Viscosity Regulator System

Differential Pressure (DP) Cell

• Contains glycerin, which is heavier than oil
• Oil pressure on top of glycerin transmits to a diaphragm
• Pressure difference is sensed electrically and generates a signal
• This signal is fed to a cascade controller as Process Value (PV)

Cascade Controller

• Receives PV from the DP cell
• Uses a flapper-nozzle mechanism for control

Flapper-Nozzle Mechanism

Components:

• Flapper
• Nozzle (0.25 mm diameter)
• Restrictor (0.20 mm diameter)

Operation:

• PV pushes the flapper, restricting flow from the nozzle
• Restriction creates back pressure

Control Mechanisms

DAT (Derivative Action Time) Restrictor:

• Pushes flapper slowly in the opposite direction of PV
• Reduces sensitivity
• Helps prevent overshoots and undershoots

IAT (Integral Action Time) Restrictor:

• Pushes flapper slowly in the same direction as PV
• Helps eliminate overshoot

Without DAT and IAT:

• Only PV pushes flapper, resulting in high sensitivity

Additional Components

• PV bellows
• SP (Setpoint) bellows
• Vent: releases air from the ATO (Air-To-Open) valve

Key Points to Remember

1. The system uses a DP cell with glycerin to measure oil pressure
2. The cascade controller uses a flapper-nozzle mechanism for precise control
3. DAT and IAT restrictors fine-tune the system’s response
4. The combination of components helps achieve accurate viscosity regulation

Study Tips

1. Understand the function of each component
2. Visualize how the components interact
3. Focus on the roles of DAT and IAT in controlling system response
4. Practice explaining the process flow from DP cell to final control