PRESENTATION ON MATERIALS AT FFBL Prepared By: Farhan Naseer Management Associate Mechanical - Project Engineering

Scope Of Presentation Classification and general categorization. General differences w.r.t. carbon contents. Types of steel. Effects of alloying elements. Alloy steel general differences w.r.t. chromium content. Applications of materials.

Contd….. Heat treatment methods. Standards to describe materials. Materials used at FFBL. Material selection criteria. Aging and replacement of materials. Recommendations / Guild lines to avoid catastrophe.

Introduction All the things we see around us are made up of certain material. Material may be of single element as iron or it may consist of two or more elements such as bronze (copper + tin). Understanding the process of selecting a material can be simplified by grouping them into metals and non-metals.

Classification And General Categorization Material Metals Ferrous Cast iron, Carbon steel, Stainless steel etc Non Ferrous Zinc, Lead, Aluminum, Copper etc Non Metals Examples: Plastics, wood, Gases, Glass etc

Metals Metals are the main material for engineering application. Metals always posses the following qualities: Good luster High conductivity High melting point Sufficient hardness Ductility Malleability Crystalline Structure

Non Metals They generally have following properties: Low luster Bad conductivity Low melting point Low ductility

Properties Of Materials Elasticity and Plasticity

Contd… Hardness Toughness Brittleness Stiffness Ductility Malleability Conductivity Strength

General Differences W.r.t. Carbon Content Iron Ore Pig iron C: 3 – 4.5% Cast Iron C: 2 – 4.5% Wrought Iron C: 0 – 0.02% Steels C: up to 1.5%

Types Of Steel Carbon steels Low Carbon Steels Medium Carbon Steels High Carbon steels Killed Carbon Steels Alloy Steels Low Alloy Steel High Alloy Steel

Effects Of Alloying Elements Corrosion Resistance Hardenability Heat Resistance

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Alloy Steel General Differences w.r.t. Chromium Content

Contd... Compositions Austenitic Stainless Steel (16 – 26 % Cr, 3.5 – 22 % Ni - Austinetic Stabilizer) Ferritic Stainless Steel (15 – 30 % Cr) Other Alloy Steels

Applications Of Materials Cast Irons Grey Cast Iron Malleable Cast Iron Nodular Cast Iron Carbon Steels Alloy Steels PP/FRP

Heat Treatment A method to change the properties of metals by controlled heating and cooling of metals. The properties improved by heat treatment are Machinability Softening Hardening Ductility Grain structure Removal of stresses in material.

Where Heat treatment Is Required? Heat treatment are generally done on Plain carbon steels only. Alloy steels are difficult to heat treat. Similarly non-ferrous metals are generally not heat treated. Plain carbon steels below 0.2% are not heat treatable. They are used without heat treatment in applications where ductility & formability is required.

Methods Of Heat Treatment Normalising Annealing Hardening Tempering Case hardening

Material Heat Treatment In Relation To Its Weldability Problems after welding Formation of heat affected zone Formation of residual stresses Pre-heating and post-heating is done to reduce these effects. Stainless steels usually have better weldabilities than carbon steels thats why no heat treatment for SS.

Standards There are several standards to describe materials; ASTM (American Society of Testing and Materials) AISI (American Institute of Steel and Iron) ASME (American Society of Mechanical Engineers) ANSI (American National Standard Institute) API (American Petroleum Institute) SAE (Society of Automobile Engineers) BSS (British Steel Standards) DIN (German Steel Standards) JIS (Japanese Industrial Standards) AFNOR (French Industrial Standards) AISC (American Institute of Steel Construction)

ASTM Description Seven technical committees of ASTM approve the standards of the following materials related subjects. Technical committee “A” approves standards for ferrous metals (C.S. Alloy Steels. SS etc) Technical committee “B” approves standards for non-ferrous metals (cu, Al and Alloys) Technical committee “C” approves standards for cement, ceramics, concrete and masonry material. Technical committee “D” approves standards for miscellaneous subjects (material testing/analyzing methods etc) Technical committee “E” approves standards for miscellaneous materials (wood paints, plastic, PVC etc) Technical committee “F” approves standards for materials for specific applications (electronic instrument materials) Technical committee “G” approves standards for corrosion, deterioration and degradation of materials.

