Valves commentary

Embracing industry 4.0 multiphysics in the modern valves industryBy Jonas Wirgart, Keith Hanna & Makoto Shibahara

Figure 1: Ancient Roman In-Line Valve from Pompeii (2)

The global valves industry is arguably one of the oldest in the world stretching back into antiquity, but today it is having to embrace the challenges of Industry 4.0 and the advent of smart factories and smart manufacturing facilities with the approach of autonomy ever closer (1). The general goal of Industry 4.0 is to use sensors, data, artificial intelligence (AI) and other real measurement and virtual simulation predictions to increase manufacturing productivity, reduce downtime & maintenance and ultimately to improve profitability. Valve manufacturers will benefit from smart manufacturing and Industry 4.0 because the Industrial Internet of Things (IIoT) will connect billions of sensors in factories and facilities around the world that detect fluid levels, pipeline pressures, flow rates, vibration levels, temperatures, and the equipment’s position during operation in real time.

This connection of valves to the IIoT will be monitored and analysed to control or regulate piping systems and due to the advent of smart manufacturing there will be a diminishing need for frequent human intervention to check on a valve’s status. The device itself will generate lots of data for subsequent analysis by both human and AI/ML systems (2).

With respect to valves, it is fascinating to look back at the Roman Empire where in the city of Pompei for instance in southern Italy, their civilisation had actually mastered flow control valves for their municipal water supply (at a pressure of 8-9 psi) by the time of its devastation by the eruption of the nearby Mount Vesuvius in 79 AD. Archaeologists found inside well-preserved ruins of the entombed buildings sophisticated in-line control valves made of bronze of large dimensions (Figure 1) connected to an extensive network

of lead piping and stone ducts under streets and into houses. Indeed, experts have discovered that these Roman plug valves were made to remarkably consistent specifications and complied to uniform standards (3) across the whole Roman world that are close to modern ASME valve standards today!

The need to keep fluids flowing and controlled over the last 1,600 years since the fall of the Roman

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Figure 2: Cradle CFD simulations of the most frequent categories of industrial valves

Empire has not gone away and, if anything, is even more important today than ever before because the cost of failure is immense in terms of environmental pollution (for nuclear, chemical and Oil & Gas valves), and death and catastrophic failure (for medical and aerospace valves). Ensuring multiple physics related performance phenomena are addressed at the design stage of creation of a valve, ensuring it is manufactured to high tolerances and that it is used throughout its lifetime without serious operating problems is mission critical. Today there are many different types of valves in operation across the world (see Figure 2) and all can benefit from CFD (Computational Fluid Dynamics) and CAE (Computer-Aided Engineering) simulations at the research & development stage as well as for subsequent retrofits in the field. Indeed, there is a growing impetus to design for sustainability and recyclability in manufacturing as a whole and in the valves industry by taking into account the full lifecycle of the valve and its components up to disposal or recycling. The need for right-first-time and right-every-time by design is clearly becoming

ever more pressing as reduced maintenance and downtime becomes essential to maintain factory and facility performance, productivity and cost constraints.

We have identified the twelve main multiphysics related mechanical design challenges facing valve designers and manufacturers today that CFD and CAE simulation can address:

Pressure drop optimisation

This is the classic well-established need from CFD tools by the valve industry over the last thirty years or so (see Figure 3). As always, there is a need for a balance between minimising pressure drop across a valve versus flow rate for the fluid going through it. What CFD is very good at is in helping engineers and designers understand where the pressure drop is happening through the valve, what impact the valve is having with the surrounding pipework, and indeed it can show any valve-valve interactions that may be occurring if valves or other pipeline pressure drop components are interacting. As well as steady state losses, transient phenomena in the valve can also be evaluated using CFD.

