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Welcome to this month's newsletter! In this issue you'll find:

• SIMUL8 Standard User? Try SIMUL8 Professional R11 for free!
• An article by Andrew Rooney on Tanks and Pipes 3
• Details on free downloads added to the website this month
• Some Hints and Tips on using SIMUL8
  

SIMUL8 Standard User? Try SIMUL8 Professional R11 for free!

Do you already own SIMUL8 Standard or have SIMUL8 Professional R10 or lower? Then why not download SIMUL8 Profesisonal R11 for 10 days for free.

If you're a regular user of SIMUL8's Visual Logic then you will find the debugging tools invaluable. If you want to share your simulations you will need the Pro version to allow your clients to see your simulation in the Viewer.

The trial enables ALL Pro features (including Viewer distribution capabilities) for 10 days. After this SIMUL8 reverts back to the version you previously had.

Download from http://www.simul8.com/protrial.htm For more on SIMUL8 Professional see http://www.simul8.com/products/s8prof.htm

Tanks and Pipes 3 by Andrew Rooney

This is the last in the 3 part series of Newsletters covering SIMUL8 Tanks and Pipes.

Last months newsletter showed a simple case where a Tank changed its infeed rates depending on the amount of stock in the tank. This months topic is what happens when something goes wrong, like a machine failure or a blockage.

SIMUL8 work centers have comprehensively developed functions for controlling failures and repair times, with multiple failure streams and repair resources available. There aren't any failure properties available on pipes or tanks, so how do you simulate random events that can affect flows?

The best thing to do is to structure a simulation to use Tanks and Pipes, so that the speed and controls of these objects are used, and to deal with the random and failure events in another way. As the control that you want is already available in work centers then go ahead and build a work center that has the MTTF and MTTR times set as you need.

This leaves the problem of how to link these all together. An example is the best way to show this.

Lets say there is a once per day chance of a pipe becoming blocked, reducing the flow to 50% and needing some servicing time to clear the blockage.

Build a model like this, using the default settings for flow rates through the pipes, setting Tanks 2, 3 and 4 to be Auto Adjust (so they will never allow any stock to build up in them - see the September newsletter for more detail on this). The clock in this example is set to 24 hours per day and a 7 day week.

Place a work center on the screen - don't link it up to anything as all we will use is its Efficiency functions. Change the work center's Efficiency property to Detailed and set an MTTF of 1440 minutes (as there are 1440 minutes in a day) and a repair time of 60 minutes. Event though the work center is not connected to anything and not processing any work its failures will still occur

So we get a failure once per day for about an hour. What's missing is the link between the failures and the flow through the pipes in the simulation. To tie everyting together use the Visual Logic in the Work Center's Efficiency to change the flow rates. You will need 2 lines of code like this:

You can monitor the flow rate through the pipe by using the Watch Window (Tools menu, Watch Window, double click to enter) and entering the pipe.constraied rate property. This is the current amount of fluid passing through the pipe.

This method is very flexible and allows repair resources to be used here too.

If this example is extended so that the pipe's flow rate is reduced to 0.5 on failure and while waiting for a Repair Resource to arrive, and to 0 at the start of the repair - when the resource is actually available then only a small change needs to be made.

Use the On Start Repair visual Logic to set the flow rate that will be used when a Repair Resource arrives. If it is delayed for any reason - off shift or busy on another job - then the rate set in the On Fail Visual Logic is used until the resource is free and arrives.

In the example there is an "Other Resource Job" work center at the top left of the screen. This work center uses the Resource and is busy all of the time. The Pipe Failure Work Center calls for the Resource as soon as the repair starts and will need to wait until the resource has finished its current job at the Other Resource Job work center before moving to the Pipe Failure work center.

Download An Example

If you have any questions on this topic please email support@SIMUL8.com, we're here to help!

Free Downloads

Our website is always being updated with new support resources. Here are details on some of the downloads that were added this month.

New Learning Zone Model
Label Based Timing - Alternative. Each work item can store unique timing information to be used at a later work center. This simulation shows how to set this up.
Download the Example

New SIMUL8 Service Pack Version 11 Build 774
A new service pack for SIMUL8 R11 has been released. SIMUL8 10.0.0 774 fixes a few issues and allows Set Shift Resources to work with Work Centers too.
Download the Service Pack | Full Details of What's in the Service Pack

Hints and Tips

Go To Simulation Time
When debugging a simulation you often want to run the simulation repeatedly to a specific time. This is really easy if you use the GO TO SIMULATION TIME option from the Clock menu. This will run the simulation at full speed to exactly this time then stop.

Work Center Shift's Option
In R11 we introduced a Shift Option for Work Centers. This means you no longer have to create seperate resources to control the Work Center's availability and can get more accurate details about the time the Work Center actually spent Working, Waiting etc.

If you have any questions generated from, or comments about this newsletter then email Newsletter@SIMUL8.com