Problems when modeling an EPS engine aqueduct system

Question

D ear Bentley Master

I am modeling an aqueduct system in 2 periods "EPS and Steady State"
In the first part, it is modeled with Steady State, solving the multiple errors presented in it.
In the second part it is modeled with EPS, I make the following configurations: 
 
 EPS motor selection 
 In Patterns, adjustment is made in the Hydraulic option 
 I make the adjustment in the Demand Control Center for the different Junctions of the system

I carry out the Control for the Set to use according to the pumps that I have in the system 
 In the alternatives, I modify in operational the creation of a child scenario with the selection of the created Set 
 
 Note: Making it clear that the system has 2 pumps that supply a tank, leaving only pump 1 activated. But the tank gets 2 more reservoirs. 
 I generate multiple errors such as: 
 
 Network Unbalanced.

Disconnected demand nodes detected; hydraulic results are likely to be compromised 
 Demands and is disconnected from a reservoir or tank during the analysis. This error occurs multiple times. System disconnected because of pipe ta1153, this error could not be solved and I believe that one time solving it, the others will be fixed 
 My doubts are enough.

I would like with the help of a bentley teacher to solve the many problems that the model presents.

I already made different applications of solutions for Network Unbalanced but I can't find the solution.

Can I model a tank as represented in the model, 2 pumps, 2 reservoirs? 
 I have been able to review different forums, videos, supplied by the bentley team and I have not been able to find a solution. Attached model for your required solution. https://wetransfer.com/downloads/fc1fd472d4bbe0558913bada6836842a20210727210127/15dd88 https://we.tl/t-c2ewNcbPEn

Sushma Choure · Answer

Hello Jefry, 
 Pump BOMBA 1 - 10HP is having issues in steady state as well before moving to EPS analysis, that pump cannot deliver flow or exceeds maximum operating point. 
 Could you please check if the correct pump curve is defined as second pump is BOMBA 2 - 15HP is off, so pump BOMBA 1 - 10HP needs to deliver required flow. Please follow below troubleshooting steps. 
 User Notification: "Pump cannot deliver flow or head" 
 If you could provide at lease 3 point curve that would yield better solution. 
 Disconnected nodes are in model because of tank PTAP, as it becomes empty and full every time step as per controls defined. Make sure that tank neither becomes empty nor full to avoid disconnected nodes. 
 There are 3 reservoirs in model and 1 tank, are these 3 continuous sources of water or elevated tanks on field? You mentioned you are modeling aqueduct, could you elaborate more on that?

Sushma Choure · Answer

Hello Jefry, 
 Thank for you for confirming the modeling case. 
 As mentioned earlier please revise the pump curve, if you don't have full pump curve i.e. fine, one point curve is to be used in such cases only. 
 The total downstream demand is around 150 lps and if only one pump is going to operate then you may need to revise the pump curve to cope up with the total demand. 
 Also the controls on the tank need to be set up correctly, you can either set level based or hydraulic grade based controls. It appears in second control below the level should be used instead of HGL, as HGL cannot be 0.05 m.

Yashodhan Joshi · Answer

Hello Jefry, 
 As Sushma pointed out in her earlier responses you need to revise the pump curve specifically for BOMBA-1 10 HP. Another thing I noticed was the size of the tank PTAP. It has a diameter of only 0.41 m. Are you sure the values entered for the tank are correct. 
 For testing I changed the value to 20 m (randomly) and the number of user notifications reduced. See the below snapshot; 
 
 And here is the percent full graph for the tank PTAP; 
 
 You can see that its more agreeable in this case and although the tank is getting 100% full at some timesteps, we don't have any disconnected nodes. With sufficient size the tank is not rapidly filling and emptying as before thereby not disconnecting the downstream and upstream pipes. 
 Check to see if the tank is as built or you can increase the volume of the tank. Note that I have randomly assumed a 20 m diameter and you would have to perform some mass balance calculations to determine the optimum capacity of the tank based on your demands downstream and the pumping capacity. 
 Let me know if this helps.