Calorised Lancing Pipes

Calorised lance pipes are prepared by rendering Calorising finish to carbon steel in a thickness of 100-150 microns on both inner and outer surface. This is a aluminum diffusion treatment which promotes the fireproof properties of steel pipes. This diffusion is an intermetallic bond, which doesn’t get damaged either by mechanical working like bending or straightening or by high temperatures. In the case of ceramic coated pipes, oxidation takes place at that part of the surface in contact with the liquid metal. In the case of Calorised pipes, the metal existing at the surface of the diffused zone is oxidized to its respective oxide, which prevents the further progress of oxidation and also melting. Hence diffused, aluminum is oxidized to alumina, which has very high melting pint such as 2050⁰C compared to the melting point of aluminum, which is 658⁰C.

This is the essential difference between ceramic coated pipes and joint Calorised pipes. A more effective result is obtained by ceramic coating on the metal diffused zone.

• The exothermic reaction and agitation promote decarbonisation and heat rise in the furnace, while foaming slag can be eliminated.
• Fusion of sub material can be accelerated
• Quality of steel will be improved.
• As the process raises the temperature of furnace, it leads to saving in electric power.
• Selection of raw materials to be charged becomes easy.
• The process raises the production capacity of an electric furnace.
• Hydrogen, Nitrogen and non-metallic inclusions can be eliminated through oxidation.
• It makes it possible to recover chrome with the use high chrome steel scrap.

Hence oxygen lancing is a must in steel making. Efficient lancing makes cleaner and cheaper steel. Therefore a Calorised pipe for oxygen lancing is the most efficient and simple alternative to achieve the above advantage.

Besides there are industrial advantages:

Lower Down Time
As infrequent replacement is required the down time is reduced directly by 6 times. This brings a minimum savings of 15 mins. Per heat and at 17/18 heats a day it translates into 255 mins., ie. 4.25 hrs/day . This is equal to 600 hrs/year.

This saving of 600 hrs/years gives the following,

• Savings in Electricity Cost equivalent to 1326 hrs/year.
• Savings in Labour Cost  1326 hrs/year.
• Higher yield equivalent to 1326 hrs/year.
• Lower Inventory Cost.
• Lesser space for storage of Calorised Lancing Pipes.  

Therefore it is prudent to use Calorised Pipes for Lancing especially in the charged scenario of the open economy where for any industry to survive in competition it is necessary to increase efficiency, quantity and decrease costs.

Comparison Chart Between Mild Steel Pipe & Calorised Pipe for oxygen lancing under same condition of oxygen pressure and flow rate,

Method of Usage

It is considered ideal to fix a Calorised lancing pipe to a lifting hook or stand or an automatic manipulator and insert it through the sight hole on the door at an angle of 25⁰C to 30⁰C to the surface of molten steel and hold the end of pipe at a depth of 150mm below the slag. Oxygen or carbon can then be injected, controlling the pressure, flow rate and the injection rate of pipes.

  Availability & Size

Pipes are available in threaded or plain end. Threaded ends are fixed with one coupling and one PVC cap. The Pipes are packed in HDPE bags.

Packing Details

  Calorising

Calorising is a metallurgical process for treating the surface of steels, stainless steels and alloy steels, with either aluminium, aluminium silicon, chromium or boron. The treatment provides protection against elevated temperature scaling and corrosion. Indra Udyog has developed its process based on aluminium silicon alloy.

Adding aluminium to carbon and stainless steels is commonly known to improve corrosion resistance. A side effect of the process, however is, unfavourable changes in the mechanical properties of the base steel.

Calorising solves this problem. Calorising diffuses the aluminium alloy into the steel surface to form an alloy with excellent heat and corrosion resistant properties, retaining the base steel’s inherent strength and rigidity, without changing the high temperature mechanical properties of the base steel. The protection provided by the calorised diffusion zone remains effective at all temperatures upto the boiling point of the base metal.

After cooling in the furnace, the treated steel is taken out of the retort. Straightening, trimming, beveling and other secondary operations are performed.

Process quality is monitored by test coupons. The coupons are of the same specification as the base steel. These are placed along with the process materials in the retort. The nature of the process, air controlled atmosphere and uniform programmed heating ensures uniform calorising over the whole surface of the process steel including the test coupons. After the process is completed the coupons are removed from the retort, sectioned and examined in the laboratory for quality and depth of diffusion. As the process is a batch process, it is fair to assume that the results of the coupons are a fair assessment of the quality of the whole batch. Different applications may require different depths of diffusion. The customer may set his own standards within the diffusion limits achievable. Higher the diffusion, does not necessarily mean that, higher will be the safety, but will surely be higher cost.

