Transient Analysis

Hi Sumith,

I recommend that you upgrade to HAMMER V8i edition, since we made the pump start up analysis a bit easier to do in that release. However, if an upgrade isn't possible, take a look at this detailed tech note that out Tech Support team put together:

communities.bentley.com/.../modeling-a-pump-start-up-transient-event-in-bentley-hammer-tn.aspx

Regards,

Mal

Hi Mal,

Thanks Mal,

I followed this technical note. The case that I am dealing with a pumping main (1200mm dia GRP pipeline) couple to a single pump (El: 43m) and pumping to a reservoir (El; 86 m). The profile is undulating and the highest point exist between Pump Stn. and Reservoir is 106m.

When I copied the initial condition with pump initial status off, and execute the transient analysis transient engine failed and user notification appeared as initial " pressure less than vapor pressure" in high elevated nodes.

I wants to analyse the transient effect of pipeline at pump startup with partially filled with water. How we define the intial condition of partially filled or empty pipeline. Usually how does the software identify the pipeline status (as completely filled/empty )?.

Thanks Best Regards,

Sumith

Hi Mal,

Thanks Mal,

I followed this technical note. The case that I am dealing with a pumping main (1200mm dia GRP pipeline) couple to a single pump (El: 43m) and pumping to a reservoir (El; 86 m). The profile is undulating and the highest point exist between Pump Stn. and Reservoir is 106m.

When I copied the initial condition with pump initial status off, and execute the transient analysis transient engine failed and user notification appeared as initial " pressure less than vapor pressure" in high elevated nodes.

I wants to analyse the transient effect of pipeline at pump startup with partially filled with water. How we define the intial condition of partially filled or empty pipeline. Usually how does the software identify the pipeline status (as completely filled/empty )?.

Thanks Best Regards,

Sumith

Hello Sumith,

HAMMER has limited modeling of partially filled pipes. Air can be introduced through an air valve and from vapor pocket formation. However, large pockets of air such as an empty pipe usually aren't modeled. You can enter an initial volume of air at certain points in the network such as a junction, but HAMMER has some limitations on the tracking of air. You can read more about it in the help or the Air Valve technote, but basically HAMMER assumes that the pocket is concentrated at the location of formation. In short, it's probably not a good idea to attempt to model an empty pipe in HAMMER.

One suggestion would be to end the network at the first high point, placing a reservoir or discharge to atmosphere node. This will first allow the pump to add the appropriate amount of head to lift the water to that high point and will also allow HAMMER to run. You could assume gravity flow in the downstream unmodeled section.

Another approach may be to start the model with the pump on, have the pump shut down, then have it turn back on. This can be done by way of the variable speed transient pump type. However, the older version of HAMMER that you're using will not properly account for high points in the initial conditions, that would normally be flowing partially full with the pump on. See this technote for more information.

I hope this helps.