System Migration, Mississippi Style

Mississippi River Corporation (MRC) operates a 400 ton/day repulping and de-inking facility in Natchez, Miss. The company produces a recycled paper fiber called "wet lap" (Figure 1) that is sold to local paper manufacturers. In the early ‘90s MRC purchased a Moore Products' APACS+ control system incorporating seven non-redundant ACMs, approximately 1,200 I/O’s and a custom HMI package. The HMI encompassed three independent systems, with a total of six conventional CRTs, as well as a stand-alone data historian.

Figure 1: Making Wet Lap

Recycled paper is re-pulped, de-inked

and sold again as "wet lap."

Over time, MRC’s distributed control system underwent numerous hardware and software additions and modifications to bring more areas of the plant under the scope of the distributed control system (DCS). All of these projects were based on expanding or developing the original HMI on its Windows 95 platform. Although it withstood almost a decade of continual upgrades, eventually the pulp processor’s control system could not meet the company’s performance requirements. During that period, the original HMI software vender also went out of business and failed to transfer the intellectual property and support for the HMI MRC had relied on for so many years.

It was high time for an upgrade. After all due diligence, MRC decided to migrate the old system to Siemens’ PCS 7 OS. Besides delivering contemporary levels of process control, the new HMI technology had the ability to communicate with the MRC’s legacy APACS+ control hardware without modifiaction (Figure 2).

Figure 2: New Into Old

MRC's decade-old hardware forms the 

backbone of the new Siemens system.

A Phased Approach, Naturally

To help spread capital outlay over a longer period, MRC tasked RSH Engineering Inc., a control systems integrator based in Monroe, La., to develop a phased approach to its proposed HMI system upgrade plan. Probably the greatest obstacle blocking the conversion was MRC’s extensive customization to the APACS+ controller library. All of the standard application library elements, such as PID control, motor control, and analog indication had been modified, and several custom control elements had been added to the application.

Another road block soon presented itself. The existing configuration contained no HMI comments, which are used to automatically create the HMI tag database from the controller configuration. Every sheet in the controller configuration would need to be modified to add the appropriate HMI comments in order for database automation to work. In addition, there was no system documentation, and the PC hardware platform was unstable.