4871 Process Controller

The control module of the Parr 4871 Process Controller is a Honeywell HC-900 Hybrid Controller. The HC-900 Controller comes with 4, 8 and 12 card capacities. We are offering the 4 card controller as our model 4871A Controller and the larger ones as our model 4871B and 4871C Controller respectively. Detail of the controller functions is provided in the following table:

A. Input / Output
The control chassis has been designed to accept up to 4 input or output modules. Depending upon the type, each module contains between 4 and 16 individual inputs or outputs, fully isolated from one another. The modules available to tailor the controller to the users application include:

Input Modules
The analog inputs are of universal type and are most commonly used for thermocouple or RTD temperature sensors, strain gage type pressure transducers, motor current monitoring and similar devices with mV, V, or resistance inputs. Input isolation, cold junction compensation, and burnout protection are incorporated into the circuitry.

The digital inputs can be logic inputs or contact closures. These are typically used for sensing valve positions or conditions of safety devices.

Output Modules
The analog outputs are 0/4-20 mA. A suitable dropping resistor can be used to convert this to 0-5 or 0-10 VDC. Analog outputs are commonly used to set stirrer motor operating speeds, position control valves, or drive mass flow controllers or pumps.

The digital outputs are open collector type capable of sinking up to 300 mA. They are commonly used to control heaters, solenoid valves for cooling or other flow control, system safety shut down, visual and/or audible alarms, and similar devices.

B. Control Loops
The controller can provide 8 PID or ON/OFF control loops in its standard configuration. These can be expanded to 32 function blocks in the extended control version. The PID control algorithm includes auto-tuning and fuzzy logic overshoot suppression for each control loop. For heating and cooling control, the PID control loops provide time proportioning output of the associated digital output.

Many temperature control applications utilize two separate time proportioning outlets with one PID controller; one for heating and one for cooling.

Control loops can be linked together to provide cascade, feed forward or ratio control for difficult or advanced control applications. Both high and low limit values can be entered for each control loop to sound alarms or initiate safety control schemes.

C. Set Point Programming
Recipes for controlling the entire process of a reactor can be written using the setpoint profiler incorporated into the control firmware. A single profile may be from 2 to 50 segments in length. A typical profile might be a ramp and soak of the reactor temperature but, in addition, the analog and digital outputs can be tied to the basic profile to start and stop flows, activate stirrers or accessories, or change alarms. Any of the setpoints within the profile can be protected with the setpoint guarantee function that assures that the process variable will be within the entered limits before the profile can proceed.

Up to eight separate profiles can be running independently (8 reactors each on their own program, for example) at one time. While a maximum of 70 profiles can be stored in the controller itself, an unlimited number can be stored in the operator’s PC for rapid transfer to the controller.

In addition to the setpoint profiling capability, the controller is also equipped with a setpoint scheduling function. This feature can operate up to 8 profiles operating on a common time base. Under this scheduler, up to 4 reactors can be operated in parallel on a single program.

D. Communications Channels
Each 4871 controller is equipped with a RS-232 and Ethernet communication port. The RS-232 port is used to establish fundamental control logic. The Ethernet port provides communication with the host PC when using the SpecView GUI program. Multiple controllers, each with a unique address, can be networked on the Ethernet interface with a single connection to the PC.

The principal advantage of the Ethernet interface is that it allows the user to use an existing network infrastructure to connect the controller to the PC. As a result, one can operate the controller over the network from anywhere within your facility. Additionally, Internet access from remote locations becomes possible. This type of connectivity offers unique possibilities, for example, related to remote diagnostics and system troubleshooting.

E. PC Requirements

• Windows 95/98/NT/2k/XP PC with at least 100 MB free hard disk space to allow for data logging and the configuration files.
• The display resolution should be set up for 1024×768 pixels and at least 16-bit color.
• A CD-ROM drive for program installation, at least one RS-232 COM port and an
• Ethernet port are required to communicate with the controller.

Screenshot of typical 4871 Controller user interface main screen.

In most laboratory and pilot plant applications, a PC will be used for the operator interface. For plant or production applications, an industrial type user interface box with a color graphic LCD is available.

