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CHAPTER- 1 QUALITY OF WELDMENTS
1.1 INTRODUCTION TO PROJECT
For manufacturing of pressure vessel, there are main two part welding.
(1) fabrication (2)
But to control of dimension of vessel during the set up and after welding processes, it is very difficult. In same process, set up of nozzle on vessel within limited. It is very difficult and quality point of view and for customer satisfaction it is very important. Set up nozzle with special fixture can avoid some dimension problem and also some fixture can control distortion problem during and after welding of nozzle. Each testing of welded joint should start with the selection of a suitable testing method and determination of extent of testing. Repair and maintenance of parts and components is a major activity in any process industry. .Repair welding can be carried out as a logical procedure that ensures that part is usable and safe.
1.2DESCRIPTION OF THE WORK PROJECTAssembly of pipe or forging to flange is called nozzle. There are different type of set up nozzle. Radial nozzle Offset nozzle Tangential nozzle Angular nozzle
(1) Radial nozzle: a nozzle, which is perpendicular to base of the shell or dished end lies on the orientation line is called radial nozzle. (2) Offset nozzle: a nozzle, which is similar to radial nozzle but offset form orientation line, is called as offset nozzle. (3) Tangential nozzle: a nozzle, which is on any tangential line of the shell, is called tangential nozzle. (4) Angular nozzle: a nozzle, which is at an angle from the reference line, is called as angular nozzle.
Nozzle identification:If not specifically defined for the project, the nozzle on a vessel shell be identified as follows. Process nozzles: N1, N2, N3 etc.. Instrument nozzles: k1, k2, k3 etc. (Where multiple nozzles for a single instrument shall be identified K\A\B\C etc.) Manways: M1, M2 etc. Relief valves: RV1, RV2 etc. Vents: D1, D2 etc. Seam out connection: SO Utility connections: U
Radial nozzles:Create and then position the nozzle to the correct-up coordination only p1 should point in the correct direction. i.e. E 45N.
Radial nozzle E 45N.
Create and then position in the nozzle at the correct-up coordinate and position it to an orthogonal distance the projection distance away from the equipment centreline. i.e. E 29. P1 should point in the orthogonal direction i.e.E
Offset nozzle:If the angle option is selected in the off-set method drop down box specify the angle at which the nozzle intersects the cylinder in the nozzles offset angle(ADY) field. This value follows the left hand rule, so a negative angle rotates the nozzle about the +X axis. 1. Offset of nozzle by distance 2. Offset of nozzle by angle When the offset is 0, the nozzle is perpendicular to the vessel.
Offset of nozzle by distance
offset of nozzle by angle
Angular nozzle:By using a combination of X rotation and offset, a nozzle can be created with any desired orientation. (position of nozzle at angles a and b input int PV designer X rotation = a-b, ADY=b)
The size of a manway is usually 24. Unless internal devices require larger size for installation. If the vessel diameter is 30 or less a flanged head may be considered instead of a manway. For mechanical reasons manway should be smaller than one half of the vessel inside diameter. As an alternative to manway, smaller vessels can be provide with an inspection hole, which is normally 8.
Mesh densityThe actual dimension of the transition region is adjusted to fit the mesh on the cylinder.
Fig. Transition mesh between nozzle and cylinder.
Key 1= nozzles on head 2=head on nozzle 3=nozzle on cylinder 4=optional raped on the cylinder 5=transition region on the cylinder NY = distance between nozzle and end of transition region in the axial direction NX > =ratio cylinder diameter NT = distance between nozzle and end of transition region in the sweep direction.
1.2.1 The marking of the nozzle set up is done in following steps: First of all the orientation marking of the nozzle on the shell is done. The elevation is marked and the radius of the nozzle is measured and marked on the shell. The marked line is punched. The cut out of the nozzle is done. Prepare the edges of the cut out section by grinding. Then the shell is leveled and the center of the cut out is found out. Then the elevation of the center is matched. The nozzle is inserted in the cut out and then the elevation is maintained. The level is also maintained. The orientation elevation and level of the nozzle are rechecked. The plate supports are tacked with the nozzle. The seam number of the nozzle is punched.
1.3 TECHANICAL DATA FOR REPORTNOZZLE SETUP STAGE INSPECTION REPORT:
Client: L&T Chiyoda LTD, Job no: M-2152, Drg no & Rev.no: M-2152 Rev-c, Item No: v-101A, Description: Stripper, Inspection by: TUV/AEL.
NOZZELS Nozzle no. Size/ rating Heat no.
ELEVATION Reqd. Actual
PROJECTION Reqd. from shell C.L/OD 500mm 0 0 524mm 0 0Actual
N1 N2 N3 N4 N5 M
50 70 70 60 50 80
345 0 180 30 0 0
342 1 184 29 1
554mm 0 0 522mm 0 0
Some dimensions are not allowable. So rectify with acceptance to given requirement . The repair set up to keep the cleat(fixture) or plate support or the moon plate.
After the repairs set up the nozzle identification. NDT OF Weld Edge: PT/ UT/ MPT Weld edge: Vee prepration Weld edge: root gap & offset
Sizing of nozzles:(1) (2) (3) (4) (5) (6) Feed inlet nozzle Vapour outlet nozzle Liquid outlet nozzle Manway Vents and drains Nozzle identification
Various inlet devices are available to improve the vapour/liquid separation. Among others the following inlet devices may be installed. A deflector baffle A slotted tee distributor A half open pipe A 90 elbow A tangential inlet with annular ring A schoepentoter
Dimension check of pressure vessel: Tolerance for formed heads Out of roundness of shell Nozzles and attachments orientation Nozzle and attachments projection Nozzle and attachment elevation Nozzles and attachments level less Weld mismatch weld reinforce ment.
