piping bellows expansion joints

TRAINING MANUAL – PIPINGBELLOWS EXPANSION JOINT

Uhde India Limited

DOC No. : 29040-PI-UFR-0035

Rev. : R0

Page : 1

CONTENTS

Page

0.0 Cover Sheet 1

1.0 Introduction 2

2.0 Application 2

3.0 Bellow Pressure Thrust 2 – 5

4.0 Bellow Types 5 – 14

5.0 System Design Considerations 14 – 16

6.0 Internal Sleeve Requirement 16 – 17

7.0 Bellow Pre-Compression 17 - 18

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Uhde India Limited

DOC No. : 29040-PI-UFR-0035

Rev. : R0

Page : 2

1.0 INTRODUCTION:

In a piping system a Bellow is like a sealed spring. Sealed because it is required to containthe fluid pressure which is flowing through it and spring because it is required to respond tothe movement of the connected piping without offering appreciable stiffness to the pipingsystem. A Bellow element employed in a piping system is an assembly of generally more thanone convolute in series. The convolutes are designed strong enough to withstand the internalpressure of the system, at the same time the typical contour of the convolute assembly allowsit to flex under thermal movement of the connected piping. As a result of this extremeflexibility the Bellow as such is highly incapable of absorbing any longitudinal loads by its own,thereby requiring external attachments to transfer these longitudinal loads to its connectedpiping for maintaining the overall stability of the piping system under question.

2.0 APPLICATION:

The Bellows are generally employed in a piping system in one of the following situations:

• When the space constraints do not permit providing adequate flexibility by conventionalmethods (e. g. expansion loops etc.) for maintaining the system stresses withinacceptable limits.

• When conventional solutions (e.g. expansion loops etc.) create unacceptable processconditions (e.g. excessive pressure drop).

• When it is not practical to limit the piping induced loads on the terminal nozzles of theconnected equipment within admissible limits by conventional methods.

• When the equipment such as Compressors, Turbines, Pumps etc. necessitate isolatingthe mechanical vibrations from being transmitted to the connected piping.

3.0 BELLOW PRESSURE THRUST:

The end anchors in a piping system employing a Bellow requires special considerations owing

the large imbalance axial force generated due to internal system pressure acting on the

bellow convolutes. At the same time the inherent weakness of the Bellow to transfer the

longitudinal force across its ends.

It is therefore imperative that a proper assessment of the imbalance Pressure Thrust of

the Bellow and its effects on the piping end terminals be evaluated prior to using the

Bellow on a piping system of large diameter and sizable internal pressure.

To understand the above phenomena let us consider a straight length of pipe of internal

diameter D capped at its both ends and subject to an internal pressure P (refer Exhibit 35.1,

Fig 1A below). The longitudinal Pressure Force acting at each capped end is:

Pf = πPD 2 / 4


Uhde India Limited

DOC No. : 29040-PI-UFR-0035

Rev. : R0

Page : 3

The above longitudinal force is carried in tension in the Pipe wall and the system remains

stable with the opposite and equal force acting at the capped end balancing each other. Now

let us introduce a Bellow in the middle of the above pipe section (refer Exhibit 35.1, Fig 1B).

Since the above Bellow does not have any appreciable longitudinal stiffness it will tend to

straighten out as shown in Exhibit 35.1, Fig 1C resulting into rapture of the convolutes. It is

therefore necessary to provide end anchors (refer Exhibit 35.1, Fig 1D below) to counter the

pressure force acting at the ends and thereby stopping the bellow convolute from flattening.

The magnitude of above force will be combined longitudinal force acting at the Bellow inside

diameter and the imbalance pressure thrust acting on the side-wall, of the convolute.

Exhibit-35.1

In order to derive the imbalance pressure thrust for a Bellow let us cut a strip of unit width

from the convolute of a Bellow subject to internal pressure p. The above can be

approximately represented by a free body diagram of a fixed ended beam with uniform load

W = ph where h is the height of the convolute (refer Figure-1, Exhibit 35.2 below).


