What is an expansion joint
Expansion joint is device containing a bellow membrane that are designed to absorb dimensional changes, such as those that occur due to thermal expansion or contraction of a pipeline, duct or vessel.
The need to solve the problems of thermal expansion are not unique to anyone industry therefore expansion joints are used in a wide variety of market sectors specifically where there is a need to control the movement of pipelines due to changes in temperature. Thermal expansion problems can be solved where the natural flexing of the pipe is practical or where it is possible to install pipe loops however this is not always possible due to economic reasons or the design of modern structures are not capable of taking the loads of flexing pipework. In these situations the design engineer must seek an expansion joint solution.
Types of Expansion Joints
- Simple Expansion Joint
- Universal Expansion Joint
- Hinged Expansion Joint
- Pressure Balanced Expansion Joint
- Gimbal Expansion Joint
- Sleeve Type Expansion Joints
- Ceramic lined pipe expansion joints
- Metallic Pipe Expansion Joints
- Pipe expansion joints
Bellows are the illustrations of the typical situations for employing Simple Expansion Joint type of Bellows depending upon the application and configuration of the piping profile.
Simple Expansion Joint:
The main use of single expansion joint in a piping system is to absorb axial & small amount of lateral & angular movements in which it is installed.
Simple Expansion Joint
A. Expansion Joint for absorbing axial displacement:
1. Single Element Bellow installed in a straight line
A typical arrangement of the above application is shown in the accompanying sketch(Figure-2) 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.
Single Element Bellow installed in a straight line
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-3) below. The application of this type is normally not recommended and will performsatisfactory only within certain limits. The axial pressure thrust of the Bellow is transmitted tothe 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.
Single Element Bellow installed in a straight line with an offset
3 Double Element Bellow employing an intermediate anchor in the middle when installed in a straight line
A typical arrangement of the above application is shown in the accompanying sketch(Figure-4) below. The arrangement is generally employed in the situations where the linearexpansion 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.
Double Element Bellow employing an intermediate anchor in the middle when installed in a straight line
4 Double Element Bellow employing a main anchor in the middle, installed in a straight 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-5) below. The arrangement is similar to that of Double Element Bellow on a straightpipeline except that the middle anchor between the 2 Bellow Elements is required to bedesigned as Main Anchor for the differential axial thrust of the 2 Bellows employed on eachside of the Reducer.
Double Element Bellow employing a main anchor in the middle, installed in astraight line at the interface of changed line size
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-6) below. The middle anchor between the 3 Bellow Elements in this case is requiredto be designed as Main Anchor for the axial thrust imposed by the Bellow of the branch pipe.
Three Element Bellow employing a main anchor in the middle, installed at thejunction of the branch connection
B. Expansion Joint for absorbing lateral movement, angular rotation and combined movement:
1. Single Element Bellow employing a directional anchor, installed in the longer leg of L shaped piping profile
A typical arrangement of the above application is shown in the accompanying sketch(Figure-7) below. The Bellow is located at 1 end of the longer leg and thereby absorbing thelinear expansion of the longer leg as axial displacement. The Main Anchor near the Bellow isa Directional Main Anchor (DMA), which prevents the pipe end from moving axially, at thesame time allowing the expansion of the shorter leg, which is absorbed by the Bellow as alateral deflection. The Anchor on the shorter leg is required to be designed, only asIntermediate Anchor. The remaining arrangement of the First and Second Alignment Guidesand rest of the Intermediate Guides remains similar to that of the Bellow installed in a straightline to prevent the straight pipe of the longer leg from rotating/ buckling.
Single Element Bellow installed in the longer leg of L shaped piping profile
2. Single Element Bellow employing a directional anchor, installed in the shorter leg of L shaped piping profile
A typical arrangement of the above application is shown in the accompanying sketch(Figure-8) below. The Bellow is located in the shorter leg and thereby absorbing the linearexpansion of the longer leg as lateral displacement. The Main Anchor near the Bellow is aDirectional Main Anchor (DMA), which prevents the pipe end from moving axially, at the sametime allowing the expansion of the long leg, which is absorbed by the Bellow as a lateraldeflection. The Anchor on the longer leg is required to be designed, only as IntermediateAnchor. Only 1 Guide is required on the longer leg for alignment purpose.
