• Author / Uploaded
• Sairam Surath

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In this presentation, we will cover : • Why the stress analysis of lines connected to Tank Nozzle is different than stress analysis of lines connected to Equipment nozzle ? • How Caesar modelling should be done to account for this ? • What are the acceptance criteria for nozzle load & pipe stress? 2

We start with : • Why the stress analysis of lines connected to Tank Nozzle is different than stress analysis of lines connected to Equipment nozzle ? • How Caesar modelling should be done to account for this ? • What are the acceptance criteria for nozzle load & pipe stress? 3

Stress analysis of lines connected to Equipment nozzle has to account in Caesar Modeling • Nozzle’s thermal movements, and • Nozzle flexibility

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Stress analysis of lines connected to Tank nozzle has to account in Caesar Modeling • • • •

Nozzle’s thermal movements Nozzle flexibility Nozzle rotations due to tank bulging Tank settlement 5

Nozzle rotations due to tank bulging

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Nozzle rotations due to tank bulging .

What is this Tank Bulging? 7

In “Tank Bulging”, we will cover • What is Tank Bulging? • What are its effect on nozzle? • Why this effect is not there in equipment? • How this is calculated? • Sample calculation for shell movements at various heights due to tank bulging, to see tank profile after bulging. • Why it is not calculated for nozzles at higher level? • Pipe routing guidelines - to minimize effect of tank bulging.

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we start with • What is Tank Bulging? • What are its effect on nozzle? • Why this effect is not there in equipment? • How this is calculated? • Sample calculation for shell movements at various heights due to tank bulging, to see tank profile after bulging. • Why it is not calculated for nozzles at higher level? • Pipe routing guidelines - to minimize effect of tank bulging.

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TANK

Tank is filled with liquid. This liquid has varying height. Due to this there is varying liquid pressure on tank wall. It has more pressure at bottom.

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TANK

Due this, tank wall try to expand more at bottom.

But the bottom plate prevent this expansion and holds bottom end of shell in position.

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TANK BULGING

Due to this, actual shape of tank is formed like this.

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Now we will see • What is Tank Bulging? • What are its effect on nozzle? • Why this effect is not there in equipment? • How this is calculated? • Sample calculation for shell movements at various heights due to tank bulging, to see tank profile after bulging. • Why it is not calculated for nozzles at higher level? • Pipe routing guidelines - to minimize effect of tank bulging.

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TANK BULGING and its effect on nozzle

Due to this, nozzle on the shell move radially outward, and rotates in vertical plane, depending upon there position. The nozzle on lower portion rotates downwards. Whereas nozzle on upper portion rotates upwards.

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Now we will see • What is Tank Bulging? • What are its effect on nozzle? • Why this effect is not there in equipment? • How this is calculated? • Sample calculation for shell movements at various heights due to tank bulging, to see tank profile after bulging. • Why it is not calculated for nozzles at higher level? • Pipe routing guidelines - to minimize effect of tank bulging.

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This effect is not seen in equipments • Equipment diameter is small (up to 3m) Therefore the amount of radial growth is insignificant

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This effect is not seen in equipments • Equipment diameter is small (up to 3m) Therefore the amount of radial growth is insignificant

• Tank diameter is large (10 m to 60 m) Therefore the amount of radial growth is significant

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• Equipment pressure is not varying so much with liquid height Equipment has internal pressure, not only pressure due to fluid weight.

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• Equipment bottom is not flat to act like stiffener to hold shell ends 19

Now we will see • What is Tank Bulging? • What are its effect on nozzle? • Why this effect is not there in equipment? • How this is calculated? • Sample calculation for shell movements at various heights due to tank bulging, to see tank profile after bulging. • Why it is not calculated for nozzles at higher level? • Pipe routing guidelines - to minimize effect of tank bulging.

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API 650 • Appendix – P : address tank bulging. • Mandatory for tank with diameters above 36m. • For tank with dia. 36 m & below : Optional , or mandatory only if specified by purchaser.

• Common practice : apply for all tanks.

