YM:MDO Heating Unit Steam

1 General

Steam is running through a heat-exchanger and heats up the oil in the primary loop. In the primary loop we can find the MDO control valves as shown in the drawing below. The MDO control valves control the temperature of the MDO rolls.

We want to keep the flow through the heat-exchanger constant even if the MDO control valves open or close. Therefore there is an automatic bypass valve installed in the primary loop (item 24.2 in drawing). The flow is measured by a pressure transducer (item 47 in drawing). The system works as follows:

• MDO control valves are closing
• Flow is decreasing
• Automatic bypass valve opens in order to keep flow at set-point

2 Commissioning

2.1 Pressure Transducer Fischer DE38 (used as flow meter)

The pressure transducer measures the pressure inside the primary loop. We can use the pressure to get the flow in the system. There is also a KiWi-article about the pressure transducer itself. But the application described there is different from the application described here. In case you need it, you can find the manual of the pressure transducer in Public:Fischer DE38 Pressure Transducer (Used as Flowmeter).

• Check name plate of pressure transducer. Output signal should be radiziert (output is linear to flow)
  • Only if NOT radiziert: Set Parameter F = 1 on pressure transducer
• Set parameter ME to measuring range of pressure transducer (see name plate, e.g. 400 mbar)
• The parameter MEF is the upper limit for range of the display value. We want to display the flow. So we need to set it to the flow which corresponds to measuring range of the pressure transducer
  • Example: 0...400 mbar. Set MEF to flow which corresponds to 400 mbar (e.g. 80 m^3/h).
  • The relation between flow and pressure depends on the system design. Ask the mechanical engineer or HAM/EMA for the correct value.

2.2 Flexotemp

We use Flexotemp to read the 4...20 mA signal from the pressure transducer. In the Flexotemp project we need to set the value for 20 mA to the same value that we used for MEF in the previous step. Then we have the same display in WinCC and on the pressure transducer. There is a factor of 0.1 in Flexotemp for calculating the display value.

• MEF = 80 -> Flexotemp upper limit range = 800

3 Mechanical adjustment of manual bypass valve

The adjustment is done by the mechanical engineer on site.

In the primary loop there is also a manual bypass valve. This needs to be adjusted so that the flow in the primary loop is the nominal flow of the pump.

Procedure for adjusting the manual bypass valve:

1. Heat up the system to 180°C
2. Close all MDO control valves (WinCC -> Manual Mode -> Controller output 0%)
3. Open automatic bypass valve fully (WinCC -> Manual Mode -> Controller output 100%)
4. Open manual bypass valve fully
5. The flow should be higher than the nominal flow now. Close manual bypass valve, until flow is reduced to nominal flow.