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Thorough 3-D Modeling Of Piping Systems

With BOSpulse you can build detailed 3-D models piping models that capture all significant, physical aspects of the actual piping system of interest. This is important because small variations in the model geometry and other model parameters can strongly affect acoustic and structural resonance phenomena which are typically the main phenomena of interest in piping systems involving periodic excitation sources such as reciprocating equipment.

A collection of element types enables you to model straight pipe segments, reducers, and common fittings such as elbows, orifice plates, and valves. BOSpulse also provides special element types for modeling reciprocating compressors and pumps, gas-filled dampeners, storage tanks, tee junctions, and curved end caps. A dedicated editor enables you to build detailed models of pulsation suppression devices that include choke tubes, baffle plates, and nozzles. By saving element definitions to a database, you can reuse model components and save time in your pulsation analysis projects.

While accuracy is an important requirement for any pulsation analysis software, efficiency is not much less important. BOSpulse therefore automatically applies acoustic length adjustments so that you can focus on the logical layout and geometry of a piping model. Acoustic length adjustments are applied at bends and other fittings, junctions, nozzles, and curved end caps. Using the graphical model verification tool, you can see at a glance where acoustic length adjustments are applied.

A unique and powerful feature offered by BOSpulse concerns support for the specification of model parameters as symbolic parameters instead of literal values. By varying the symbolic parameters in a parameter study, you can determine how the acoustic and structural response of the system is affected by those parameters. This not only enables you to assess the performance of the system over a range of operating conditions but also provides you with a powerful tool to address modeling uncertainties.

Powerful, Efficient, And Intuitive User Interface

BOSpulse comes with a graphical user interface that offers a streamlined model definition procedure and extensive post-processing capabilities. The interface consists of two main areas: an area on the left that is made up of a series of tab pages providing input, selection, and control elements; and an area on the right, named the model viewer, that provides a graphical representation of the piping model. The model viewer can be used to interact with the model, select parts of the model graphically, and view the simulation results.

BOSpulse provides support for defining overlapping groups of elements and nodes that enable you to partition your model in a logical way and apply bulk operations to different parts of the model. In addition to user-defined groups, BOSpulse maintains a collection of built-in groups that enable you to select elements and nodes based on their properties. This can save a lot of time when you need to adapt operating conditions or pipe-related data.

Parts of a model can be excluded from analyses with a few simple operations. Excluded parts are rendered translucently so that they are visible at a glance and so that you can keep graphically interacting with them.

BOSpulse automatically updates model parameters that refer to elements, nodes, and other entities when those entities are renamed or removed. This means, for instance, that a reference to a connected node in a restraint remains correct when renumbering the nodes in a model. This also means that you can more easily duplicate parts of a model as references to elements and nodes within those parts are duplicated correctly. This, together with the possibility of creating multiple duplicates with one operation, can save a lot of time when modeling repetitive structures.

API 618 And API 674 Compliance Assessment

BOSpulse assesses API 618 compliance for reciprocating compressors and API 674 compliance for reciprocating pumps. This means that, with a minimum of effort, you can determine whether your piping system and reciprocating equipment meet the applicable API allowable limits, and if not, at which locations in the system the limits are exceeded. If you are performing an analysis for a range of operating conditions then BOSpulse assesses API compliance for each operating condition and indicates for which conditions (if any) the API allowable limits are exceeded.

If the piping system involves compressors, then BOSpulse assesses the pressure pulsation amplitudes within the piping and at compressor flanges; the amplitudes of the shaking forces acting on the piping and on Pressure Suppression Devices (PSDs); and the pressure drop (both the static and the total pressure drop) over PSDs.

If the piping system involves pumps, then BOSpulse assesses the pressure pulsation amplitudes within the piping; the minimum pressure in the system (compared with the vapor pressure of the liquid); and the maximum pressure in the system (compared with the set pressure of safety relief valves, if present).

In addition to the standard API pressure pulsation limits, you can specify custom limits to cover situations in which an operator applies other limits than those prescribed by the applicable API standard. Custom limits are specified as user-defined functions, enabling you to specify arbitrary functions of the piping geometry and flow conditions. When you specify a custom limit then this is clearly indicated in the API compliance report.

Reciprocating Equipment And Dampener Models

BOSpulse provides various levels of detail when modeling reciprocating compressors and pumps. Both models require a description of the geometry of the cylinders, pistons, crankshaft, and (connecting) piston rods, the loading condition, and a specification of the relevant fluid properties and thermodynamic parameters.

The less-detailed models ignore the suction valve dynamics and assume that the pressure at the discharge or suction side is constant. These models essentially impose a flow boundary condition that matches the expected flow going into or coming out of the cylinders. The advantage of these models is that you do not need to know the valve characteristics and that the flow boundary condition can be generated a priori, thereby reducing the time required for a pulsation analysis.

The more detailed models are implemented as special flow elements that must be part of the piping model. These models no longer assume that the suction or discharge pressure is constant; they use the pipe flow equations to determine the actual suction and discharge pressure. They also, optionally, take the valve dynamics into account. As a consequence, they enable you to have a detailed look at the actual operating conditions within the cylinders and at the dynamic motion of the suction and discharge valves.

