Micro-Organisms of Cooling Tower Problems and How to ... | CiteSeerX

Micro-Organisms of Cooling Tower Problems and How to Manage Them Amir Samimi Department of Chemical Engineering, Mahshahr Branch Islamic Azad University, Mahshahr, IRAN [email protected] Abstrak – Microorganisms are found everywhere in nature. In air, water and soil are scattered and they are crucial role in the health of humans and animals. many microorganisms are beneficial, while others are pathogenic. Life and activity of microbial processes are effective in many industries. For example, Zugloel bacteria in activated sludge and in the refinery are benefit. They make sludge polysaccharides that help other bacteria digest organic material otherwise organic material into the water receiving effluent and will cause pollution. Conversely, microorganisms that are present in the water cooling system that can be bad effects on the corrosion and deposition create operational efficiencies. Key Words – Microorganism; air; pathogenic; water; polysaccharides

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Introduction

Microorganisms are found everywhere in nature. In air, water and soil are scattered and they are crucial role in the health of humans and animals. Many microorganisms are beneficial, while others are pathogenic. Life and activity of microbial processes are effective in many industries. For example, Zugloel bacteria in activated sludge and in the refinery are benefit. They make sludge polysaccharides that help other bacteria digest organic material otherwise organic material into the water receiving effluent and will cause pollution. Conversely, microorganisms that are present in the water cooling system that can be bad effects on the corrosion and deposition create operational efficiencies. This paper discusses problems caused by micro-organisms in the corrosion of iron will take. Since water of cooling towers are the good conditions for the growth of organisms from their troubles and problems, and methods used to control them will express.

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Microorganisms of Cooling Water

Microorganisms are two ways to enter the cooling system, by water supply (inflow water) or the air that passes through the cooling tower. Algae, bacteria and fungi are three important microorganisms that are found in water cooling towers. 2.1

Algae

There are three basic parameters for algae growth: air, water and sun. Remove any of these are required to prevent algae growth, distribution platform and side walls have required of each cooling tower provides suitable environment for growth. Table 1 shows some general categories of algae found in the cooling tower, the necessary temperature and PH for them. Algae maker oxygen that can speed

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up the corrosion reaction to the nonpolar and corrosion. Green-blue algae can be extract nitrogen of air and conversion to other compounds. Nitrogen fixation by algae also cause to rapid decomposition of nitrite. Diatoms are known to cause the accumulation of silica, because the cell walls are impregnated with silica polymer. Table 1.

Growth of Algae and Various Species Algae Group

Green

Blue – Green

Diatoms With Dye Material (In the Cell Walls of Brown and Silicum)

2.2

Growth Conditions

Example

Temperature (OF)

PH

68 – 59

9/9 – 6/5

59 – 401

8/9 – 6/5

81 – 58

9/9 – 6/5

protozoan )Chlorella) string )Ulothix) string )Spirogyra) protozoan )Anacystis) string )Phomidium) string )Osillatoria) The long and thin string Flagilaria Convoluted (Cyclotella) Rectangular Shape and String (Diatorma)

Fungi

Fungi are often put in the category non photosynthetic plants. There are nearly 80,000 known types of fungi, algae numbers from 18000 to 25000. Yeast fungi are causing water and wood discoloration. Table 2 summarizes some important characteristics of fungi live shows. PH and temperature can be seen in the above table for further growth in the cooling system there. Fungi do not have chlorophyll, so they do not feed through photosynthesis and metabolism of organic materials is provided. The most important is the cooling tower, because ten percent of the fungi are able to use wood as a food source, so they can destroy wood of cooling tower. Table 2.

Growth of Fungi and Various Species Growth conditions

Types of Fungus Mould String

Like paste

Basisdiomy Cetes

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Example

Properties

Aspergillos

Black, Blue, Tan, Green, Yellow, White, Gray

Penecilium

Brown, tan

Fusarinm Alternaria

Brown, pink

Torula

Leather or RubberLike Growth

Saccharomces

Usually with Dye Material

Poria Lenzites

White or Brown

Problems

Temperature (OF)

PH

32-100

2-8 Best 5-6

Sediment Surface and Wood Rot Bacteria

32-100

2-8 Best 5-6

Sediment Bacteria such as Bad Color of Water and Wood

32-100

2-8 Best 5-6

Internal of Wood Decay

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Bacteria

The cooling device many species of bacteria are found. Generally in terms of morphology, temperature, an oxygen and food requirement to be classified as follows: 1.