Uhde India Limited

DOC No. : 29040-PI-UFR-0035

Rev. : R0

Page : 4

One half of the above uniform load W is carried in tension at the crest of the convolute and

the other half is carried in compression at the inside diameter of the convolute resulting into

the Reaction at the ends of above beam

Rid = Rod = ph / 2

Figure-1 (Exhibit 35.2)

The tensile force Rod at the crest of the convolute is balanced due to equal and opposite side

walls of the convolute and hence the only force contributing to the imbalance pressure thrust

is the compressive force Rid which needs to be absorbed by the end anchors.

The total effective area of the full ring of the convolute taking part in generating the above

imbalance pressure thrust is therefore

Sw = π { (D + 2h/ 2) 2 - D 2 } / 4

Hence the total effective pressure thrust area

= Area of the pipe I. D. + Sw

= πD 2 / 4 + π { (D + 2h/ 2) 2 - D 2 } / 4

= π { (D + 2h/ 2) 2 / 4


Uhde India Limited

DOC No. : 29040-PI-UFR-0035

Rev. : R0

Page : 5

= π Dm 2 / 4 (where Dm is the Mean diameter of the Bellow)

Hence the Total Pressure Thrust to be absorbed by the End Anchors

= p π Dm 2 / 4

4.0 BELLOW TYPES:

• Simple Expansion Joint.• Universal Expansion Joint.• Pressure Balanced Expansion Joint.• Hinged Expansion Joint.• Gimbal Expansion Joint.

Following paragraphs illustrate the typical situations for employing the above type of Bellowsdepending upon the application and configuration of the piping profile.

SIMPLE EXPANSION JOINT:

1.0 Expansion Joint for absorbing axial displacement.

1.1 Single Element Bellow installed in a straight line

A typical arrangement of the above application is shown in the accompanying sketch (Figure-1, Exhibit 35.3) below. The Bellow is locked between the end anchors (Main Anchors) and isnormally located close to one of the above Main Anchors. The other end of the Bellow isaccompanied by First Alignment Guide G1 (as close as possible to the below) followed bySecond Alignment Guide G2 at a distance of 14 D (as per EJMA recommendation). TheSecond Alignment Guide G2 is, followed by the Intermediate Guides (located as per thenormal support span) if required as per the length of the line.


1.2 Single Element Bellow installed in a straight line with an offset.

A typical arrangement of the above application is shown in the accompanying sketch (Figure-2, Exhibit 35.3) below. The application of this type is normally not recommended and willperform satisfactory only within certain limits. The axial pressure thrust of the Bellow istransmitted to the Main Anchor through the offset, resulting into bending moment in the piping.The remaining arrangement of the Main Anchors, First and Second Alignment Guides andrest of the Intermediate Guides remains same as that of the Bellow installed in a straight line.


Uhde India Limited

DOC No. : 29040-PI-UFR-0035

Rev. : R0

Page : 6


1.3 Double Element Bellow employing an intermediate anchor in the middle wheninstalled in a straight line

A typical arrangement of the above application is shown in the accompanying sketch (Figure-1, Exhibit 35.4) below. The arrangement is generally employed in the situations where thelinear expansion of the line is of a very large magnitude. The Bellow assembly consists of 2elements separated by an Intermediate Anchor. Thereby absorbing the linear expansion ofthe 2 sections of the pipeline individually. It may be noted that the above Intermediate Anchorneed not be designed for the bellow axial force, which cancels out between the 2 BellowElements. The remaining arrangement of the Main Anchors, First and Second AlignmentGuides and rest of the Intermediate Guides remains same as that of the Bellow installed in astraight line.


1.4 Double Element Bellow employing a main anchor in the middle, installed in astraight line at the interface of changed line size (i.e. reducer)

A typical arrangement of the above application is shown in the accompanying sketch (Figure-2, Exhibit 35.4) below. The arrangement is similar to that of Double Element Bellow on astraight pipeline except that the middle anchor between the 2 Bellow Elements is required tobe designed as Main Anchor for the differential axial thrust of the 2 Bellows employed on eachside of the Reducer.



Uhde India Limited

DOC No. : 29040-PI-UFR-0035

Rev. : R0

Page : 7

1.5 Three Element Bellow employing a main anchor in the middle, installed at thejunction of the branch connection

A typical arrangement of the above application is shown in the accompanying sketch (Figure-1, Exhibit 35.5) below. The middle anchor between the 3 Bellow Elements in this case isrequired to be designed as Main Anchor for the axial thrust imposed by the Bellow of thebranch pipe.


