Carbon steels with low-Si (< 0.10 %) content can corrode at an accelerated rate when exposed to sulfidation corrosion conditions. Detecting silicon content in carbon steel via X-ray fluorescence (XRF) and optical emission spectroscopy (OES) has been performed in recent years, though typically during downtime under ambient temperatures.
Recent advancements in handheld X-ray Fluorescence (XRF) to quantify levels of silicon (Si) in carbon steel as it pertains to API RP 939-C’s avoiding sulfidation corrosion failures in oil refineries will be discussed. The utility of handheld XRF is explained in practical terms that apply directly to industrial material testing and specifically the surface and environmental variables that affect in situ trace Si testing in high temperatures.
Recent developments are identified and their impact as related directly to this application. Dramatically improved hardware and software bring a new level of speed, improved accuracy and precision to the detection of silicon at concentrations below 0.10 wt % in carbon steel process piping systems and components up to 900F. Specifically, better detector/signal processing (1.5X higher count rate, resolution <145 eV) produces improved sensitivity and allows reduced test times in high temperature environments. Additionally the heat sink, standoff and fan design of current instruments mitigate the effects of heat on the instrument.
Glenn Lazarus- Why Your Observability Strategy Needs Security Observability
Trace Silicon Detection Advances in On-Line Steel Analysis
1. XRF Advancements Improve Detection of Trace Silicon
in Carbon Steel in On-Line, High-Temperature Process
Piping and Components
Olympus | Michael W. Hull, Alex Thurston, Dianne Hillhouse
ASNT | Long Beach, CA | 27 October 2016
2. Advances in low-Si testing
Importance of low-Si testing
Challenges of low-Si testing
4. Why positive material identification (PMI)?
“Final Investigation Report: Chevron Richmond Refinery Pipe Rupture and Fire” U.S. Chemical Safety and Hazard
Investigation Board. Report No. 2012-03-I-CA. January 2015
“Positive Material Verification: Prevent Errors During Alloy Steel Systems Maintenance” Safety Bulletin, U.S. Chemical
Safety and Hazard Investigation Board. Report No. 2005-04-B. October 2006
7. Factors affecting sulfidic corrosion
OLYMPUS Scientific Solutions
Temperature
Source: NCSS Statistical Software, https://www.ncss.com/software/ncss/ncss-plots-and-graphs/
SH
S
S
S
SH2
CO2H
S
R
CO2H H2
[ ]n [ ]n
[ ]n [ ]n
[ ]n
11. History and variation in steel specifications
OLYMPUS Scientific Solutions
C
(max)
Si
(min)
P
(max)
S
(min)
Ti
(max)
V
(max)
Cr
(max)
Mn
(max) Fe
Ni
(max)
Cu
(max)
Mo
(max)
A53B 0.30* --- 0.05 0.045 --- 0.08 0.4 1.20* bal. 0.4 0.4 0.15
API 5L 0.28* --- 0.08* 0.03 0.06 --- --- 1.85* bal. --- --- ---
A105 0.35* 0.1 0.035 0.04 --- 0.08 0.3 1.05* bal. 0.4 0.4 0.12
A106 0.35* 0.1 0.035 0.035 --- 0.08 0.4 1.06* bal. 0.4 0.4 0.15
A181 0.35* 0.1 0.05 0.05 --- --- --- 1.10 bal. --- --- ---
A234 0.35* 0.1 0.05 0.058 --- 0.08 0.04 1.06* bal. 0.04 0.04 0.15
12. OLYMPUS Scientific Solutions
API Recommended Practice 939-C
- Guidelines for Avoiding Sulfidic Corrosion Failures in Oil Refineries
§ Result of naturally occurring sulfur compounds found in crude oil.
§ Causes accelerated corrosion in steel fittings, piping, heater tubes, and
pressure vessels when the oil is heated for separation.
§ A significant cause of leaks and failures of piping systems within the refining
industry.
§ Process streams with hydrogen free, sulfurous material may exhibit corrosion in
carbon steel piping with less than 0.1% Si (McConomy Curves)
– Increasing Cr content of the alloy can provide increasing resistance to this
form of corrosion
§ Streams with a combination of hydrogen and sulfur-containing materials at
elevated temperature can corrode steels with Cr levels below 12% (i.e. non-
stainless alloys, Couper-Gorman curves)
– Recommended to use 18Cr-8Ni stainless steel to avoid corrosion
16. Environmental variables
Source: U.S. Energy Information Administration, U.S. Energy Mapping System, http://www.eia.gov/state/maps.cfm
Source: Climate.gov
https://www.climate.gov/maps-data/data-snapshots/averagetemp-monthly-cmb-2015-10-00?theme=Temperature
17. Low concentration
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0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100
FluorescenceYield
Atomic Number
Fluorescence yield of elements
K Series
L Series
M Series
Mass attenuation
coefficient (Fe)
Si 2457.94
Cr 110.97
Mn 87.85
32. Future Endeavors
§ Certified samples of lower concentration
§ High temperature calibration for light elements
§ Industrial partners for field testing