Static and dynamic forces, torques & spring loadings

All valves have mechanical control mechanisms and when they are operated or turned on or off assorted transient spikes in force and torque moments caused by the fluid can happen. This can cause significant loads on springs and mechanical components within the valve including deformation. Cyclical durability and fatigue effects that might lead to damage or component failure inside the valve or associated system can also be important. MSC Software has tried and trusted structural analysis tools like MSC Nastran or Marc to simulate fluid-structure interaction effects accurately when coupled with CFD and Adams for multibody dynamics simulation can easily pick up fluidic impact on the valve control mechanisms or even flexible deformation effects. Temporary pressure surges in fluid systems can be important in terms of simulating safety control valves and for bursting disk situations for flow blow-outs. Finally, as valves move from being purely metal constructions to using more exotic materials and combinations of materials (plastics,

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composites, new alloys...) CAE simulations can offer benefits including durability, corrosion prevention and lightweighting (especially 3d printing of parts) assessments. It is generally recognised that structural integrity and structural performance will become more and more critical in valve design and manufacture.

Heat transfer & thermal shock effects

Some valves have to operate in extremely high or low operating temperatures or in flow systems and processes where heat transfer is important. This can lead to hotspots in or near valves with consequent fatigue and even thermal shock issues. Transient and periodic thermal loads can impact valve performance over time quite significantly. Temperature effects can also impact fluid mixing

phenomena in pipework, tanks and vessels. Similarly, chemical reaction processes and catalysis, plus combustion and allied processes can impact the performance of a valve with significant thermal strains being experienced. Such valves will require both CFD and CAE related simulations to understand their operating envelopes better. And with all sorts of metals and different forms of steel being used in metal valve design, their differential thermal coefficients may be crucial to valve performance. And with the advent of composite materials, new ceramics and new polymers, thermo-mechanical properties of valves are increasingly becoming more complicated and sophisticated to simulate.

Noise level estimation

Noise has become a big issue in valve operations. Fluidic noise and

mechanical vibrational noise affect the function of a valve and can cause fatigue in adjacent piping which will reduce the valve’s service life (4). Hence, how to control the noise of valves is becoming an important strand in valve research and development. Together with health hazards associated with the decibel limits plant operators are exposed to and environmental noise hitting those people living near the facility, noise is a sustainability issue. Such things as pressure and shock waves in pipe networks can also cause structural vibration and water hammer noise. Indeed, some valves have to deal with transonic and even supersonic gaseous flows and with complex turbulent mixing after a valve; all sources of noise. Sonic flow effects require good compressible solver CFD simulation capabilities such as in Cradle CFD tools.

Figure 4: Control Valve showing acoustic levels inside Actran when it is 70% open

Figure 3: Control Valve Opening versus Flow Coefficient prediction curve for a series of Cradle CFD simulations of a ball valve versus experiment

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Dynamic motion, oscillation, 6 Degrees of Freedom (DOF) & valve closing effects

Increasingly, many new types of exotic valves with complex moving parts are being devised for applications like biomedical and space. Reed valves and self-regulating/self-actuating valves where control is flow dependent make for very complex CFD simulations. Cradle CFD is uniquely placed to deal with such complex valve body motions and valve seal contacts because motions of rigid bodies driven by fluid forces can easily be simulated. Contact between moving bodies can also be calculated with Cradle’s overset meshing capability easily allowing for 6 DOF motions. Finally, ‘pinch points’ occur in CFD meshes near contact points at closure that some CFD solvers cannot deal with whereas Cradle CFD has special formulations to deal with the numerical issues involved.

Particle-laden fluids & non-Newtonian flows

Flows with particulates, slurries and sediments are common in some sectors like Oil & Gas or the Water industry. Such particulates hit each other and the surfaces of the valve components with sediment movement and even buildup being a performance issue. Understanding complex turbulent flow fields inside valves and the way particles are carried and even projected against surfaces is critical for avoiding valve damage, closure of narrow passageways and ultimately expensive maintenance and downtime. Cradle CFD has very powerful Discrete Element Models (DEM) to simulate all granular particle sizes and it can pick up deposition issues and particulate buildup as well as the consequent flow channel shape changes and

resultant pressure drop increases and reduced flow rate effects. Being able to simulate what is happening at the valve seat where sand particles for instance can become trapped between the valve and the valve seat causing leakage is also important.

