Intrinsically Safe Flow Control for Acetylene Sampling

In ethylene production, acetylene (C₂H₂) is an unwanted byproduct of steam cracking. Even in trace amounts, it is unstable and highly reactive, creating downstream process risks and potentially impacting product quality. Many facilities employ thermal-catalytic hydrogenation to selectively convert acetylene into ethylene, but precise control is essential. Both under- and over-conversion can cause operational and economic issues.

 

Monitoring acetylene levels after hydrogenation often requires precise lab-based sampling through online process analyzers. In one North American Class I, Division 1 (C1D1) process laboratory, a closed-loop sampling system was used to verify post-hydrogenation acetylene concentrations. A side-stream from the process line was carried via a heated transfer line to prevent condensation, then chilled in an insulated icebox to remove particulates and volatiles.

 

After preconditioning, the sample was routed through an Alicat® Scientific IS-MAX™ intrinsically safe mass flow controller before entering a gas analyzer. Operating at 0–200 CCM with ±0.5% of reading accuracy at 15 PSIG, the IS-MAX maintained stable sampling flow. The system’s Modbus RTU connection to the plant PLC allowed real-time monitoring of flow, pressure, temperature, and other parameters, supporting both process control and diagnostic functions.

The IS-MAX combines sensing, actuation, and communication in a single C1D1- and Zone 0-certified package. This integrated approach reduces panel space, minimizes wiring complexity, shortens installation time, and improves safety while maintaining high-accuracy closed-loop control in hazardous environments.

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Key Features and Benefits:

• Integrated flow, pressure, and temperature sensing with ±0.5% accuracy

• C1D1 and Zone 0 certification for safe operation in hazardous areas

• Fast 30 ms response for stable, high-throughput sampling

• Direct PLC integration via Modbus RTU for real-time control and diagnostics

• Reduced system footprint and wiring compared to multi-component setups

Technologies like the IS-MAX improve compliance, cut maintenance time, and ensure more consistent analytical results across multiple facilities. For operators in oil, gas, and petrochemicals, this means lower total cost of ownership, higher uptime, and more reliable product quality verification.

 

At Kaizen Controls and Automation, we’re proud to work alongside Alicat Scientific in bringing this level of performance and safety to our customers’ hazardous-area gas sampling applications. You can read Alicat’s full case study, Acetylene Analysis in a CID1 Environment, on their website here: https://www.alicat.com/articles/acetylene-analysis-in-a-cid1-environment/.

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