1、 Item No. 24002 NACE International Publication 1C184 (2008 Edition) This Technical Committee Report has been prepared by NACE International Task Group 137*on Hydrogen Permeation Measurement and Monitoring Hydrogen Permeation Measurement and Monitoring Technology June 2008, NACE International This NA
2、CE International (NACE) technical committee report represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any respect preclude anyone from manufacturing, marketing, purchasing, or using products, processes, or procedu
3、res not included in this report. Nothing contained in this NACE report is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against l
4、iability for infringement of Letters Patent. This report should in no way be interpreted as a restriction on the use of better procedures or materials not discussed herein. Neither is this report intended to apply in all cases relating to the subject. Unpredictable circumstances may negate the usefu
5、lness of this report in specific instances. NACE assumes no responsibility for the interpretation or use of this report by other parties. Users of this NACE report are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and for determining their applicabilit
6、y in relation to this report prior to its use. This NACE report may not necessarily address all potential health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this report. Users of this NACE report are a
7、lso responsible for establishing appropriate health, safety, and environmental protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of this report. CAUTIONARY NOTICE: Th
8、e user is cautioned to obtain the latest edition of this report. NACE reports are subject to periodic review, and may be revised or withdrawn at any time without prior notice. NACE reports are automatically withdrawn if more than 10 years old. Purchasers of NACE reports may receive current informati
9、on on all NACE International publications by contacting the NACE FirstService Department, 1440 South Creek Drive, Houston, Texas 77084-4906 (telephone +1 281-228-6200). Foreword This NACE technical committee report has been prepared to provide basic information on hydrogen permeation measurement and
10、 monitoring technology. It describes the background of hydrogen permeation measurement and monitoring technology, types of hydrogen monitors available, and some applications. This report is intended for use by professionals in the oil and gas industry (including production, transportation, and refin
11、ing) concerned with equipment service in which hydrogen enters metals and alloys, usually steels. Applications fall into two categories: hydrogen entry in aqueous corrosive environments containing hydrogen promoters, and hydrogen entry associated with more diverse sources of hydrogen at higher tempe
12、ratures (100 C 212 F). When steel corrodes in acidic media, atomic hydrogen is typically produced as a product of the cathodic corrosion reaction. A portion of the atomic hydrogen penetrates the steel and the balance combines to form molecular hydrogen (H2) and is released as bubbles of gas. The pre
13、sence of promoters such as fluoride, sulfide, arsenic, or selenic compounds sometimes causes a significant portion of the hydrogen atoms to diffuse into steel. Hydrogen uptake of metals is not limited to acidic systems below pH 7. It can also occur at higher pH values when hydrogen is produced _ * C
14、hair Dharma Abayarathna, Williams Gas Pipeline, Houston, TX. NACE International 2 cathodically from hydrogen-containing oxidants, such as when bisulfide (HS1) is reduced to sulfide (S2), or by improperly operated cathodic protection systems. At higher temperatures, increased permeability of hydrogen
15、 in metals frequently causes appreciable hydrogen entry consequent to any reaction that liberates hydrogen at the metal surface, including the dissolution of H2gas itself. An increase in temperature often also releases trapped hydrogen within a metal, which then migrates to the metal surface and is
16、released as a hydrogen flux. Field applications for measurement of hydrogen flux from aqueous corrosion primarily involve sulfur compounds, especially hydrogen sulfide (H2S), which often occur in produced crude oil and gas streams. H2S may also be present in process stream condensates downstream fro
17、m crude oil and gas production (e.g., in gas plants and sulfur-removal units). Additional H2S is released from the breakdown of sulfur compounds during certain refinery processes (e.g., in desulfurization processes such as hydrotreating and hydrocracking). Additionally, hydrogen flux is used to moni
18、tor hydrofluoric acid (HF) corrosion in HF alkylation units where the HF is a catalyst. High-temperature field applications for hydrogen flux measurement include naphthenic acid and sulfidic corrosion, which accompany distillation of acidic and high-sulfur oil feedstock. Hydrogen also enters into me
