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 many different input, selection and control elements; and an area on the right, named the 3-D viewer, that provides a graphical representation of the piping model. The tab pages in the left area are arranged in such a way that you normally proceed from left to right in order to define the piping model; to define the analyses that are to be performed; to run one or more simulations; and to analyze the results. The 3-D viewer provides graphical feedback of the changes you make to the piping model. It can be used to interact with the model, to select parts of the model in a graphical way, and to 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 to 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 on the basis of 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 interacting with them in a graphical way.

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 in a correct way. This, together with the possibility to create multiple duplicates with one operation, can save a lot of time when modeling repetitive structures.

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 de 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, including the operating speed of the equipment, then BOSpulse assess API compliance for each operating condition, and indicate for which conditions (if any) the API allowable limits are exceeded.

API 618 compliance report example.

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. In particular you can specify a fixed pressure pulsation limit or a limit that is equal to a fraction of the mean line pressure. When you specify a custom limit then this is clearly indicated in the API compliance report.

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 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 structural solver. This decreases the time required to perform fully coupled analyses. More importantly, it decreases the scope for errors. This, in turn, helps to increase the amount of certainty which which you can determine whether the harmonic pressure waves can lead to non-acceptable structural behavior of the piping system.

The structural solver interface is currently limited to the ANSYS solver. DRG aims to extend the structural solver interface to other solvers in the future.

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 which which you can determine whether the harmonic pressure waves can lead to non-acceptable structural behavior of the piping system.

In order to increase the accuracy of the structural model, BOSpulse provides support for 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, input files for CAESAR II and input files for Bentley AutoPIPE. In this way you can manually perform one or more structural analyses in the structural analysis tool of your choice.

If you do not use the structural solver interface, then you do not necessarily need to set up separate models for the pressure pulsation analysis and the structural analysis. BOSpulse can import piping models from different formats, including Piping Component Files, CAESAR II neutral files and spreadsheets specifying pipe profiles. BOSpulse can also export its models to CAESAR II neutral files (including structural steel files).

BOSpulse enables you to define multiple 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 in order 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.

Modify groups of elements in different scenarios.

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 a 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 symbolic model and analysis parameters and to perform a so-called parameter study in which the symbolic parameters are varied in a specified number of steps, called parameter 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 lock step 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 custom parameter schedule and describe the exact path that is to be followed in a multi-dimensional parameter space.

Vary two model parameters by means of a parameter study.

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 enables you to quickly drill down the essential information. The results can be displayed in the 3-D viewer, in a variety of 2-D graphs and in textual form. You can compare different scenarios and view how the results depend on the symbolic parameters that have been varied.

View the results from different scenarios and different parameter variations.

The steady state, or average, flow conditions are the starting point of a harmonic flow analysis, both when using a harmonic and a time-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 in order to obtain a specific pressure at a compressor flange. BOSpulse can simplify and speed up this procedure by automatically tuning the steady state conditions.

BOSpulse enables you to specify a target pressure for a compressor flange node. When you do that, you also must add a so-called terminal point node to the piping model. BOSpulse will then automatically determine the required pressure at the terminal point node in such a way that the steady state pressure at the compressor flange node matches the specified target pressure. You therefore need not to know the exact pressure at the boundary of your model; you only need to indicate where you want to impose a fixed pressure boundary condition.

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 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 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.

Because of their strengths and weaknesses, you could use the frequency-domain solver to narrow down your problem space and use the time-domain solver to perform a final assessment of the piping system under consideration.

BOSpulse provides more and less detailed models for reciprocating compressors and pumps. Both models require a description of the geometry of the cylinders, pistons, crank shaft 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.

Definition of a reciprocating compressor using the less detailed model.

The more detailed models are implemented as special flow elements that must be part of the piping model. These models no longer assumes 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.

Definition of a reciprocating compressor using the more detailed model.

Whether you are using the 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 crank shaft as function of the rotation angle. All this information can help you to verify the correctness of the compressor input parameters and to 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.

P-V diagram generated a priori.

The reciprocating compressor models implemented by BOSpulse support the simulation of stepless flow control. This means that you can specify the desired capacity as a fraction of the full flow rate. BOSpulse then will automatically determine how long the suction valves need to be forced open in order to obtain the desired flow rate. This works both for the less and more detailed compressor models.

BOSpulse does not limit you to the built-in models for reciprocating equipment as you can model any positive displacement equipment by specifying arbitrary periodic flow boundary conditions. That is, you can specify one period of the flow rate as a piece-wise linear function of time that BOSpulse will repeat indefinitely. The piece-wise linear function can be entered manually, specified as a mathematical expression, or imported from a text file or spreadsheet.

DRG strongly believes that the piping models you create should not be locked away in some propriety 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.

You can perfectly well manipulate BOSpulse models in a text editor.

BOSpulse model files are structured in such a way that you can easily write scripts that automatically modify and/or create these files according to your work flow. For instance, if you frequently need to analyze systems with a similar set up, you could build a base model once, then generate variations of that model with a custom script, and process those models by running BOSpulse in batch mode. You could even process the results by extracting the data of interest from the HDF5 output files.

View the contents of the HDF5 output files with free tools.

If your BOSpulse license has expired, you can still use BOSpulse to view your models and results. You can no longer, however, save any changes to your models or perform new pulsation analyses. In this way you are always able to review the models and results from past projects.

Because we frequently use BOSpulse in our engineering projects we are very able to assist you in your use of BOSpulse. Our engineers and software developers can help you setting up your piping models, including the reciprocating equipment, help you to define the analyses to be performed, and help you with the interpretation of the results. In the event that you are not able to perform a particular pulsation study yourself, you could ask us to perform the study for you.

The software developers at DRG all have a background in physics or aerospace engineering and are highly motivated to keep improving our software. This means that if you would make an investment in BOSpulse now, you are investing in a tool that continuously gets better and better. You can actually influence the development process as we actively listen to our user base; most changes and improvements in BOSpulse are the result of feedback from BOSpulse users.