Many process controls look like they’ve been touching their toes and going out for a jog. That's because their software, support components and networking are increasingly unhitching from traditional, rigid, hardware-based and hardwired formats to become simpler, more flexible, easier-to-implement solutions that give users new freedom to run and optimize applications.
This trend is illustrated by isotropic graphite manufacturer Toyo Tanso USA Inc. in Troutdale, Ore., which offers silicon carbide surface treatments to protect substrates. Its batch automation process is performed in multiple reactor vessels with varying specializations that require careful management. To better automate this process with many I/O points and controls that need to be easily programmed and deployed, Toyo Tanso recently implemented eight Opto 22 Snap process automation controllers (PAC) that are configured to communicate with other controllers, use the PACs' distributed control and intelligence features, and preserve uptime.
"Ladder logic is useful for basic, on/off procedures and control, but it can be difficult to troubleshoot. Snap PAC's scratch pad features and PAC Project tools can step in and out of a control block to pinpoint exactly what’s happening, which makes troubleshooting easier."
I/O modules and Snap PACs in Toyo Tanso's batch surface treating application control pumps and motors, temperatures, and power and pressure to the vessels; heat to the vessels; and the cooling water supply during the coating process. Pressure and temperature are both controlled using PID loops that run on Snap PACs’ built-in I/O brain. Other vessel dynamics are controlled by Snap PAC, including dozens of valves in each vessel. As a result, Snap PAC and I/O help monitor pH and pressure during coating, while maintaining setpoints using PID loops and other control points. The vessels have more than 1,000 I/O points for control and monitoring during batch runs.
“Our production environment is busy and physically demanding, but it also requires precise control of all its interacting systems,” says Peter Souvanna, IT manager at Toyo Tanso USA. “Ladder logic is useful for basic, on/off procedures and control, but it can be difficult to troubleshoot. Snap PAC's scratch pad features and PAC Project tools make it easy to move data in and out of the controller. They can step in and out of a control block to pinpoint exactly what’s happening, which makes troubleshooting much easier. Plus, their HMI tools offer standard features in the software that let us to build rich HMI screens to know exactly what’s going on with our process at all times.”
In addition, Toyo Tanso USA implemented Opto 22's groov mobile interface tool to develop a gas monitoring system that can be accessed directly by operators’ mobile devices. During the coating process, potentially dangerous gases are used, and groov acts as a backup to the standard control system HMI. “Our groov Box also supports unlimited concurrent connections and user accounts, allowing the entire plant to use one unit for all of our operators,” adds Souvanna, who also took advantage of the redundant Ethernet jacks on the PAC controllers to connect to its production network and business network. “If there’s a broadcast storm or network outage on the business network, the controller isn’t affected and continues to operate.”
Of course, the main benefit of simpler, more flexible controls is they can make migration projects easier to design and implement. Such was the case with a polypropylene unit at Braskem Europe GmbH in Schkopau, Germany, which recently upgraded from a Dow Chemical Co. Manufacturing Operating Discipline (MOD) 5 proprietary distributed control system (DCS) to a Honeywell Process Solutions Experion Process Knowledge System (PKS) R430.
The project in Schkopau began in 2013, and I/O cutover, loop checks and startup occurred in August-September 2015 during downtime scheduled every five years. "This was a complicated and risky migration that required many resources," says Michael Martin, senior process control engineer at Braskem. "We've had no DCS-related plant shutdowns since cutover, and we gained new technologies and capabilities from this migration. Production rates and online time percentages have been greater than or equal to yearly targets."
Overall, the MOD 5 to PKS R430 migration at the Schkopau facility included:
- About 7,000 I/O;
- More than 700 MOD 5 graphics migrated to Experion HMI;
- More than 1 million lines of MOD 5 software code and comments;
- Tracking, documenting and migrating about 100,000 MOD 5 variables;
- Transitioning more than 6,000 MOD 5 modules to about 4,500 Experion control modules;
- Migrating more than 50,000 AspenTech IP21 historian tags;
- Moving nine Siemens GC analyzer data links to Modbus/TCP via peer control data interface (PCDI) blocks; and
- Developing 30 control module templates.
"We also used Honeywell's worldwide cloud development system, which was employed by users in Germany, India, the Czech Republic, the U.S. and elsewhere," explains Martin. "We had to understand MOD 5's state-based control and automation architecture, so we could replace the sequence for each unit with sequence control modules (SCMs) as state drivers. Each sequence was comprised of modules for alarms, digital output (DO) logic, analog output (AO) logic, step logic, special calculations other tasks, and they had to be replaced with control modules."
Martin adds that migration challenges and solutions in Braskem's MOD 5 to Experion upgrade included:
- Identifying and developing similar functions when updating its HMI solutions;
- Translating and normalizing MOD 5 equations;
- Updating the polypropylene application's alarms because MOD 5 had limited alarms, and combined many process and hardware alarms to keep totals down; and
- Replacing MOD 5 interfaces to third-party devices with Honeywell's Peer Control Data Interface (PCDI) and Modbus TCP network.
"MOD 5 operators were required to read Dowtran code to run their plant, and MOD 5 was a closely combined basic process control system and safety instrumented system, which we had to break apart. This also meant migrating from MOD 5 PIDs with output ranges depending on fail open/fail closed to Honeywell PIDs."