2.0 Expansion Joint for absorbing lateral movement, angular rotation and combinedmovement

2.1 Single Element Bellow employing a directional anchor, installed in the longer leg ofL shaped piping profile

A typical arrangement of the above application is shown in the accompanying sketch (Figure-1, Exhibit 35.6) below. The Bellow is located at 1 end of the longer leg and thereby absorbingthe linear expansion of the longer leg as axial displacement. The Main Anchor near the Bellowis a Directional Anchor, which prevents the pipe end from moving axially, at the same timeallowing the expansion of the shorter leg, which is absorbed by the Bellow as a lateraldeflection. The Anchor on the shorter leg is required to be designed, only as IntermediateAnchor. The remaining arrangement of the First and Second Alignment Guides and rest of theIntermediate Guides remains similar to that of the Bellow installed in a straight line to preventthe straight pipe of the longer leg from rotating/ buckling.

Figure-1 (Exhibit-35.6)


Uhde India Limited

DOC No. : 29040-PI-UFR-0035

Rev. : R0

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2.2 Single Element Bellow employing a directional anchor, installed in the shorter legof L shaped piping profile

A typical arrangement of the above application is shown in the accompanying sketch (Figure-2, Exhibit 35.6) below. The Bellow is located in the shorter leg and thereby absorbing thelinear expansion of the longer leg as lateral displacement. The Main Anchor near the Bellow isa Directional Anchor, which prevents the pipe end from moving axially, at the same timeallowing the expansion of the long leg, which is absorbed by the Bellow as a lateral deflection.The Anchor on the longer leg is required to be designed, only as Intermediate Anchor. Only 1Guide is required on the longer leg for alignment purpose.


2.3 Single Element Bellow employing a tie rod in place of a directional anchor, installedon the shorter leg of L shaped profile

A typical arrangement of the above application is shown in the accompanying sketch (Figure-1, Exhibit 35.7) below. This is a modified arrangement wherein, by employing a tied Bellow (inthe shorter leg) the need of the Directional Anchor is eliminated. Owing to tie rods the bellowcan only absorb lateral deflection (other than its own axial growth) and hence the axial growthof shorter leg must be accommodated by the flexibility in the longer leg.



Uhde India Limited

DOC No. : 29040-PI-UFR-0035

Rev. : R0

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UNIVERSAL EXPANSION JOINT:

1.0 Bellow with tie rod installed in a Z shaped piping profile in a single plane

A typical arrangement of the above application is shown in the accompanying sketch below(refer Figure-1, Exhibit 35.8). Typically the assembly employs 2 Bellow elements tied across.The above bellow is purely lateral, and hence the axial expansion of the leg (excluding theexpansion of the Bellow itself) housing the Bellow is, required to be accommodated by theFlexibility of the adjoining legs. To prevent the longer legs from rotating necessary DirectionalGuides are provided as shown. The End Anchors are required to be designed as IntermediateAnchors only.


2.0 Bellow with tie rod installed in a Z shaped piping profile in two plane

A typical arrangement of the above application is shown in the accompanying sketch (referFigure-2, Exhibit 35.8) below. The arrangement is completely similar to that of the earliersituation except that the Bellow is subject to lateral deflection in a resultant plane derived fromthe magnitude of the 2 linear expansion components of the longer legs.



Uhde India Limited

DOC No. : 29040-PI-UFR-0035

Rev. : R0

Page : 10

3.0 Bellow with pantographic linkage

A typical arrangement of the above application is shown in the accompanying sketch (Figure-2, Exhibit 35.9) below. Owing to the limited space between the 2 directly connected equipmentnozzles the Bellow is required to absorb axial as well as lateral deflection. In such case theequipment nozzles must be designed to take the axial force due to Bellow imbalance area.The Pantographic linkage is provided to distribute the expansion between the 2 Bellows andcontrol their movements.

Figure 1 (Exhibit 35.9)

PRESSURE BALANCED EXPANSION JOINT

As it is evident from the forgoing discussion the axial thrust imposed by the imbalance area ofthe Bellow under internal pressure is a main concern in designing the Piping Systememploying such Bellows. The conventional method of designing such systems is by employingMain Anchors to absorb the above axial force. It is however not always practical (due tospace/ access constraints) to achieve these conventional solutions. The excessive magnitudeof the axial force could also become prohibitive in some instances. The Pressure BalanceBellow design, which basically is a combination of a Flow Bellow and a Balancing Bellow,comes handy in addressing many of such situations.

