api 571 part 6

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pitting corrosion

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General or uniform corrosion

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stress corrosion cracking

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Erosion corrosion

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4.3.4.6 Prevention / Mitigation

a) Cooling water corrosion (and fouling) can be prevented by proper design, operation and chemical treatment of cooling water systems.

b) Design for process side inlet temperatures below 140°F (60°C).c) Minimum and maximum water velocities must maintained, particularly in salt

water systems. d) The metallurgy of heat exchanger components may need to be upgraded

for improved resistance, especially in waters with high chloride content, low velocity, high process temperatures, and/or poorly maintained water chemistry.

e) Periodic mechanical cleaning of tube ID’s and OD’s should be performed in order to maintain clean heat transfer surfaces.

f) With very few exceptions, cooling water should be on the tube side to minimize stagnant areas.

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4.3.4.7 Inspection and Monitoring

a) Cooling water should be monitored for variables that affect corrosion and fouling including, pH, oxygen content, cycles of concentration, biocide residual, biological activity, cooling water outlet temperatures, hydrocarbon contamination and process leaks.

b) Periodic calculation of U-factors (heat exchanger performance measurement) will provide information on scaling and fouling.

c) Ultrasonic flow meters can be used to check the velocity of water in the tubes.

d) EC or IRIS inspection of tubes.e) Splitting representative tubes.

4.3.4.8 Related Mechanisms

Microbiologically induced corrosion (see 4.3.8), chloride stress corrosioncracking (see 4.5.1) and galvanic corrosion (see 4.3.1).

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Figure 4-81 – Cooling water corrosion on the I.D. of a CS heat exchanger tube operating at 86°F (30°C).

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Biofilm corrosion MIC生物膜腐蚀


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冷却水的腐蚀学习重点:

1. 温度: 操作温度2. 受影响材料:碳钢,低合金钢,奥氏体不锈钢,双相不锈钢,3. 损伤原理: 潮湿腐蚀(碳钢,低合金钢)/氯化物应力腐蚀开裂(奥氏体不锈钢/双

相不锈钢).4. 关键因素: 易感温度(碳钢 -10oF~350oF) / (奥氏体不锈钢 140oF~400oF), 损

坏保温层,保温层突漏点(T点,垂直高点,阀门突漏点)5. 预防/缓解:表面处理和适当的涂料应用,低氯绝缘应使用在300系列不锈钢,6. API 510/570 考试学习项.

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4.3.5 Boiler Water Condensate Corrosion 锅炉冷凝水腐蚀4.3.5.1 Description of Damage

General corrosion and pitting in the boiler system and condensate return piping.

4.3.5.2 Affected Materials

Primarily carbon steel, some low alloy steel, some 300 Series SS and copper based alloys.

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api 571 part 6

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