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API 650 : Appendix – P Formula for outward radial growth of the shell due to tank bulging : W = 9.8x10-6 GHR2x[1-e-βL cos(βL)-L/H]/Et Where, G= Design Specific Gravity of Liquid H = Liquid Height (mm) R = Nominal Tank Radius (mm) t = Shell Thickness of Opening (mm) β = Characteristic Parameter, 1.285/(Rt)0.5 (1/mm) E = Modulus of Elasticity (MPa) L = Vertical distance of Opening Centreline from Tank Bottom (mm) 22

API 650 : Appendix – P Formula for rotation of the shell due to tank bulging : θ = 9.8x10-6 GHR2x[1/H-βe-βL[cos(βL)+sin(βL)]/Et Where, G= Design Specific Gravity of Liquid H = Liquid Height (mm) R = Nominal Tank Radius (mm) t = Shell Thickness of Opening (mm) β = Characteristic Parameter, 1.285/(Rt)0.5 (1/mm) E = Modulus of Elasticity (MPa) L = Vertical distance of Opening Centreline from Tank Bottom (mm) 23

Now we will see • What is Tank Bulging? • What are its effect on nozzle? • Why this effect is not there in equipment? • How this is calculated? • Sample calculation for shell movements at various heights due to tank bulging, to see tank profile after bulging. • Why it is not calculated for nozzles at higher level? • Pipe routing guidelines - to minimize effect of tank bulging.

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A Sample calculation as per API 650 : Appendix – P with, G= Design Specific Gravity of Liquid = 1.0 H = Liquid Height = 10,000 mm R = Nominal Tank Radius = 11250 mm t = Shell Thickness of Opening = 16 mm For varying heights. 25

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TANK

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API 650 • Appendix – P : • Mandatory for tank with diameters above 36m and • Applicable / valid for nozzles on lower half of bottom shell course. Because, formula does not address varying shell thickness of tank, which is common practice for tank.

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Now we will see • What is Tank Bulging? • What are its effect on nozzle? • Why this effect is not there in equipment? • How this is calculated? • Sample calculation for shell movements at various heights due to tank bulging, to see tank profile after bulging. • Why it is not calculated for nozzles at higher level? • Pipe routing guidelines - to minimize effect of tank bulging.

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Nozzle rotations & movement due to tank bulging, for nozzles at higher level.

We do not calculate this for nozzles at higher level.

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Why it is not calculated for nozzles at higher level? Reasons : For nozzles at higher level, • Effect of tank bulging on nozzle is insignificant,

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Maximum radial shell movement is at 710 mm from bottom.

Height above this peak is 9.29 m. Which is 13 times (9.29/0.71 = 13) of 0.710 m.

Thus slope in top portions would be 13 times less than slope in bottom portion.

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Max. Slope is 0.654 degree at bottom. Whereas in upper portion it is 0.051 degree at 1 m height (which is 12.8 times less w.r.t. 0.654),

And there is constant slope of 0.022 degree from height 3m onwards (which is 30 times less w.r.t. 0.654). 33

Why it is not calculated for nozzles at higher level? Reasons : For nozzles at higher level, • Effect of tank bulging on nozzle is insignificant

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Why it is not calculated for nozzles at higher level? Reasons : For nozzles at higher level, • Effect of tank bulging on nozzle is insignificant • Effect of nozzle movement and rotations on the piping and nozzle load is insignificant. Because piping from nozzles at higher level is not short and rigid. 35

Now we will see • What is Tank Bulging? • What are its effect on nozzle? • Why this effect is not there in equipment? • How this is calculated? • Sample calculation for shell movements at various heights due to tank bulging, to see tank profile after bulging. • Why it is not calculated for nozzles at higher level? • Pipe routing guidelines - to minimize effect of tank bulging.

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To minimize the effect of tank bulging, on piping. Due to bulging, nozzle at lower levels rotates downward. This causes pipe to move vertically downwards. To minimize the amount of this movement : • Piping shall be rotated through 90° as close to the tank wall as practical. (2D spool may be provided to avoid elbow stiffening due to flanged elbow) 37

In other words we can also say,

.

