STEADY STATE, AIR VALVE,HYDROPNEUMATIC TANK (BLADDER), Sudden closure of NRV

1. How to perform steady state condition in Hammer & how could it be reported?

Steady state conditions are computed at the initial stage in Hammer to understand if system is hydraulically stable before performing transient analysis.

However if you want to make any modeling changes in hydraulic operations you should do that in WaterGEMS / WaterCAD first and then import model back in Hammer.

 To compute the steady state results, go to Analysis / Home > Initial conditions, this will compute the steady state conditions. And the results of steady state can be seen in the calculation summary and in element flex tables as well.  

2. While performing the analysis considering Hydropneumatic tank keeping the Junction as true, pipeline experience negative pressure. But, if the same option is changed to false and providing HGL, initial capacity, Pump cannot deliver flow or head in the initial condition. What is the problem with the inputs?

Selecting "True" for the "Treat as Junction" allows the software to compute HGL at tank location in initial conditions. If you already know HGL then you can select false and enter HGL.

So for your case if you initial HGL enter that, else select true for "Treat as Junction". And then enter initial  volume of gas under the "Transient" section of the tank properties that corresponds to the hydraulic grade during the initial conditions

Please read detailed information on this using below wiki.

https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/3104/modeling-reference---hydropneumatic-tanks

For pump cannot deliver flow or hear notification, it means that pump is either operating at shutoff head or more head is required by pump than defined. 

3. I have a condition - When the pump trips & NRV closed. How this case shall be performed. I have modelled Check Valve and given the open, close timing. Is there anything should I mention to perform the above case?

You are on the right track for this, here is information about modeling check valve closure in Hammer.

https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/4558/modeling-reference---check-valves-in-hammer  

4. Is it advisable to perform analysis with Hydropneumatic tank and without air valves? thats a requirement from client. without air valves pipeline experience negative pressure. Is that a good approach ? please suggest.

If you believe air valves are also required in model along with hydro tank then you could model two scenarios with two different cases. One case would be only hydro tank and in other case hydro tank + air valve.

Compare results between two scenarios which would help you take the decision.

https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/4508/scenario-and-alternative-management 

5. Air Valve - Triple acting valve is used. With air flow curve negative pressure is huge. But with orifice as per size mentioned in datasheet transients are fine. pressures are within limits. What can be the reason?

Air flow curve is generally used when you don’t know the orifice sizes. Please check if you have entered the correct air flow curve in correct format, which can be checked using below link, look for section- “Using a Custom Air Flow Curve”.

https://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/3400/modeling-reference---air-valves

Thank you Sushma for the response. 

In continuation to that, I have another query. Is it possible to view Pressure and HGL graphs for Steady State condition.

For steady conditions, you will get bar graphs since you don't have a time axis.

I think the bar graphs are a bit dull. I'd rather color code the pipes by pressure or HGL. You can also do contouring or annotation.

Thank you Tom, Which option to see bar graph of steady state condition? 

1. How to view Air flow curves for each air valve? 

2. Liquid Level Vs Time; Liquid volume vs Time & Gas pressure Vs Time graphs for Surge Vessel? 

3. While viewing the flow vs air/vapor volume curve of an air valve through transient result viewer, The air/vapor volume shows  17500 litres, Will the air valve perform for the specified volume ? 

regards,

Marzook K H 

1. How to view Air flow curves for each air valve?

Air flow curves defined can be seen under Components > More > Air flow curves.

2. Liquid Level Vs Time; Liquid volume vs Time & Gas pressure Vs Time graphs for Surge Vessel?

You can see the graphs of gas pressure, gas volume, water inflow etc. vs time in extended node tab, please see below screenshot.

About liquid level in the surge vessel, please see section “Tracking the Liquid level” in the hydro tank technote provided to you earlier.

3. While viewing the flow vs air/vapor volume curve of an air valve through transient result viewer, The air/vapor volume shows 17500 litres, Will the air valve perform for the specified volume ?

That is upon your engineering judgement and modeling experience to take this decision. However please check if the pressure is remaining zero at the air valve, or the outflow orifice is too small to release the air at a reasonable rate.

Here is similar forum discussion that might help you.

Air valves - forum discussion