Contd... InA216 WCB, A216 specified the scope of carbon steel casting which are suitable for high temperature and fusion welding. WCB indicates its grade and chemical composition. General Nomenclature: A 27/A 27M – 95 (2000)

Generic Names Of Materials Compared With ASTM Designations A material has a name stated in terms of its chemical compositions. For example: 1 ¼ Cr ½ Mo is equivalent to A-127 Gr.WC6

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Materials At FFBL There are some common materials and their product forms at FFBL

Material Stored In FFBL Warehouse Piping Materials C.S. A-53, A-106 S.S. A312 TP -304, TP 316, TP-347, TP-321, A-358 etc Killed carbon and alloy steel pipes for low temperature A-333 Gr. 1,2,3,4 etc. A-335 Ferritic alloy steel pipes for high temperature, e-g, A-335 P1, P2, P11, P22 etc

Contd... Castings A-216 WCB Carbon steel casting for high temperature. A-217 WC1,4,5,6 Alloy steel casting for high temperature. A-296 CF8, CF8C Corrosion resistant Fe-Cr, Fe-Cr-Ni corrosion resistant application (martensitic castings) A-351 FC8, CF8C Austenitic steel castings for high temperature. A-352 LCB Ferritic steel casting for low temperature service.

Contd... Forgings Carbon steel forgings Stainless and alloy steel forgings For example A-105 is for carbon steel forgings (flanges, fittings and valves etc) for ambient and higher temperature service. A-350 is for carbon and low alloy steel forgings (flanges, fittings and valves etc) for low temperature service. A-182 is for alloy steel and stainless steel forgings, e-g, A-182 F1, F2, F6, F11, F22 for alloy steels and A-182 F-304, 316 for stainless steels.

Important Piping Material Used In FFBL General Utilities Utlities in Urea unit Utlities in DAP unit Utlities in Ammonia unit

General Utilities

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Utilities In Urea Unit

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Utilities At DAP Unit

Utilities At Ammonia And General

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Special Materials In FFBL Austenitic Stainless Steel Benfield solution pump impeller and its wear rings. E-2002 Ammonia unit heat exchanger shell and tubes are made up of Austenitic stainless steel (SS-304) Urea solution, carbamate, internal of urea stripper. Composition: Cr: 25%, Ni: 22%, Mo: 2%

Contd... Duplex Stainless Steel Fittings of acid bowsers. Ball valve type V150 Control valve seats. Composition: Cr: 22%, Ni: 5%, Cu: 3%, Mo: 2%, Mn 1%, Si: 1%, P: 0.04%, S: 0.04%

Material Selection Criteria Main factors affecting material selection

Material Selection As Per Service Problems to be considered when selecting a material for a particular service. Process fluid corrosion Localized corrosion External corrosion Operating temperature and pressure of the service

Addressing Corrosion In Material Selection Corrosion rates are expressed in terms of inches per year of surface wastage. This is used to provide a corrosion allowance in the design thickness of equipment such as vessels and pipe work when carbon steel is chosen. Stainless steel is chosen if corrosion allowance of carbon steel proves to be too much for a particular fluid. Plastics and polymer materials are also being used to address this kind of problem, e-g; PP/FRP, HDPE etc.

Comparison Advantages Disadvantages Carbon Steel Stainless Steel Plastics/Poly-mers Advantages Cost effective Easily available Morecommonly used. Usually a first choice. No corrosion allowance. Usually no rubber lining or any liner required. Little to worry about heat treatment. Takes less space for being thinner. Lighter. Less to worry about corrosive damage. Usually a common choice for acidic fluids. Disadvantages Corrosion allowance to cater corrosivity. In case of corrosive fluid, protective liner has to be installed. Extreme measure of cathodic protection. Heat treatment. Costlier than CS. Little helpful in case of crevice corrosion. In case of damage, hard to repair. More thickness than CS and SS hence more space. Very regular inspection required as sometimes stresses built-up at joints may cause ruptures. No matter how small the issue of corrosion with it but swelling does happen sometimes due to operating conditions.

Performance Test For Material Selection There are a variety of test methods available. Strip or coupon of material of interest is introduced to the concerned fluid as test specimen. Weight loss of test specimen with time gives its corrosion rate. The test can be carried out at plant or in laboratory.

