RE: Fire flow: all nodes failed - ouch!

Hello Alex,

I split this into a new thread since the other one was so old.

The following TechNote has information on troubleshooting cases like this: communities.bentley.com/.../understanding-automated-fire-flow-results

Ultimately, the best thing to do would be to look at the fire flow report flextable to see at what nodes the issue is occurring. In particular, take a look at the zone pressure and the node where the lowest zone pressure is occurring for a given fire flow run. This is oftentimes where the issue is occurring.

Another thing to look at would be if your fire flow Alternative is accounting for a system lower limit. You can check this in the upper right of your fire flow Alternative. The default setting for this is to not account for system pressure lower limits, but if this option is checked, the program will not only look at the pressure at the fire flow node and the pressures for the junctions in the same zone, but any node in the model. If this is causing an issue in your model, unchecking that option may help.

If this doesn't help, we will likely need to see a copy of the model file. There are two options for sharing your model files on Communities. If you would like the files to be visible to other members, compress the files into a zip file and upload them as an attachment using the ‘Advanced Reply editor’ before posting. If your data is confidential, you can follow the instructions in the link below to send it to us via Bentley Sharefile. Files uploaded to Sharefile can only be viewed by Bentley.

communities.bentley.com/.../7079.be-communities-secure-file-upload

If you upload a model to Sharefile, please post here with the name of the file so we know it is available.

Regards,
Scott

Scott,

Thank you for your response. I realized there was an issue with the zones that I had defined within the system. I corrected this issue which resolved my previous fire flow issue as well. However, I have an additional question regarding the automated fire flow procedure. I understand that this procedure runs a series of steady state analyses until the minimum available fire flow is determined at each specified node. However, I am curious how the duration of the fire flow event is accounted for. For example, in the case when you have to apply a 3,000 gpm fire flow for 3 hrs. Can you please help explain how this is accounted for in the automated approach or does this have to be done separately by defining a EPS simulation and a fire flow pattern?

Thanks,

Alex,

There is a perfect example of how to do this in the quick start lessons that come with our software. The quick start lesson titled "Automated Fire Flow Analysis" goes through the exact steps for how to set up a 3 hour fire flow run.

Regards,
Mark

Alex,

It looks like I gave you the wrong quick start lesson. Have a look at the one titled "Extended Period Simulation". In step 11 it shows how to setup a the 3 hour pattern. If you haven't gone over the over quick start lessons these are a great place to start learning about the software. You can also go to our technotes and FAQ page found here

and have a look at the wikis we have listed under the WaterGEMS/WaterCAD section. Another good place to start for a newer user is learning and resource guide that puts a lot of this information together in one location. That can be found here:

Regards,

Mark

Regards,

Mark