The end result of the calorising process is a true aluminde with the base steel. The process is not a coating and there is no mechanical interface with the substrate. This layer is not visible to the naked eye. It can only be observed under magnification. The protective diffusion zone cannot be removed except by a machining operation.

Calorising is used to enable engineered materials to better resist high temperature sulfidation, oxidation, carburization, scaling and hydrogen permeation. All types of wrought and cast steels, plain carbon and low alloy carbon steels, ferritic and austenitic stainless steels can be calorised. Temperature and process materials determine the specifications of the steel to be used for calorising.

The calorising process as described above is unique in its approach. Conventially pack cementation and out of pack gas calorising  has been followed by some manufacturers. These processes are fraught with extreme dangers and are unreliable for long and complex parts, such as small diameter tubes 6m and above. Indra Udyog’s process overcomes all these drawbacks and gives a much higher and reliable product. The process patent has been applied for.

Salient Features of Calorising.

Advantages over Coatings

• Elimination of problems inherent in coating processes due to difference in the thermal expansion coefficient between the coating and the substrate.
• Ease with which fabricated shapes, internals, long tube internals and complex contours can be treated. Line of sight is not required.

Technical & Commercial Benefits

• High Corrosion resistance
• Diffusion depth upto 300 microns.
• Continuous operation upto 900⁰C
• Inherent properties of the base steel are unaffected and retained.
• High Life, lower maintenance and higher efficiency.
• Lower down times
• Increases tube life upto about 20 years
• Cheaper in the longer run.

Common Applications

• Fertilizer: Sulphuric acid/ Phosphoric acid equipment, gas ducts for SO₂
• Refining : Recuperators, charge heaters, sour gas treaters, sulphur recovery plants and heat exchangers.
• Petrochemical : Reformers, distillation columns, ammonia heat exchangers, pipelines.
• Boilers: Pulp and Paper boilers, waste heat recovery boilers, fluidized bed boilers
• Steel : Lancing pipe, water wall panels
• Nuclear : Low Hydrogen Permeation heat exchangers.
• Sugar : Refining Section Piping, Air heaters  

Stainless Steel and Calorised Steel

• Calorised steel out performs stainless steels in high temperature and corrosive environments
• Stainless steels are often considered the final answer to every kind of corrosion problem.
• Austenitic Stainless Steels are used because they offer excellent resistance to high temperature oxidation. Generally higher the temperature of exposure, higher the nickel content of the steel. Stainless steel 201 (16/18% Nickel) can withstand a continuous temperature of 850⁰C, while Stainless steel 310 ( 19/22% Nickel) can withstand temperatures as high as 1150⁰C.
• Higher the nickel, higher are the chances of high temperature sulfidation. Nickel preferentially combines with sulphur to create a low melting temperature nickel sulphide eutectic. The melting temperature of this eutectic is 645⁰C
• At temperature as low as 550⁰C Sulphur will begin to penetrate towards the nickel in the steel, causing rapid embrittlement. Once the eutectic is formed, nickel is preferentially melted out of the alloy, leading to catastrophic corrosion and failure.
• Calorising stainless steel will passivate the surface of the steel, tying the nickel into an iron aluminium aluminide and preventing the formation of the eutectic. No eutectic means no corrosion.
• In a study of direct reduction of iron ore, the process pipe was made of high nickel proprietory alloy. In a 17 hour period of exposure to high temperature sulphur bearing gases, the pipe wall was completely penetrated in a number of places.
• The replacement calorised pipe remained sound and unaffected by many subsequent exposures to the same gases under the same operating conditions.

Hydrogen Permeation

• Calorised ferritic and austenitic steels reduce hydrogen permeation by three orders of magnitude as compared to untreated alloys of the same composition.
• Hydrogen permeation is also related to other types of degradation, such as sulphide stress corrosion cracking and hydrogen blistering.
• In a study by Dr. I.H. Gundiler of New Mexico Institute of Technology, he states “ Since aluminium has a very low hydrogen permeability, the aluminium will act as a hydrogen barrier and is expected to decrease Sulphur stress corrosion susceptibility. Both aluminium layer and the iron aluminium intermettalic layer have hydrogen permeability rates, which are several order of magnitude less than that of iron. Consequently, aluminising produces an excellent barrier for hydrogen diffusion and induced sulphur stress corrosion failure of high strength steels”
• In a study by K C Forcey, D K Ross, JCB Simpson and D S Evans, as reported by them in the Journal of Nuclear Materials, they state that “ The permeation rate of tritium through aluminised material was nearly four order of magnitude lower than untreated steel. Hence it is inferred that permeation of tritium through aluminised martensitic and austenitic steel could be greatly reduced, particularly at operating temperatures in the range of 600⁰C ”
• In another study, the heat exchanger was of the bayonet type. Hydrogen diffusion through the walls of the inner tube was providing a means of conducting heat from the heating medium within the inner tube to the annulus space between it and the outer tube. Calorising the inner tube on both its surfaces reduced the hydrogen permeation by almost three orders of magnitude.

