# Analysis of Vessel-Boiler Design and Material-Article

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This article for Boiler Design and Material course. It was submitted to Dr. Khalil Zaman as an assignment at Ambedkar University, Delhi. Its main points are: Analysis, Vessels, Design, Welded, Construction, Joint, Catego...
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NB-3339.7 NB-3000 — DESIGN NB-3351.3

TABLE NB-3339.7(c)-1 STRESS INDICES FOR INTERNAL

Nozzles in Spherical Shells and Spherical Heads

Stress Inside Outside

sn 2.0 − d/D 2.0 − d/D

st −0.2 2.0 − d/D

sr −4t/(D + t) 0

S larger of: 2.2 − d/D or 2.0 − d/D 2.0 + [4t/(D + t)] − d/D

Nozzles in Cylindrical Shells

Longitudinal Plane Transverse Plane

Stress Inside Outside Inside Outside

sn 3.1 1.2 1.0 2.1

st −0.2 1.0 −0.2 2.6

sr −2t/(D + t) 0 −2t/(D + t) 0

S 3.3 1.2 1.2 2.6

section (ordinarily the circumferential stress around the hole in the shell), psi

srp stress component normal to the boundary of the section, psi

stp stress component in the plane of the section under consideration and parallel to the boundary of the section, psi

(c) When the conditions of NB-3339.1 through NB- 3339.6 are satisfied, the stress indices given in Table NB-3339.7(c)-1 may be used. These stress indices deal only with the maximum stresses, at certain general locations, due to internal pressure. In the evaluation of stresses in or adjacent to vessel openings and connec- tions, it is often necessary to consider the effect of stresses due to external loadings or thermal stresses. In such cases, the total stress at a given point may be determined by superposition. In the case of combined stresses due to internal pressure and nozzle loading, the maximum stresses shall be considered as acting at the same point and added algebraically. If the stresses are otherwise determined by more accurate analytical techniques or by the experimental stress analysis proce- dure of Appendix II, the stresses are also to be added algebraically.

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NB-3340 ANALYSIS OF VESSELS

The provisions of NB-3214 apply.

NB-3350 DESIGN OF WELDED CONSTRUCTION

NB-3351 Welded Joint Category

The term Category defines the location of a joint in a vessel, but not the type of joint. The categories established are for use in specifying special requirements regarding joint type and degree of examination for certain welded joints. Since these special requirements, which are based on service, material, and thickness, do not apply to every welded joint, only those joints to which special requirements apply are included in the categories. The special requirements apply to joints of a given category only when specifically stated. The joints included in each category are designated as joints of Categories A, B, C, and D. Figure NB-3351-1 illustrates typical joint locations included in each cat- egory.

NB-3351.1 Category A. Category A comprises longi- tudinal welded joints within the main shell, communicat- ing chambers,13 transitions in diameter, or nozzles; any welded joint within a sphere, within a formed or flat head, or within the side plates14 of a flat sided vessel; and circumferential welded joints connecting hemispherical heads to main shells, to transitions in diameters, to nozzles, or to communicating chambers.

NB-3351.2 Category B. Category B comprises cir- cumferential welded joints within the main shell, com- municating chambers, nozzles, or transitions in diameter, including joints between the transition and a cylinder at either the large or small end; and circumferential welded joints connecting formed heads other than hemi- spherical to main shells, to transitions in diameter, to nozzles, or to communicating chambers.

NB-3351.3 Category C. Category C comprises welded joints connecting flanges, Van Stone laps, tube- sheets, or flat heads to main shell, to formed heads, to transitions in diameter, to nozzles, or to communicating chambers13 any welded joint connecting one side plate14

to another side plate of a flat sided vessel.

13 Communicating chambers are defined as portions of the vessel which intersect the shell or heads of a vessel and form an integral part of the pressure-retaining closure, e.g., sumps. 14 Side plates of a flat sided vessel are defined as any of the flat plates forming an integral part of the pressure-retaining enclosure.

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NB-3351.4 1998 SECTION III, DIVISION 1 — NB NB-3352.4

FIG. NB-3351-1 WELDED JOINT LOCATIONS TYPICAL OF CATEGORIES A, B, C, AND D

NB-3351.4 Category D. Category D comprises welded joints connecting communicating chambers or nozzles to main shells, to spheres, to transitions in diameter, to heads, or to flat sided vessels, and those joints connecting nozzles to communicating chambers. For nozzles at the small end of a transition in diameter, see Category B.

NB-3352 Permissible Types of Welded Joints

The design of the vessel shall meet the requirements for each category of joint. Butt joints are full penetration joints between plates or other elements that lie approxi- mately in the same plane. Category B angle joints between plates or other elements that have an offset angle a not exceeding 30 deg. are considered as meeting the requirements for butt joints. Figure NB-3352-1 shows typical butt welds for each category joint.

