large planned CCUS projects in the Golden State. Overall, gas will be used in about 4% of new-build generation constructed in the western United States over the next five years; by contrast, developers plan to build far more renewable generation—about 49 GW worth—in that region over that timeframe.

Gassier regions include the Great Lakes, where about 6 GW of new-build gas generation is slated to start turning dirt over the next five years. Developers also plan to begin construction of about 5 GW of gas generation in the Southwest during 2024-2028. In the Mid-Atlantic, about 3.6 GW of new gas generation is expected to begin construction over the next five years.

Electric asset owners have paid more volatile prices in recent years when com-pared with the quieter period of 2015-2020 when prices averaged a little more than $3 per million British thermal units (MMBtu) (

). But Winter Storm Uri in early 2021, and Russia’s invasion of Ukraine in early 2022, briefly brought gas price volatility back with a vengeance, according to the EIA. Market forces of supply and demand have since reasserted control, driving pieces back down to pre-Uri levels.

Figure 7: Gas Prices Paid by Electric Generators since 2002

Electric generators are expected to pay an average of between $3 and $4 per MMBtu during 2023 and 2024, the agency predicted. Longer term, the EIA expects gas use for electric generation to fall about one-third, from approximately 12 trillion cubic feet (Tcf) in 2022 to less than 8 Tcf by 2030, though the agency’s Annual Energy Outlook acknowl-edged there could be a high level of variance under alternate scenarios (

). Demand for gas among electric generators will fall as renewables capture market share.


Renewables continue to rock the new-build electric generation market, but gas-rich Texas, and some locals, are pushing back.

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