Reduce Downtime and Ensure Accurate Sulfur Results with Sulfinert®-Treated Sampling Path

Accurate analysis of part-per-million and part-per-billion levels of sulfur-containing compounds is critical to effectively managing process streams and meeting regulations for low-level sulfur.Many organo-sulfur compounds, like hydrogen sulfide (H2S), methyl mercaptan, and ethyl mercaptan, adsorb to metal surfaces during sampling, resulting in false negatives or artificially low values.Additionally, these compounds are slow to desorb from untreated metal surfaces, which can lead to unpredictable levels of carryover between samples. Both scenarios contribute to inaccuracies and compromise the ability of operators to optimally manage process streams. Using Sulfinert®-treated sampling and transfer equipment results in more accurate sulfur sampling and faster cycle times, ultimately improving productivity and preventing costly process upsets.

Sulfinert® Coating Ensures Sulfur Detection
Sulfinert® is a proprietary (U.S. Patent #6,444,326), silicon, chemical vapor-deposited coating, specifically designed to improve the inertness of steel, stainless steel, alloys, glass, and ceramics. It is used to passivate sampling vessels, transfer tubing, fittings, and custom parts to prevent sulfur adsorption along the sample path. As shown in Figure 1, Sulfinert® treatment significantly improves the recovery of sulfur compounds, such as hydrogen sulfide, compared to untreated cylinders. Here, a gas containing 17 parts-per-billion (ppbv) hydrogen sulfide was stored for 7 days in both untreated and Sulfinert®-treated stainless steel high pressure
sample cylinders. The relative response of hydrogen sulfide to dimethyl sulfoxide was measured over time to indicate level of inertness. Data show that adsorption occurred rapidly in the untreated cylinder, with
complete loss occurring within 24 hours. In contrast, the Sulfinert®-treated cylinders reliably stored low levels of active sulfur compounds for the entire 7-day test period.

A similar benefit is seen when Sulfinert®-treated tubing is used; the inert surface created by this treatment prevents adsorption and delivers a representative sample without delay (Figure 2). In this case, the sulfur transport properties of 100 foot (30.5 meter) lengths of Sulfinert®-treated, electropolished, and raw commercial grade stainless steel tubing were compared using 500 part-per-billion (ppbv) methyl mercaptan. The Sulfinert®-treated electropolished tubing did not adsorb the methyl mercaptan to any measurable extent, whereas the untreated electropolished tubing totally adsorbed methyl mercaptan for more than 75 minutes and the sulfur gas level did not stabilize until 130 minutes. Conventional 316L seamless tubing totally adsorbed methyl mercaptan for more than 90 minutes, and the sulfur gas level did not stabilize until 140 minutes. Compared to untreated material, the use of Sulfinert®-treated vessels and tubing clearly reduces sulfur adsorption, resulting in more accurate sampling and less downtime due to process upsets.