Appearance a. Cocos (korea curved); b. Bacilli (rod-shaped); c. Aspy Rylvm (spiral-shaped); d. Coma (curved shape).

2.

Temperature a. Saicrofilic (low tempreture 0 – 20OC); b. Mezofilic (medium tempreture 20 – 45 OC); c. Termofilic (high tempreture 45 – 70OC).

3.

Oxygen a. Aerobic bacteria: they need air to live; b. Bacterial arbitrary: with air or without air can live, though growth in air is increased; c. Bacteria, no difference: can be in air or no air to live, but growth without air is increased; d. Anaerobic bacteria: environments must be able to live without air.

4.

Food a. Automatic food bacteria: the energy gain from oxidation minerals; b. Various food bacteria: the energy gain from mineral and organic; c. Parasite bacteria: parasites gain food from living organic material; d. Dead-eating bacteria: they live on dead and decaying material.

There are some of the most important bacteria that are found in the cooling system in Table 3. This table does not include everything, but it shows examples of their population and problems that are causing the cooling system. Table 3.

Growth of Bacteria and Various Species

Types of Bacteria

Example

Growth conditions Temperature (OF)

PH

Problems

Aerobic Sheath

Aerobacter Aerogenes Flavobacteriom Proteus Vulgais Psudomonas Aeroginosa Serratia Alcaligenes

68-104

4-8 best 7.4

Many bacteria can produce sediment

Aerobic Shielded

Bacillus Mycoides Bacillus Subtilis

68-104

5-8

Sediment bacteria (it is hard to dispel the shield)

Aerobic Sulfur

Tiobacillus Thio o Xdans

68-104

0.6-6

Sulfur is oxidized to sulfur ink

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Types of Bacteria

Example

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Growth conditions Temperature (OF)

PH

Anaerobic Reduction of Sulfate

Desulfuricoms

68-104

4-8

Iron

Crenotrix Leptotrix Gallionella

68-104

5.9-7.4

Problems Grow under aerobic sediment build hydrogen sulfide is causing the corrosion Ferric hydrate deposits like sheath around the cell covers, ogy of sediment process.

Usually bacteria grow at about 68-104OF but some species grow at about 40-158OF at some conditions. In general, the growth of microorganisms depends on the physical conditions (temperature, PH, sunlight, pressure, etc.) and food (water, CO2, nitrogen, phosphorus, etc.). Most microorganisms grow with increasing temperature is high. In different conditions micro and macroorganisms able to adapt them to the water temperature. Best temperature for most microorganisms is higher than 10 OC and for organism of soil and water is 35-25 OC. PH of water does not have any major impact on the growth of microorganisms, best PH for SRB bacteria is equal to 7. It should be explained that the effects of microbial herbicides with high PH improves. Continuous growth and accumulation of microorganisms in the water cooling system is causing a serious problem. Facility that can not be controlled microbial growth in the water, often with erosion and sedimentation problems we face. Another problem that microbial invasion of the cooling tower is causing wood rot. This not only decreased operational efficiency, but also increased the cost of the plant is operational. Many microorganisms are found in cooling water to use hydrogen in their metabolism that often the result of being nonpolar and cathodic corrosion reactions. The release of hydrogen from the metal surface corrosion reaction conditions is provided. By algae release oxygen as part of their metabolism causes nonpolar cathodic reaction and corrosion is accelerated. In general metabolic processes of living organisms on microscopic methods can be effective corrosion behavior. a. The adverse effects caused by chemicals (sulfuric acid, organic sulfides, and inorganic and organic acids and other corrosive compounds). b. Formation of localized corrosion and electrochemical cells with changes in oxygen levels, salt concentration, PH, sulfur and other parameters. c. The cathodic polarization occurs which results in the growth of anaerobic bacteria. d. Remove or less number of decreasing corrosion materials (such as the oxidation of nitrites and amines). Basically, bacteria due to the different mechanisms are classified into different groups which briefly most important ones and their problems as follows. Iron-Oxidizing Bacteria These bacteria are usually found in fresh water and salt water occasionally. These bacteria are aerobic and enabling to grow in environment that amount of oxygen is 5.0 ppm. They produce large amounts of sludge mass. Iron bacteria such krinvtriks, lipvtriks, Galivnla, use the iron soluble salts for their growing and deposite unsoluble iron compounds as secondary products of metabolism, the reaction is as follows: 4FeCO3 + O2 + 6H2O → 4Fe(OH)3 + 4CO2 + 81000 calori

