Detection of early PFA seals (perfluoroalk-oxyethylene) degradation exposed to process gases inside a reactor chamber.

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Problem Statement

Replacement of PFA seals inside the reactor chamber is performed according scheduled maintenance and life expectancy of the seals. Early degradation of seals goes completely undetected until there is a complete failure of the seal, letting atmospheric contaminants inside the reactor and forcing an unscheduled reactor downtime.

IRGAS Applicability

The IRGAS Turnkey Gas Analysis Solution is based upon FTIR Spectroscopy, Short and/or Long Path Gas Cells, and Quantitative Software, SPGAS. FTIR spectroscopy is capable of detecting and measuring all infrared active gas and vapor species; not included are the monatomic and homopolar diatomics. A Short or Long Path Gas Cell can be selected with the appropriate pathlength to match the detection limit required. The SPGAS Quantitative Gas Analysis Software provides ppb sensitivity and fast time response, along with internal gas calibrations.

IRGAS System Description

IRGAS-100, consisting of: ABB Bomem WorkIR FTIR with DTGS Detector; Hated 4Runner 6.5-meter Gas Cell with AR-coated ZnSe windows; CICP f/5 optical Couplers; SPGAS and SpectraStream Software.

Solution Achieved

The IRGAS System was capable of detecting moisture in the low PPB range. Since FTIR Spectroscopy scans the complete mid-infrared region, it also allowed the detection of multiple gas species, making it possible to detect the presence of an unexpected gas species. The following charts show a case where the system was set up for the detection of moisture (Figure 1). Figure 2 shows the collected spectrum at the 3800 cm-1 IR region; at first sight, the spectrum seems to contain water absorption only. Figure 3 shows a comparison of the collected spectrum against the water spectrum; there are some absorption peaks that are not accounted for. By subtracting the water absorption spectrum at calculated concentration from the collected spectrum (Figure 3), the unexpected absorption peaks become more evident (see Figure 4). In this case the unexpected gas species was HF at a concentration of 140ppb (see Figures 5 and 6). Since HF is not used at any time during the entire process, it was determined that the only possible source of fluorine to produce HF was from the degradation of PFA seals used inside the reactor chamber.