Single Element Bellow installed in the shorter legof L shaped piping profile
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-9) below. This is a modified arrangement wherein, by employing a tied Bellow (in theshorter leg) the need of the Directional Main Anchor (DMA) is eliminated. Owing to tie rods thebellow can only absorb lateral deflection (other than its own axial growth) and hence the axialgrowth of shorter leg must be accommodated by the flexibility in the longer leg.
Single Element Bellow employing a tie rod in place of a directional anchor, installedon the shorter leg of L shaped profile
Expansion joints come in two forms either restrained or unrestrained styles and although the bellows membrane incorporated in both styles look similar it is of great importance to recognize that they are used for entirely different applications.
Unrestrained expansion joints accommodate pipe movement by compressing and /or extending along their axis and hence they are also known as axial expansion joints. Axial expansion joints are very compact, adaptable and relatively inexpensive. Generally axial expansion joints are designed to accommodate movements between 25mm and 75mm however special bespoke expansion joints can be manufactured to suit specific site conditions. They must be suitably anchored and guided so as to prevent damage from the forces imposed on the pipework system. An installation with unrestrained expansion joints is called a non-pressure balanced solution
Restrained expansion joints are fitted with tie bars and / or hinges and therefore preventing the joint from moving axially. There are several expansion joint models that fall into the restrained group of expansion joints and are called Lateral, Fully Articulated, Hinged or Gimbal. The benefits of installing these types of expansion joints are that anchor forces are generally lower than installing unrestrained bellows and therefore savings can be made when selecting suitable anchors and guides. Restrained expansion joints are used in more complex pipe arrangements specifically on equipment where forces have to be kept to a minimum and, there is a requirement to take up large movements. Although retrained expansion joints are more expensive than unrestrained units significant cost savings on the total installation can be made due to reduced anchor and guide costs. An installation with restrained expansion joints is called a pressure balanced solution
The difference between metallic and rubber expansion joints
Metallic expansion joints prevent damage from thermal expansion, vibration and other movements such as building settlement. Metallic expansion joints are generally manufactured from stainless steels or for more demanding environments or extreme conditions can be produced in materials such as Inconel, Incoloy, Hasteloy and Monel.
Expansion joints can also be produced from a variety of synthetic rubber materials such as ethylene propylene diene monomer (EPDM), Nitrile, Hypalon and Viton materials. Rubber expansion joints are primarily used on pumps, chillers and other reciprocating machinery to reduce noise and vibration. Whilst rubber bellows have the capabilities of compensating small amounts of axial, lateral and angular pipe work movement Yaang always recommend a specifically designed metallic expansion joint to accommodate pipe movements when solving thermal expansion problems.
Are expansion joints the same as movement joints?
Expansion joints – sometimes called expansion bellows, flexible joints, compensators or movement joints. The variety of terminology for the same piece of equipment can be misleading. However expansion joints are designed to safely absorb dimensional movement changes and therefore the different names given to this critical unit are all related to its ability to accommodate a variety of movements such as expansion & contraction due to temperature difference, vibration due to reciprocating machinery, installation misalignment or building settlement.
Complying with the highest standards
At Yaang, we offer a vast selection of expansion joints to serve a variety of purposes and are always on hand to provide you with accurate, high-quality advice whenever you require it. Our range of expansion joints includes axial, lateral, angular and gimbal joints. Our expansion joints are designed and calculated to the latest prevailing standards and pressure directives and therefore where applicable conform to latest Expansion Joint Manufacturers Association (EJMA) calculations. We reserve the right to make changes in the technical calculations without notice. All products are supplied with detailed installation and maintenance instructions where applicable to ensure your pipework system is fully in accordance with recommended engineering practice.
Find the right expansion joints for your needs
We oversee a large amount of stock, which ensures we can minimise downtime and respond to your requests quickly. We can supply joints with a bespoke flexible lagging jacket if needed. Why not contact us today if you do have any queries about the products that we supply? More and more discerning clients are heading straight to Yaang when they do require expansion joints of the highest quality. We are renowned for only supplying products of the highest quality that do the job to the best standard possible and are more than happy to talk you through the options available so you can easily come to an informed decision and invest in the products that are right for you.
Universal expansion joints contain two bellows with multiple convolutions joined by a center pipe or spool. These joints, also known as double or tandem bellows expansion joints are used for the purpose of absorbing any combination of axial, lateral, or angular movements in a piping system.
