Rhein Chemie Benefits by Choosing Remote I/O

Rhein Chemie is a global company in the chemical industry that has been successfully providing tailor-made additives and service products for more than a century. These additives provide the desired properties to end products such as tires, dashboards, industrial lubricants, and radiator hoses. The company is headquartered in Mannheim and is a 100% owned subsidiary of LANXESS, based in Leverkusen, Germany.

The multi-purpose plant plays a key role in the manufacture of products for the lubrication industry in Mannheim. It comprises nine plants for the manufacture of various products. The majority of these plants consist of a central stirring reactor (fig. 1) with a volume of 6-12 m³ and various peripheral field devices. In the reactors, the products are produced in batches from the supplied liquid and solid raw materials with a retention time of approximately 24 hours and at temperatures of 10° to 200°C. The plant surroundings are classified as hazardous area Zone 2, the reactor manhole Zone 1, and the reactor Zone 0.

In 1992, the plants were converted from pneumatics to electrical systems, and in 2004, a new Process Control System was installed (Freelance 2000, ABB) with PROFIBUS fieldbus technology. A decision needed to be made regarding the way to connect the field devices to the process control system. There were two options:

• Connection with Remote I/O technology (RIO) while retaining the available equipment and the existing field cabling. Advantages were space and cost-saving installation between RIO and Process Control System, and the possibility of central access to the field devices.
• A new installation connecting (new) PROFIBUS PA field devices directly to PROFIBUS with improvements in topology, bus power supply, interchangeability of the devices, comprehensive diagnosis, etc.

Rhein Chemie opted for Remote I/O. The right side of Figure 2 (below) shows the previous plant topology with point-to-point connections to the controller and the Process Control System. The new concept is shown on the left side of Figure 2 and in Figure 3. All parts of the multi-purpose plant have now been converted. The field devices are connected with point-to-point technology to the Remote I/Os using RPI, Remote Process Interface from Pepperl+Fuchs, and installed in the control cabinet. Several RPIs are located in each switch cabinet, according to the number of inputs and outputs.

Signal transmission from the RPI takes place via PROFIBUS DP – in a combination of wire and fiber-optic cables with corresponding converters – to the switch room, and from there to the allocated Freelance Controller (Figure 3). The fiber optic cable transmission path between the field and switch room is either in a loop (Figure 2, left) or a star (Figure 2, center) configuration.

All switch cabinets have an identical design, which greatly simplifies TÜV approval, maintenance, or copying documentation and software. The cabinets are made at the Pepperl+Fuchs plant in Bühl/Germany.

With Remote I/O technology, operators can use the features of both 4…20 mA technology as well as fieldbus technology, such as:

• Unchanged field installation of devices and their point-to-point connections to the Remote I/O
• Continued use of economical 4-20 mA devices
• Continued use of available knowledge and experience in commissioning, maintenance and servicing
• Live exchange of components during operation (hot swapping)
• Economical and space-saving wiring from the Remote I/O to control room
• Central access to all devices, e.g., from a maintenance system
• Subsequent upgrades (comprehensive diagnoses, central operation, introduction of PROFIBUS PA devices)

Plant advantages

• Faster and easier maintenance
• Possibility of online extensions
• On-site modifications without downtime
• Availability of plant information

1 - Connections between RPI and field devices
2 - PROFIBUS DP between RPI and DP/fiber optic converter
3 - Output from DP/fiber optic converter to the switching room
4 - Input into fiber optic/DP converter from the switching room
5 - Output from the fiber optic/DP converter to the DCS