Cavitation & phase change effects

Cavitation is a phase change phenomenon by which the static pressure of a liquid reduces to below the liquid’s vapour pressure leading to the formation of small vapour-filled cavities in the liquid at nucleation sites. When subjected to higher pressure, these cavities, called “bubbles” or “voids”, collapse generating shock waves on surfaces ultimately damaging nearby equipment and surfaces. These cavitation shock waves can be strong when they are very close to the imploded bubble, but rapidly

weaken as they propagate away from the implosion. Cavitation is possible in valve liquid flow installations and it can be a significant cause of pipeline and valve wear due to surface fatigue of the metal. “Supercavitation” can also occur in some instances when the pressure differential in a system is so high that the location of the cavitation moves several pipe diameters downstream from the source, and wear, noise and pipe damage moves there too. Cavitation generally is associated with strong external noises in the system. Check valves can also experience flashing and cavitation.

Simulation software like Cradle CFD can predict detailed processes such as evaporation and condensation using its inbuilt well validated cavitation models so that users can investigate the region cavitation will form and how it propagates (5). CFD can also estimate the efficiency of the valve under cavitation and show

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where erosion and damage is likely to occur. Fluid-acoustic co-simulation with Cradle CFD, Actran and Marc can uniquely assess acoustic, fluid and structural effects simultaneously – see Figure 5.

Erosion effects within the valve

Erosion mostly occurs due to hard particles (for example sand) damaging the inside of a valve, its mechanisms and surrounding pipework. It may also occur due to the collapse of cavitation bubbles, and in certain piping under the right conditions it might also lead to corrosion due to chemical reactions at the flow/pipe interface. As erosion proceeds it also alters the shape of the pipework and valve thus altering the valve’s performance and flow characteristics possibly leading to poor

sealing of the valve when fully closed. Erosive damage may require stoppages and downtime for repairs and is an undesirable cost to fix. Sometimes, once erosion starts it can alter flows through the valve and surrounding pipework to the extent that erosion moves to another location in the system. Cradle CFD and its Discrete Element Models (DEM) can estimate and visualise the movement of particles in the flow field and show what regions are susceptible to erosion and damage. For cavitation, Cradle CFD provides the output of 4 erosion indices on the valve’s surface so designers can evaluate mitigation strategies at the design stage.

Structural deformation effects

MSC Software’s structural analysis tools like MSC Nastran, MSC Apex or

Figure 6: Sand particle erosion in a valve bend system near a valve in Cradle CFD

Figure 5: Azbil Control Valve Cradle CFD prediction with cavitation effects simulation vs. experiment (5)

Marc can co-simulate multiphysics fluid-structure interaction effects accurately with Cradle CFD and with Adams multibody dynamics simulation, users can easily determine flexible deformation effects. Such phenomena can cause valve catastrophic failures due to fatigue and vibration inside pipelines. Cradle CFD has a very powerful overset meshing approach such that co-simulation with MSC Nastran or Marc yields detailed information on structural deformation. Valve designers can then invent new deformable valve components that reduce manufacturing costs and times. Safety valves such as bursting disks can act as pressure relief/release valves and have significant deformation characteristics.

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simulations can be extremely difficult and inaccurate. Cradle CFD has dedicated features for accurate and robust transonic simulations that will yield force and deformation predictions especially through narrow channels and in the final valve pinch points during closing motions.

Smarter valves – autonomy, AI and the IIOT

The advent of Industry 4.0 and ‘digital twins’ - virtual representations of physical objects or systems across their lifecycle, using real-time data to enable understanding, learning and reasoning - will include many technologies that bridge the gap between the physical and digital worlds. These will include the Industrial Internet of Things (IIoT), Artificial Intelligence (AI), machine learning, augmented reality, robotics, data analytics and 3D printing (6). All of these technologies and their application inside manufacturing are, and will, rapidly change the way products and processes are designed, built and used. These will allow data in a control room to be accessed in real time to ensure safety is complied

with. The creation of more predictive simulation models with Machine Learning and cloud computing will allow for more “what if...” scenarios to be assessed in real time. CFD/CAE simulation is uniquely positioned to provide the required training data for valve operators and support of Controller / Sensor Learning will yield better training data. This approach will also replace costly programming processes thus enabling the creation of autonomous systems.

