The very important phase to construct a pressure vessel is “DESIGN PHASE” Design phase is carried out with the care with the help of “CODES ” . The values of which ensure the safety performance of vessel . α INTRODUCTION:“ PRESSURE VESSELS ARE VESSELS WORKING UNDER INTERNAL OR EXTERNAL / VACUUM PRESSURE WITH VARIOUS TEMPERATURES CONDITION.” Pressure vessel is the basic equipment for any processing system. The liquid and gaseous hydrocarbons are processed in this vessels. These processes are: • Regeneration • Separation • Splitters • Buffers • Chemical Reaction These processes take place only in predetermined pressure and temperature conditions. In this modern era, there is need for petrol, diesel And various petrochemical products. It difficult to think life without any petrochemical products. passing through This product reaches refineries and petrochemicals plants after various processes. It means process industries become primary requirements. η PROCESS OF MANUFACTURING PRESSURE VESSELS:As we know understand the criticality of pressure vessel This becomes mandatory to take the care in each example every stage of. Manufacturing of pressure vessel Any disobey of code rule may be lead to either chemical leakage or explosion of vessel. We must remember the code of union carbide at “BHOPAL”, where the poisonous gas leakage took place and 1000’s of people took their lives. The processes of manufacturing of pressure vessel can be classifies as: Design Phase Material procurements phase Testing Phase Transportation / Handling phase Erection and commissioning Phase. χ TYPES OF PRESSURE VESSELS:There are various types of Pressure Vessels defined base upon its construction and manufacturing. Single-wall Vessel Multi-wall Vessel Claded Vessel Overlayed Vessel High thick Vessel. χ MATERIAL FOR PRESSURE VESSELS:• • • • Carbon Steel Carbon Manganese steel Carbon Manganese Silicon Steel Chromium Steel 1. 1Cr.-0.5Mo. Steel 2. 2Cr- 1 Mo. Steel 3. 2- ¼ Cr. - ½ Mo. Steel • Stainless steel • Titanium Generally Carbon Steel is used to construct vessels. But Sometimes where the corrosion is higher than the Normal corrosion at that time Stainless Steel may be Used or sometimes Titanium is also used due to process Requirement and highly corrosive condition. χ DESIGN OF PRESSURE VESSELS:Pressure Vessel is contain following main equipment. SHELL DISHED END [ D’END] NOZZLES MANWAYS LUGS SUPPORTS But in this Report we are looking only for Design of SHELL, DISHED END & NOZZLES. As Shown in the figure. “The portion between Top D’end and Bottom D’end is known as SHELL” Shell is made from rectangle plate. The material used to make a shell is SA516 GR 70. SA means in India we describe the material in IS. While in America they are described their standard which is called SA. SA516 means Carbon Steel and GR THICKNESS OF SHELL means Grade. Grade is depending upon the different material which we used for Pressure Vessel. The thickness of shell is depending upon the type of shell and stresses. Generally Shell can be classified in 2 categories. 1. Cylindrical Shell 2. Spherical Shell Stress can also classified in 2 categories. 1. Circumferential Stress 2. Longitudinal Stress Thickness for Cylindrical Shell : Circumferential Stress T= PR SE - 0.6P +C.A. OR P= SEt + C.A. R + 0.6t OR P= 2SEt + C.A. R - 0.4t P= 2SEt R + 0.2t Longitudinal Stress: T= PR +C.A. 2SE + 0.4P Thickness for Spherical Shell :T= PR 2SE - 0.2P +C.A. OR Here, P = Internal Design Pressure + C.A. t = Minimum Required thickness of Shell in inches. R = Inside radius of Shell S = Maximum Allowable Stress value in Psi E = Joint Efficiency Shown in the figure , the portion above and below the shell is known as “ DISHED-END OR HEAD ”. The portion above the shell is known as “ Top Dished-End ” and the portion below the shell is known as “ Bottom Dished-End ” . There are many Types of Dished-End like :- Hemispherical head Elliptical Head Torispherical Head Conical Head Toriconical Head [1] HEMISPHERICAL HEAD:- As the name implies ,. The profile of this type head is half sphere. This type of head has through out constant radius This is also widely used especially for high thick vessel like REACTORS. It’s