NB-3352.1 Joints of Category A. All welded joints of Category A as defined in NB-3351 shall meet the fabrication requirements of NB-4241 and shall be capa- ble of being examined in accordance with NB-5210.

NB-3352.2 Joints of Category B. All welded joints of Category B as defined in NB-3351 shall meet the fabrication requirements of NB-4242 and shall be capa- ble of being examined in accordance with NB-5220. When joints with opposing lips to form an integral backing strip or joints with backing strips not later removed are used, the suitability for cyclic service shall be analyzed by the method of NB-3222.4 using a fatigue strength reduction factor of not less than 2.

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NB-3352.3 Joints of Category C. All welded joints of Category C as defined in NB-3351 shall meet the fabrication requirements of NB-4243 and shall be capa- ble of being examined in accordance with NB-5230. Minimum dimensions of the welds and throat thickness shall be as shown in Fig. NB-4243-1 where:

(a) for forged tubesheets, forged flat heads, and forged flanges with the weld preparation bevel angle not greater than 45 deg. measured from the face:

t, tnp nominal thicknesses of welded parts, in. tcp 0.7tn or 1⁄4 in. (6 mm), whichever is less twp tn /2 or t /4, whichever is less

(b) for all other material forms and for forged tube- sheets, forged flat heads, and forged flanges with the weld preparation bevel angle greater than 45 deg. measured from the face:

t, tnp nominal thicknesses of welded parts, in. tcp 0.7tn or 1⁄4 in. (6 mm), whichever is less twp tn or t /2, whichever is less

NB-3352.4 Joints of Category D. All welded joints of Category D as defined in NB-3351 shall be in accordance with the requirements of one of (a) through (e) below.

(a) Butt Welded Nozzles. Nozzles shall meet the fabrication requirements of NB-4244(a) and shall be capable of being examined in accordance with NB- 5242. The minimum dimensions and geometrical re- quirements of Fig. NB-4244(a)-1 shall be met, where

r1p 1⁄4t or 3⁄4 in. (19 mm), whichever is less

r2p 1⁄4 in. (6 mm) minimum

tp nominal thickness of part penetrated, in.

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NB-3352.4 NB-3000 — DESIGN NB-3352.4

FIG. NB-3352-1 TYPICAL BUTT JOINTS

tnp nominal thickness of penetrating part, in. (b) Full Penetration Corner Welded Nozzles. Nozzles

shall meet the fabrication requirements of NB-4244(b) and shall be capable of being examined as required in NB-5243. The minimum dimensions of Fig. NB- 4244(b)-1 shall be met, where

r1p 1⁄4t or 3⁄4 in. (19 mm), whichever is less

r2p 1⁄4 in. (6 mm) minimum

tp nominal thickness of part penetrated, in. tcp 0.7tn or 1⁄4 in. (6 mm), whichever is less tnp nominal thickness of penetrating part, in.

(c) Use of Deposited Weld Metal for Openings and Nozzles

(1) Nozzles shall meet the fabrication requirements of NB-4244(c) and shall be capable of being examined in accordance with NB-5244.

(2) When the deposited weld metal is used as reinforcement, the coefficients of thermal expansion of

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the base metal, the weld metal, and the nozzle shall not differ by more than 15% of the lowest coefficient involved.

(3) The minimum dimensions of Fig. NB-4244(c)- 1 shall be met, where

r1p 1⁄4t or 3⁄4 in. (19 mm), whichever is less

tp nominal thickness of part penetrated, in. tcp 0.7tn or 1⁄4 in. (6 mm), whichever is less tnp nominal thickness of penetrating part, in. (4) The corners of the end of each nozzle neck

extending less than √ dtn beyond the inner surface of the part penetrated shall be rounded to a radius of one-half the thickness tn of the nozzle neck or 3⁄4 in. (19 mm), whichever is smaller.

(d) Attachment of Nozzles Using Partial Penetration Welds

(1) Partial penetration welds used to connect noz- zles as permitted in NB-3337.3 shall meet the fabrication

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NB-3352.4 1998 SECTION III, DIVISION 1 — NB NB-3362

requirements of NB-4244(d) and shall be capable of being examined in accordance with the requirements of NB-5245.

