Chemical company processes critical data via wireless Ethernet
By Control Engineering Staff -- Control Engineering, 8/7/2008
In recent years, the value of data has increased as the cost of implementing wireless networks has decreased. Industrial users, however, have remained reluctant to trust wireless to transfer process or production data in critical applications. Below, Dave Eifert, automation sales engineer, Phoenix Contact, explains why a chemical company that engineers thermoplastic material switched to wireless communications. The company saved money by eliminating costly trenching and increased reliability compared to an earlier hard-wired system.
| Wireless application: thermoplastic manufacturer |
| -New fiber optics could involve trenching or expensive conduit runs for several hundred feet in Class 1, Division II areas. -During cold weather, prior wired system often would stop communicating; downtime compromised just-in-time delivery of critical material. -Misdiagnosis could cause up to two days of missed information. -Data historian contents showed zero missed samples in the initial half-year period with wireless. |
The company needed to convey process data from its new Emerson Process Management DeltaV system to its historian database. This data is used to calculate inventory levels of one of the company’s feedstock chemicals. When the company switched from PLCs to the DeltaV system, it implemented a wireless Ethernet system.
An outdoor tank farm stores raw materials stored in large spherical tanks, several hundred feet from the offices that house the historian database server. Legacy instrumentation was connected via Foundation Fieldbus to a gateway that transferred the data onto a Modbus Plus network to the PLCs, and ultimately, to the historian. Besides the gateway, there were several junction boxes where various copper conductors and network cables were spliced.
During cold weather, the system often would stop communicating, resulting in downtime and compromising just-in-time delivery of critical material.
In addition, errors in the initial diagnosis often led to the wrong type of personnel being dispatched to make repairs, further increasing downtime. For example, IT would be tasked with the issue, only to find it was a production maintenance issue. Such a misdiagnosis could cause up to two days of missed information.
Several years ago, the chemical company began replacing PLCs with an Emerson DeltaV distributed control system, using an Ethernet network. The new system offered an opportunity to bypass the suspect wiring and network of the previous system. However, running new fiber optics could involve trenching or expensive conduit runs, for several hundred feet, through Class 1, Division II areas. The plant would have trouble justifying the return on such an investment. The plant manager and system integrator decided to investigate an industrial wireless Ethernet system.
Management obtained samples of two Ethernet radios and associated adaptors, lightning and surge protection, and antennas from Phoenix Contact and tested the items over several months. Initial tests suggested that this system would work in the application. The real test, however, would come when the system endured the change of seasons from summer through winter.
After the initial six months of installation, the plant manager reviewed data historian contents and found zero missed samples.
New wireless system performance delivered better reliability and data integrity than the older wired system.
Learn from other wireless applications.
– Edited by Mark T. Hoske, editor in chief
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