Sour Gas

·         Natural Gas is considered sour if H₂S exceed 5.7milligrams/ m³

·         Sour gas is undesirable, harmful, lethal to breathe and extremely corrosive.

·         Typical composition of Natural Gas.

Methane  CH₄ ----------------------------------------- 70 – 90%

Ethane C₂H_6, Propane C₃H₈, Butane C₄H_{10 -------------}  0 – 20%

CO₂     --------------------------------------------- ----- -  0 – 8%

O_{2  ----------------------------------------------------------------------------------------} 0 – 0.2%

N₂ --------------------------------------------------------- 0 – 5%

H₂S-------------------------------------------------------- 0 – 5%

·         Sour gas from the feed fractionator, after being stripped of heavy hydrocarbons, is sent to the gas sweetening facilities where the acid gases are removed by physical and chemical absorption. The acid gas is sent to the Claus sulphur recovery unit.

·         H₂S is removed by the Gridler Process using Monoethnolamine (MEA)or Diethnolamine (DEA).

·         Further Elemental  Sulphur from H₂S solution is removed by the Claus Process.

·         In the Claus process, H₂S in the acid gas stream is partially oxidized in the reaction furnace. This reaction is highly exothermic. The sour gas plant is designed around a preset exit high gas temperature. The plant contains two Sulphur recovery units, each having two reaction furnaces and waste heat boilers operation in parallel.

·         All carbon steel tubes are Calorised to eliminate high-temperature sulphidation in the Claus recovery equipment.

·         One of the largest sour natural gas processing facilities in the world, successfully used Calorised tubes in their Claus Process equipment to eliminate high-temperature sulphidation .

·         The plant, which began operation in 1992, is designed to process 8,533,000m³/day of sour gas. The overall sulfur recovery for the facility is 99.8%. The total sulfur recovery production is approximately 4,000 tons/day.

·         Calorised tubing is specified in a number of gas plants to protect the tubes in the waste heat boilers and condensers. A wide variety of metallurgies and configurations are Calorised for use in many types of gas-processing plants.

Flue Gas

·         The composition of flue gas is approximately the following:    N₂ -  78 to 80%, CO₂ – 10to14%, O₂ – 2 to 6%, CO – 70 to160ppm,No_x – 50to 110ppm, SO₂ – 180 to 2000 ppm, C_xh_y – Methane CH₄,Butane C₄H₁₀ (Alkanes) below 60ppm, Soot – Balance

·         SO₂ and CO in the presence of Moisture are highly corrosive. Hence the flue gas is exhausted below the dew point loosing a lot of heat and reducing the efficiency of the recuperator.

·         Life of the recuperator tubes is severely impaired.

·         Calorised pipes in the recuperator completely eliminate the deficiency, increase the efficiency and reliability of the equipment.

·         Huge cost saving in the running cost. This is minimal as compared to the cost of calorised tubes.

·         Lower allowances in the wall thickness of the tube while designing the recuperator. This translates to lower weight and higher heat transfer rate leading to higher efficiency.

Coal Fired  Power Plant

·         The emission levels for a power plant using different fuels is:

Kg/Billion K Joule of Energy input

­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­CO₂                                 53070                                      74390                      94340

CO                                  18                                            15                            94                           

NOx                                42                                            203                          207

SO₂                                 0.45                                         508                          1175

Particulate                     3.10                                         38                            1245

Hg                                   0                                              0.003                    0.007

·         Because of high levels of SO₂ and CO in Oil and Coal fired power plants, it is imperative that only calorised pipes are used where ever the flue gases are being transported.

·         Calorised pipes will reduce the downtime and increase the efficiency of the plant.

·         Higher initial capital cost will be offset by higher saving in running cost.

Design Criteria and Availability of Materials.

·         Pipes and tubes of Low Carbon Steel, Medium Carbon Steel, Alloy Steels and Stainless Steels are available in the calorised form.

·         The base material of construction need not be changed. This will not change the initial design criteria.

·         Calorising neither changes the shape nor increases the dimensions of the pipes or tubes. Corrosion allowance can be decreased.