Whether you are using less or more detailed reciprocating compressor models, BOSpulse can display the expected P-V diagram, the mean flow rate, the flow rate curve, and the torque curve. The latter indicates the torque acting on the crankshaft as a function of the rotation angle. All this information can help you verify the correctness of the compressor input parameters and assess the performance of the compressor without having to perform a pulsation analysis. If you are using the detailed compressor model, then BOSpulse will also provide the actual P-V diagram that includes the interaction between the compressor, its valves, and the connected piping system.

The reciprocating compressor models implemented by BOSpulse support the simulation of stepless flow control and active valve control. The first feature enables you to specify the desired capacity as a fraction of the full flow rate. BOSpulse will then automatically determine how long the suction valves need to be forced open to obtain the desired flow rate. The second feature enables you to specify the opening profile of the suction and discharge valves. You can use this feature to simulate valves that are driven by active electromechanical actuators. 

Dampeners play an important role in reducing the pressure pulsations and shaking forces below the allowable limits. BOSpulse therefore provides support for modeling a wide range of dampeners that are typically connected to compressors and pumps. A dedicated PSD editor enables you to create detailed models of pulsation suppression devices, including choke tubes, baffle plates, nozzles, and the parameters that are required to assess the allowable limits imposed by the API 618 standard. You can save these models to a database so that they can be used in multiple projects. A special element is available for modeling gas-filled dampeners in liquid-filled systems. This element enables you to specify the gas conditions both at operating and at installation conditions.

Support For Full Mechanical Response Analysis Of Coupled Fluid-Structures Systems

BOSpulse can not only be used to assess the shaking force amplitudes (according to the API 618 standard, Design Approach 2) but also to determine the actual impact of the shaking forces on the structural behavior of the piping system (Design Approach 3). In fact, when you use the ANSYS structural solver interface provided by BOSpulse, you can run a structural harmonic analysis directly from within BOSpulse and review the computed displacements and stresses within BOSpulse too. To be precise, you can define a structural harmonic analysis that imposes the shaking forces resulting from an API 618 or API 674 analysis on a structural model of the piping system.

You can specify all aspects of the structural model, including restraints, structural steel elements, and insulation layers within BOSpulse so that you do not need to set up and keep track of separate models for pressure pulsation analyses and structural analyses. BOSpulse also enables you to control the way that the finite element model is generated so that, in general, you do not need to make any manual modifications to the model before it is passed to the ANSYS structural solver. This decreases the time required to perform fully coupled analyses and decreases the scope for errors.

BOSpulse implements both the ASME B31.3 and ASME B31J piping codes. The latter is increasingly used to calculate more accurate flexibility factors, sustainable stress indices, and stress intensification factors for branch connections and specific types of piping components and geometries. By adopting this piping code BOSpulse can more accurately predict the stresses and displacements resulting from harmonic pressure waves occurring in piping systems. This, in turn, helps to increase the amount of certainty with which you can determine whether the harmonic pressure waves can lead to non-acceptable structural behavior of the piping system.

To increase the accuracy of the structural model, BOSpulse provides support for manually specifying geometry parameters, flexibility factors, stiffness parameters, and stress intensification factors that are associated with tee junctions. A dedicated tee junction configuration window not only simplifies the specification of these parameters but also shows the default values determined by the applicable piping code. Those values are also listed in one of the standard analysis reports.

You do not have to use the structural solver interface to perform a structural harmonic analysis as BOSpulse can export the shaking forces (both amplitudes and phase angles) in different formats, including spreadsheets, and input files for CAESAR II, Bentley AutoPIPE, and CSiPlant. In this way, you can manually perform one or more structural analyses in the structural analysis tool of your choice.

Effortless Modeling Of Hundreds Of Operating Scenarios

BOSpulse enables you to define an arbitrary number of scenarios in one piping model. A scenario can be viewed as a context or scope in which the model parameters are defined. Multiple scenarios can be defined to study different variations of the piping model. For instance, if you are interested in the effects of an orifice diameter on the pressure pulsations amplitudes you could define multiple scenarios that specify different diameters for that orifice. In fact, you can change any model parameter, except the pipe geometry, in a scenario.

By default, a piping model comprises only one scenario, called the main scenario, that defines the primary model parameters and the piping geometry. Any other scenario is implicitly derived from the main scenario. That is, any change to the main scenario, such as a change in pipe diameter, is propagated to all other scenarios. On the other hand, a change to any scenario other than the main scenario only affects that particular scenario.

In addition to scenarios, BOSpulse enables you to specify a symbolic model and analysis parameters and to perform a parameter study in which the symbolic parameters are varied in a specified number of variations.  For instance, instead of specifying a literal value for the API base frequency and operating speed of the reciprocating equipment, you could specify a symbolic parameter that is varied from the minimum operating speed to its maximum. This capability is not limited to the API base frequency (although that is a common application); almost any model parameter can be specified as a symbolic parameter so that you can efficiently study correlations between model parameters and the predicted pressure and shaking force amplitudes. You can also use this feature to build generic, parametric models that can be tuned to specific applications by simply adjusting the values associated with the symbolic parameters.