.

nozzle orientation should be such that, it does not directly points towards pipe’s primary direction to which it has to run.

It should point to 90°to the pipe’s primary direction to which it has to run.

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Converts nozzle loading into favorable direction As the pipe’s downward movement is restricted by next pipe support, it causes vertical reaction load and moment on tank nozzle. This (rotating piping by 90°), converts the longitudinal moment acting on tank nozzle to torsional moment. This is of minor consequence as nozzle is much more stronger against torsional loading, than longitudinal loading. 39

Stress analysis of lines connected to Tank nozzle has to account in Caesar Modeling • • • •

Nozzle’s thermal movements Nozzle flexibility Nozzle rotations due to tank bulging Tank settlement 40

In “Tank Settlement”, we will cover • Why Settlement is not seen in equipments? • How much Settlement to be considered? • Pipe routing guidelines - to minimize effect of tank settlement. • Use of Spring support 41

we start with • Why Settlement is not seen in equipments? • How much Settlement to be considered? • Pipe routing guidelines - to minimize effect of tank settlement. • Use of Spring support 42

Why Settlement is not seen in equipments • Equipment diameter is small (up to 3m) It is possible to design its foundation with large raft (say 10 m), to minimize or have insignificant settlement.

• Tank diameter is large (10 m to 60 m) It is impractical to design it’s foundation with much bigger raft than this, to have insignificant settlement.

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Now we will see • Why Settlement is not seen in equipments? • How much Settlement to be considered? • Pipe routing guidelines - to minimize effect of tank settlement. • Use of Spring support 44

How much Settlement to be considered IN CASE OF SAND : • Majority of the total settlement occurs during hydro test of tank (before piping is connected). This is generally permanent. … typically 60% • For balance 40% of settlement, which occurs after piping connection, piping needs to be designed. IN CASE OF CLAY : Progressive settlement. 45

How much Settlement to be considered

• It is more at the center of tank, and typically 50% at the edge of tank. (Since our nozzles and tank roof are connected / supported on shall, that is on outer edge of tank, we need to consider the settlement at outer edge of tank.) 46

Data to be obtained from civil for each tank • Total long term settlement. • Settlement that will occur during construction and hydrotest of tank. • Recovery (if any) following construction and hydrotest of tank. • Further settlement, after hydrotest of tank, (at the edge of the tank). 47

Sample Data from civil for each tank Settlement at Centre of Tank.

Settlement at Edge of Tank.

Tank no. 40% of total Settlement at Edge of Tank.

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Now we will see • Why Settlement is not seen in equipments? • How much Settlement to be considered? • Pipe routing guidelines - to minimize effect of tank settlement. • Use of Spring support 49

To reduce effect of tank settlement • Keep first support away

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Now we will see • Why Settlement is not seen in equipments? • How much Settlement to be considered? • Pipe routing guidelines - to minimize effect of tank settlement. • Use of Spring support 51

To reduce effect of tank settlement • Keep first support away • Large dia. piping with large settlement may call for spring support however avoid spring support - because accidental draining of line will cause excessive upward force on nozzle

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If Spring support is used • WNC (Weight with No Content) load case is required (since it will be liquid line). • Nozzle should be OK in OPE & WNC case. - Spring should be under tuned. (to pass nozzle in OPE & WNC case) -This will increase nozzle load in normal operating case, but will reduce load in WNC case. 53

This can be done by specifying Operating load in Caesar.

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You can see in this example,

.

all piping is rotated through 90°,

.

and first support is away from the nozzle.

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Now we will see : • Why the stress analysis of lines connected to Tank Nozzle is different than stress analysis of lines connected to Equipment nozzle ? • How Caesar modelling should be done to account for this? • What are the acceptance criteria for nozzle load & pipe stress? 56

To model in Caesar

• Settlement along with

• Nozzle’s thermal movement • Nozzle movement due to tank bulging • Nozzle’s local flexibility 57

First we will concentrate on

• Settlement along with

• Nozzle’s thermal movement • Nozzle movement due to tank bulging • Nozzle’s local flexibility 58

For nozzles on tank bottom to account for Nozzle’s thermal movement • Do not model tank, to account for its nozzle movement. • In-stead specify total nozzle movement & rotations (at tank shell junction), [due to thermal growth and tank bulging]. 59

How to calculate total nozzle movement, due to thermal growth and tank bulging? • API-650 formula calculates nozzle movements due to tank bulging only.