The working principle of the above Bellow relies on the fact that since both Flow andBalancing Bellow have identical cross sectional area, they will produce equal, but opposite indirection, forces under the same internal pressure. If the ends of these Bellows are locked toeach other by a suitably designed tie-rod, the above equal and opposite forces will cancel outto transmit no axial force on the end terminals of the connected piping. At the same time theabove tie rod will not interfere with the Flow Bellow in absorbing axial/ lateral deflections.

1.0 Single Element Bellow installed at the 90 O turning of a piping profile

The sketches below show a typical arrangement of 3 such applications (refer Figure-1,Figure-2 and Figure-3 of Exhibit 35.10). In all the 3 cases the Bellow is capable of absorbingprimarily axial movement along with a small amount of lateral movement. Since the axialthrust due to internal pressure is cancelled out between the two Bellows the system requiresonly Intermediate Anchors wherever applicable.


Uhde India Limited

DOC No. : 29040-PI-UFR-0035

Rev. : R0

Page : 11

Figure-1

Figure-2

Figure-3

Exhibit 35.10


Uhde India Limited

DOC No. : 29040-PI-UFR-0035

Rev. : R0

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2.0 In-line Pressure Balanced Bellow

A typical arrangement of the above application is shown in the accompanying sketch (Figire-1,Exhibit 35.11) below. The above arrangement is typically employed in the situations where thebellow is required to be, installed on a long line without the possibility of installing the MainAnchors. The common balancing Bellow effectively nullifies the imbalance axial force of the 2flow Bellows, at the same it allows the required deflection to be absorbed within the assembly.The piping end anchors are, therefore required to be designed as intermediate anchors only.

Figure – 1 (Exhibit 35.11)

3.0 Double Element Bellow installed at the 90 O turning of a piping profile for absorbinglarge lateral movements

A typical arrangement of the above application is shown in the accompanying sketch below.Where large amount of lateral deflections, are involved a Pressure Balanced Universal Joint(with tie rod) may best suit to the situation. By a proper design of the tie rods to rotate aroundits attachment points it is possible to absorb the lateral deflection by the combination of 2 flowbellows where as the balancing bellow is subject to only axial deflection.

Figure – 2 (Exhibit 35.11)

HINGED EXPANSION JOINT

Hinged expansion joints are usually used in sets of 2 or 3 elements to absorb lateraldeflection in one or more directions in a single plane. Each element of the assembly is subjectto pure angular rotation by its hinge pin. Each pair of bellow element connected by a segmentof pipe will act in unison to absorb lateral deflection in much the same way as universal joint ina single plane. The hinges are designed strong enough to take the axial pressure thrust andalso to transmit the piping deflections in a plane perpendicular to the plane of hinge rotation.The magnitude of the lateral deflection that could be absorbed by a hinged bellow is directlyproportional to the length of spool piece connecting the bellow elements.


Uhde India Limited

DOC No. : 29040-PI-UFR-0035

Rev. : R0

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1.0 Two Element Bellow

A typical arrangement of the above application is shown in the accompanying sketch (Figure-1, Exhibit 35.12) below. Since the axial pressure thrust is absorbed by the hinges the pipingend anchors need to be designed as intermediate anchors only. The position of the pipeguides on the axial pipes should provide adequate flexibility to absorb the expansion of theoffset leg housing the bellow.


2.0 Three Element Bellow

A typical arrangement of the above application is shown in the accompanying sketch (Figure-1, Exhibit 35.13) below. The above arrangement is typically employed in the situations wherethe flexibility in Z shaped profile (in a single plane) is not sufficient to absorb the thermalexpansion of the offset leg.



Uhde India Limited

DOC No. : 29040-PI-UFR-0035

Rev. : R0

Page : 14

GIMBAL EXPANSION JOINT

A typical arrangement of the above application is shown in the accompanying sketch (Figure-1, Exhibit 35.15) below. Just as hinged expansion joints offer a great capacity to absorb lateralexpansion in a single plane, the Gimbal Expansion Joints offer the same feature in a multipleplane system. Generally the ability of Gimble Joint to absorb the lateral movement in anyplane is best utilized by employing 2 of such bellows connected together by a pipe spool. Thestructure of the Gimble ic adequately designed to absorb the axial pressure thrust and hencethe piping end Anchors need to be designed as Intermediate Anchors only. Similar to hingedjoint the growth of the offset leg accomodating the bellows must be absorbed by the adjoiningpiping legs.