19、tals and alloys at high temperatures in hydrogen-containing atmospheres or during manufacturing or fabrication operations. Measurement of hydrogen during bake-out operations following such processes is also of interest. Applications also exist in other industries, such as the chemical industry and p
20、lating industry (e.g., hot-dip galvanizing, electrochemical, and electroless metal plating). Hydrogen monitors are used for various purposes depending on the design of the monitor. Each type of monitor is suited to one or more purpose. These include:(a) Quantifying the amount of atomic hydrogen form
21、ed by a corrosive environment, providing an indirect measurement of corrosion rate (all types of monitors); (b) Quantifying the amount of atomic hydrogen transmitted through a pipe or vessel wall because of a corrosion reaction at the entry face, providing a direct measurement of hydrogen flux avail
22、able for damage mechanisms such as hydrogen-induced cracking (HIC) (external, nonintrusive monitors); (c) Quantifying the amount of hydrogen out-gassed from a metal or alloy during thermal treatments to remove hydrogen prior to operations such as welding (hydrogen collection method); and (d) Evaluat
23、ing the effects of corrosion inhibitors (all types of monitors). This technical committee report was originally prepared in 1984 by NACE Task Group T-1C-9, a component of former Unit Committee T-1CCorrosion Monitoring in Petroleum Production. Unit Committees T-1C and T-1D were combined, and this rep
24、ort was reviewed and reaffirmed in 1995 by Unit Committee T-1DCorrosion Monitoring and Control of Corrosion Environments in Petroleum Production Operations. This report was revised in 2008 by Task Group (TG) 137Hydrogen Permeation Measurement and Monitoring. TG 137 is administered by Specific Techno
25、logy Group (STG) 62Corrosion Monitoring and Measurement: Science and Engineering Applications and is sponsored by STG 31Oil and Gas Production: Corrosion and Scale Inhibition and STG 34Petroleum Refining and Gas Processing. It is issued by NACE International under the auspices of STG 62. NACE techni
26、cal committee reports are intended to convey technical information or state-of-the-art knowledge regarding corrosion. In many cases, they discuss specific applications of corrosion mitigation technology, whether considered successful or not. Statements used to convey this information are factual and
27、 are provided to the reader as input and guidance for consideration when applying this technology in the future. However, these statements are not intended to be requirements or recommendations for general application of this technology, and must not be construed as such. 2 NACE International 3 Hydr
28、ogen Monitors Hydrogen monitors are sometimes divided into three basic types based on the hydrogen measurement transducer: (1) pressure or vacuum type, (2) electrochemical type, and (3) hydrogen collection type. Type (1) monitors register the increase in pressure or the loss of vacuum as a result of
29、 accumulation of H2gas in a sealed volume. Type (2) monitors measure the amount of hydrogen that permeates through a metal surface by measuring the electrical current typically used to oxidize atomic hydrogen in an electrochemical cell. Type (3) monitors collect hydrogen in an air stream, which is t
30、hen remotely detected. A variety of hydrogen probes using these monitors are currently available for both laboratory and field use. Descriptions of specific probes are provided in the following sections. Type (1)Pressure Hydrogen Probes Pressure hydrogen probes are available in both intrusive and no
31、nintrusive types (see Figures 1 and 2). Pressure hydrogen probes are generally accurate and easy to use. The accuracy depends on the precision of the pressure measurement. The main disadvantage to using pressure hydrogen probes is related to the increasing hydrogen pressure. Periodic bleeding is oft
32、en conducted when using pressure hydrogen probes. Figure 1 Schematic of an intrusive, type (1) pressure hydrogen probe. Coated area Internal volume Exposure area Cross-sectional view NACE International 3 NACE International 4 Figure 2 Schematic of a nonintrusive, type (1) pressure hydrogen probe. The
33、 intrusive-type probes assess the corrosiveness of the test environment and respond quickly to changes in the environment because the tube wall is usually much thinner than the pipe or vessel wall. The tube walls are available in common carbon steel types that are in general use. They are usually ma
34、de from steel similar to the pipe or vessel wall; however, they do not provide accurate information regarding the concentration of atomic hydrogen in the pipe or vessel wall itself, and therefore do not provide accurate information regarding susceptibility to hydrogen damage. Intrusive probes, also