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How to use this • First copy e-BMS excel file with tank & nozzle name. • Within excel file, copy sheet for different temperature cases, such as T1 (Max. Design), T2 (Oper.), T3 (Min. Design) 61

To apply this in Caesar • Input this in Caesar as D1 → T1 (Max. Design) D2 → T2 (Max. Oper.) D3 → T3 (Min. Design),

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Now for combining this with Settlement • Input Settlement in Caesar as D4 → Settlement

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Max. Oper. Temp. • I would just like to add here, ADCO commented us to use Max. Oper. Temp., in place of Normal Oper. Temp., for OCC load cases (e.g. T2+WIND). • From Process we got confirmation that Ope. Temp. listed in line list are Max. Oper. Temp.

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Max. Oper. Temp. • As per SHELL DEP 01.00.01.30-Gen. “DEFINITION OF TEMPERATURE, PRESSURE AND TOXICITY LEVELS” 4.1.2 Maximum operating temperature (MOT) • The MOT is the highest temperature which provides sufficient flexibility for the control of the intended operation. • In many cases this flexibility is not required and in those cases the MOT is equal to the OT. • The MOT is determined by the process engineer in consultation with the process control engineer. 65

Load cases for “before settlement” W+P1+T1+D1

→ OPE, at Max. Design Temp.

W+P1+T2+D2

→ OPE, at Max. Ope. Temp.

W+P1+T3+D3

→ OPE, at Min. Design Temp.

W+P1

→ SUS

build the load cases as above, for scenario before settlement. 66

Load cases for “before settlement” W+P1

→ SUS

It may be noted that we do not add bulging movements to SUS case (with tank filled). The reason is, in SUS case, we include only primary loads. Nozzle movement due to bulging (or in fact any movement), is secondary load. 67

Load cases for “after settlement” W+P1+T1+D1+D4 → OPE, at Max. Design Temp. W+P1+T2+D2+D4 → OPE, at Max. Ope. Temp. W+P1+T3+D3+D4 → OPE, at Min. Design Temp. W+P1+D4

→ SUS

(Where, D4 → SETTLEMENT) build the load cases as above, for scenario after settlement. 68

Now incorporating nozzle flexibility along with settlement, and nozzle rotations in Caesar

• In Caesar define Nozzle at nozzle-shell junction node.

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.

Enter node on nozzle pipe piece, at shell junction

Select “API 650”

. Select “Nozzle” Enter node on shell , at shell junction Nozzle flexibility is inserted by Caesar between these nodes Input other data required by Caesar to calculate nozzle flexibility No input field for nozzle orientation in which nozzle stiffness's will be inserted Caesar insert nozzle stiffness's in direction of element 70

Now to enter shell displacements and rotations.

Enter “Tank node” (node on shell ), which we have entered in “Nozzle” input data

. . Select “Displacements”

Enter D1, D2, D3, nozzle movements due to temp. & bulging. Enter D4, Tank settlement

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. .

If we are modelling this nozzle. Then this is not a radial nozzle. It is along X axis, but has offset. If we model this nozzle along X, then nozzle stiffness will be inserted along X, not in radial direction. Therefore model small element (equal to shell thickness) in radial direction, and input nozzle on this element. Shell movement & rotations calculated are also in radial direction, and needs to be resolved in X & Z axis. 72

We will have nozzle orientation plan.

.

.

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.

Where offset will be specified.

.

Tank outer radius we know.

Therefore we can calculate radial direction.

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Resolving radial shell thickness and radial shell movements & rotations, is a tedious job.

. . Therefore enter shell thickness and shell movements & rotations along nearest principal axis (Z axis in this case).

Observe the nozzle orientation here, before rotation.