A. User Interface Software
SpecView describes their product as “Software for people with other jobs”. That
seems to be an excellent description of this software package used with the 4871
controller to:

• Configure the control package
• Develop the graphical screen layout
• Establish the data logging profiles
• Prepare custom reports
• Create bar graphs
• Generate time trend graphs
• Monitor alarms
• Create flexible recipes
• Retrieve and replace logged data
• Operate the reactor system(s)

The full software package, not just a run-time version, is supplied with 4871 controller so operators can enhance their system as they get familiar with it or expand / change their applications.

Demonstration versions of the SpecView software can be downloaded at
www.specview.com.

B. Configuration
An integral part of the Honeywell Controller is the control builder software. This is the “Drag and Drop” software that enables Parr to rapidly establish the controller’s internal logic and adapt it to individual systems requirements.

The user can employ this same software to change or enhance the fundamental logic of the controller as additional components are added to the system or as functions need to change.

4875 Power Controller

Parr designs, builds and furnishes power controllers to adapt the analog and digital outputs from the 4871 controllers to the reactors or systems being controlled. These power controllers handle all of the high current power circuits so that the control circuitry is isolated from these loads. This also makes it possible to install the controller in a control room some distance from the system being controlled. The power controller or controllers will be designed for each individual system, but as an example, a 4875 power controller includes:

• A solid-state relay sized to handle the current drawn by the vessel heater. This is commonly a 25-amp relay with its protective fuses.

The 4875 Power Controller module is flexible and can be used in remote locations from the system being controlled.

• A solid-state relay sized to drive a solenoid valve to control the flow of cooling water to the vessel.
• A motor speed controller that converts the analog output signal from the controller to the electrical signal required to drive the specific stirrer motor. A circuit breaker for the motor is also provided.
• A lockout relay to shut down the heater circuit should an alarm condition be detected.
• Status lights for the principal functions.
• Connections of appropriate style for the power input and device outputs.

Note: One model 4875 Power controller is required for each reactor in a parallel system.

The software and the Operating Instructions for the 4871 come on a CD furnished with the Controller.

Multi-Reactor System with 4871 Process Controller

Expansion Capabilities
This custom order is set up to run sixteen reactors, two 4871 Process Controllers, with sixteen 4875 Power Controllers all through one PC.

If any of the input, output, control or programming limits described here for a single controller are a limitation in building a control system, a limitless number of controllers can be linked together in a network to a single host PC.

Third Generation Technology
The 4871 Controller is the third generation of process control Parr has offered to its customers for integrated process control. Starting with the terminal based 4850 introduced in 1989 and the graphical based 4860 introduced in 1998 we have developed a good appreciation of the requirements for integrated process controllers.

The combination of the Honeywell HC-900 controller with the SpecView software system provides a major step forward in the capabilities, flexibility, ease of programming and adaptability of these controllers for small to moderate size systems.

Current Industrial Standards
Modbus, Ethernet, auto-tuning, fuzzy logic, auto-configuring man machine interface (MMI), supervisory control and data acquisition (SCADA), multi-loop control; these are a few of the terms and capabilities designed into the hardware and software incorporated into the Parr 4871 controller.

This is a very modern and powerful package that enables us to offer turnkey systems ready to run within weeks of order at very attractive prices compared with custom programmed systems previously available.

The photo above illustrates a six station multi-reactor system. Each reactor is equipped with it's own constant pressure gas delivery system. The 4871 Controller maintains all of the important system parameters, including temperature and stirring speed, and records the gas consumption of each of the reactors.

The 4871 Controller provides two options for controlling the temperature Ramp and Soak programming of the individual reactors.

1. Set Point Scheduler
Using the Set Point Scheduler, different temperature profiles could be programmed for each reactor, but the length of time for each segment of the profile was fixed for all reactors. For example, each reactor could be heated to an individual temperature set point, but the time allowed to reach this set point was the same for all reactors as would be the time they were held at this set point.

2. Set Point Programmer
Using the Set Point Programmer, completely independent temperature profiles could be established which vary not only in the set point, but also in the length of the segment.

The 4871 Controller includes Operational Sequence Control
The sequence control function offered by the 4871 Controller greatly expands the capabilities of this control for users who wish to control reactor systems. The operation of valves, pumps and meters can be programmed on either a time or an event basis. Sequences can be very simple timed events or they can be very complex with multiple nested default sequences programmed to occur only if process feedback indicates a need to take alternative actions.