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These reactions produce more energy and ultimately created a lot of ferric hydroxide which cause to bulk deposition, reduce heat transfer and corrosion such as smallpox. They often find in iron water pipes or wells, if these resources are water of cooling tower, they entered to cooling system and can cause a lot of problems. These bacteria are heterotrophic, meaning that they required energy provide from organic sources such as alcohols and organic acids. The most famous of these bacteria are Pseudomonas, Enterobacteriaceae, Micrococcus, and Basylas. Pseudomonas type hydrocarbons as an energy source are used. They can because problems include: the electrochemical cell, clogging of pipes and pumps, clogging of injection wells and oil and filter clogging. These bacteria are able to live in salt water, only one type of bacteria that can grow in aerobic systems, whereas some anaerobic systems can also provide growth and proliferation, which are being under of the bulk deposition that produce by Construction sediment bacteria, due to not reach oxygen break the aerobic bacteria. This is a good food source for anaerobic bacteria that reduce sulfate. If there are chloride and bacterial oxidant iron such as gallinsela in system together, they produce FeCl3 ferric chloride is a strong acid that occur frequently will accelerate metal corrosion. Aerobic baggily bacteria produce sediment. Such as Basil bacteria and other organisms that are correct shield compared with baggily Bacteria make less sediment. Sheathed bacteria growth that leads to the deposition of high sticky to the surface, especially occurs in the heat transfer and suspended matter in water, such as mud, sand, gravel, soil and corrosion products on the network interconnected with the sediment and make the sediment is more bulky. The experiments show that small part of the weight of sediment is microbial organic matter. It should be noted that almost 90 percent of the volume of sediment is the biological material. Acid Bacteria Causing Two major types of acid-producing bacteria are: aerobic sulfur bacteria capable to oxidize sulfur and sulfate into vitriol (sulfuric acid) and another type of bacteria which are able to produce organic acids. 1

Corrosion of Organic Acids The process of metabolism produces the anaerobic bacterial of organic acids such as lactic acid. Except of bacteria, some fungi affect of your metabolism produce organic acids such as acetic acid and formic acid. The acid in the presence or absence of oxygen leave negative effects on metal corrosion and material. High temperature and humidity conditions that are produced by fungi cause to corrosion electronics in stores. Table 4 shows the severity of soft iron corrosion is caused by organic acids under massive microorganisms 5mm thickness. Table 4. The Severity of Soft Iron Corrosion is Caused by Organic Acids under Massive Microorganisms 5mm Thickness Pitting Corrosion Rate (mm/yr)

Weight Reduction (mdd)

Acid

2.0

730

Formic

0.8

140

Acetic

0.7

130

Propionic

0.6

100

Butiric

1.2

225

Citric

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Pitting Corrosion Rate (mm/yr)

Weight Reduction (mdd)

Acid

1.0

190

Lactic

Sulfate-Reducing Bacteria The most common bacteria involved in the biological corrosion are sulfate reducing bacteria (SRB). Usually these bacteria are abundant in the environment in soil and water. In general, the sulfate reducing bacteria called which are able to regenerate inorganic sulfate to sulfide. These bacteria are anaerobic and in the environment that there is no oxygen able to grow and multiply. There are other species aerobic bacteria and anaerobic that able to regenerate sulfur compounds to sulfide and the importance of bacterial sulfate reduction. These bacteria are able to consume hydrogen and some other organic material and reducing sulfate ions to sodium sulfite gain energy needed for their growth. Sulfide ion induced adverse effects on steel corrosion. The presence of these bacteria is characterized by the deposition of iron sulfides. Sulfide compounds produced by the bacteria are deposited on surfaces compared to steel; the situation is more cathodic and accelerated corrosion to the steel. Some anaerobic bacteria have different types able to feed organic materials such as pirvat choline and lactate and grow on their even in situations that is no ambient sulfate ions in the environment. The main role of sulfate-reducing bacteria give electron from organic and inorganic substances present in the environment (oxidized to them) and deliveries to sulfate as the final receiver of electrons (reducing them). Several mechanisms have been suggested for the corrosion of sulfate-reducing bacteria witch the most important mechanism of formation of cathodic dipolarization and galvanic couple iron sulfide with Fe. In mechanism dicathodic polarization of iron corrosion is considered to be a thin layer of hydrogen on the surface that it is polarized. SRB bacteria removing hydrogen cathodic by hydrogenated enzymes from itself that are able to spent it for regenerate sulfate ions and thus cathode region are dipolarized that lead to increase metal corrosion. For example, the corrosion of steel, the following reactions have been reported: Anodic reaction Water Analysis Cathodic reaction Cathodic depolarization Corrosion product Corrosion product Final reaction