When lateral movements are too excessive for a single axial expansion joint to accommodate or when there is a limitation on the amount of lateral forces allowed on the connecting piping or equipment, universal expansion joints are installed to accommodate these movements.
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-10). Typically the assembly employs 2 Bellow elements tied across. The above bellow is purely lateral, and hence the axial expansion of the leg (excluding the expansion of the Bellow itself) housing the Bellow is, required to be accommodated by the Flexibility of the adjoining legs. To prevent the longer legs from rotating necessary Directional Guides are provided as shown. The End Anchors are required to be designed as Intermediate Anchors only.
2.0 Bellow with tie rod installed in a Z shaped piping profile in two planes
A typical arrangement of the above application is shown in the accompanying sketch (refer Figure-11) below. The arrangement is completely similar to that of the earlier situation except that the Bellow is subject to lateral deflection in a resultant plane derived from the magnitude of the 2 linear expansion components of the longer legs.
3.0 Bellow with pantographic linkage
A typical arrangement of the above application is shown in the accompanying sketch (Figure-12) below. Owing to the limited space between the 2 directly connected equipment nozzles the Bellow is required to absorb axial as well as lateral deflection. In such case the equipment 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 and control their movements.
Hinged expansion joints are usually used in sets of 2 or 3 elements to absorb lateral deflection in one or more directions in a single plane. Each element of the assembly is subject to pure angular rotation by its hinge pin. Each pair of bellow element connected by a segment of pipe will act in unison to absorb lateral deflection in much the same way as universal joint in a single plane. The hinges are designed strong enough to take the axial pressure thrust and also 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 directly proportional to the length of spool piece connecting the bellow elements.
1.0 Two Element Bellow
A typical arrangement of the above application is shown in the accompanying sketch (Figure-18) below. Since the axial pressure thrust is absorbed by the hinges the piping end anchors need to be designed as intermediate anchors only. The position of the pipe guides on the axial pipes should provide adequate flexibility to absorb the expansion of the offset leg housing the bellow.
2.0 Three Element Bellow
A typical arrangement of the above application is shown in the accompanying sketch (Figure-19) below. The above arrangement is typically employed in the situations where the flexibility in Z shaped profile (in a single plane) is not sufficient to absorb the thermal expansion of the offset leg.
The pressure balance expansion joint or bellow design, which basically is a combination of a Flow Bellow and a Balancing Bellow, comes handy in addressing many situations.
The axial thrust imposed by the imbalance area of the Bellow under internal pressure is a main concern in designing the Piping System employing such Bellows. The conventional method of designing such systems is by employing Main Anchors to absorb the above axial force. It is however not always practical (due to space/ access constraints) to achieve these conventional solutions. The excessive magnitude of the axial force could also become prohibitive in some instances.
The working principle of the above Bellow relies on the fact that since both Flow and Balancing Bellow have identical cross sectional area, they will produce equal, but opposite in direction, forces under the same internal pressure. If the ends of these Bellows are locked to each other by a suitably designed tie-rod, the above equal and opposite forces will cancel out to transmit no axial force on the end terminals of the connected piping. At the same time the above 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-13, Figure-14 and Figure-15 below. In all the 3 cases the Bellow is capable of absorbing primarily axial movement along with a small amount of lateral movement. Since the axial thrust due to internal pressure is cancelled out between the two Bellows the system requires only Intermediate Anchors wherever applicable.
2.0 In-line Pressure Balanced Bellow
A typical arrangement of the above application is shown in the accompanying sketch (Figure-16) below. The above arrangement is typically employed in the situations where the bellow is required to be, installed on a long line without the possibility of installing the Main Anchors. The common balancing Bellow effectively nullifies the imbalance axial force of the 2 flow 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.
3.0 Double Element Bellow installed at the 90 O turning of a piping profile for absorbing
large lateral movements
A typical arrangement of the above application is shown in the accompanying sketch Fig.17 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 around its attachment points it is possible to absorb the lateral deflection by the combination of 2 flow bellows where as the balancing bellow is subject to only axial deflection.
The gimbal pipe expansion joint is basically same as the hinge type, except that instead of being limited to deflection in only one plane gimbal Expansion Joints are used to absorb angular rotation in any plane, using two pairs of hinges attached to a common floating gimbal ring.
