Complete control of a thermal fluid heater with multifunction PID controller

• Thermal fluid heater is a very simple and cost effective solution for instant heating process up to 350°C (662°F), easy maintenance and does not require boiler regulation
• 3850T multifunction controller provide complete control including PID control, safety interlocks, plant logic and remote access for monitoring, control and maintenance

Thermal fluid is a mineral or synthetic oil, with the characteristic of a high boiling temperature (400-500°C) (752-932°F) at atmospheric pressure, it is used as the heat transfer medium.
Thermal fluid heaters are used in various processes requiring heating temperature up to 350°C (662°F). Typical applications are found in the food, chemical, petrochemical, plastic extrusion, paper transformation processes.
It is preferred over steam generators or heated water because of its low freezing point, good thermal stability and the absence of corrosive action. Additionally, the excellent viscosity and energy saving up to 50% when compared with steam and heated water systems makes it popular choice.
In superheated water and steam systems increase in temperature lead to higher pressures which calls for licensed operation.
Whereas there is no high pressure in thermal fluid heating system and thus does not require any particular surveillance.

Overall process flow control
The thermal fluid circulates in the concentric coil which is heated by the gas or oil burner flame and the resulting combustion gases. It is then distributed through a low-pressure network to the process plant for its use.
On the return circuit a degasser / expansion vessel, atmospheric or pressurized by inert gas, ensures the elimination of air, steam and light fractions before the thermal fluid returns to the oil heater.
The thermal fluid typically works up to 350°C (662°F) at atmospheric pressure, while remaining pumpable up to -20°C (- 4°F) and beyond with the addition of special fluid.

Process variable control
Temperature of the thermal fluid, even in the event of changes to its request by the connected users.
The pressure of the fluid in the closed circuit.

Remote access
The Fluid heater is continuous process and it keeps running on its own for long period. The system needs to have remote access for monitoring its health and to plan preventive and scheduled maintenance.

Multifunction PID controllers 3850T

Core functions

• Precise and multiloop loop PID control (up to 16 loop PID)
• Logic interlocks and Math functions
• Custom graphic interface

Valued added functions to make the equipment robust and trouble free

• Wide and brilliant graphic touch display
• One solution device
• Precise and pre-configured multiloop loops PID controls
• Logic control, interlocks and sequences, Math functions, timers, batch recipes for automated process flow
• Data monitoring and encrypted recording (Archiving) (Figure 2)
• Graphic display, process mimics, local visualization and operator interface
• Menu driven configurator tool
• Quick set up and easy configuration to suit the application
• Modbus TCP and Ethernet VNC Remote access

3850T multifunctional controller meets the complete control requirement of this application and supports automated operation

Precise Process variable and logic control

• Pressure PID control of the thermal fluid in the closed circuit by driving the circulating pump
• Temperature control by driving gas or oil burner
• Management of process flow, process alarms & logics and plants safety interlocks (Figure 3)

Pre-scheduled automated operations and remote access

• Preheating can be automated after scheduled shut down or weekly break.
• A graphical display with specific plant mimics, and alarming pages enables operators to interact with the plant in most user-friendly way – this eliminates human error
• The Ethernet VNC enables remote access to the control system for monitoring its health and to plan preventive and scheduled maintenance (Figure 4)