1) 2) 3) 4) 5) 6) 7)

4Fe → 4Fe+2 + 8e8H2O → 8H+ + 8OH8H+ + 8e- → 8H0 SO4-2 + 8H → S-2 + 4H2O Fe+2 + S -2 → FeS 3Fe+2 + 6 OH- → 3Fe (OH) 2 4Fe + SO4-2 + 4H2O → 3Fe (OH) 2 + FeS + 2OH-

The reaction is done until third equation if there are not sulfate-reducing bacteria. Sulfide ions produced strongly affect to anodic and cathodic reactions. Some investigators have proposed another mechanism is the formation of iron sulfide with iron galvanic couple. In the mechanism composed thin layer of iron sulfide by sulfate-reducing bacteria absorb hydrogen cathodic. In thin layer sulfide acts as the cathode and with steel form a galvanic couple and cathodic dipolarization function is performed by sulfate-reducing bacteria is done on the sulfide layer and thus increases the corrosion of steel. Table 5. Corrosion of Various Sulfides

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Corrosion of Iron Sulfide

Percent Sulfur

Types of Iron Sulfide

1.0

46

Pyrites

0.3

44

Smythite


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Corrosion of Iron Sulfide

Percent Sulfur

Types of Iron Sulfide

0.2

44

Greigite

0.12

37

Mackinawite

0.07

37

Pyrhotite

Other Bacteria Nitrogen eating bacteria attend to the various reverse reactions (both sides). They just have ammonia or oxidize nitrites (reduced corrosion providers). NH4+ + OH- + 1/2O2 → 5H+ + NO-2 + 4eNO-2 + 1/2O2 → NO-3 There are other types of string bacteria as they iron eating bacteria accumulate iron, analyze and accumulate oil and hydrocarbons. Change in this material lead to product harmful material such as HCL, H2S, and CO2: 2CH3CH2COONa + MgSO4 → 2CH3COONa + CO2 + MgCO3 + H2S + H2O New water (fresh water) are used to cool the system may be in the condenser water boxes there are other organisms such as worms, mites, snails can accumulate and cause clogging. The cooling tower that are used salt water, water boxes may found marine like shells, starfish and other deposits that can reduce the efficiency of system.in the time of stop machine, analyzed of organic organisms produce organic acids which is caused by Increase the corrosion of machine. It is necessary when stoped machine must be rinsed cooling water with fresh water until removing solid waste and water organisms; surface condenser tubes are rinsed with fresh water to prevent corrosion by the salt sea.

3

Limit of Microorganisms for Different Systems

Microbial limit to various systems in terms of number and type is varriable. They should have different instructions for different numbers. For example, the number of bacteria entering the cooling tower must not increase of 400 cell/ ml and in closed cooling system must be less than 10000 cell/ ml and water of cooling tower must not be increase 100000 cell/ ml. But some of the instructions allowed number of funguses up to 1000 cell/ ml, that more than it is dangerous, in the oil industry saves and transport of petroleum systems, the number of bacteria is dependent on other system conditions; the amount of sulfate, PH, oxygen concentration in the water phase and the organic carbon content of oil tanks, if the amount of sulfate and TOC is low leads to risk of sulfate-reducing bacteria is low. Suitable PH for the growth of SRB is 5.9-6.0 and concentration of dissolved oxygen is important for the growth of SRB. High concentrations of dissolved oxygen do not mean that the SRB under of sediments is not available. Also the lack of sulfide is important. Classification of corrosivity of water in the fuel by bacterial sulfate-reducing is reported as follows:

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Environment with a little corrosion Amount of sulfide Environment with a medium corrosion Amount of sulfide Environment with a high corrosion Amount of sulfide * Cell = bacterial cells

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103 cell/ ml 10 – 15 ppm >103- 105 cell/ ml > 155 ppm >105 cell/ ml >100 ppm

number of sulfate-reducing bacteria number of sulfate-reducing bacteria number of sulfate-reducing bacteria

In the environment is very corrosive chemical treatment alone is not useful.It is better that Stopped the circuit of systems and physical washing done. Also in polluted air transfer of bacteria from the air is very high. In this condition should try to seal fuel tanks so that there is no possibility of entering bacteria through the air. 3.1

Control of microbial corrosion

Because of presence of microbes in air, water and soil, creating conditions in which microbes exist in the system, it is very difficult. In this section, the methods by which these problems can be avoided in the industry are briefly described. Microbiological and chemical analysis of the water inlet and the water circulating is very important. The number and type of microbes that exist in the system (aerobic, anaerobic, iron-eater, producing sediment, etc.) are known exactly. How corrosive anaerobic bacteria sulfate samples for testing is difficult, although it can easily be cultured and measured. Standards on how the sampling and cultured and measured the microbes are as follows: a. API – SP – 38 b. NACE Standard TM - 01 - 73 (1976 Revision) 3.2

Importance of chemical test to measure parameters such as PH, O2, SO4, and S2

Sources that contaminate the system are identified and characterized, and the biological control program should be adjusted based on the number and type of bacteria. Cleaning and keeping surfaces clean and remove deposits in the biological control is very important. Entering any waste particles and contaminants to the system should be avoided. If the incoming water tower is a large floating particles in the incoming water before it gets physical treatment. Circulating cooling water system with high amount of particles floating in it, passes 1 to 3 percent of the water circulating sand filter is recommended to remove suspended particles. The use of germicidal chemical methods is different. It is very important that the correct amount of germicidal matter will come in the next sections, it should be noted that a good bactericide but fungicides are not good and vice versa. For very dirty infected systems, chemical methods of bactericidal materials are not removed until the sediment and sludge mass is low impact. Inspection procedures and regular visits to determine the corrosion and electrochemical tests should take place with microbiological analysis. Information on how the sample, due to corrosion and corrosion, where corrosion and corroded areas should provide exactly defined statistics are collected, the data bank is important in this case.

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4 a.

b. c. d.

e.

f. g.

h.

i. j.


Conclusion Accumulation in sediments and iron bacteria produce the sediments and induce cell concentration in the iron pipe. They create an environment for the growth of B type anaerobic bacteria in the environment; Anaerobic bacterial reduction of sulfate with create sulfide can cause corrosion in different environments are no air; Sulfur-oxidizing bacteria that is able to create sulfuric acid and sulfate in different environments; Consuming bacteria are hydrocarbons. They are able to analyse organic cover and cover of bitumen from tar species. They influence into the cover, creating an environment for bacteria type B (anaerobic). They also able to grow in fuel tanks with small amounts of water and they will cause corrosion; Bacteria and fungi able to attack and analysis polymers such as synthetic rubbers and organic coatings of poly orital in the fuel tank. They can also make organic cover such as vinyl polymer is analyzed; Often they are algae that able to cause sediment on wet surfaces in air or water inside the tubes can grow and produce organic acids, also provide a good environment for anaerobic bacteria; Fungi and bacteria are causing sediment and some of them are producing organic acids and some hydrocarbons as a source of food do they eat that leads to provide cell density and suitable conditions for anaerobic bacteria; Mud in the water can be a good environment for microbial growth they create environments without oxygen, anaerobic bacteria growth can cause corrosion of the pillars that are based on the sea or river; Inorganic sludge, sediments and corrosion products, and so they are suitable for electrochemical cells and these conditions can be a good environment for the growth of other bacteria; Waste particles (mostly organic) on the metal surface suitable to the growth of bacteria and microbes produce organic acids to create. For example, when food is infected aircraft, this will cause mold to grow and accumulate and finally lead to corrosion in aircraft.

