cht13er
Civil/Environmental
- Jul 14, 2010
- 33
We're a small consulting firm and have recently been required to provide fire flow analyses (max day plus fire) for small sites and subdivisions. The municipality provides us with modelling from their region-wide H2OMAP Water GIS, and the issue is how to input the data into EPANET to ensure that we have sufficient fire flow in our site.
The EPANET layout for the site looks like this: the Node1227 in the modelling (attachment) is just a reservoir in EPANET.
The required on-site fire flow is 45 L/s with 20m residual pressure at all nodes, so my approach was to take the residual pressure at node1227 with 45 L/s demand (39.6 m head), add that to the elevation of the node (303 masl) and use that resultant as the reservoir's pressure (342.6 m head). Next, I would add demand of 45 L/s at an internal node (in addition to the very minor max day residential demands) and run EPANET.
My supervisor says that I'm "double counting" and that the pressure at Node1227 (the reservoir in EPANET) should be set at the max day HGL - 365.6 m head (see first page of modelling).
Obviously this difference of 23 metres of head has a profound impact on the EPANET analysis and sizing of the pipes. Which approach is correct, and why ... and is it sufficient enough to model our node as a reservoir (I'm reading a lot about storage tanks and pumps on this site).
Thank you very much in advance for reading all the way to the bottom, and even more thanks if you're able to help out!
Chris
Ontario, Canada
The EPANET layout for the site looks like this: the Node1227 in the modelling (attachment) is just a reservoir in EPANET.
The required on-site fire flow is 45 L/s with 20m residual pressure at all nodes, so my approach was to take the residual pressure at node1227 with 45 L/s demand (39.6 m head), add that to the elevation of the node (303 masl) and use that resultant as the reservoir's pressure (342.6 m head). Next, I would add demand of 45 L/s at an internal node (in addition to the very minor max day residential demands) and run EPANET.
My supervisor says that I'm "double counting" and that the pressure at Node1227 (the reservoir in EPANET) should be set at the max day HGL - 365.6 m head (see first page of modelling).
Obviously this difference of 23 metres of head has a profound impact on the EPANET analysis and sizing of the pipes. Which approach is correct, and why ... and is it sufficient enough to model our node as a reservoir (I'm reading a lot about storage tanks and pumps on this site).
Thank you very much in advance for reading all the way to the bottom, and even more thanks if you're able to help out!
Chris
Ontario, Canada