Industry 4.0 will undoubtedly make valves smarter by connecting them to sophisticated control systems and the IIoT. The advent of ROM (reduced order modelling) for valve CAE simulations will help facilitate this. Smart sampling technologies will also reduce the number of CAE simulations compared to traditional CAE optimisation approaches thus visualising flows through new designs without running extensive arrays of simulations. Basically, valve users will be able to leverage any type of data, be it test data or CFD/CAE simulation data, to make intelligent decisions in a factory or facility in the not-too-distant future.

Steam & superheated flow effects

Superheated steam is frequently use in many chemical processing facilities as a powerful form of heat transfer in for example heat exchangers and reaction vessels. However, it requires the management of flow control to cope with unique thermodynamic characteristics like nucleate boiling, cooldown, phase change and other steam related combined heat and mass transfer phenomena. Nucleate boiling can be simulated well in Cradle CFD (Figure 7).

High speed & high-pressure effects

In some high pressure, high speed gaseous flows the fluid in a system can become transonic and even supersonic inside and beyond the valve body. These systems tend to have complex geometries and are characterised by high pressure drops through very narrow passageways. Indeed, shock waves can form in these networks and propagate pressure waves. When dealing with transonic and supersonic gaseous flows through valves, CFD

Figure 7: Nucleate boiling prediction inside Cradle CFD of a serpentine pipe (experiment black on the left, CFD blue on the right)

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Figure 8: EdgeCAM machining simulation

Figure 9: MÜLLER Quadax® butterfly valve on a Leitz LSP-X1h Stationary CMM Scanner

The benefits of multiphysics-focused CFD to the valves industry

CFD and CAE have the powerful capacity to do “what if..” scenarios in real time on your desktop or in the cloud to meet competing valve design criteria:

• Optimise Pressure Drop• Reduce Noise• Reduce Structural Vibrations• Reduce Thermal Stresses• Minimise Erosion• Visualise flows inside the valve

and systems• Explore the complete design

envelope• Understand co-simulation

multiphysics characteristics of your valve-pipeline system

CFD helps users understand valve – flow – pipeline interactions virtually without having to create prototypes. This allows for near Real Time design exploration. Entire Cradle CFD simulation processes can be automated and thus companies can save significant money and time on successive simulations while allowing anybody to utilise CFD in the company without operating it. This also avoids long, complex and costly traditional (pre/solve/post) CFD simulation processes.

Computer-aided manufacturing and machining of valve components with Hexagon MI solutions

Industrial valve manufacturers all require quality manufactured products with high precision tolerances especially in valve seals and mechanical parts to ensure reliability especially in sectors like nuclear and Oil & Gas (7). EdgeCAM from Hexagon Production Software has been used extensively for CAM programming of the creation of many parts for process control valves, such as at Fisher Valves. Everything from mild steel and aluminium valve gear components can be milled on 3 or 5 axis machine tools and because they need to be high precision users know that with Edgecam’s NC code they always will be (see Figure 8).

Whether it is gate, globe, check or ball valves, from design to production, premium steel valves need to be made to high precision in a wide variety of models and dimensions and Hexagon’s Contact Measurement Machines (CMM) – see Figure 9 – have been tried and proven to ensuring manufactured valves meet customer tolerances (8).

Finally, non-destructive industrial CT scanning allows for the investigation of valves during normal operation and as installed. This approach goes way beyond what can be accomplished using conventional destructive or other non-destructive inspection methods. Individual parts of a valve or the system in which it is installed can be measured in situ without having to disassemble the valve. VGSTUDIO MAX from Hexagon allows valve manufacturers to perform 2D and 3D industrial CT measurement tasks directly on voxel data sets to yield insights into cavities and gaps within the valve body.

