Internal corrosion system

Internal corrosion system, including corrosion problems that are likely to occur with regard to the fluid (water, gas, oil, its temperature and pH, its velocity, its TDS,. ..), the lining,. .. 

As far as corrosion-related bacteria are concerned, in this chapter we will focus on both external and internal corrosion systems of a buried metallic pipeline. 

A recently developed drying appHcation for zeoHtes is the prevention of corrosion in mufflers (52,55). Internal corrosion in mufflers is caused primarily by the condensation of water and acid as the system cools. A unique UOP zeoHte adsorption system takes advantage of the natural thermal cycling of an automotive exhaust system to desorb the water and acid precursors. 

An interesting and novel use of a soHd desiccant, the reduction of cold condensate corrosion in automotive exhaust systems, illustrates a hybrid closed—open system. Internal corrosion occurs in mufflers when the water vapor in the exhaust condenses after the engine is turned off and the muffler cools. Carbon dioxide dissolves in the condensate to form an acidic soup. In an essentially closed static drying step, an acid- and heat-resistant desiccant located in the muffler adsorbs water vapor from the exhaust gas as it cools to prevent formation of corrosive acidic condensate. When the engine is restarted, the system becomes open, and the desiccant is regenerated by the hot exhaust gas to be ready for the next cooldown step (19). 

Internal Corrosion of Water Distribution Systems, Cooperative Research Report, AWWA Research Foundation, Denver, Colorado, DVGW-Forschungsstelle, 1985. 

Terminology The International Standards Organization has recently defined a corrosion inhibitor as a chemical substance which decreases the corrosion rate when present in the corrosion system at a suitable concentration, without significantly changing the concentration of any other corrosive agent. This last point is significant since it excludes chemicals employed for deaeration or pH control from the definition of a corrosion inhibitor. On the other hand, it should be noted that the inhibitor is .. . present in the corrosion system. . . , and thus arsenic when added to brasses to prevent dezin-cihcation may be classified as an inhibitor. 

Pressure vessels and appurtenances should be constructed of stainless steel or other corrosion-resistant materials. Ideally, these steam generators should receive hot demineralized FW to minimize chemical treatment requirements. Alternatively, where a main boiler plant is installed, 100% steam condensate provides a good source of FW. In practice, it is very difficult to accurately control the correct amount of chemical feed. Chemicals are typically restricted to potable grade, deposit control agents such as polyacrylates, and other materials listed under the Code of Federal Regulations, CFR 21 173.310, or National Sanitary Foundation (NSF International) approval system. These boilers may be electrically heated or gas-fired. 

Amine salts of ether carboxylates inhibit internal corrosion of oil storage tanks and pipelines [230]. Furthermore it is possible to use ether carboxylates as corrosion and scale inhibitors for industrial recirculating cooling water systems, metalworking fluids, and hydraulic fluids [28,231-233]. 

As a means of maintaining the integrity of its pipeline system, each operating company shall establish and implement procedures for continuing surveillance of its facilities. Studies shall be initiated and action shall be taken where unusual operating and maintenance conditions occur, such as failures, leakage history, drop in flow efficiency due to internal corrosion, or substantial changes in cathodic protection requirements. 

Most fuel system storage tanks, transfer lines, and underground pipelines are composed of 1018/1020 carbon steel. These system components are all susceptible to internal corrosion whenever fuel containing water is introduced. Other factors which can enhance fuel storage and transportation system corrosion include ... 

S. Srinivasan, Role of Expert System in Technology Transfer of Materials for Petroleum Applications , Proceedings of the 12th International Corrosion Congress, 19-24, September 1993, NACE International, Houston, TX, 1993. 

The need for metrics is particularly important in process safety, in no small measure because the hazards may not be readily evident. Unlike some other safety risks where dangerous situations are more apparent—such as unsafe scaffolding, unsecured cables, trenches, and other excavations—information on the status and safety of hazardous containment systems (e.g., internal corrosion, an improperly sized relief valve) is not generally visible. Without a constant and reliable flow of information on process safety performance and management systems, leaders may, in essence, be flying blind. 

Franque, O, Meyer, E. and Sauter, W. (1995), Operation of a test rig to assess the suitability of alloys in different types of water. Proceedings of International Corrosion Workshop and Seminar, Internal corrosion in water distribution systems, Chalmers University of Technology, Goteborg. 

J. E. Gerguson, Ov. Franque, Internal Corrosion of Water Distribution Systems, American Water Works Associations, Denver, Colo., 1996, pp. 231-268. 

A large percentage of mains (57%) and services (46%) are metallic systems (steel/cast iron/copper), and corrosion is a major problem. For distribution pipe, external corrosion is the primary problem and internal corrosion has also been observed in some instances. The methods of corrosion monitoring on cathodically protected piping are similar to the methods used in the case of transmission pipelines... 

