Results from the Extreme Pressure and Heads table are different from results found in the transient profiles

  Product(s): HAMMER
  Version(s): 08.11.xx.xx
  Environment: N\A
  Area: Output and Reporting

Problem

Results from the "Extreme Pressure and Heads" are different from results found in the transient profiles. Why is that occurring?

Solution

The "Extreme Pressure and Heads" report looks at what is happening at the nodes only. The profile will also show what is happening at increments within the pipe. For instance, if you look at the data tab for a profile, you will see data points for a given point within the pipe itself. Depending on the system, the maximum or minimum pressure or hydraulic grade may occur at some point within the pipe rather than at the ends of the pipe.

As an example, please see the screenshot below.

This shows the Extreme Pressure and Heads tab in the Transient Calculation Summary. In it the end point P-2:Pump has a maximum hydraulic grade of about 182.9 meters. However, the profile for the system appears to show a maximum hydraulic grade just downstream of the pump is actually higher than this.

That is because points within the pipe sees these higher maximum hydraulics grades. You can see that by looking at the Data tab of the transient profile.

The maximum hydraulic grade at point P-2:Pump is the same as that found in the Extreme Pressure and Heads report, but at points downstream of the pump and between the pump and downstream node have a higher maximum hydraulic grade.

A part of the strength of the Method of Characteristics workflow that HAMMER uses is that the program will look at points between the end nodes to find areas that may see high pressures or negative pressures.

See Also

How can you find the minimum and maximum transient pressure or hydraulic grade results in a HAMMER model?

General HAMMER V8i FAQ

  • Created by Bentley Colleague
  • When: Wed, Dec 23 2015 11:14 AM
  • Last revision by Bentley Colleague
  • When: Mon, Jan 23 2017 1:22 PM
  • Revisions: 4
  • Comments: 0
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