Setting controller
Set the Yokogawa UT150 temperature controller (Fig. 4) according to Heatec Tec-Note 8-04-144. During auto-tune, the modulating actuator (K, Fig. 3) will open and close the thermal fluid inlet valve (I, Fig. 3) several times while the controller automatically sets PID settings.
Note: If there is no heat load or the heat load is cycling on and off, the controller cannot auto-tune. Run auto-tune when a steady heat load is available.
You should write down the PID settings the controller set during auto-tune. Also write down the date and the ambient temperature at your plant. This information may be very useful for future troubleshooting or in case you have to replace the controller.
After auto-tune is complete, the preheater is ready for normal operation. The preheater is designed for fully automatic operation, so no other settings should be necessary.
Daily Shutdown
For normal daily shutdown, simply turn off the fuel pump. Because the fuel pump is electrically interlocked with the thermal fluid inlet valve (I, Fig. 3), the actuator (K, Fig. 3) will set the valve to bypass fluid from the preheater.
Replacing actuator, valve and coupling
In the event that you ever dismantle or replace a modulating actuator, 3-way valve or coupling, it is essential to make sure they are re-assembled properly. The information shown in Figures 1, 2 and 6 should enable you to properly reassemble these parts.
Flow direction in three-way valves is indicated by a small notch or step in their stem as shown in Figure 6. The notch is near the end of the stem as shown.
The stem can be rotated a quarter turn so that the notch faces either one of two flanges. The notch faces the flange that is closed or blocked. Thus, flow is through the other two flanges.
Figure 6. Direction of flow in 3-way valve.
Take special note of the visual position indicator on the Triac EM300. The “OPEN” reading can be changed to read “CLOSED” and vice-versa by lossening the retanining screws on its housing and simply rotating it 90 degrees (Fig 7).
Figure 7. Visual position indicator on Triac EM300.
