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FAQ -- Frequently Asked Questions

This page contains answers to common questions handled by our support staff, along with some tips and tricks that we have found useful and presented here as questions.

  1. In DRAINS the total inflow to a pit does not match the total outflow.   Why?
  2. Can PIPES interface to CAD and GIS packages?
  3. What is the difference between the Normal and Building Services versions of PIPES?
  4. What if we use pipes which are not included in the pipe data base?
  5. Can PIPES model variable speed pumps?

 

In DRAINS the total inflow to a pit does not match the total outflow.  Why ?

The flows shown on the normal plan view are maximum values that occur in each pipe or overflow route. They do not occur at the same time and therefore you cannot simply add them. You must look at the flow hydrograph for each pipe/overflow route. You can then read off the flows at a particular time, and compare those inflows and outflows.  Actually its a bit more complicated than that because the flows shown are at the upstream end of the pipes/overflow routes. So for incoming pipes/overflow routes you need to allow for travel time in the pipe/overflow route.  You can do a comparison for on-grade pits, but sag pits are more complicated because there may be a change in storage happening at the time you are considering and you don't have information on this.

In essence you are trying to do a continuity check. Drains helps you with this - try copying results to a spreadsheet and look at the bottom of the spreadsheet under Continuity Check. This shows a continuity check in terms of total volumes in and out over the full duration of the analysis.

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Can PIPES interface to CAD and GIS Packages ?

PIPES and PIPES++ can interface with any programs which can read and write DXF files. If you already have pipes drawn in a CAD program such as Autocad it is easy to save the drawing as a DXF file and then read that file into PIPES. If the DXF file is drawn to scale PIPES will automatically determine the length of all pipes in the network (after you specify the length for one pipe).

Of course there are some conventions which you must follow in your DXF drawing. The pipes must be on a layer in which they are the only lines (ie don't draw property boundaries on the same layer as pipes).

You will also need to draw nodes (circles) on a layer of the DXF file to help PIPES interpret the drawing. This is because a single pipe can be drawn as a simple straight line or as a series of line segments (a pipe with kinks). A node is used to indicate each end of a pipe.

PIPES and PIPES++ can also produce a DXF file. The file can contain various items of data for each pipe and each node. This feature can be used to customise presentation of results.

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What is the difference between the Normal and Building Services versions of PIPES?

In the design of pipework in buildings (plumbing) it is common practice to use diversity factors which reduce the probable simultaneous flow per fitting as the total number of fittings increases. The Building Services version of PIPES includes automatic diversity calculations based on loading units. In technical terms this means that the equation of continuity is satsified in the Normal version but not in the Building Services version.

In practical terms the dialog boxes which appear when you double click on a node look different. In the Building Services version you specify numbers of various fittings (eg water closets, basins, showers etc) and loading units are provided for each type of fitting. In the normal version you specify demands for various classes of consumers (eg residential, industrial etc) and multiplying factors for each consumer class.

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What if we use pipes which are not included in the pipe data base?

Pipe materials and dimensions vary in different Countries and locations. The pipe data base supplied with PIPES includes pipe materials and dimensions commonly found in Australia. The data base is easily modified from within PIPES and it is intended that you should delete pipes not used in your locality and add those which you do use.

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Can PIPES model variable speed pumps?

PIPES++ can model variable speed pumps. Pump speed is automatically adjusted to maintain the HGL at a specified node at a constant level. You can use this feature to analyse variable speed pumps even if you do not have a pressure sensor at a critical node. For example, you may wish to use a PLC to control pump speed based on flow through the pump so as to approximately maintain a minimum HGL at some node. In this case you would model the system with the variable speed pump controlled by HGL at the node (not flow through the pump) for a range of system demands. The results of this analysis would provide you with a performance specification for programming the PLC (ie the required pump speed at a number of flow rates).

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