The way that the symbolic parameters are varied is determined by the selected parameter schedule. When you select a linear parameter schedule, all parameters are varied in lockstep from a lower bound to an upper bound. The linear parameter schedule essentially defines a one-dimensional parameter space and suffices in the majority of pulsation analyses. In those cases where you need more flexibility, you can select a multi-dimensional or custom parameter schedule.

The number of simulations that need to be performed increases linearly with the number of scenarios and the number of parameter variations. Fortunately, BOSpulse can reduce the total analysis time by scheduling different scenarios and different parameter variations on different processor cores. BOSpulse can even take advantage of multiple processor cores when performing a single simulation with the time-domain solver.

To make sense of all these simulations and their results, BOSpulse provides flexible and powerful post-processing capabilities that enable you to quickly drill down the essential information. The results can be displayed in the model viewer, in a variety of 2-D graphs, and textual form. You can compare different scenarios and view how the results depend on the symbolic parameters that have been varied.

Fast And Accurate Time-Domain And Frequency-Domain Solvers

BOSpulse comes with both a time-domain flow solver and a frequency-domain flow solver. The former makes use of the method of characteristics to solve the non-linear, time-dependent flow equations in the time domain. The harmonic pressure and shaking force amplitudes are then obtained by applying a Discrete Fourier Transform to the calculated pressures and shaking forces as a function of time. The frequency-domain flow solver, on the other hand, solves a linear approximation of the flow equations directly in the frequency domain. This procedure yields the harmonic pressure and shaking force amplitudes without the need for a Discrete Fourier Transform.

Because the time-domain solver solves the full, non-linear flow equations, it can more accurately predict the harmonic pressure and shaking force amplitudes, especially when the flow fluctuations are relatively large in comparison with the mean flow rate. The drawback of the time-domain solver is that it can take a substantial amount of time; it is typically one or two orders of magnitude slower than the frequency-domain solver. Note that the upcoming major BOSpulse release will incorporate a significantly improved frequency-domain solver.


The steady state, or average, flow conditions are the starting point of a harmonic flow analysis, both when using the time-domain and the frequency-domain solver. BOSpulse therefore comes with a full-fledged steady-state solver that is also used in BOSfluids, our general flow analysis package. This means that you only need to specify the relevant flow boundary conditions and BOSpulse will automatically determine realistic and consistent steady-state flow conditions; there is no need to specify the flow rates manually.

The steady-state solver requires the specification of at least one pressure boundary condition, typically at a boundary of the piping model. In some situations, however, the exact pressure at that point is not known but must be determined by trial and error to obtain a specific pressure at a compressor flange. BOSpulse can simplify and speed up this procedure by automatically tuning the steady state conditions.

Outstanding Support For Importing Piping Component Files And Other Standard Formats

While you can perfectly build complex piping models in BOSpulse, you can also import piping models from different file formats, including Piping Component Files, CAESAR II neutral files, and spreadsheets defining pipe profiles. When you import a model, you have the choice to replace the current model, extend the current model, or update the current model by using the geometry defined by the imported model. The latter option is useful if you need to work with BOSpulse and another piping analysis tool on the same piping system.

BOSpulse has exceptionally good support for importing Piping Component Files. When doing so, BOSpulse will apply various, automatic algorithms to correct common problems such as overlapping elements and disjoint piping sections. Various parameters are available to tweak the import algorithms so that you can end up with a correct and consistent piping model. Before importing a set of PCFs, you can specify the relevant geometry parameters for the piping specifications referred to in those PCFs. BOSpulse simplifies this process by automatically extracting a list of the piping specifications after you have selected the PCFs to be imported. This generally happens without any noticeable delay because efficiency has been an important requirement for the PCF interface in BOSpulse. It can easily handle hundreds of PCFs that define a single piping model.

BOSpulse can export piping models to CAESAR II neutral files and ANSYS input files, facilitating mechanical response analyses with your tool of choice.

Extensive Reporting And Open-Standards Access To Analysis Results

The BOSpulse user interface provides a wide range of possibilities to view the results of one or multiple analyses. The results can be shown in different ways in the piping model itself. They can also be displayed in various types of plots, including min-max plots, profile plots, harmonic plots, time history plots, and case plots. The latter enables you to view the key differences between a large number of cases at a glance. The results are also available in textual form using a collection of standard reports and the possibility to generate custom reports containing the data of most interest.

With BOSpulse you can share models and selected results with your clients while maintaining control over which data are made available. This involves exporting the model and results to its companion application BOSview which can be downloaded and used for free. BOSview is not only capable of displaying BOSpulse models and results but can also display piping models that are stored in different file formats, including Piping Component Files.

We strongly believe that the piping models you create should not be locked away in some proprietary and inaccessible format. BOSpulse models and results are therefore stored in human-readable text files and HDF5 database files that can be accessed with free and open-source tools. You can even access and modify these files from Python and Matlab scripts so that you can use BOSpulse as a building block in your own, custom solution procedures.

If your BOSpulse license has expired, you can still use BOSpulse to view your models and results. However, you can no longer save any changes to your models or perform new pulsation analyses.

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