I am working on one sewerage network on SewerCAD. Its have 6 zones and 6 pumping station. I prepared model of this network in one single file. So, its consist 6 pumping station with 6 pumps and 12 pressure pipes. Initial, I give 100mm diameter to all pressure pipe & gravity pipe. gravity pipe is designed by its own but presser pipe remain with same diameter. My calculation type is design from Base calculation option. (1) So, its possible to design pumping main in sewerCAD? (2) I also entered data of flow and head loss in pump definition. pumps type is Design point (1 point). But its working on higher flow. So its necessary to calculate headloss manually and feed in pump definition as head for proper design?

### 4 Replies (Most Recent Reply)

• Hello Sagar,

The automated design feature of SewerCAD is for gravity pipes only. Pressure pipe sizes must be selected by the engineer.

Regarding the pumps - when selecting the design point pump curve type, you only enter the design head and flow, but SewerCAD generate a full head curve using extrapolation. The pump could potentially operate anywhere on that curve, depending on the system head characteristics at that time. You can use the system head curve tool to help design the pump curve.

Basically you'll have to use engineering judgment to design the pressure part of your sewer system. If you have a certain pump in mind, you could enter that with an estimate of what the pipe sizes should be, then look at the system head curve tool and tweak the design from there. It's up to you.

Jesse Dringoli

Bentley Systems, Inc.

• In reply to Jesse Dringoli:

Hello Jesse Dringoli,

I am using local available RCC pipe of different diameter for sewerage network in SewerCAD. For that I am adding detail of this pipe in Conduct Catlog box.

On left corner of Conduct Catlog box, two options are given, Conduct Shape and Diameter. So, my quarries are as below:

(1) Value provided in diameter box is internal or external?

(2) It’s possible to provide thickness of pipe? If yes then how and where?

(3) If it’s internal diameter, how the SewerCAD calculate proper cover of pipe without thickness of pipe?

(4) If it’s external diameter, how SewerCAD calculate internal diameter without thickness for calculation?

Thank you,

Sagar Chandra

Environmental Engineer

Reply to : sagar.chandra@mottmac-india.com or sagar_er2000@yahoo.com

• In reply to sagar chandra:

Sagar,

SewerCAD does not consider wall thickness and assumes it is negligible. Therefore the diameters you enter are inside/internal diameters and the cover is calculated as the difference between the ground elevation and the pipe end invert+diameter. So for example if the conduit is 0.5 m in diameter with an upstream invert of 97 m and upstream node ground elevation of 100 m, the upstream cover is calculated as 2.5 m.

With that being said, SewerCAD is flexible enough to allow you to make your own cover field that will be computed differently. For example, you can create a static user data extension field to store the wall thickness, then create a formula based user data extension that subtracts the thickness for each pipe from the computed cover, giving you your custom cover that considers wall thickness. You'd need to have two of these fields if you want to have both a start and stop cover, and you'll need to consider if your pipe invert is the bottom of the inside of the pipe (in which case you'd subtract the thickness) or the bottom of the outside of the pipe (in which case you'd subtract two times the thickness.) Of course, the automated design routine will always use the original cover field, but this might be useful for reporting purposes, or if you'll tweak your design manually.

If you have any other technical questions, I encourage you to contact technical support.

Jesse Dringoli

Bentley Systems, Inc.

• In reply to sagar chandra:

Also, if you want to be precise, you can adjust the cover requirements for each pipe based on the pipe size. This way, as the pipes get bigger and the walls get thicker, you can make the minimum cover requirement larger to account for the thicker walls. So if the pipe wall thickness is 100mm, its internal diameter is 1000mm, and you want 1500mm cover to the top of the pipe, you could set the minimum cover requirement to 1500mm+100mm = 1600mm.

To do this click Components > Default Design Constraints > Cover, then set Cover Constraints Type to Table. Now you can enter a table of min/max cover versus pipe size.

P.S. We may also add an external diameter field at some point in the future.

Regards,

Mal