35、known as finger probes, consist of a steel tube sealed on one end and a bleed valve on the other end, creating an inner cavity with a known volume (see Figure 1). A pressure gauge attached to the valve end shows the measurement of the increase in pressure within the inner cavity as a result of accum
36、ulation of H2gas. The outer surface of the steel tube is partially coated with polytetrafluoroethylene to provide a fixed surface area of exposure to a test environment. After probes are installed in the system, the fixed exposure area corrodes, generating atomic hydrogen. A portion of atomic hydrog
37、en generated diffuses through the tube wall into the fixed probe volume and forms H2gas through recombination on the hydrogen effusion side. The formation of H2gas inside the probe cavity generates an increase in the gauge pressure. The use of intrusive probes of any type is limited by the availabil
38、ity of suitable access fittings or flanges to install the probes. Further, intrusive probes are typically only installed at fixed points and in fixed orientations and cannot be moved. If a suitably sized, valved connection to provide in-service access for insertion of an intrusive probe is not avail
39、able, a system shutdown is usually necessary to install the probe in an existing nonvalved connection or to perform system modifications to install an access connection for insertion of the probe. In some instances, probe access connections have been installed by hot tapping the in-service system. A
40、 risk-based assessment of the hot tap, considering safety and reliability issues associated with the in-service welding, is typically performed. Nonintrusive pressure probes, also known as patch probes, consist of a stainless steel body machined to fit the exterior surface of the pipe or vessel. The
41、 probes are normally installed on the exterior surface of the pipe or vessel wall using clamps or adhesive to form a sealed cavity. The sealed cavity is connected to a pressure gauge and bleed valve directly or via capillary tubing (see Figure 2). In this case, some of the atomic hydrogen generated
42、by reactions at the internal surface of the pipe or vessel wall permeates through the pipe or vessel wall into the sealed cavity and forms H2gas that is registered as an increase in pressure by the pressure gauge. Nonintrusive probes have the ability to measure the hydrogen flux through the actual p
43、ipe or vessel wall material and are often more easily located at any orientation or location in a system. They assess the susceptibility of hydrogen-related damage if critical permeation conditions are known for this specific material; however, the sensitivity Pressure gauge Pipe or vessel wall Blee
44、d valve NACE International 4 NACE International 5 and time response to changes in the corrosive environment decrease significantly with increasing wall thickness. Type (1)Vacuum Hydrogen Probes The vacuum hydrogen probes use vacuum-ion pumps to collect and measure hydrogen and are similar to pressur
45、e hydrogen probes that use H2gas pressure as the monitored parameter. The measurement techniques used in vacuum hydrogen probes vary from straightforward vacuum loss measurement to sophisticated measuring instrumentation that typically provides sensitive and accurate measurements. The vacuum hydroge
46、n probes are available in both intrusive and nonintrusive types. The most common type of vacuum hydrogen probe available, depicted in Figure 3, is similar to a nonintrusive-type pressure hydrogen probe (see Figure 2). However, once a vacuum hydrogen probe is installed, a vacuum is established in the
47、 probe cavity using a hand-held vacuum pump. The atomic hydrogen that diffuses through the pipe or vessel wall creates a loss in vacuum as H2gas is formed within the cavity. The main advantage of this type of approach when compared to the pressure probes is increased sensitivity. It is difficult to
48、ensure the absence of air leaks into the system for long periods of time, inducing measurement uncertainties, because a reduction in vacuum is often related not only to hydrogen ingress. A vacuum hydrogen probe that measures low partial pressures of H2gas using a hydrogen ion gauge was developed by
49、Lawrence.1The hydrogen ion gauge consists of a palladium/silver (Pd/Ag) alloy window that is sealed in the chamber in which H2gas is accumulated. The chamber is then charged with an inert gas to ensure only diffused hydrogen is detected at the gauge. The internally heated Pd/Ag alloy window allows hydrogen into the gauge. The accumulated hydrogen is ionized using an internal heater when the hydrogen partial pressure reaches a certain level (1 Pa). Schematic of a nonintrusive, type (1) vacuum hydrogen probe. A vacuum hydrogen probe that maintains a