·         Tubes and pipes in the range 15mm OD to 300mm OD and lengths upto 6m can be processed. Longer lengths upto 10m can be supplied. Rolled sections such as angles, channels and beams upto 150mm width can also be processed

·         Base material as per BIS, ASME , DIN, GOST and JIS standards can be processed for calorising. Indra Udyog does tests for the depth of calorising, the base properties being unaffected. Surface hardness increases marginally. Tensile strength decreases because the calorising process is carried at temperatures close to the annealing temperature of some alloys. Chemical composition does not change in any manner except at the depth of calorising. Aluminides are diffused within the interstitial spaces.

·         Pipes can be processed for exact diameter, wall thickness and length according to customer requirements, in our own pipe drawing plant. The limit in OD for this plant is 63mm.

Manufacturing Facilities

Indra Udyog has the following plant:

·         Pipe/ rolled profile Surface Cleaning and processing section

·         Pipe/rolled profile Fluxing and hot dip aluminising section

·         Pipe/rolled profile Calorising section

·         Quality control laboratory

·         Laboratory equipment to decide on calorising procedures on different base materials before production

·         The process is proprietory and patent has been applied for.

Plain Ceramic Coated Oxygen Lancing Pipe  

Introduction

Oxygen is used in the manufacture of metals like Steel, Copper, Zinc. Chlorine is used in the manufacture of Aluminium. These gases react with the undesirable impurities and form their respective oxide or chlorides. These  oxides or  chlorides  then  float  to  the surface of the molten metal and are removed.

To transfer these gases to the molten metal , a pipe is needed. This  pipe  is  the Lancing Pipe and the process of injecting gases into molten metal is known as Lancing.

Traditionally an ordinary Pipe has been used. The material of construction is Low Carbon Steel ( Mild Steel ) , Electrically  Resistance Welded ( ERW ) in  the shape of  a pipe. Since the molten metal is Steel or Copper or Zinc, and the pipe is of Mild Steel, the pipe melts into the Molten Metal, at the end which is dipped into it . Besides because of the high temperature of the Molten Metal , the pipe  also gets oxidized and  melts  faster into the Molten Metal. Hence the pipe gets consumed and has to be replaced .

The rate of replacement decides the cost of production. Therefore in order to contain the cost  it is imperative to reduce the rate of replacement of these pipes.

Ceramic Coated Pipes do exactly this reduction in the rates of replacement . As against the usage of 2.5 pipes of plain MS variety , one has to use only 1 plain Ceramic Coated Pipe . The cost of the plain Ceramic Coated Pipe is not 2 ½  times the cost of the plain MS pipe . Hence there is a net savings in the cost of pipes used .  

Besides there are other industrial advantages:

Lower Down Time:

As infrequent replacement is required the down time is reduced directly by 2.5 times. This brings a minimum savings of 10 mins. Per heat and at 12/13 heats a day it translates into 120 mins., ie. 2 hrs/day. This is equal to 600 hrs/year.

This saving of 600 hrs/years gives the following,

• Savings in Electricity Cost equivalent to 600 hrs/year.
• Savings in Labour Cost  600 hrs/year.
• Higher yield equivalent to 600 hrs/year.
• Lower Inventory Cost.
• Lesser space for storage of Lancing Pipes.

Therefore it is prudent to use PCC Pipes for Lancing especially in the charged scenario of the open economy where for any industry to survive in competition it is necessary to increase efficiency, quantity and decrease costs.

Construction of Plain Ceramic Coated Pipes  

The Pipes are Low Carbon ERW Pipe as the base Pipe. Refractory coating is applied on both the inner and outer surfaces of the Pipe. The process is hydraulic extrusion so that the coating is dense and gives a good bonding with the pipes.

Both ends of the pipes are threaded . The threads are normal BSPT threads. One socket is provided at one end . The other end has a PVC Shrink Film cap to protect the threads during transit. At one end of the pipe , on the outer surface, a distance of about 200 to 210 mm maximum is left uncoated. This uncoated portion is required for gripping the pipe during coupling. The uncoated portion is painted with aluminium paint. Pipes are made in a standard length of 5.5/6 meters . Pipes can also have a sleeve as against a threaded end and socket.

The availability of sizes and their specifications are :

Packing

The pipes are strapped together and Packed in HDPE bag for protection during transit.

No. of Pipes/ Pack

M/s. Indra Udyog

W-9/W-15, MIDC Industrial Estate,

Taloja, Navi Mumbai – 410 208.

INDIA

Phone No. :  00 – 91 – 22 - 27410277

Fax No.     :  00  – 91 – 22 - 27402645