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Sour Water Corrosion

Sour Water Corrosion

Corrosion of steel due to acidic sour water containing H2S at a pH between 4.5 and 7.0. Carbon dioxide (CO2) may also be present. Sour waters containing significant amounts of ammonia, chlorides or cyanides may significantly affect pH but are outside the scope of this section.

Primarily affects carbon steel. Stainless steels, copper alloys and nickel base alloys are usually resistant.

At a given pressure, the H2S concentration in the sour water decreases as temperature increases. Increasing concentrations of H2S tend to decrease solution pH down to about 4.5. Streams with a pH below 4.5 indicate the presence of a strong acid which would be the main corrosion concern. Above a pH of about 4.5, a protective, thin iron sulfide layer limits the corrosion rate. In some instances at a pH above 4.5, a thicker, porous sulfide film layer can form. This can promote pitting under sulfide deposits. Typically, this does not affect the general corrosion rate.

Critical factors include H2S content, pH, temperature, velocity and oxygen concentration. The H2S concentration in the sour water is dependent on the H2S partial pressure in the gas phase as well as temperature and pH. Other contaminants have a significant affect on water pH. For example, HCl and CO2 lower pH (more acidic). Ammonia significantly increases pH and is more often associated with alkaline sour water where the main concern is ammonia bisulfide corrosion. The presence of air or oxidants may increase the corrosion and usually produces pitting or underdeposit attacks.

Acid sour water corrosion is a concern in overhead systems of FCC and coker gas fractionation plants with high H2S levels and low NH3 levels.

Corrosion damage from acidic sour water is typically general thinning. However, localized corrosion or localized underdeposit attack can occur, especially if oxygen is present. Corrosion in CO2 containing environments may be accompanied by carbonate stress corrosion cracking. 300 Series SS are susceptible to pitting attack and may experience crevice corrosion and/or chloride stress corrosion cracking.

UT, RT, Corrosion Probes/Coupons – Evidence of locally thinned areas can be found using scanning ultrasonic thickness methods or profile radiography. For carbon steel, damage is usually in the form general thinning but may be highly localized to specific areas of high velocity or turbulence, typically where a water phase is condensing. Process and corrosion monitoring are important aspects of a well-developed program to minimize the effects of acidic sour water corrosion. The water draws of overhead accumulators should be monitored periodically to measure pH. Properly placed corrosion probes and corrosion coupons provide additional information on the rate and extent of potential damage.

300 Series SS can be used at temperatures below about 140°F (60°C) where Chloride Stress Corrosion Cracking (CSCC) is not likely. Copper alloys and nickel alloys are generally not susceptible to acid sour water corrosion. However, copper alloys are vulnerable to corrosion in environments with ammonia.

Other factors to consider in these environments include wet H2S damage and carbonate SCC.

“Impurities in Turbine : Deposition, Liquid Film Formation and Condensation”

This blog discusses about the formation of different kinds of deposition during turbine functioning and the relevant damage mechanisms that operate.  Even though the functioning of Turbine involves complex stages and use of exotic materials , but with the advances in the technology and research on turbine damage mechanisms the composition of the inlet steam can be determined. It is very important to evaluate the inlet composition of the steam and the composition of the droplets that form on the internal surface of the turbine. One of the main parameter that determines the energy losses is the condensate particle size . As a rule of thumb , the larger the droplet size the larger the frictional energy loss. The pure steam accompanying the moisture is also very detrimental to turbine functioning, as it decreases the efficiency thermo-dynamically  and can lead to corrosion /erosion of the blades. So its very important to study the phenomenon of moisture film formation and the associated nucleation process.

steam-turbine-bucket-foreign-object-damage-field

The nucleation seeds on the turbine surfaces can be provided multiple impurities. The oxide impurities and dry-wet transition of the steam can always provide initiation of the droplets. A very small size of the impurities on the scale of the angstrom can be very dangerous to the steam path surface. As they can eventually assist in the liquid film formation on the surface oxides.

Networking For Project Managers

AMCO is an autonomous and independent Consulting Company with the objectives of best Metallurgical Services to Saudi Arabian Oil and Gas, Petrochemical, Power Generations, Fertilizers, Refineries, Manufacturing, Construction, Manufacturing, Defense and Automobile Industries.