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Samimi, A. (2012). Investigation Results of Properties of Stripe Coatings in Oil and Gas Pipelines. International Journal of Science and Investigations, France. Samimi, A. (2012). Studying Corrosion Electrochemical Mechanism in Tube Line and Gas Wells. International Journal of Science and Investigations, France. Samimi, A. (2012). Preventing Hydrate Formation in Gas Transporting Pipe Lines with Synthetic Inhibitors. International Journal of Science and Investigations, France. pp.48-50 Samimi, M., & Samimi, A. (2012). Non-Climatically Factors Causing Weather Changes. International Journal of Science and Investigations, France, pp.35-31 Samimi, A., Zarinabadi, S., & Setoudeh, M. (2012). Experimental Study of Factors Affecting Corrosion in Gas Wells Using Potantio Acetate and Galvan Acetate Tests. International Journal of Science and Investigations, France, pp.13-16 Samimi, A., Zarinabadi, S., Setoudeh, M., & Safavian, A. (2012). Review Applications to Prevent Corrosion Reducing Gas Pipe Line. International Journal of Basic and Applied Science, Indonesia, pp. 423-428 Samimi, A., Zarinabadi, S., & Setoudeh, M. (2012). Safety and Inspection for Preventing Fouling in Oil Exchangers. International Journal of Basic and Applied Science, Indonesia, pp. 429-434 Samimi, Amir, Zarinabadi, Soroush, "The Comparison of Increasing Method for Petroleum Pits Output (Fluids Dynamic). International Journal of Basic and Applied Science, Indonesia, pp. 435-439. Samimi, A., & Afkhami, M. (2012). Check Solution Corrosive a–MEDA on 316 & 304 Stainless Steel in Hydrogen Unit. International Journal of Basic and Applied Science, Indonesia, Samimi, A. Review Applications to Prevent Corrosion Reducing Gas Pipe Line. International Journal of Basic and Applied Science, Indonesia, pp. 423-428 Samimi, A. (2012). Causes of Increased Corrosion in Oil and Gas Pipelines in the Middle East. International Journal of Basic and Applied Science, Indonesia, pp.572-577 Samimi, A., Dokhani, S., Neshat, N., Almasinia, B., & Setoudeh, M. (2012). The Application and New Mechanism of Universal Produce the 3-Layer Polyethylene Coating. International Journal of Advanced Scientific and Technical Research (IJAST), India, pp. 465-473 Samimi, A. (2012). Normal Paraffin Production Process of Kerosene in Oil Refinery Company. International Journal of Innovation and Applied Studies, 1(2), Dec. 2012 Samimi, A. (2012). Offer a New Model to Prevent Formation of Hydrate in Gas Pipeline in Gas Refinery. International Journal of Innovation and Applied Studies, 1(2), Dec. 2012 Samimi, A. (2012). Study an Analysis and Suggest New Mechanism of 3 Layer Polyethylene Coating Corrosion Cooling Water Pipeline in Oil Refinery in Iran. International Journal of Innovation and Applied Studies, 1(2), Dec. 2012 Samimi, A. (2012). Use of Polyurethane Coating to Prevent Corrosion in Oil and Gas Pipelines Transfer. International Journal of Innovation and Applied Studies, 1(2), Dec. 2012 Samimi, M., & Samimi, A. (2012). Explotion of Resources Management in Iran. International Journal of Innovation and Applied Studies, 1(2), Dec. 2012 Samimi, A., & Zarinabadi, S. (2012). Investigation of Corrosion of the Pipeline Using TOEFLT in Iran Refinery. International Journal of Innovation and Applied Studies, 1(2), Dec. 2012 Setoudeh, M., Samimi, A., Zarinabadi, S., Almasinia, B., Nazem, Esmaeil, R., & Rohollah, H. A. (2012). Experimental Study of Factors Affecting Corrosion in Gas Wells Using Potantio Acetate and Galvan Acetate Tests. International Journal of Science and Investigations, pp.1316 Zarinabadi, S., & Samimi, A. (2012). Scrutiny Water Penetration in Three-layer Polyethylene Coverage. International Congress of Chemical and Process Engineering, CHISA 2012, and 16

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