I am attaching the write up on our calorised pipes for your information as under: Indra Udyog Manufacturer of Lancing Pipes, Calorised Pipes, Bright Bars & Fabricators W-9/W-15, MIDC Industrial Estate, Taloja, Navi Mumbai %E2%80“ 410208, INDIA. Tel - 27410277/27402645 %E2%80“Fax - 27402645 Mobile: - 9820641077 E Mail: info@indraudyog.com, Web Site: www.indraudyog.com Calorising Calorising is a metallurgical process for treating the Process quality is monitored by testing coupons ( of surface of steels, stainless steels and alloys, with the same grade of metal) that are run in the retort with aluminium that provides protection against elevated- the production materials. The nature of the process, temperature, scaling and corrosion. the air-tight retorts and the controlled atmospheres ensure uniform alloy protection over the entire surface Adding aluminium to carbon and stainless steel is of the Calorising materials. After the process is commonly known to improve corrosion resistance. A completed, the coupons are removed from the retort, side effect of the process, however, is unfavorable sectioned and examined in a laboratory for quality and changes in the mechanical properties of the base steels. depth of diffusion. Special standards and processes may be selected by the client. Calorising solves this problem. Calorising diffuses aluminium into the steel surface to form an alloy with The end result of the Calorising process is a true alloy excellent heat and corrosion-resistance properties, with the base steels. The process is not a coating and retaining the base steel%E2%80™s inherent strength & rigidity, there is no mechanical interface with the substrate. but does not change the high-temperature mechanical The protective diffusion zone cannot be removed properties of the base steels. The protection provided except by a machining operation. by the Calorising diffusion zone remains effective at all temperatures up to the boiling point of the base metal. Calorising is used to enable engineered material to better resist high temperature sulfidation, oxidation, During the Calorising process, the steel is chemically carburization, scaling and hydrogen permeation. All cleaned, treated with flux at 700C and then again types of wrought and cast steels can be Calorised: treated with another flux at 7300C. After this, the plain carbon and low alloy grades, ferritic and steel dipped in molten aluminum alloy at 7700C. austenitic steels, high-temperature values of the process This results in an evenly aluminium coated steel. Then determine the specification of steel to be Calorised. it is positioned in retort. The retort is sealed and placed in an atmosphere-controlled furnace. The Advantages of an Calorised surface include: aluminium diffuses into the surface of the steel at * Elimination of problems inherent in coating elevated temperatures and forms an alloy with the processes due to the difference in thermal substrate. retort and excess powder is removed. expansion between coating and substrate; After furnace cooling, the steel is taken out of the * Ease with which fabricated shapes, internals retort. Straightening, trimming, beveling and and tube internal diameters can be treated; line other secondary operations are the performed of sight is not required. if required. Technical Benefits %E2%80%A2 High corrosion resistance. %E2%80%A2 Case depth up to .015%E2%80%9D for tubing. %E2%80%A2 Operates in continues temperatures up to 1750 degrees F. %E2%80%A2 Retains the base steel%E2%80™s inherent strength and rigidity, depending on base material. %E2%80%A2 Does not change the high-temperature mechanical properties of the base steel. %E2%80%A2 Utilizes Indra Udyog Technologies%E2%80™ patented diffusion alloying process. Common Applications %E2%80%A2 Sulfuric acid/ acid gas removal : Resists sulfidation from H2S, SO3; increases tube life up to 20 years. %E2%80%A2 Refining: Charge heaters, delayed cokers, sulfur recovery, heat exchangers. %E2%80%A2 Petrochemical: Reformers, ammonia, heat exchangers. %E2%80%A2 Reformers %E2%80“ DRI: Secondary reformers, waste heat boilers. %E2%80%A2 Boilers : PR boiler (pulp and paper), waterwall panels, traditional boilers. When Stainless Steel Fails Calorised steel performs well in high-temperature The nickel sulfide eutectic has a melting temperature environments where even stainless steel fails. of 6450C. However, at temperatures as low as 5500C, sulfur will begin to penetrate the nickel alloy, Stainless steel are often considered the final answer causing rapid embrittlement. to every kind of corrosion problem. But there are those situations in which stainless steel, because of Once the eutectic forms, the nickel is preferentially its metallurgical or chemical properties, is almost melted our of the alloy, leading in many cases to certain to fail (e.g. catastrophic sulfidation of high- catastrophic corrosion and failure. nickel stainless materials). Calorising stainless steel will passivate the surface of Austenitic grades of stainless steel are used because the material, tying the nickel into an iron-aluminum of their excellent resistance to high-temperature alloy and preventing the formation of the eutectic. oxidation. Generally, the higher the temperature to which the metal will be exposed, the higher the nickel In an experimental plan in which a technique content of the alloy must be. for direct reduction of iron ore was being studied, one For example, a type 201 stainless (16/18% nickel) of the components was a 1%E2%80%9D IPS schedule 160 pipe can withstand a continues operating