Then click here to rotate that element. 75

. .

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. . That is because shell thickness is rotated (on which nozzle is specified).

Now observe the nozzle orientation here, after rotation.

This also rotated shell displacements and rotations.

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• In this case, while checking the nozzle loads also, we have to get load & moments about radial & lateral axis (not X & Z).

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. .

For this, you need to select entire model, and rotate it about Y axis, by the angle of nozzle (in this case 9.2°), so that radial direction of nozzle is along nearest principal axis (Z axis in this case).

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. . Now observe the nozzle orientation here, after rotation.

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Sign convention for nozzle rotations : As per API-650, θ +ve is upwards

and, θ -ve is downwards

But when it comes to Caesar convention, it is not always +ve is upwards.

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Caesar follows Right hand rule. • Put the thumb of your right hand along the positive axis • The direction your fingers curl is positive rotation about that axis

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Sign convention for nozzle rotations : when θ is +ve,

Then when θ is +ve,

Rz is also +ve,

Rz is -ve, RZ (-)

Y θL (+)

Z

X

Y RZ (+) RZ (+)

RZ (+)

Z θL (-)

If nozzle is in +X direction,

RZ (-)

θL (+)

Rx is also +ve, Y Z

Similarly, if nozzle is in -Z direction,

Z

X

θL (-)

But, if nozzle is in -X direction,

Z

RZ (+)

NOZZLE AXIS : (+X)

when θ is +ve,

θL (+)

NOZZLE AXIS : (-X) Y

RX (+) RX (-)

RX (-)

θL (+)

Then when θ is +ve,

Z

X

Rx is -ve,

θL (-)

X

NOZZLE AXIS : (-Z)

X

RX (+)

X RX (+)

RX (+)

θL (-)

NOZZLE AXIS : (+Z)

But, if nozzle is in +Z direction, 83

This can be presented in form of table: Nozzle rotation in API-650 Nomenclature

θL (+)

θL (-)

Caesar Nozzle Axis

Input of Nozzle rotation in Caesar

+X

+ RZ

-X

- RZ

+Z

- RX

-Z

+ RX

+X

- RZ

-X

+ RZ

+Z

+ RX

-Z

- RX 84

Sign convention for nozzle rotations : It is better if this chart & table is put on a paper, and circulated to stress team / out side 3rd party like GRE vendor, to avoid any mistakes.

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Now we will see : • Why the stress analysis of lines connected to Tank Nozzle is different than stress analysis of lines connected to Equipment nozzle ? • How Caesar modelling should be done to account for this ? • What are the acceptance criteria for nozzle load & pipe stress? 86

Acceptance criteria for:

• Nozzle load • Pipe Stress

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Acceptance criteria for Nozzle loads : • For nozzle loads, of-course it should be within allowable limit. • In earlier version of API 650 (up to 10th Edition – 2003 with Addendum-3), it had section P.3 in Appendix-P, which was based on WRC 297 88

Acceptance criteria for Nozzle loads : as per Appendix-P.3 of earlier version of API650

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Acceptance criteria for Nozzle loads : • In present version of API 650 (11th Edition – 2007), in Appendix-P, Section P.3 is Deleted in its Entirety. - not included in any other section, - No alternate method suggested. 90

Acceptance criteria for Nozzle loads : This leaves us the option to check nozzle • as per WRC 297 (P.3 was based on WRC 297) OR • To continue using method as per P.3 of previous version of API 650.

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Acceptance criteria for Nozzle loads : • Under section 1.0 Scope of API 650 It is stated that [under clause 1.1.22 of 11th Edition – 2007]

“An alternative or supplemental design may be agreed upon by the Purchaser or Manufacturer.”

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Acceptance criteria for Nozzle loads : Based on this, we can specify • WRC 297 OR • Appendix P.3 of previous version of API 650 [10th Edition – 2003 with Addendum-3]. 93

Acceptance criteria for:

• Nozzle load • Pipe Stress

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Acceptance criteria for Stress : ASME B31.3 CHAPTER II : DESIGN Para 301 defines various temp, pr., forces, and considerations to be accounted in design.