Figure-1 (exhibit 35.15)

5.0 SYSTEM DESIGN CONSIDERATIONS:

Following design considerations shall apply to the Piping System employing a Bellow.

• The design of the piping system employing a Bellow shall take into account therecommendations made by EJMA Standard.

• The specification for the Bellow shall as a minimum provide technical information as perSpecification Sheet given as Appendix-A of EJMA. The same is enclosed as attachmentto this chapter.

• The type of the Bellow shall be selected depending on the

Magnitude of the thermal movement of the connected pipingThe configuration of the piping profile in relation to the location of the Bellow.

• In general, caution shall be exercised in employing a Bellow in a piping system operatingunder cyclic loading condition (e. g. due to temperature cycle). If no solution is availableas an alternative to Bellow then the number of temperature cycles anticipated during thedesign life of the system shall clearly be indicated in the Bellow Specification for theVendor to confirm the Fatigue Life Expectancy.


Uhde India Limited

DOC No. : 29040-PI-UFR-0035

Rev. : R0

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• Under normal circumstances stress relieving or annealing shall not be specified for theBellow since the life of a Bellow greatly relies on its improved fatigue strength due workhardening of Austenitic Stainless Steel during the forming operation of the convolutes.

• The supporting of the piping system employing a Bellow shall be such that the movementof the connected piping at the Bellow ends is positively predictable. As a golden rule thesupporting system in relation to the location of the Bellow and the configuration of thepiping profile shall be similar to any one of the numerous examples given in Section 4 ofthis chapter based on EJMA recommendations. The support shall be adequatelydesigned for the highest pressure either during operation or hydro test condition.

• The Bellow shall not be subjected to Torsional Rotation.

• The Bellow material shall be compatible with the flowing medium. Specific considerationshall be given to the following.

• Series 300 Stainless Steel against Chloride Stress Corrosion.

• Nickel Alloys against Caustic induced Stress Corrosion.

• Nickel Alloys against presence of Sulphur.

• Compatibility of Bellow material against pipeline cleaning chemicals if they are dozed inthe piping system on regular intervals.

• Leaching of the Bellow material from the insulation material.

• Requirement of Internal Sleeves shall be specified in an application involving fluidvelocities which, can induce resonant vibrations. The evaluation of acceptable flowvelocity limits (based on EJMA, Section C-3) is covered in Section (Internal SleeveRequirement) of this chapter. The sleeves are normally installed in the direction of flow.However in case back flow is anticipated during operation the same shall then behighlighted clearly in the Specification to allow the Bellow manufacturer to provide extraheavy sleeve and thereby preventing a possible damage of the Bellow resulting from thebuckling of the sleeve.

• The Design Pressure of the Bellow shall be based on the actual maximum workingpressure of the pipeline under question. No ad-hoc cushion shall be allowed in specifyingthe Design Pressure.

• The Hydraulic Test Pressure of the Bellow shall be 1.5 times the design pressure (1.1times in case of pneumatic test pressure) with due allowance for temperature correctionfactor. However the Test Pressure calculated in the above manner must not producemembrane stresses in excess of Yield Strength at room temperature.

• The Maximum, Minimum and Installation temperature shall be specified accurately and asuitable pre-compression of the Bellow shall be considered and specified accordingly ifambient temperatures may vary significantly during pipeline construction. The aboveaspect is addressed in Section (Bellow Pre-Compression) of this chapter in detail basedon EJMA recommendation (Section B-2.1.2 and B-2.1.3)

• The Insulation Guard Sleeve shall be specified in case of insulated Bellows.

• The displacements to be absorbed by the Bellow shall be based on the expected pipinggrowth including the terminal movements. In addition to the above the specifieddisplacements shall also account for the following eventualities:


Uhde India Limited

DOC No. : 29040-PI-UFR-0035

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• The actual metal temperature of the piping may not necessarily attain the designtemperature used for calculation of the expected thermal growth of the piping.