Our specialization is: Plant Life Assessment /Extension, Failure Investigation, Asset Integrity Management, Boiler Inspection, Boiler Tube Condition Assessment, Tube Failure Analysis, RCM Studies, RAM Studies, Single Point of Failure(SPOF) Studies, Plant Cycling, Cost Analysis, Plant Benchmarking, Crack Assessment, Risk Based Inspection/Maintenance, Probabilistic Assessment, Fitness-for-Service Assessment, Conditional Assessment, Plan Reliability Studies, Vibration Analysis, Condition Monitoring, Stress Analysis, Support and guidance in Plant Operation and Maintenance, Advice in weld repairs, Support with Materials, Inspection and Monitoring; Corrosion and oxidation issues, Technology Development, Finite Element Analysis, Stress Analysis, P91 Steel Assessment, Metallography, SEM/EDS Analysis, Contamination Analysis, Plant Mechanical Improvement Studies with years’ experience around the globe.

The AMCO Blogs are offered within the following areas:
i. Plant Life Management
ii. Fitness for Service
iii. Risk Based Inspection/ Maintenance
iv. Advance Materials
v. Reliability Engineering
vi. Qualification, Quality and Safety Methodology
vii. Materials Technology
viii. Pipelines and Risers
ix. Asset Operation
x. Quality Control/Assurance
xi. Corrosion and Erosion
xii. Inspection and NDT testing
xiii. Microstructures and damage mechanisms
xiv. Operations and Maintenance
xv. Vibration and Condition Monitoring
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Social Networking for Project Managers

Introduction

Technology is the most powerful tool today in every aspect of our lives. It has altered the way in which we conduct our business and manage today. Even in our daily socializing we rely on Skype, Smartphones and numerous social networking sites.
When we talk about Project Management, social networking has another useful form of productive outcomes as the project manager and the team members may not work under the same roof and within different country and region. Here in this blog, we are going to see different social media networking tools that might be beneficial and to increase the efficiency of the project.

Internal Project Blog

Use a SharePoint to upload your project development progress. This is a great way to get and provide feedback online with project managers and team members instead via phone which is quite expensive and time taking. By the use of blogs, project managers can instantly convey the updates regarding project for instance the manager can use the RSS feed update to keep up the checking state. Also with the use of blogs, a team member can check the past posts to get an instant project update anytime and can get views and help on the project related issue within seconds and without any time restrictions.

Using Skype for collaboration Skype is a tremendous tool and can help project managers to collaborate their capabilities and allows an efficient way to send instant message with video conferencing. It helps them to conduct a quick virtual meeting with all your team members without moving anywhere.Facebook, Twitter, LinkedIn – Maintain personal relationships Relationships are as important to maintain good projects as there is any other important factor in management. These social media sites are being used widely now in order to develop and flourish relationships that yields beneficial project results. The project manager can create communities with closed groups and can become a cooperative system of feedback, communications and collaboration which ultimately leads to fewer mistakes.

Remaining Life Assessment of Reformer Catalyst Tubes and Pigtails

Reformer furnaces are used widely in the petrochemical industry to produce hydrogen from hydrocarbons. The hydrogen production takes place in radiant tubes containing a catalyst, as a result of endothermic reactions between hydrocarbons (mostly methane) and water vapor. The design of reformer furnaces has improved greatly over the past 30 years. New alloys and manufacturing processes have been developed to meet the severe requirements imposed on the tubes in the radiation zone and in the hot reaction gas outlet. There has been improvement in catalysts to provide lower reaction temperatures. However, at the same time, there has been a trend towards increased temperature and pressure to achieve further increases in production and efficiency.  The number of columns varies between 15 and 200, depending on the number and size of the walls. Most modern furnaces are of the top-fired type with burners disposed in rows on both sides of the columns, while older furnaces may be of the side-fired type with burners distributed in two or more layers. The columns receive the charge through the inlet pigtails of Cr–Mo low alloy steel above the roof of the radiation chamber. The pigtails have a shape that provides flexibility to accommodate the axial displacement of the horizontal inlet manifold and of the vertical columns produced by thermal expansion.