Migrating to a DCS brings multiple benefits

Staff -- Control Engineering, 1/1/2006

Based in Pennsylvania's Lehigh Valley, near Allentown, and operating in 30 countries, Air Products and Chemicals Inc. (AP) is a top world supplier of gases, chemicals, and equipment to high growth markets, including: electronics, performance materials, refinery hydrogen and energy, and healthcare. Cost reductions and efficiency improvements at AP's Wichita, KS, facility are going straight to the bottom line.

To keep its leading edge status, the Wichita plant completed the first of two migratory phases—from a 20-year-old, continuous process-control system—to Siemens' Simatic, PCS-7 distributed-control system with Simatic Batch management software. An integrated approach was used to control and safety, reducing the complexity of having two separate systems, by creating a common engineering environment and a unified operator interface. AP also selected Profibus open fieldbus technology for an automation upgrade at the plant's drumming and blending facility.

By the end of 2005, AP expected the automation upgrades to reduce costs by several million dollars. Slated savings come from a combination of:

• Improved product yield;
• Lower energy costs; and
• Reduced requirements for raw materials and laboratory analyses.

The migration also successfully preserved AP's existing investment in field wiring and devices.

The first phase of AP's automation control initiative focused on its South Plant—a hydrogen reaction facility specializing in polyurethane curing agents, and additives sold to chemical, coatings, paint, and foam producers. Depending on customer orders, the plant normally produces 35 products, but has the capability of manufacturing up to 250.

The project team had only 21 days to complete the installation that would control the South Plant's 75 unit vessels and 50 equipment modules before the onset of cold weather. During the outage, the team installed the new PCS 7 system, assured transitioning of over 2,500 I/O points, and tested the Simatic Batch software-configuration for sequencing of product production.

Additionally, existing field device wiring, up to the terminals, was retained and undisturbed. AP kept the existing, TDC3000 field-terminal assembly (FTA) cabinets, but replaced the FTA boards, one-for-one, with Siemens FTA boards. No additional cabinet space was required.

After taking the process down for migration, the plant was up and running 18 days later—three days ahead of schedule.

Plant manager Ramon Lopez said, "The startup went very well. We had around-the-clock coverage from a cross functional team. Any issues were quickly resolved during the site acceptance testing, and nothing delayed the critical timing of the startup."

Lopez said the time devoted to the startup was greatly accelerated because Simatic simulation software was used during field acceptance testing at Spring House and to train the operators.

Simatic simulation software, which makes use of the existing controller configuration to generate the simulation program, allowed simulation of values of all the I/O points without modifying the actual system configuration. In addition, operators were able to practice with the graphics and batch manager software before startup. Today, Lopez said, operators receive on the job training because of the intuitive and easy-to-use qualities of the PCS 7 system. PCS 7 control system installation included:

• Four Siemens Simatic-S7400 controllers;
• A redundant pair of Siemens process-safety HF-systems;
• A redundant pair of operator system servers;
• Six operator system multi-clients;
• One engineering system server; and
• A stand-alone operator system archive.

The Safety Matrix engineering-tool was also used to help simplify the configuration of the safety system.

Lopez also expects to increase the capacity of the plant and improve visibility of the process with the new software. He said, "We now have a more precise way of making our chemicals, and it will be consistent, shift after shift, hour after hour. That reduces raw material costs. Being able to operate the equipment consistently all the time will also reduce the maintenance of that equipment. Reducing downtime by 5% is a big improvement."

The control system and S88 reporting features of the batch software simplify troubleshooting the plant. In the past, operators read some of the plant information directly off of panel mounted controllers. Information was available at that moment, but there was no way to automatically log the information for future reference.

Today, all information is reported automatically through the PCS 7 system to the control room and logged into electronic history.

As part of the automation upgrade at the plant's drumming and blending facility, AP installed a Simatic PCS-7 process-control system using Profibus for field device integration as the control system and Profibus accommodate multiple vendors' equipment. Embedded diagnostics—enabling preventative and predictive maintenance—keep operating costs low.

"Implementing Profibus has set us up for a leap in technology and engineering," said Lopez. "We also get better commissioning and long-term maintenance."

At the beginning of the project, AP worked closely with Siemens engineers and a consulting firm specializing in design and implementation of fieldbus systems to develop the technical layout. A traditional star topology was chosen to accommodate anticipated future expansions and retrofits.

Results have been impressive. Material, labor, and field installation costs have been reduced by approximately 30% after one year of operation.

Eighty smart devices, from multiple vendors, at the drumming and blending facility communicate with the Simatic PCS-7 process-control system via Profibus. Devices include: Micromotion mass flowmeters; Fisher valve positioners; Emerson and Siemens transmitters; Mettler-Toledo weigh scales; Siemens Simocode motor-control and protection devices; and Endress+Hauser level switches.

The fieldbus system includes both Profibus DP and PA layers to accommodate common devices, including transmitters and valve positioners, as well as smart motor protection and control devices. PCS 7 operator stations are located in Class-1 Division-2 process areas in suitable enclosures. Field devices can be accessed from a central location, if necessary, for maintenance purposes or to make configuration changes.

"Siemens support was very good," Lopez said. "We worked as a team and nothing delayed the timing of any of our activities. Our expectations to reduce costs, increase quality, and reduce downtime are being realized."