2 replies to this topic

[B.M. Process]

Dear Engineers of Cheresources,

 

Sorry to bug you with this basic stuff, but I was wondering if anyone could spot any flaws in the system I made the sketch of (see the sketch). I wanted to propose some water supply to some rural area by using whose data is included on the sketch. The pipeline information is also included on the sketch. 

 

The problems with this system (ones that I would someone's opinion for ) are the following:

 

1. the new system (light blue on the sketch) will use HDPE PN10 and 110 mm (4") this will tie-in via reducing tee ( galvanized carbon steel). A gate valve for insolated is proposed and a butterfly valve is proposed for flow regulation. The butterfly valve is deemed necessary because only 20m3/hr is required as allowing higher flow rate into the 4" would cause high system losses will cause back pressure to the Pump, P-xxxA/B which trips if that happens. A bypass is also added if any of valves goes under maintenance.

 

2. 4" HDPE has a rating of PN10 whereas the 6" HDPE is PN16. 

 

3. level control valve is proposed to be one that has a floating valve, but such a valve is prone to failure. Any better recommendations?

4. Any good examples of water level control out there?

 

You are free to give any opinion that will make this system better. 

 

Thanks in advance for your responses.

 

 Rural Area Water Distribution.xlsx   313.38KB   7 downloads

[thorium90]

The inner diameters of CS pipe and HDPE pipe is not the same.

If the required flow is only 20cmh, 4in is probably way too big.

The gate valve or the butterfly valve in the blue line in the upper sketch cannot possibly be taken out for maintenance while online. There is no need for a maintenance line anyway since there is nothing special there to maintain.

Why would allowing more flow from the blue line lead to higher pressure at the pump? More flow from the pump should lead to lower pressure, not higher. A typical centrifugal pump curve has a higher pressure at low flows and lower pressure at high flows, not the other way around.

If the pipe nominal diameter and pressure rating is also different, the inner diameter is quite different, especially so for HDPE pipes.

 

Overall, your description of control is easily accomplished by a valve called an altitude valve.

I have found a nice video for you.

 

https://www.youtube....h?v=_9QsmF8CWs4

 

Edited by thorium90, 18 July 2018 - 06:00 AM.

[B.M. Process]

Thanks, Thorium90, for your inputs.

 

I will respond to your inquiries as follows:

 

1. 20 C.M/hr. in the 4" pipeline (3.9km) was chosen to avoid high-pressure drop that would otherwise cause back pressure to the pump. That is why flow adjustment is necessary at the tie-in point (TP-1). It is, of course, true that when the centrifugal pump is operated at high pressure, the flow will be low. This is why when a zero at a shut-off head of the pumps. For this particular case, the size of 4" was chosen to minimize the high-pressure drop, thus avoiding the pumps operating the pumps at high-Operating pressure and low flow. This flow regulating will be achieved by having a butterfly valve (see the updated sketch).

 

2. For the bypass at the tie-in point (TP_1), your right, there is no need for having it since there is no instrument or any other special equipment to maintain at this tie-in.

 

3. For the level valve, the video you provided is amazing, but it will be expensive and the client needing this help may not avoid it. I am not sure of the price, though. There are, however, cheaper ones that can be used such as the one in the video I have attached herein.

 

4. On the nominal pipe diameter, there will be a reducing Tee at the TP_1. For the 4" HDPE leading to the elevated tank, the will be no problem this is flange-flange joint. Or maybe, I am getting your concern right.    

 

https://www.youtube....h?v=5hQzeTfj7AI

 

____________________________________________________________________________________________________________________________________

 

The inner diameters of CS pipe and HDPE pipe is not the same.

If the required flow is only 20cmh, 4in is probably way too big.

The gate valve or the butterfly valve in the blue line in the upper sketch cannot possibly be taken out for maintenance while online. There is no need for a maintenance line anyway since there is nothing special there to maintain.

Why would allowing more flow from the blue line lead to higher pressure at the pump? More flow from the pump should lead to lower pressure, not higher. A typical centrifugal pump curve has a higher pressure at low flows and lower pressure at high flows, not the other way around.

If the pipe nominal diameter and pressure rating is also different, the inner diameter is quite different, especially so for HDPE pipes.

 

Overall, your description of control is easily accomplished by a valve called an altitude valve.

I have found a nice video for you.

Attached Files

•  Sketch.docx   209.04KB   1 downloads

Edited by B.M. Process, 18 July 2018 - 09:41 AM.