Rod DryDec 2013

Worked Example

Training Module #4: Problem Statement

Water at a (constant) feed pressure of 4 barg flows through a DN400 pipe fitted with an equal percentage globe valve. Downstream there is a restriction of 200 mm ID and beyond this the sink pressure is 2 barg. The sink is elevated about 6m above the source.

1. What is the maximum water flow through this system when the valve is 100% open?

2. Will the valve provide reasonable flow control?

3. If the globe valve is replaced by a (possibly cheaper) butterfly valve, will flow control be reasonable?

Water Flow Through a Control Valve

Training Module #4: Step 1 of 111. Click on the Quick Start Icon ( ) and say “Yes” to the current project

overwrite warning.2. Select “Pipe with Globe Valve and Downstream Orifice”, select

parameters as indicated and press “Go”.

4 barg source

2 barg sink

valve 100% openorifice 200 mm

DN400 Sch 40

Water/Steam

Training Module #4: Step 2 of 111. Right-click in the fluid sink, select “Edit” and re-name it to “2 barg Sink”

then click “Modify Current Fluid Sink”. (We want it re-named so we can use it later.)

2. Click on “Edit Existing Line” to open the Line Editor.3. Press “Remove Last Section” to remove the sink.

Training Module #4: Step 3 of 111. Click “Edit” on Bend 1, check DN400 Pipe Sch 40 is selected and click “Accept”

Training Module #4: Step 4 of 111. Press “Turn Up”2. Press “Add Pipe 1”3. Press “Turn North”4. Press “Add Pipe 1”5. Select the sink (“2 barg Sink”) then press “Add Sink”

If you are working with a single screen, you can click “Toggle Opacity” to make the line builder semi-transparent. You will then be able to see through it and view the pipeline as it grows…

Training Module #4: Step 5 of 111. Right-click on the vertical pipe section and select “Edit”2. Set the length to 6 m and press “OK”3. Click the “Solve” arrow

Training Module #4: Step 6 of 111. Select “Pressure”

Maximum flow rate (valve 100% open) is

1121 t/h

Training Module #4: Step 7 of 111. Right-click on the valve and select “Valve Curve”2. Select “10 Steps Across the Range” and press “Calculate” (be patient – it may take a while)

Training Module #4: Step 8 of 11Installed valve characteristic looks OK for flow control…

Training Module #4: Step 9 of 111. Right-click on the valve, select “Edit” then press “Edit Valve Type”2. Select “Butterfly Valve” then press OK.

Of course, you can edit the

valve curve if you wish…

Training Module #4: Step 10 of 111. Right-click on the valve and select “Valve Curve”2. Select “10 Steps Across the Range” and press “Calculate”

Training Module #4: Step 11 of 11Installed valve characteristic is not really suitable for flow control…(control action is essentially in the bottom 30% of stem position range)

Training Module #4: Solution Review

Water at a (constant) feed pressure of 4 barg flows through a DN400 pipe fitted with an equal percentage globe valve. Downstream there is a restriction of 200 mm ID and beyond this the sink pressure is 2 barg. The sink is elevated 6m above the source.

1. What is the maximum water flow through this system when the valve is 100% open? Answer: 1121 t/h

2. Will the valve provide reasonable flow control? Answer: Yes

3. If the globe valve is replaced by a butterfly valve, will flow control be reasonable? Answer: No, not really…

Water Flow Through a Control Valve

Final Step: Save For Future Reference1. Select File Save ΣPipe Project As… and call this case “Water Control

Valve Example”, then press “Save”.

2. Select File Open ΣPipe Project and verify that the case is there, ready to be opened when you need it again.

Well done, we are now ready to move on to Module #5