temperature of made of a high nickel proprietary alloy. During a 15500 F while a type 310 stainless (19/22% nickel) 17-hour period in which this piece was exposed to can withstand continuous service temperatures as high-temperature sulfur bearing gases, the pipe wall high as 21000 F. was completely penetrated in a number of places. Alloys with greater nickel contents can withstand even The replacement piece was Calorised and the pipe higher working temperatures. There is a limit, remained sound and unaffected by many subsequent however, to the maximum amount of nickel that can exposures to the same reagents at the same be used in an alloy exposed to high-temperatures temperatures sulfidation. With nickel contents of 25% or more, the nickel will preferentially combine with sulfur to create a low- melting temperature nickel sulfide eutectic. Reducing Hydrogen Permeation Calorising the surface of a steel substrate is very Example # 3: A bayonet- type heat exchanger in effective in reducing hydrogen permeation, especially which a heating medium was losing sensible heat when both the inner and outer surfaces of the steel are through the annulus between the inner tube and outer processed. Evidence suggests that Calorised ferritic tube. It was postulated that hydrogen diffusion and austenitic steel reduce hydrogen permeation by through the wall of the inner tube the annulus was three orders of magnitude compared to untreated providing a means for conducting heat from the inner alloys of the same composition. tube. Thereby reducing the temperature of the Example # 1: Hydrogen permeation is also related to heating medium and causing the failure. other types of degradation, such as stress corrosion cracking and hydrogen blistering. In %E2%80%9CSulfide Stress The metallurgy of the inner tube was a low-chromium cracking Studies on Aluminized Steel,%E2%80%9D Dr.L.H. ferritic steel, API 5-A grade N-80. A section of this Gundiler (New Mexico Institute of Technology) states: tube was Calorised inside and out and tested for %E2%80%9Csince AI has a very low hydrogen permeability hydrogen permeation by the designer, a major coating with AI will act as a hydrogen barrier and is industrial firm in the United States. It was found that expected to decrease SSC susceptibility%E2%80%9D. Dr. the double Calorised surface reduced total hydrogen Gundiler%E2%80™s studies were carried out on dip aluminized permeation by almost three orders of magnitude. the substrates, which develop a thin intermetallic layer. entire heat exchanger (over two miles of pipe) was When the surface aluminium is lost, the intermetalic then Calorised. The process worked under this new layer remains effective. His report further states (p. configuration to its theoretical design efficiency. 63): %E2%80%9CBoth aluminum layer and the iron-aluminum intermetallic layers have hydrogen permeability rates several order of magnitude less than that of iron. Consequently, aluminizing produces an excellent barrier for hydrogen diffusion and prevent (hydrogen induced) sulfuric stress cracking (SSC) failure of high strength steels.%E2%80%9D Example # 2 : Calorising reduces the permeation of deuterium through an austenitic or martensitic steel substrate. One study (K.C. Forcey, D.K. Ross, J.C.B. simpson, and D.S. Evans, Journal of Nuclear materials, 160 (1988) 117) found that the permeation rate of tritium through aluminized material was nearly four order of magnitude lower than through untreated steel. The authors inferred from this data that permeation of trirum through aluminized martensitic and austenitic steel coupons would also be greatly reduce, particularly at the operating temperature range to 6000C (11000F). Sour Gas Plant Waste heat Boiler The Shell Caroline gas plant, one of the largest sour All carbon steel tubes were Calorised to eliminate natural gas processing facilities in the world, high-temperature sulphidation. Although the hot successfully used Calorised tubes to eliminate high- gases pass through the inside of the tube, both temperature sulphidation. surfaces were Calorised. Care was taken to eliminate any aluminum alloy in the area of the tube, both The Caroline plant, which began operation in 1992, is surfaces were Calorised . Care was taken to eliminate designed to process 8,533,000m3/ day of raw gas any aluminum alloy in the area of the tube that was and gas equivalent of liquid hydrocarbons. The welded into the tube sheets during assembly. overall sulfur recovery for the facility is 99.8% of the total sulfur recovery production is expected to be In accordance with standard practice, the tubes were approximately 4,000tonne/day. Gas is Calorised, then rerounded by passing them through a contaminated with H2S (approximately 35%). roller straightener to bring them to ASTM A450 tolerances. The tubes were trimmed to final length, During operation, the total raw gas and liquid ends dressed, and protective plugs inserted in the hydrocarbons from the field are processed in the inlet ends. The tubes were then trucked to Tulsa for feed facilities. The overhead sour gas from the feed assembly. fractionator, after being stripped of heavy hydrocarbons, is sent to the gas sweetening facilities NOTE: The heat of the Calorising process may cause where the acid gases are removed by physical and a slight change in tube length. For this reason tubes chemical absorption. The acid gas is sent to the or pipes with a finish length of longer than about 16%E2%80™ claus sulphur recovery unit. (4,900mm) are typically ordered 1% over length and then trim cut to final length after Calorising. In the Claus process, H2S in the acid gas stream is partially oxidized in the reaction furnace. This Calorised tubing is specified in a number of gas plants reaction is highly exothermic. The Caroline plant is to protect the tubes in the waste heat boilers and designed around a predicted exit gas temperature condensers. A wide variety of metallurgies and between 22000F and 23000F(12040C / 12600C). The configurations are Calorised for use in many types of exit gas temperature of other plants is between gas-processing plants. 