UK-based Servomex is offering cryogenic ASU operators increased flexibility in their operations, with the launch of its new SERVOPRO Chroma.

Combining the latest Plasma Emission Detector technology with improved operational and communications capabilities, the SERVOPRO Chroma gives total flexibility in measuring hydrocarbons present in ambient air.

Constant hydrocarbon measurement is crucial in ASU production, as hydrocarbons that build up in the cryogenic portion of the process pose an explosion risk when mixed with enriched air or pure oxygen.

Depending on the results of an ambient air test to determine the types and level of hydrocarbons present, plant operators must decide whether to measure for Total Hydrocarbons Measurement (THC), methane and non-methane hydrocarbons (CH4 & NMHC), or measure for individual hydrocarbons including methane, acetylene, propane, propylene, ethane and ethylene.

By housing two separate Plasma Emission Detectors, each with separate valve and column channels to individually and simultaneously measure CH4 and NMHC, the SERVOPRO Chroma is the complete solution for the coincident measurement of methane and non-methane hydrocarbons.

As the Chroma’s Plasma technology requires only an argon or helium carrier gas to function, and does not require the constant flowing fuel gas required by FID detection techniques, installation costs – including the installation of shut-off valves & LEL Gas Detectors – and overall cost-of-ownership for the Chroma is considerably reduced in comparison to using FID technologies for this application.

The Chroma is designed for easy operation, with integrated software that improves on the Chroma’s predecessor, the KA k4000, to offer full access to all functions, measurements and system status via a intuitive user interface.

Separate measurements
THC Measurement, where the variety of hydrocarbons in ambient air is limited, can be monitored using Flame Ionization Detector (FID) technology such as that provided by Servomex’s SERVOPRO FID.

However when the ambient air at a plant contains a variety of hydrocarbons that have different Lower Explosive Limits (LEL), many operators choose to separate the total measurement into two measurements for methane and non-methane hydrocarbons.

These measurements usually require setting separate trip points at which a plant can be shut down to avoid an explosion, with CH4 usually measured over a 0-100 ppm range and the lower-LEL NMHC measured over a 0-5 ppm range.

However, if a plant trip point set for a FID analyser is based solely on a CH4 measurement range, the potential exists for non-methane hydrocarbons to accumulate above their LEL and the possibility of dangerous operating conditions. Conversely, if a trip point is based on a lower NMHC ppm level, then the FID analyser may initiate an unnecessary and costly plant shutdown too early and too often as the safe CH4 level activates the lower NMHC trip point.

By housing two separate Plasma Emission Detectors, the SERVOPRO Chroma is the complete solution for the coincident measurement of methane and non-methane hydrocarbons.