Effects Of Operating Conditions On Material Selection The selection of the material of construction should take into account the worst case process conditions that may occur under foreseeable upset conditions Should be applied to all components including valves, pipe fittings, instruments and gauges. Both composition (e.g. chlorides, moisture) and temperature deviations can have a significant direct effect on the rate of corrosion. The use of plastic linings is widespread in equipment such as tanks, pipes, and drums. However, their use is limited to moderate temperatures and they are generally unsuitable for use in abrasive duties. Stainless steel (e-g; austenitic) can be considered as an option in above case.

Contd... Many metals suffer from stress corrosion cracking under certain conditions. In piping the most frequent failures from stress corrosion cracking occur with austenitic stainless steels in contact with solutions containing chloride. Even trace quantities of chlorides can cause problems at temperatures above 60°C. Duplex could be an option in above case. Operating pressure is usually the matter which decides thickness of the material chosen considering corrosion and operating tempratures.

Common Industrial Practices Chlorine The flow rate of liquid chlorine through carbon steel pipe work is restricted to 2 m/s to avoid removing the ferric chloride coating on the pipe surface which protects against erosion / corrosion of the carbon steel. Wet chlorine gas corrodes mild steel. PVDF (preferably), ebonite, or rubber lined steel is used for this duty. Chlorine gas handled at temperatures in excess of 200°C in carbon steel can result in chlorine / steel fires. Zinc can be used for this duty. For low temperature (e.g. liquid) chlorine special steels are required to avoid embrittlement. Titanium is unsuitable for Chlorine duty and should be avoided.

Contd... Sulphuric Acid Corrosion protection of mild steel vessels occurs by the formation of an iron sulphate coating. Any condition leading to excessive turbulence can result in the removal of the coating and corrosion. Accelerated corrosion can also occur at air/acid interfaces due to interfacial dilution. Chemical lead is sometimes used where steel is unsuitable and PVC or fluorocarbon plastics can be used in certain applications. In FFBL, along with C.S. , HDPE piping is also used for sulphuric acid.

Contd... Phosphoric Acid SS-317 can be considered a suitable material for phosphoric acid service. As far as non-metals are concerned, PP/FRP may be used as is under application at FFBL. If carbon steel is used, it has to be rubber lined.

Contd... Ammonia Materials of construction for ammonia are dependent on the operating temperature. Whilst carbon steel may be used at ambient temperature special steels are required at low temperatures to avoid embrittlement. Impurities in liquid ammonia such as air or carbon dioxide can cause stress corrosion cracking of carbon steel. Ammonia is highly corrosive towards copper and zinc.

Aging And Replacement Of Materials Aging of materials may be in the following forms; Aging At High Temperatures Oxidation Sulphidation Carborization Chlorination Creep Plastic deformation

Contd... General uniform corrosion Pitting Crevice corrosion Aging At Ambient Temperatures General uniform corrosion Pitting Crevice corrosion Galvanic corrosion Intergranular corrosion Stress corrosion cracking Corrosion fatigue Aging At Low Temperatures Brittle mechanical failures at temperatures lower than ductile-brittle transition temperatures.

Replacement Of Materials Following factors should be considered when replacing material on an incident of failure. Identify root cause of material aging at site of failure. In case of high temperature failures, select a material for replacement which is relatively more heat resistant and less prone to surface oxidation or creep at high temperatures. In case of ambient temperature failures, the replacing material should be of higher tensile strength and less prone to pitting. Usually in such cases higher stainless steels are chosen. Depending upon the concentration or corrosivity of the fluid, plastic / polymer material (e-g, PP/FRP, HDPE etc) may be employed for replacement especially in case of piping. In case of low temperature failures, replacing material should have lower ductile-brittle transition temperature than the service (operating) temperature it is subjected to.

Material Failure Case Of DT-5013 At DAP DT-5013 storage tank at DAP is made up of carbon steel with internal rubber lining for protection against corrosive fluid. Failure occurred on its shell at the spot where rubber lining was slightly diminished causing a leakage. The tank was subjected to the category of ambient temperature failure / material aging.

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Contd... Replacing the material with stainless steel with higher Cr, Ni content (e-g; SS-317) to resist corrosion.

Recommendations / Guildlines To Avoid Catastrophe Proper design of a system should include a thorough materials selection process in order to eliminate materials that could potentially be incompatible with the operating environment. Routine maintenance will lessen the possibility of a material failure due to extreme operating environments. Routine inspections can sometimes help identify if a material is at the beginning stages of failure. If choosing a material which is susceptible to corrosion in inevitable then corrosion allowance should be considered.

Suggestions Any Suggestions?

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