(2) The minimum dimensions of Figs. NB-4244(d)- 1 and NB-4244(d)-2 shall be met, where

dp outside diameter of nozzle or of the inner cylin- der as shown in Fig. NB-4244(d)-2

r1p 1⁄4tn or 3⁄4 in. (19 mm), whichever is less

r2p 1⁄16 in. (1.6 mm) minimum

r3p r2 or equivalent chamfer minimum r4p

1⁄2tn or 3⁄4 in. (19 mm), whichever is less tp nominal thickness of part penetrated, in.

tcp 0.7tn or 1⁄4 in. (6 mm), whichever is less tnp nominal thickness of penetrating part or the

lesser of tn1 or tn2 in Fig. NB-4244(d)-2, in. lp 1⁄16 in. (1.6 mm) minimum lp tn maximum, in. (3) The corners of the end of each nozzle, ex-

tending less than √ dtn beyond the inner surface of the part penetrated, shall be rounded to a radius of one-half of the thickness tn of the penetrating part or 3⁄4 in. (19 mm), whichever is smaller.

(4) Weld groove design for partial penetration joints attaching nozzles may require special consider- ation to achieve the 1.25tn minimum depth of weld and adequate access for welding examination. The welds shown in the sketches of Figs. NB-4244(d)-1 and NB- 4244(d)-2 may be on either the inside or the outside of the vessel shell. Weld preparation may be J-groove as shown in the figures or straight bevel.

(5) A fatigue strength reduction factor of not less than four shall be used when fatigue analysis is required.

(e) Oblique Full Penetration Nozzles. Internal or external nozzles shall meet the fabrication requirements of NB-4244(e) and shall be capable of being examined in accordance with NB-5246. Radiography of the nozzle weld may be waived by NB-5246, provided the require- ments of (1) through (6) below are met.

(1) The inside nozzle diameter shall not exceed 6 in.

(2) The angle which the nozzle axis makes with the vessel wall at the point of attachment shall not be smaller than 40 deg.

(3) The opening shall be completely reinforced, with the reinforcement located in the shell or head of the vessel.

(4) The nozzle shall be subjected to essentially no pipe reactions and no thermal stresses greater than in the vessel itself.

(5) The nozzle wall and the weld shall develop the full strength of the nozzle.

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(6) The minimum dimensions of Fig. NB-4244(e)- 1 shall be met, where

r1p 1⁄2t or 3⁄4 in. (19 mm), whichever is less

tp nominal thickness of part penetrated, in. tcp 0.7tn or 1⁄4 in. (6 mm), whichever is less tnp nominal thickness of penetrating part, in.

NB-3354 Structural Attachment Welds

Welds for structural attachments shall meet the re- quirements of NB-4430.

NB-3355 Welding Grooves

The dimensions and shape of the edges to be joined shall be such as to permit complete fusion and complete joint penetration, except as otherwise permitted in NB- 3352.4.

NB-3357 Thermal Treatment

All vessels and vessel parts shall be given the appropriate postweld heat treatment prescribed in NB-4620.

NB-3360 SPECIAL VESSEL REQUIREMENTS

NB-3361 Category A or B Joints Between Sections of Unequal Thickness

In general, a tapered transition section as shown in Fig. NB-3361-1 which is a type of gross structural discontinuity (NB-3213.2) shall be provided at joints of Categories A and B between sections that differ in thickness by more than one-fourth the thickness of the thinner section. The transition section may be formed by any process that will provide a uniform taper. An ellipsoidal or hemispherical head which has a greater thickness than a cylinder of the same inside diameter may be machined to the outside diameter of the cylinder provided the remaining thickness is at least as great as that required for a shell of the same diameter. A uniform taper is not required for flanged hubs. The adequacy of the transition shall be evaluated by stress analysis. Stress intensity limitations are given in NB- 3220. The requirements of this paragraph do not apply to flange hubs.

NB-3362 Bolted Flange Connections

It is recommended that the dimensional requirements of bolted flange connections to external piping conform to ANSI B16.5, Steel Pipe Flanges and Flanged Fittings.

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NB-3363 NB-3000 — DESIGN NB-3412.2

FIG. NB-3361-1 CATEGORY A AND B JOINTS BETWEEN SECTIONS OF UNEQUAL THICKNESS

NB-3363 Access Openings

Access openings, where provided, shall consist of handhole or manhole openings having removable covers. These may be located on either the inside or outside of the shell or head openings and may be attached by studs or bolts in combination with gaskets or welded membrane seals or strength welds. Plugs using pipe threads are not permitted.

NB-3364 Attachments

Attachments used to transmit support loads shall meet the requirements of NB-3135.

NB-3365 Supports

All vessels shall be so supported and the supporting members shall be arranged and attached to the vessel wall in such a way as to provide for the maximum imposed loadings. The stresses produced in the vessel by such loadings and by steady state and transient thermal conditions shall be subjected to the stress limits of this Subsection. Additional requirements are given in NCA-3240 and Subsection NF.