Gimbal systems generally consist of two gimbal expansion joints or two gimbal and one hinged expansion joint/bellow.
The advantages of this type of construction is it provides a close control over the movement imposed up on the bellows and also supports the dead weight of the pipe.
In addition, the wind and shear loads are also taken care of by the gimbal structure.
Gimbal bellows joints are designed to absorb the full pressure thrust load of the expansion joint and thus guard the adjacent equipment from damage due to thrust loading.
Since gimbal bellows joints are not restricted to a single plane they offer greater flexibility of usage.
The use of gimbal bellows joints results in the best system which eliminates the effects of thermal growth and lowers both reaction forces and installation costs. Expensive main anchors are eliminated and only minimal guiding is required.
A typical arrangement of the above application is shown in the accompanying sketch (Figure-20) below.
Just as hinged expansion joints offer a great capacity to absorb lateral expansion in a single plane, the Gimbal Expansion Joints offer the same feature in a multiple plane system. Generally the ability of Gimble Joint to absorb the lateral movement in any plane is best utilized by employing 2 of such bellows connected together by a pipe spool. The structure of the Gimble is adequately designed to absorb the axial pressure thrust and hence the piping end Anchors need to be designed as Intermediate Anchors only. Similar to hinged joint the growth of the offset leg accommodating the bellows must be absorbed by the adjoining piping legs.
Main features of Gimbal Expansion Joint:
- Permits angular movement in any plane
- Eliminates pressure thrust forces
- Transmits shear and wind loads, so low forces on the pipe anchors
- No main anchors required
- Prevents torsion or twisting of the expansion joint
- Internal ﬂow liners for eliminating velocity problem
- Anchors only required to absorb spring forces
- Low forces on piping system
Advantages of Gimbal Expansion Joint:
- Absorbs angular movements in all planes and angular rotations, or any combinations of these
- Eliminates pressure thrust loads
- Positive control over the movements
- Supports dead weight of the intermediate piping
- Transmits external loads like wind loading and shear loading
- Prevents torsion on the bellows elements
- Guiding requirement is minimized
- Eliminates main actors
Limitations of Gimbal Expansion Joint:
- More space is required for gimbal bellows joints as compared to axial expansion joints
- Change of pipe direction is required
- Two or more gimbal expansion joints required to work as a system
Applications of Gimbal Expansion Joint:
- Steel mills
- Petro Chemical
- Power Generation
- Shipbuilding industry
- Water treatment
- Cement plants
- Paper industry
Sleeve Type Expansion Joints are primarily designed to compensate for thermal expansion but it is not the only movement being imposed on the pipeline system.
Sleeve Type Expansion Joints
With stainless steel
Other types of movements can occur that need to be taken into account when providing a pipework flexibility solution such as building settlement, wind loading, vibration from rotating and reciprocating machinery.
Inner size measurment
Expansion joints with stainless steel bellows
Metallic expansion joints are designed to safely absorb the dimensional changes of pipework systems and ducts caused by heat induced expansion and contraction. They are essential in pipework systems that are used to convey substances of a high temperature, such as steam, heated water or exhaust gases.
Expansion joints can also be designed for other applications, such as noise and vibration caused by reciprocating machinery, building settlement and in some extreme environments earthquake movement. Expansion joints are very important components with in a pipework system as they not only solve the problems associated with pipework movement but offer such advantages as reducing stresses and loads to connecting equipment such as pumps and steam turbines.
Specifications & size range of ceramic lined pipe
Hoop strength is the resistance against radial pressure. The strength of the ceramic -lined steel composite pipe is 300 to 500MPa.
Wear-resisting comparative table of ceramic lining pipe
|Sand injection test||30% Transfer test of sludge with SiO2|
Main Properties of Ceramic
|Content of Alumina||≥95%|
|Rockwell Hardness||≥80 HRA|
|Impact Strength||≥850 Mpa|
|Coefficient of Linear Thermal Expansion||20W/m.K|
Ceramic layer Ceramic Lined Reducer Pipe with flange reducer Al2O3 content greater than 95% , micro-hardness HV1000-1500, which has a high abrasion resistance, wear resistance than ten times higher than carbon steel after quenching , superior tungsten carbide drill.