The forms of internal corrosion in water systems are uniform corrosion, galvanic corrosion, localized corrosion, concentration cell corrosion, MIC, and erosion- corrosion. 

Major internal corrosion can occur in pipes made of cast iron, ductile iron, steel, galvanized steel, and cement-based materials. Table 3.3 summarizes the types of corrosion occurring in different piping materials and the possible tap water quality problems caused by them, as described by the AWWA Research Foundation in 1996 in a reference book on internal corrosion of water distribution systems (17). 

A large percentage (57%) of mains and services (46%) is metal (steel, cast iron or copper), and corrosion is a major issue. For distribution pipe, external corrosion is of primary importance, although internal corrosion has been noted in some cases. The methods of monitoring corrosion on cathodically protected pipe are similar to those in the transmission pipeline sector, including pipe-to-soil potential and coating surveys. One difference is that in distribution systems, leak detection is an acceptable method of monitoring for these pipelines without CP (nearly 15% of the steel mains). 

The second system is based on the application of impressed current that is forced through anodes to the protected structure such as the tank by a current source of sufficient potential. Properly designed CP systems that are well maintained and operate at the correct current density are a proven method of protecting tanks from the corrosive effects of contact with corrosive soils. In addition to protection of underground tanks, CP is also useful for aboveground double-bottom tanks and for internal corrosion protection. 

The mechanism of material degradation in sewer pipes is similar to potable water systems. The internal corrosion may be more severe than in potable water because the wastewater is not clean. The winterizing treatments of roads are a source of chloride, which comes into contact with the pipe. Cement-based pipe experiences corrosion of reinforced steel. The corrosion control method consists of using thicker pipe walls, which provide for larger corrosion tolerance and a longer design life. 

A consequence of the use of advanced technology in oil production from a reservoir results in increase in the corrosivity of the oil production environment. The extent of corrosion increases because (i) oil, water, and gas are present in the field. Seawater or fresh water is injected downhole to drive oil out of formation. As time passes, the amount of water to the amount of oil increases and the degree of internal corrosion increases. Water injection from seawater or fresh water sources causes souring of oilfields with H2S and increases in corrosion rate. These water sources require biocide injection and deaeration to avoid the introduction of new corrosion pathways into the existing system. Tertiary recovery techniques involve miscible and immiscible gas floods that may contain as much as 100% CO2. This leads to high corrosivity of the fluids. 

It is usefiil to consider the case of an installation of a subsea gathering system for a natural gas production field. The pipeline design for a new gas production facility consisted of 20 cm diameter subsea gathering lines (flow lines) emptying into a 19 km, 50 cm diameter subsea transmission gas pipeline. The pipeline was to bring wet gas from an offshore producing area to a dehydration facility on shore. The internal corrosion was estimated to be 300-400 mpy. The corrosion mitigation options considered were (i) carbon steel treated with a corrosion inhibitor (ii) internally coated carbon steel with a supplemental corrosion inhibitor (iii) 22% Cr duplex stainless steel (iv) 625 corrosion-resistant alloy (CRA). The chance for success was estimated from known field histories of each technique, as well as the analysis of the corrosivity of the system and the level of sophistication required for successful implementation (Table 4.42). 

Visual examination and the metal ion content of the water samples shows internal corrosion of pipe in various locations in the hot water distribution system that compromises the quality of hot water. The internal pipe corrosion is because of the following factors or a combination of the factors. 

Table 5.11 summarizes the major accidents reported to the US Department of Transportation by the operators for the 6-year period between 1994 and 1999. The data show that for transmission pipeline systems, inclusive of hazardous liquid and natural gas, approximately 25% of all reported accidents were because of corrosion (see Table 5.10). Of the hazardous liquid pipeline accidents caused by corrosion, 65% were because of external corrosion and 34% were because of internal corrosion.

Houghton CJ, Nice PJ, Rugtveit AG. The computer based data gathering system for internal corrosion monitoring at Greater Ekofisk, 2nd International Conference on Corrosion Monitoring and Inspection in the Oil, Petroleum and Process Industries, London, Febr. 1984. 

VK. Chexal, J.S. Horowitz, D.P. Munson, K. Shye, C.S. Spalaris. Using predictive technology to control corrosion in raw cooling water systems. Paper IWC-97-84, Proceedings of the International Corrosion Conference, PA, 1997. 

However, in today s harsh oil/gas production environments where facilities and equipment are becoming old, with attendant increases in maintenance costs, the use of inhibitors as opposed to the use of other expensive corrosion mitigation methods becomes an obvious choice as cost-saving solutions to extend the life of assets and infrastructures. Researchers have now focused on the use of volatile inhibitors mixed with oil and water-soluble inhibitors for use in mitigating corrosion in multiphase systems such as in the control of internal corrosion of pipelines and corrosion of... 

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