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Acceptance criteria for Stress : Sub Para 301.8 states, Effect of pipe support movement due to - Thermal expansion - Settlement - Tidal movement - Wind sway to be accounted in design. 96

Acceptance criteria for Stress : Para 319 : Piping flexibility, Sub Para 319.2.1(c) states, Movement due to earth settlement, since it is a single cycle effect, will not significantly influence fatigue life. A displacement stress range greater than that permitted by para. 302.3.5(d)

{i.e. SA = f [1.25(Sc + Sh) – SL ] } may be allowable if due consideration is given to avoidance of excessive localized strain and end reactions. 97

Acceptance criteria for Stress :

However it does not specify exact value to which it can be allowed.

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Acceptance criteria for Stress : ASME Section III, Division 1, Subsection NC (Rules For Construction Of Nuclear Facility Components) Para NC-3653.2(b) states, for effect of single non repeated anchor movement i MD / Z ≤ 3Sc Where, MD = resultant moment due to any single nonrepeated anchor movement (e.g., predicted building settlement) 99

Acceptance criteria for Stress : Thus NC code specifies limit as 3Sc. ⁻ This includes SIF ⁻ The stress is only due to anchor movement (settlement), (does not include stress due to weight, temperature or pressure) This should be spelt out in project stress analysis design basis, as this is not part of ASME B 31.3.

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That is, if Load cases for “before settlement” are L1 = W+P1+T1+D1

→ OPE, at Max. Design Temp.

L2 = W+P1+T2+D2

→ OPE, at Max. Ope. Temp.

L3 = W+P1+T3+D3

→ OPE, at Min. Design Temp.

L4 = W+P1

→ SUS

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, and Load cases for “after settlement” are : L5 = W+P1+T1+D1+D4 → OPE, at Max. Design Temp. L6 = W+P1+T2+D2+D4 → OPE, at Max. Ope. Temp. L7 = W+P1+T3+D3+D4 → OPE, at Min. Design Temp. L8 = W+P1+D4

→ SUS

(Where, D4 → SETTLEMENT)

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Then : L8 – L4 ≤ 3Sc Where, L8 = W+P1+D4 → SUS, after Settlement L4 = W+P1

→ SUS, before Settlement

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Qualification or acceptance criteria for Stress : However, ⁻ The tank nozzle allowable are generally of such a low value, that it becomes governing criteria (not pipe stress) ⁻ When you qualify to tank nozzle, pipe stress value will be very low, as compared to allowable value. ⁻ It will even pass in normal displacement stress range criteria itself.

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That is : L1 – L7 ≤ f [1.25(Sc + Sh) – SL ] Where, L1 = W+P1+T1+D1

→ OPE, at Max. Design Temp., giving highest nozzle position

L7 = W+P1+T3+D3+D4 → OPE, at Min. Design Temp., giving lowest nozzle position. 105

RECAP

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Thus today we have seen : • Why the stress analysis of lines connected to Tank Nozzle is different than stress analysis of lines connected to Equipment nozzle ? • How Caesar modelling should be done to account for this ? • What are the acceptance criteria for nozzle load & pipe stress? 107

Under this, about “Tank Bulging”, we have seen • What is Tank Bulging? • What are its effect on nozzle? • Why this effect is not there in equipment? • How this is calculated? • A Sample calculation for shell movements at various heights due to tank bulging, to see tank profile after bulging. • Why it is not calculated for nozzles at higher level? • Pipe routing guidelines - to minimize effect of tank bulging.

108

And about “Tank Settlement”, we have seen

• Why Settlement is not seen in equipments? • How much Settlement to be considered? • Pipe routing guidelines - to minimize effect of tank settlement. • Use of Spring support 109

Then we have seen : • Why the stress analysis of lines connected to Tank Nozzle is different than stress analysis of lines connected to Equipment nozzle ? • How Caesar modelling should be done to account for this (nozzle movements due to tank bulging, and settlement, along with nozzle flexibility)? • What are the acceptance criteria for nozzle load & pipe stress? 110