1, coal pulverizing system of power plant pipeline, including, powder transmission pipeline, thick powder separator pipeline, coal drop pipe, combustion system of a wind pipe, a secondary air pipe, three pipeline and burner pipelines, in addition to ash slagging system the discharge pipe, powder pipe, dry ash conveying pipe;
2, iron and steel plant raw material conveying pipeline, collecting pipe, dust pipe, ash pipe, ash pipe, mixing pipe, grinding export pipeline, coal pipeline, coal pipeline, separator pipe, burner radius pipe, etc.;
3, cement plant selection machine outlet pipe, choose machine inlet pipe, pipe dust pipe, vertical mill outlet pipe, circulating air duct, high temperature air blower, lower material pipe, etc.;
4, petroleum, chemical, mining, coal, coal washing plant, smelting, paper, aluminum, building materials, powder engineering, food machinery and other processing and conveying material pipe.
Ceramic materials are neutral , chemically stable , has excellent corrosion resistance and acid resistance , resistant to various inorganic acids, organic acids , organic solvents , and its degree of corrosion of stainless steel is more than ten times.
Temperature above 2000celsius degree, long-term work in the range of -50 -900 celsius degree.
Ceramic adjustable tube can be welded , flanged , flexible connectors and other fast way links , very easy to install.
Clean and easy maintenance
Smooth wall, can prevent scaling , fouling, self-cleaning function. Tightness.
1． Under the direction of the arrow diagram for the export direction.
2． Bend radius is usually 1.5-5 times the diameter of steel pipe (1.5-5D).
3． Othe specifications of the compsite pipe can be manufactured accord to the user requirments.
4． The weight is caculate by theoretics, maybe have some tolerance, the real weight will be weigh in afer them finished.
Hoop strength is the resistance against radial pressure. The strength of the ceramic -lined steel composite pipe is 300 to 500MPa.
Metal pipe expansion joints can withstand the design temperatures, pressures, as well as, provide the capacity necessary to absorb thermal growth of the piping system.
The thermal movement required can be axial, lateral or angular. In some cases, the pressure thrust of a pipe expansion joint must be restrained by the use of tie rods, hinges or gimbal while allowing the bellows to move through its design deflections.
Expansion joints with stainless steel bellows
Yaang offers a wide range of expansion joints, suitable for numerous specific applications.
The Yaang expansion joints portfolio basically consists of three main series:
- Standard series: expansion joints up to DN 150 (6″)
- Industrial series: expansion joints up to DN 1.000 (40″)
- Special series: expansion joints >DN 1.000
The heart of all expansion joints is the metal bellows. Thanks to modern design and manufacturing facilities, all BOA expansion joints offer the following advantages:
- High flexibility
- Short build length
- Large movement capacity
- Durability and excellent chemical resistance
Metallic Expansion Joints Installation Guide
1. Store expansion joints in a dry/cool location such as a warehouse.
2. Store flange face down on a pallet or wooden platform.
3. Do not store other heavy items on top of expansion joint (s).
4. Ten-year shelf life can be expected with ideal conditions.
Do not lift with ropes or bars through the bolt holes. If lifting through the bore, use padding or a saddle to distribute the weight. Do not let expansion joints sit vertically on the edges of the flanges for any period of time. Do not lift on the shipping restraints.
Make sure the expansion joint rating for temperature, pressure, movements, and selection of materials match the system requirements. Contact the manufacturer if the system requirements exceed those of the expansion joint selected.
Expansion joints are not designed to make up for piping misalignment errors. Check with the manufacturer if piping misalignment is present.
The main function of expansion joints is to compensate for axial pipe thermal expansion. Metal expansion joints must have the protection of adequate anchoring against the internal and thrust pressures of the media to prevent damage. Anchoring must be installed as close to the down stream end of the expansion joint as possible, with the originating equipment serving as the opposite anchor. Anchors must prevent pipe movement in any direction. Hangers or pipe pedestals cannot be considered to be anchors as they offer no restriction against side or end motion.
When designing an anchor for a metal expansion joint, consult the internal thrust force table from the appropriate expansion joint catalogue. The weight of piping, valves, and media, as well as the resistance of the piping to deflection, must be included as part of the design weight and strength of an anchor.