APPLICATION TO THE NOZZLE: Nozzle is used for inlet or outlet connection Used for man way Used for hand hole Used as pressure, temperature, and level indication For vent connection Fire proofing cleats Davit assembly Farthing, lifting and tailing lug. Name plate bracket & name plate
Level the job and set the surface speed within specified range. Check mounting arrangement of the spool to ensure uniform feeding. The limit in order to get better alignment. To improve dimension stability &accuracy. To improve material mechanical properties. To relieve internal stress concentration. To improve product reliability. To determine acceptance to given requirement. To give information on repair criteria. For good look of component. Ensure cleanness of the surface to be overlaid.
Welding Procedure Qualification (WPQ) covers
The making and testing of a welded joint, and recording of welding parameters, to prove that the following are suitable for its intended use in production: 1. Welding processes. 2. Joint type, position and preparation. 3. Parent materials. 4. Welding consumables. 5. Run sequence. 6. Welding parameters (e.g. voltage, amps, polarity, travel speed). 7. Heat treatment (preheat & PWHT as applicable).
Welding consultation:1. To solve welding problems and failures. 2. To select suitable materials, processes equipment. 3. To reduce the rework, scrap and wastage. 4. To increase production. 5. To obtain the qualification you need. 6. To confront shortage of good welders. 7. To improve your bottom line.
CHAPTER-2 LITERATURE SURVEY2.1 ABSTRACT
Pressure vessels are typically designed, fabricated, installed, inspected, and tested In accordance with the ASME Code Section VIII. Section VIII is divided into three Separate divisions. This course outlines the main differences among the divisions. It then concentrates on and presents an overview of Division I. This course also Discusses several relevant items that are not included in Division I A literature survey on Quality of Weldments in Pressure Vessels is shown with detailed description and related figures as follows:
2.2 INSPECTION AND TEST RECORDS:Test Records Vendor shall submit to Owner the following records for each vessel: Material mill test certificate Hydrostatic and pneumatic test Dimensional inspection Non-destructive examination Post weld heat treatment Welding procedure qualification Production weld test Other inspection and tests, where specified
Vendor shall provide the following information in the first part of all the records of Inspection and tests: Name of Owner (end user) Job No., Item No., and name of vessel Name of Vendor Date of manufacture and inspection
Short specification of vessel
2.3 INSPECTION AND TEST ITEMSGeneral Unless otherwise specified in the Owners specification or drawings, the Application of the inspection and tests for each vessel shall be as shown in the List of inspection and test items which are provided for each classification of vessel. Where the application of any item in the list is considered impractical, the Vendor shall submit a suggested alternative in detail to Purchaser/Owner for approval. Inspection and test items specified in the codes and standards shall govern where applicable.
STANDARDS :2.4.1 Material Test 1. Vendor shall submit the mill test certificates for the followings: Shell, head, nozzle Tube sheet, channel cover, flange Tube, tray made of alloy steel* Pressure retaining bolt and nut, and alloy steel* bolt and nut.
Note: *Including high and low alloy steel such as C-Mo, Cr-Mo, 3.5 Ni steel, etc. 2. Submittal of mill test certificates for materials may be exempted for any of the Followings: Materials conformed with ASTM A-36 Rolled Steel for General Structure and their equivalent. Stocked materials shall not be used in pressure retaining parts. Stocked
materials used in pressure retaining parts, but not main parts, where their mill test certificates are not readily obtainable. In such cases Vendors certificates may be substituted for the original mill test certificates.
3. Vendor shall, prior to fabrication of the vessel, check the charge number and the following items for the materials: Chemical compositions Mechanical properties Heat treatment Other items specified in the applicable codes and standards
4. Materials shall be free from injurious defects, such as surface flaw and Lamination and these shall be visually inspected. 5. Material conformed with ANSI (Austenitic stainless steel containing Molybdenum) or their ASTM equivalent not used in major parts of any vessel and without mill test certificates shall be checked for molybdenum content by Qualitative analysis. 6. As type 316 and 316L stainless steel (plate, pipe, forging material and welded Deposit), examination for molybdenum detection shall be done.
2.4.2 Impact Test of Material for Low Temperature Service Test procedure shall be in accordance with ASTM A370: Test specimens of 2mmV (ASTM A379 Type A) shall be used. Test temperature shall not be warmer than the minimum design temperature. Acceptable impact energy are: Average for three specimens: 15 ft-lb and over Minimum for one specimen: 12 ft-lb
2.5 Welding Procedure Qualification :
Test procedure and acceptable standards of the welding procedure qualification shall be in accordance with the applicable codes and standards.
Inspection and Tests of Welds : 1. Welders who participate in the welding operation of the main seams of vessels, such as longitudinal and circumferential welding seams, nozzle-to-shell welds and other pressure retaining welds, shall be checked for their qualification licenses. Purchaser/Owner may request Vendor re-qualification of the welders, when necessary. 2. Prior to or during welding, the following items shall be inspected: a. Dimension of welding groove b. Alignment tolerances of plate edges
TABLE 2.1: ALIGNMENT TOLERANCES OF PLATE EDGESNormal Plate Thickness t(mm) For Circumferential Joint t(mm)
4.5 < t 6
6 < t 20
t x 0.25
20 < t 38
38 < t
t x 0.125, max.6
Normal Plate Thickness (mm) t 4.5
For Longitudinal Joint t (mm) 1.0
4.5 < t 6