The Prime Directive

The Prime Directive:  The Simulation is Always Correct.

For some reasons, many software developers seem to be major Star Trek and/or Star Wars fans. I remember listening to multiple discussions in the lunchroom on which Star Trek series was the best. The conversation then turned to how the Prime Directive has changed over the years. I provide a link so you non-Trekies can catch up.

Applying this to Engineered Software, every time we came out with a new version, the support group was on pins and needles. They were apprehensive that a major bug somehow made it through our testing process (Refer to my previous blog Testing 1.2.3…). After a couple of weeks with no major program bugs discovered, everything returned to normal.  Just to ease everyone’s mind, I came up with our own Prime Directive: “The PIPE-FLO simulation is always correct.” 

Back to the current situation, I have just returned home from a series of customer visits. While conversing with PIPE-FLO customers at operating plants, a common question is, “How can I used PIPE-FLO to troubleshoot a piping system?” 

My answer is always the same. Build an accurate model by:

1. Drawing an accurate system configuration using a current P&ID or flow diagram.
2. Getting actual pump performance data and enter it into the piping system model.  This should be either a test curve provided by the manufacturer, or a manufacturer’s catalog curve.
3. Getting actual manufacturers supplied control valve data to enter into the model.
4. Entering the manufacturers supplied pressure drop vs. flow data for each process element in the system.
5. Entering pipeline details of fluid property, pipe diameter, major valves, and pipe length.
6. Specifying system-operating parameters such as tank levels & pressures, operating equipment, set points for controls.
7. The final step is to compare the simulated results with actual plant operating data to gain an accurate correlation.

That said the next question is, “What if the results of the simulation don’t match the results appearing on the plant’s instrumentation."

I then mention the Prime Directive, “The PIPE-FLO simulation is always correct.”

If the piping system design and operating data is correct then the simulation will closely reflect the operation of the actual system being simulated. Some of our customers with accurate models of their system state the calculated results closely match data displayed on plant instrumentation within 1 – 2%. 

Now with that said, the most difficult step is getting the simulated results to compare with actual plant data. The reason for this is that over time the actual system changes due to wear and tear on the equipment or even undocumented changes.

For example, if the internal clearances in a pump are excessive the pump will not be operating on its published pump curve. If the pump impeller was replaced and its impeller diameter was not trimmed to the original pump, there will be a difference.  If the control valve seat/plug assembly, the valve position will not be where it should be. If a heat exchanger has excessive fouling, that effects the correlation between the actual system and the model. Finally, if there is cavitation in either the pump or control valves the simulated results will not match the actual system. 

This is the value of the PIPE-FLO simulation; it accurately represents the system in operation.  If for any reason the model doesn’t reflect the operation of the actual system then you have a starting point for knowing how the system should be operating and then use the result to troubleshoot problems within the actual operating system. 

Remember the Prime Directive:

“The PIPE-FLO simulation is always correct.”

Now I don’t expect you will take my word for it but many of our customers use the PIPE-FLO simulation to help them balance their systems, help in the troubleshooting system problems, and evaluate changes to their processes. 

One final point to remember, our support people are always available to help you work through your PIPE-FLO simulations.  If you have any questions on how to improve the value of your PIPE-FLO simulation please give us a call. We will not rest until you too feel comfortable with the PIPE-FLO’s prime directive “The PIPE-FLO simulation is always correct.”

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