benefit is it gives half thickness but when we have very small space at that time it is not use . FIGURE THICKNESS The thickness of the Hemispherical D’end is calculated by Following formula:T= PL + C.A. 2SE - 0.2P [2] ELLIPTICAL HEAD:This type of head consist of 2:1 ellipse profile as shown in the figure. This type of head is widely used in pressure vessel which is used in Tower. FIGURE:- THICKNESS The thickness of the Elliptical Head is calculated by following formula:T= PD + C.A. 2SE - 0.2P [3] TORISPHERICAL HEAD:- As shown in figure. This type of head consist of profile generated by two different circle having crown radius and knuckle radius. There various aspects for selection of type head like volume inside of head are used for low thick vessel. FIGURE THICKNESS: The thickness of Torispherical Head is calculated by following formula T= 0.885 PL SE - 0.1P + C.A. [4] CONICAL HEAD:- As shown in the figure, this type of head consist of inside radius of cone head at the point under consideration measured perpendicular to the longitudinal axis. This is not generally used as a dished end of Pressure Vessel because this is worked under lower pressure. FIGURE THICKNESS The thickness of Conical head is measured by following formula:T= PD + C.A. 2Cosά (SE - 0.6P) [5] TORICONICAL HEAD:- This type of head consist of profile generated by different radius like crown radius, knuckle radius etc. This type of head is used when there is different diameter of shell are used and we want to join these to shell. FIGURE THICKNESS The thickness of Toriconical head can calculate by following formula:T= Here, PDi 2Cosα(SE - 0.6P) Di = L X 2Cosα + C.A. Νοzzle are opening in vessel for various purpose like inlet , outlet , pressure indicator , level indicator ,etc. CONSTRUCTION :There are various constructions available in code , which is allowed for pressure vessel . As defined earlier , the nozzle are opening in vessel . Hence the compensate the strength of cutout , the nozzle are reinforced using various constructions . To elaborate little more , when we make cutout in shell reduces in that local region & to compensate this reduction strength nozzle are reinforced . The various construction are :1. Nozzle with Pipe & Flange 2. Nozzle with Pipe , flange & reinforcement pad 3. Long weld neck type nozzle 4. Self Reinforced Nozzles [1] FLANGE PIPE CONSTRUCTION :- This type construction consist of a flange with pipe intruding vessel wall. The flanges used in such construction are generally standard flanges from ASME B16.5. These flanges of forged grain structure. Another important part is pipe which is either seamless or fabricated from plate with long seam. Seamless Pipes are manufactured using extrusion methods. These type of nozzles are either SET-IN type (in which pipe enters till inside of vessel ID) or SET-ON type (in which pipe up to OD of vessel).Generally, this type of nozzles are used for low pressure services. [2]Flange Pipe Construction with Reinforcement pad : This type of construction is similar like Flange type construction with difference of additional reinforcement provided to compensate the reduction in strength due to cutout in vessel wall, using pad. As can be nicely understood from figure the pads are provided outside the vessel wall & welded with shell using fillet welds. These pads are provided with 1 or 2 No of holes which is used for removal of hot gases between pad & vessel wall during heat treatment. These holes are also used for air test of pad weld with shell. [3] Long Weld Neck Construction: This is another type of construction widely used in pressure vessel. The constructional details can be seen in figure. Long weld neck flanges are the flanges manufactured as per manufacturer standards like Taylor Forge. These flanges are readily available in market with various lengths. ASME Code allows use these flanges in ASME jobs. [4]Self Reinforced Nozzles: This is the most widely used construction of High thick vessel & reactors. In this type of construction, the nozzle opening is made of forged material machined to suit the shape required for reinforcement of nozzle cutout. This construction allows very pressures & temperatures.