• The installed location of the Piping Supports (e.g. guides/ anchors etc.) in the field maynot necessarily be exactly in accordance with the design.

• The temperature range attained during actual operation cycle may not necessarily beexactly same as anticipated in the design.

• The Bellows when handling process fluids which can solidify or scale to pack theconvolutions shall be provided with necessary means to avoid the same. Use of internalsleeve, purge connections (for gas/ vapour mediums) and drip hole (for trapped liquid) aresome of the ways to achieve the same.

• Depending on the severity of the process/ design condition the Bellow may be specifiedwith extra safety features as below:

• Extra heavy external cover which would impede the effect of the jet/ splash of escapingfluid in case of a Bellow failure.

• Limit Rods employed from the consideration of dynamic loading can be designed forrestraining the pressure thrust in case of a an anchor failure.

• A two-ply or concentric double shell Bellow with both the ply’s capable of withstanding thefull line pressure.

• It is normally a good practice to provide a sketch of the piping system with details of allsupports and other design data as part of the Bellow Specification for establishing a clearunderstanding with the Bellow Manufacturer.

• The supports on a piping system employing a Bellow shall have clear space around thesupports to allow access for their inspection during hydro test and during plant operation.

6.0 INTERNAL SLEEVE REQUIREMENT:

• Internal sleeves are recommended when it is necessary to reduce the system pressure

drop to minimum.

• Internal sleeves are recommended when flow velocities exceed the following values.

• Air, steam and other gases:

Up to 6” diameter 4 ft/ Sec./ inch of diameter.Over 6” diameter 25 ft/ Sec.

• Water and other Liquids:•

Up to 6” diameter 2 ft/ Sec/ inch of diameterOver 6” diameter 10 ft/ Sec.

Note:When turbulent flow is generated within 10 pipe diameter of the Expansion Joint by use ofvalve, tee, elbow or cyclonic devices the actual flow velocities should be multiplied by 4before applying the above criteria.


Uhde India Limited

DOC No. : 29040-PI-UFR-0035

Rev. : R0

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• An internal sleeve shall be provided when flow velocities exceed 75 % of the value of the

resonant velocity calculated based on the following equation

∨ = (0.81 * σ √ ksr / W) / Cν

where

σ = inside convolution width (inch)

W = Weight of Bellow including reinforcement (lbs.) and including weight of liquid

contained between convolutions if applicable.

Ksr = Overall Bellow Spring Rate (lbs./ inch) - data supplied by Bellow manufacturer

Cν = Correlation factor as per Fig C16 of EJMA (for U shaped convolutions Cν = 0.22)

• The Bellows when used in a fluid service carrying Crystals (e.g. slurry service) shall be

provided with internal sleeve to avoid any possibility of erosion.

7.0 BELLOW PRE - COMPRESSION:

On certain occasions when the piping system employing a bellow is required to function in awide band of operating temperature (i.e. to swing on both sides of the installationtemperature) the bellow will require to be designed to absorb both axial compression as wellas expansion. It is however possible in such situations, to specify a bellow with axialcompression only by suitably pre-compressing the bellow, as illustrated in the followingexample.

Example:

Given a 150 Feet of Carbon Steel straight pipe operating between 25 O F and 375 O F(installation temperature to be considered as 70 O F.

Expansion Rate at 375 O F = 2.48 in./ FootExpansion Rate at 25 O F = -0.32 in/ Foot

Total change in length of pipe = 150 * (2.48+0.32)/ 100= 4.2 inches

The above change in length is made of 2 components

• Contraction of pipe from its installed condition when operating at 25 O F to causeexpansion of the bellow by an amount of 0.48 inches (i.e. 0.32*150/100)

• Expansion of Pipe from its installed condition when operating at 375 O F to causecompression of the bellow by an amount of 3.72 inches (i.e. 2.48*150/100)

Assuming that we select a bellow with Rated Movement of 5 inches.

The required pre-compression of the bellow = 5 * 0.48 / 4.2= 0.57

In general terms the above pre-compression can be expressed by following expression:


Uhde India Limited

DOC No. : 29040-PI-UFR-0035

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Pre-compression

= (Rated Movement) * (Exp. Coeff. At T inst - Exp. Coeff. at T min)Exp Coeff. at T max – Exp. Coeff. at T min

piping bellows expansion joints

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