Remote I/O in Biogas Plant

In biogas upgrading plants of Purac Puregas Turck’s I/O-system excom enables convenient maintenance directly in Zone 1

With its gas company Purac Puregas the Swedish Läckeby Water Group offers biogas upgrading plants. The Purac Puregas gas plants take raw biogas and upgrade it to practically pure bio methane. With its chemical absorption process, called CApure, the plants remove carbon dioxide and hydrogen sulfur (H2S) from the raw biogas. That increases the efficiency of the biogas plant and improves its ecobalance.

excom for compressor room

For the gas plant of a local energy company in Savsjo Purac Puregas looked for a better remote I/O solution for its biogas plant skids. In the compressor room of every plant module a remote I/O system in zone 1 collects all sensor and other signals from the hazardous areas. The former remote I/O could not be operated directly in zone 1. For maintenance, the customers always had to shut down the plant module and de-gas the compressor room. A lot of time, work and money were required - often for minor problems like, for example, a wire break.

Convenient maintenance

Turck introduced its remote I/O system excom to Purac Puregas. Unlike the system being used, excom can be mounted directly in zone 1. Additionally, the excom status LEDs are easily visible through the window of the stainless steel box the excom is mounted in. The electrical staff of the local waste company, for example, can now easily identify potential problems. And if necessary, the customer can get simple remote support just by calling Purac Puregas and describing what the status LEDs are signaling or the diagnostic messages show.

According to Anders Rosengren, senior electrical engineer at Purac Puregas, the easy maintenance of excom was the major reason for the system change: “The well visible LEDs and the easier maintenance through hot swap in run were our main reasons for excom. Besides that, excom matches aesthetically. We try to build everything in stainless steel. With its designated stainless steel housing excom fits like a hand in a glove.”

BL67 withstands Swedish winters

During the project Purac Puregas found other solutions in the Turck portfolio to enhance their gas plant. In the outdoor parts of the plant, at the CO2--absorption tower, a fieldbus system has to connect several valve indicators to the Profibus of the PLC. Turck’s modular fieldbus I/O system BL67 with a temperature range up to -40 °C can be used outdoors even in harsh Swedish winters. The Profibus is connected to the PLC via the same node as excom. The Turck segment couplers SC12 provide the intrinsically safe Profibus. The direct outdoor mounting of the BL67 saves Purac Puregas the construction of a preheated control cabinet and that accounts for the energy efficiency of the gas plant as the preheaters would use energy themselves.