Anchors are required whenever a piping system changes direction. Expansion joints should be located as close as possible to anchor points. For additional expansion joint protection, it is recommended that control rods be installed on the expansion joint to prevent excessive movements from occurring due to pressure thrust of the line.
Expansion joints must be properly guided and anchored in accordance with EJMA standards.
Piping must be supported so expansion joints do not carry any pipe weight.
Install the expansion joint flange against the mating pipe flanges and install bolts so that the bolt head is against the expansion joint flange. Bolts should be installed from the bellows side (so that the bolt heads are adjacent to the bellows) to insure that the bolts do not interfere with the bellows during periods of compression. Flange-to-flange dimensions of the expansion joint must match the required opening.
Make sure mating flanges are clean and are matched to the type supplied with the expansion joint. Gaskets of appropriate material, size and temperature ratings must be used in all flange-to-flange type installations.
Tighten bolts in stages by alternating around the flange. Never tighten an expansion joint to the point that there is
metal-to-metal contact between the expansion joint flange and the mating flange.
The expansion and compression movements are preset at the factory. The shipping restraints protect the expansion joint in its neutral position prior to installation. Remove the shipping restraints after installation and before hydro-testing the system.
1. Insulation or thermal blankets over a metal expansion joint should be supplied by the expansion joint manufacturer to preclude the use of corrosive chloride bearing insulation materials. Insulation should be installed to permit easy access to the flange area, to check bolting.
2. Do not weld in the near vicinity of a non-shrouded expansion joint without protecting the expansion joint from damaging weld splatter.
3. If an expansion joint is to be installed underground, or will be submerged in water, contact the manufacturer for specific guidelines.
4. Consider ordering a spare expansion joint. The cost of downtime of a critical expansion joint far exceeds the cost of a spare unit placed and protected in reserve on-site.
5. Whenever possible, install the expansion joint next to an anchor as indicated below not exceeding maximum distance to the 1st guide with at least two concentric pipe guides on the opposite side of the joint. Added guides are required to prevent bowing or bending of the pipe.
6. When an expansion joint is placed elsewhere in the line, at least two concentric guides must be used on each side of the joint with added joints installed as recommended in pipe guide spacing diagram.
7. The inside of all piping must be clean before installing and testing the expansion joints. Expansion joints should not be subjected to hydrostatic pressure tests beyond their rated working pressure.
8. Secure all anchors and guides before testing. Remove shipping bars prior to testing.
9. Expansion joints must be removed from the lines while the system is being tested hydrostatically at pressure exceeding allowable working pressure.
10. Expansion Joints fabricated with flow liners must be installed with the flow arrow pointing in the same direction of the media flow.
11. Single externally pressurized expansion joints must be installed with the moving end adjacent to the moving end of the pipe responding to the thermal expansion induced during system heat-up.
12. Failure to install according to instructions will void warranty.
Pipe expansion joints are also known as compensators, as they ‘compensate’ for the thermal movement.
Pipe expansion joints are necessary in systems that convey high temperature commodities such as steam or exhaust gases, or to absorb movement and vibration. A typical type of expansion joint for pipe systems is a bellows which can be manufactured from metal (most commonly stainless steel), plastic (such as PTFE), or an elastomer such as rubber.
A bellows is made up of a series of one or more convolutions, with the shape of the convolution designed to withstand the internal pressures of the pipe, but flexible enough to accept the axial, lateral, and/or angular deflections. Expansion joints are also designed for other criteria, such as noise absorption, anti-vibration, earthquake movement, and building settlement.
Piping Expansion Joint Construction
Tube – A protective, leak proof lining made of synthetic or natural rubber. The tubes primary function is to eliminate the possibility of materials being handled penetrating the carcass.
Carcass – The carcass or body of the expansion joint consists of fabric, and when necessary metal.
Cover – The exterior surface of the joint.
Fabric Reinforcement – The carcass fabric reinforcement is the flexibility and supporting member between the tube and cover.
Metal Reinforcement – Wire or solid steel rings imbedded in the carcass, often used for strengthening.
Retaining Ring – Used to compress the expansion joint flange to the mating flange to create a seal. Also called clamp bars or backing bars. Applies to most all expansion joints.
Mating Flange – Used to connect the pipe joint to the pipe in which it is being installed.