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NB-3400 PUMP DESIGN

NB-3410 GENERAL REQUIREMENTS FOR CENTRIFUGAL PUMPS

NB-3411 Scope

NB-3411.1 Applicability. The rules of NB-3400 apply to (a) through (j) below.

(a) pump casings (b) pump inlets and outlets (c) pump covers (d) clamping rings (e) seal housing and seal glands (f) related bolting (g) pump internal heat exchanger piping (h) pump auxiliary nozzle connections up to the face

of the first flange or circumferential joint in welded connections, excluding the connecting weld

(i) piping identified with the pump and external to and forming part of the pressure-retaining boundary and supplied with the pump

(j) mounting feet or pedestal supports when inte- grally attached to the pump pressure-retaining boundary and supplied with the pump

NB-3411.2 Exemptions. The rules of NB-3400 do not apply to (a) through (c) below.

(a) pump shafts and impellers; shafts may be de- signed in accordance with Appendix S

(b) nonstructural internals (c) seal packages

NB-3412 Acceptability

NB-3412.1 Acceptability of Large Pumps. The re- quirements for the design acceptability of pumps having an inlet connection greater than 4 in. nominal pipe size (DN 100) diameter are given in (a), (b), and (c) below.

(a) The design shall be such that the requirements of NB-3100 and of NB-3200 or Appendix II (provided the requirements of NB-3414 and the minimum wall thicknesses of NB-3430 are met) are satisfied.

(b) The rules of this Subarticle shall be met. In cases of conflict between NB-3100 and NB-3200 or Appendix II and NB-3400, the requirements of NB-3400 apply.

(c) The requirements for prevention of nonductile fracture as set forth in NB-3211(d) shall be met.

NB-3412.2 Acceptability of Small Pumps. The re- quirements for the design acceptability of pumps having an inlet connection 4 in. nominal pipe size (DN 100) diameter or smaller are given in (a) and (b) below.

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NB-3412.2 1998 SECTION III, DIVISION 1 — NB NB-3432

(a) The design shall be such that the requirements of NB-3100 or Appendix II are satisfied.

(b) The rules of this Subarticle shall be met. In cases of conflict between NB-3100 or Appendix II and NB- 3400, the requirements of this Subarticle shall apply.

NB-3414 Design and Service Conditions

The general design considerations, including defini- tions of NB-3100 plus the requirements of NB-3320, NB-3330, NB-3361, and NB-3362 are applicable to pumps.

(a) Loads imposed on pump inlets and outlets by connected piping shall be considered in the pump casing design. The forces and moments produced by the connected piping on each pump inlet and outlet shall be provided by the Owner in the Design Specifications.

(b) Stresses generated in the pump casing by the connected piping shall be combined with the pressure stresses in accordance with the requirements of NB- 3200.

(a) The effects of earthquake shall be considered in the design of pumps, pump supports, and restraints. The stresses resulting from these earthquake effects shall be included with the stresses resulting from pressure or other applied loads.

(b) Where pumps are provided with drivers on ex- tended supporting structures and these structures are essential to maintaining pressure integrity, an analysis shall be performed when required by the Design Speci- fications.

NB-3418 Corrosion

The requirements of NB-3121 apply.

Cladding dimensions used in the design of pumps shall be required as in NB-3122.

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NB-3420 DEFINITIONS

A radially split casing shall be interpreted as one in which the primary sealing joint is radially disposed around the shaft.

NB-3422 Axially Split Casing

An axially split casing shall be interpreted as one in which the primary sealing joint is axially disposed with respect to the shaft.

NB-3423 Single and Double Volute Casings

Figures NB-3423-1 and NB-3423-2 show typical single and double volute casings, respectively.

NB-3424 Seal Housing

Seal housing is defined as that portion of the pump cover or casing assembly which contains the seal and forms a part of the primary pressure boundary.

NB-3425 Typical Examples of Pump Types

Figures NB-3441.1-1 through NB-3441.6(a)-1 are typical examples to aid in the determination of pump type and are not to be considered as limiting. Bearing locations and inlet and outlet orientations are optional.

NB-3430 DESIGN REQUIREMENTS FOR CENTRIFUGAL PUMPS

NB-3431 Design of Welding

(a) The design of welded construction shall be in accordance with NB-3350.

(b) Partial penetration welds are permitted for piping connections 2 in. nominal pipe size and less when the requirements of NB-3337.3 and NB-3352.4(d) are met.

NB-3432 Cutwater Tip Stresses

(a) It is recognized that localized high stresses may occur at the cutwater tips of volute casings (Fig. NB- 3441.3-2). Adequacy of the design in this area shall be demonstrated either by an investigation through experimental stress analysis in accordance with Appen-

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