Simulation Modes

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Navigation: User Guide -> Model Libraries or Solver

Introduction

SysCAD comes in two principle simulation modes, Steady State and Dynamic. There are two options for dynamic simulation, generally referred to as Dynamic Transfer and Dynamic Full (hydraulic) modes. There is also the option for using SysCAD for Mass Balance simulation only or for a full Mass & Energy balance. This applies to steady state or dynamic simulation modes.

The SysCAD License determines which are available to the user. All modes share the same flowsheet.

The Simulation Solve and Heat modes for a project can be set from the Project Settings dialog box prior to loading of the project. If the Steady State (PROcess BALance, PROBAL) mode is selected, then the user can access the Solver Setup (Probal) dialog box to set the solve options. If one of the Dynamic modes is selected, then the user can access the Solver Setup (Dynamic) to set the run options.

Steady State Simulation Mode

Steady State (Process Balance) -- In Steady State mode, SysCAD is used to simulate a plant model under steady state condition in order to produce a plant material and energy balance. There are a number of application for steady state modelling including data evaluation; feasibility studies to test various operation conditions and assess flowsheet options.

The available models in SysCAD are outlined in Model Libraries.

The user can specify the accuracy of solution for the mass and energy balance. The Solver Setup dialog box Convergence Tab presents these options.

Dynamic Transfer Simulation Mode

Dynamic Transfer is the basic dynamic license option for flow based dynamic simulation. All pipes are modelled as transfer links, where fixed flow capacities are specified directly. The mode easily handles Accelerated time with large step sizes, allowing users to analyse long term forecasts and focus on macro effects and major equipment.

Dynamic Transfer has been developed to handle the following simulation applications efficiently:

  1. Material handling processes;
  2. Surge & Availability studies; and
  3. Production Planning.

Models constructed in Dynamic Transfer mode can be used for:

  • Design verification;
  • Plant equipment sizing;
  • As a tool to assist in Process Control strategy development;
  • Control System/PLC testing; and
  • Operator training.

In this mode the user may set the piping networks to either Transfer Push mode of Transfer Pull mode. These two modes are discussed below:

Transfer Push Mode

Transfer Push mode is essentially a ‘Push’ method of calculating flow through a stream, i.e. the first pipe or unit in the "local network" determines the flow through that network.

This mode is required for the correct operation of Mass transfer models such Conveyors, Screens, Mills and Crushers.

The Pump2 and Valve2 piping models have been developed specifically for Transfer Push mode. They have a number of improvements in this mode and we therefore recommend their use for Transfer Push mode.

NOTE: The flowrate through the Pump2 and Valve2 models is still defined in a ‘Push’, or feed-forward, manner, normally in the upstream pipe exiting a tank or connecting feeder. This works well for single pump / valve systems, and in slightly more complex systems the Piping System Model is well suited because in this model a linear collection of pipe segments, pumps and valves can be configured. But things become more complex for a piping network consisting of a number of pumps and/or valves and parallel paths.

To use the Transfer Push mode and Pump2 and Valve2 within a complex piping network the user must calculate and set the required feed into the system based on the required flow through each branch of the network. This can lead to long and complex control logic within a General Controller. Transfer Pull may be more suitable to these more complex "local networks".

Please see Transfer Push mode for more information.

Transfer Pull Mode

The Transfer Pull mode is a ‘Pull’ method of determining flow through a "local network". Each unit in the "local network" determines the maximum allowable flow through that unit and the "local network" then determines the maximum required feed to that network so that one (or more or all) of the units achieve the required flow. This mode works well for "local networks" of pipes with ties, valves and pumps only, and allows parallel paths.

The source for a Transfer Pull "local network" can be either a unit with surge (e.g. Tank) or a Feeder. A Feeder will normally be configured with a large flowrate to satisfy the maximum demand from the downstream units.

Transfer Pull mode can be viewed as the same as Transfer Mode with an additional preliminary step. The additional step is the identification of the "local network" and "Pull Demand" analysis to determine a maximum desired flow which is then used as the flow for the "Push" Transfer mode solution.

Currently only the Pump1 and Valve1 unit models work in this mode. In addition to this, ALL pipes in a Transfer Pull Network must contain at least one Pump or Valve. The user specifies a flowrate in the pumps and/or valves to emulate pull demand.

Pipes in a Transfer Pull Network with neither a pump nor valve will NOT have any flow, unless (a) the user specifies a required flowrate in the pipe (which conceptually is a simplistic pump/valve model); or (b) there is excess flow available after meeting requirements in all other paths.

Recycle is not permitted within a Transfer Pull network.

Please see Transfer Pull mode and Setting up Transfer Pull Network for more information.

Mixing Transfer Push and Pull Modes in a Project

A project may only use Transfer Mode. However you can use both Transfer Push and Pull modes within the same project. An understanding of "local Networks" is important when using both modes. All the pipes in a "local network" MUST be in the same mode, you can not mix modes within a local network.

Not all models can operate in Transfer Pull mode.

A "local network" is a group of inter connected pipes and permitted units (e.g. ties, valves, pumps) bounded by "network isolators" such as tanks and feeders.

Please see Setting up Transfer Pull Network for more information.

Changing SysCAD Project Solve Mode

The following applies in SysCAD 9.3 Build 137 and later.

The SysCAD unit model selection is dependent on the project solve mode. For example, the conveyor belt, tailings dam, multi-storage etc are dynamic only models, so these models can only be included in a Dynamic Solve mode configuration file.

Therefore when changing the project from one solver mode to another, the project must be opened with the appropriate configuration file.

Step 1) Make a copy of the configuration file, Edit the configuration file to contain the required solve mode
Step 2) Open the project using alternate configuration, and select the configuration under the required solve mode.

For more information please see FAQ - Project mode change