14000F and 23000F(7600C and 12600C). with most in the range of 17000F/ 22000F (9270C/ 12040C). The Caroline plant contains two sulphur recovery units, each having two reaction furnaces and waste heat boilers operating in parallel. Each boiler contains 1010 tubes, 2 %C2%BC%E2%80%9D (57.1mm) diameter, approximately 12 meters in length, and has a generating capacity of approximately 100t/hr at 3650 kPa. Performance Data on Calorised Pipes A comparison between ordinary steel pipes, expensive imported Alloy Steel Pipes and Stainless Steel Pipes under different corrosive conditions is as following : Effect of SO2 Gas TIME HOURS EXPOSURE (a) Effect of H2S Gas SO2 GAS 103 gm Wt. Change (b) Comparison between Stainless Steel, and Calorised Stainless Steel under Co. CI & CO2 Depth of Carbon Penetration x 10-1 inch HOURS EXPOSURE (c) Comparison of Lancing Pipe of Mild Steel, Stainless Steel and Calorised Mild Steel. OXIDATION AIR : * METAL TEMPERATURE 0F %E2%80%A2 Temperature at which scaling is negligible (less than 10 mg / sq. cm.) FREQUENTLY ASKED QUESTIONS Is Calorising a coating? Can Calorising be performed on the outside Calorising is a diffusion is an alloying process, NOT a coating diameter and inside diameter? Calorising diffuses aluminum molecules directly into the substrate of the steel. Coatings such as hard chrome have Calorising can be performed on any or all surface of an interface with the host material, which means they can tubes or other parts. Areas that are not to be Calorised separate. can be %E2%80%9Cmasked off%E2%80™ to protect them from diffusion alloying. This is quite common for boiler tubes being What is Calorising? fabricated into tube sheets. During the Calorising process, the steel is chemically Can Calorising be applied to other products? cleaned, treated with flux at 700C and then again treated with another flux act 7300C. After this, the The Calorising process can be applied to a wide range steel dipped in molten aluminium alloy at 7700C. of materials used in many different industries where This result in a evenly aluminium coated steel. Then carburization, sulfidation, oxidation and corrosive it is positioned in retort. The retort is sealed and placed environments exist. in an atmosphere-controlled furnace. The aluminum diffuses into the surface of the steel at What happens to the mechanical properties of elevated temperatures and forms an alloy with the the substrate material? substrate. The mechanical properties vary from material to After furnace cooling, the steel is taken out of the material after they have been processed. Test data retort. Straightening, trimming, beveling and supporting the mechanical properties of some materials other secondary operations are the performed after processing is available. Some customers do if required. however request tensile and yields for large size projects. This is usually provided at the customer%E2%80™s What are the turn around times for Indra Udyog cost. products? What is the maximum operating temperature of Processing time depends on the volume of tubes ordered. the Calorised surface? Processing other parts generally takes 2-5 weeks, depending on the size and material of the part and The maximum continuous operating temperature is Indra Udyog production schedule. Rush jobs can 1750 degree F. or 955 degrees C. sometimes be completed more quickly. Cool down duration is subject to the mass of the retorting and required Can the Calorised surface be machined? mechanical properties. Yes, the Calorised surface can be machined; but the thickness of the case depth must be considered. What is the diffusion zone thickness of case Machining of the surface of a processed component will depth of Calorising? reduce the case depth of the diffused zone. The normal thickness for the alloy formed is about Can I weld to the Calorised surface? 0.076mm for austenitic grades of steel, cobalt-based alloys, and super alloys; .127mm for ferritic alloys: Yes, Calorised pipe welding procedures are available and about 0.178mm minimum for carbon steels. from Indra Udyog. The case depth can be substantially thicker when required on many materials, as high as 0.300mm. Can the Calorised surface be repaired if the diffused surface is damaged? What is the largest part that can be processed? No, but the part may be processed again to re-establish Parts up to 450mm diameter and length up to 8 mtr a Calorised surface. can be processed by Indra Udyog. The part to be processed must be able to fit into one of our furnaces. What is the largest tube that can be processed? Indra Udyog can process pipe/tubing up to 8 mtr in overall length and from very small to very large diameter. Our normal tube diameters are limited to 150mm but custom fixturing can allow for processing larger diameters. What materials can be Calorised? Plain carbon steels with no, or few alloys are the best material for Calorising. Indra Udyog can also treat low alloy steel, stainless steels, iron-, nickel, and cobalt -based superalloys, as well as copper-based alloys.