Summary

The global valves industry today is currently going through a paradigm shift (3) as manufacturers need to deal with digital transformations across various industry sectors that are embracing Industry 4.0 and smart technologies such as AI and Machine Learning. Digital transformations in factories and manufacturing facilities and the need to deal with ever more stringent environmental legislation requirements are propelling this shift. There are many benefits to multiphysics-focused CFD simulations in the valves industry:

• The ability to virtually see flow effects inside valves before they are manufactured

• Assessing ‘what if’ scenarios for valves before they are installed on site

• Create right-first-time designs cost effectively at the conceptual stage

• Minimising downtime and maintenance by designing out mechanical faults

• Understanding complex multiphysics interactions inside the valve

• Increasing the full lifetime of the valve by improving its performance, and

• Preventing environmental leakage of toxic or damaging fluids and resultant pollution penalties.

Hexagon | MSC Software’s unique and unrivalled CAE solutions with its buy-once and use various multiphysics simulation tools as needed inside the MSCOne token system allows valves manufacturers to address all physics types during design of modern valves – fluids, structures, system dynamics and acoustics all in one. This means that mission critical valves can be designed quickly and accurately to a high quality and standard and then manufactured and deployed with confidence.

Fast design decisions for R&D engineers and valve designers can include Cradle CFD’s unique overset meshing capabilities that allow for accurate closing/contact motions for valve closure predictions in particular. Deformable and moving valve motions can also be captured accurately such as in reed valves, diaphragm valves and poppet valves as well as special Oil & Gas, biomedical and aerospace valves. All flow regimes and fluids can be simulated using CFD including high pressure/high speed gas flows and acoustic and cavitation predictions can be simulated accurately. Finally, damaging erosion and particulate build up effects can be simulated inside valves with a modern DEM model. Hexagon Manufacturing

Intelligence’s world-leading Optical and CT-Scanning technologies as well as market leading Computer-Aided Manufacturing (software) such as EdgeCAM can be coupled to CAE simulation predictions to deliver ‘digital twins’ of your valve. This unique combination of virtual and real data creation can allow valve manufacturers to speed up their manufacturing, ensure high accuracy designs, and improve the quality and productivity of end products as installed on site.

References

1 “Implementing the Fourth Industrial Revolution”, B. Donohue, Valve Magazine, 17 Dec 2019 http://valvemagazine.com/magazine/sections/features/10349-implementing-the- fourth-industrial-revolution.html2 “Ancient Roman Valves”, W.F. Lorenz, 19 Feb 2013 https://www.valvemagazine.com/web-only/categories/manufacturing/4947-ancient-roman-valves.html3 “Digital Twins: Connecting Real and Virtual Space”, B. Donohue, Valve Magazine, 10 Mar 2020 http://valvemagazine.com/web-only/categories/technical-topics/10488-twins-connecting-real-and-virtual-space.html4 “The Flow Noise Characteristics of a Control Valve”, X. Nie*, Y. Zhu and L. Li, The Open Mechanical Engineering Journal, 2014, 8, 960-966 https://benthamopen.com/contents/pdf/TOMEJ/TOMEJ-8-960.pdf5 “Achieving Size Miniaturization and Noise Reduction of Control Valves”, Azbil Control Valve Cradle CFD Customer Story: https://www.cradle-cfd.com/media/sc_tetra/sc_tetra_case/a186 “The Emergence of Artificial Intelligence in CAE Simulation”, K. Bouchiba, K. Kayvantash and K. Hanna, MSC Software White Paper, 2020 https://www.mscsoftware.com/artificial-intelligence-manufacturing-report 7 “EdgeCAM for Valve Production”, 2021 https://www.hexagonmi.com/en-gb/solutions/case-studies/other-cool-stuff/full-steam-ahead-with-edgecam8 “Meeting the Tightest Sealing Requirements is top priority”, MÜLLER CO-AX AG Customer Story, Leitz LSP-X1h and PC-DMIS: https://www.hexagonmi.com/en-GB/solutions/case-studies/general-manufacturing/meeting-the-tightest-sealing-requirements-is-top-priority

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