Control Rod – Used to limit the axial movements during operation, and prevent the joint from exceeding its movement capabilities. The rods attach the mating flange and expansion joint. Typically used on piping joints, but can be installed on most any joint when required.
Expansion joints are an assembly designed to safely absorb sound, expansion, con traction and vibration to ensure expansion jointsthat the application stays in fully working order.
When we apply this technique to pipe systems, we brand the term ‘pipe expansion joint’ or ‘bellows’.
These pieces of equipment are used in pipe work where movement, thermal expansion and much more could cause problems. The pipe expansion joints are made up from one or more convolutions, which are designed to move or expand to relieve the stress from the solid pipe. The amount of movement or expansion within the application will determine the number and shape of convolutions required. Expansion joints can be manufactured from a range of different materials, from stainless steel and PTFE, to rubber.
Pipe expansion joints are also designed for other criteria, such as noise absorption, anti vibration, earthquake movement and building settlement. Metal expansion joints have to be designed according to rules. Pipe expansion joints are used in a number of industries, including; oil, petrochemical and paper industries.
Pipe expansion joints are often manufactured to withstand temperatures from minus 300°F, up to 4000°F, as well as being able to resist at full vacuum or 2000 psig. Expansion joints can be manufactured from a range of different materials aforementioned. Before the introduction of pipe expansion joints, engineers were battling with the task of combating problems regarding thermal expansion, corrosion and abrasive factors that took effect on the functionality of various applications. Fabric joints can be used in a number of applications for turbines and pipelines, which can defend against resistance, heat and a range of other environmental factors.
Pipe expansion joints are crucial components in the pipe technology sector, which serve a huge number of industries. They are used to counterbalance length changes that generally occur in pipelines from temperature changes and can also absorb vibrations. It is a cost effective solution to increase the life span, reliability and costs of many applications through equipment and process management.
Application of Expansion Bellows:
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.
EXPANSION JOINT 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 internaldiameter D capped at its both ends and subject to an internal pressure P (refer Fig.-1Abelow). The longitudinal Pressure Force acting at each capped end is:
Pf = πPD 2 / 4
The above longitudinal force is carried in tension in the Pipe wall and the system remainsstable with the opposite and equal force acting at the capped end balancing each other. Nowlet us introduce a Bellow in the middle of the above pipe section (refer Fig 1B). Since the above Bellow does not have any appreciable longitudinal stiffness it will tend to straighten outas shown in Fig 1C below resulting into rapture of the convolutes. It is therefore necessary toprovide end anchors (refer Fig 1D below) to counter the pressure force acting at the endsand thereby stopping the bellow convolute from flattening. The magnitude of above force willbe combined longitudinal force acting at the Bellow inside diameter and the imbalancepressure thrust acting on the side-wall, of the convolute.
The net Pressure Thrust to be absorbed by the End Anchors, due to incorporation of the bellow in a straight pipe line, therefore it based on the Mean Diameter of the bellow and isgiven by
pπDm 2 / 4 where :
- Dm = Mean Diameter of the bellow
- P = System internal pressure.
Expansion joints have rectangular sections and waveform with similar shape. A single expansion joint in the pipe bears two-dimensional displacement. The pipeline comprising two expansion joints can bear three-dimensional displacement. Metal expansion joints could be classified into full-height expansion joints and half-height expansion joints.
1. After the user pick the appropriate expansion joint in accordance with the thermal displacement of the piping system, they have to provide details about the medium from the pipe, design pressure of the duct, the greatest temperature during operation, the general dimension of sections of the duct, the chosen waveform and the quantity of the waveform to be able to design and manufacture structure of expansion joints.
2. The maximum allowable expansion of each waveform
Full-height type: △α = ± 24 mm Half-height: △α = ± 12 mm.
3. The ash board: For pipes with less dust, the ash board doesn%u2019t need to be utilized for flue pipes with much dust, the ash board ought to be adopted.
4. In order to reduce the number of the waveform, we have to take into account the cold-drawn process for expansion joints.
5. Expansion joints are suitable for pipes whose cross-sectional areas are less than 4.6 square meters and one side of the overall dimension of the air and flue gas duct which is less than 1.5m but greater than 0.6 mm. Standard full-height expansion joints can be applied to all air and flue gas ducts.
Source: China Expansion Joints Manufacturer – Yaang Pipe Industry (www.steeljrv.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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