Axial Expansion Joint is the simplest form of expansion joint. A flexible element either with flange end or Butt Weld End to absorb any combination of three basic movements. i.e. Axial movement (Compression / Extension) in its longitudinal axial direction. Lateral deflection and Angular rotation can be accommodated.
These Axial expansion joints do not restrain the internal pressure thrust, The piping must have the system with separate anchoring and guiding to resist the pressure thrust. Where small thermal movements are involved and proper anchoring and guiding are feasible, a single metal expansion joint is the most economical installation.
Hinged Bellows, either Axial or Universal type, are designed to absorb angular rotation in one plane only by the use of a pair of pins through hinge plates attached to the expansion bellows.
A single bellows with overall length restrained by hinge hardware designed to accommodate pressure thrust. A hinged expansion joint allows angular movement in a single plane.
Hinged Expansion Bellows should be used in sets of 2 or 3 to function properly. Hinged Bellows are normally prevented by their design from deflecting axially, either an extension or compression. The hinge mechanism is usually designed to accept full pressure thrust and also shear loads such as from the weight of the adjacent piping, can be accepted by these type of expansion joints thereby doing away with provision of additional supports and anchors.
Hinged Bellows also have added benefits of positive control over the movements, eliminates pressure thrust forces, transmits external loads, prevents torsion on bellows and are the most efficient in absorbing of thermal deflections.
Double Bellows are the type of expansion joints where two bellows are provided. The use of these expansion joints is for applications where absorption of high thermal expansion or contraction of straight pipe runs is desired. The joint can be located near the centre of the run, and proper anchors and guides have to be provided. Each Bellows in this case act as a single expansion joint.
Two bellows separated by a pipe spool with overall length restrained by hinge hardware designed to contain pressure thrust. A hinged universal expansion joint accepts large lateral movements in a single plane with very low spring forces.
Gimbal Bellows which can permit angular rotation in any plane, consist of two pair of hinges affixed to a common floating gimbal ring. The Gimbal Bellows Expansion Joints are similar to Hinge type except that unlike Hinged Bellows which are limited to deflection in only one plane, Gimbal Bellows can accept bending or angulations in any plane.
A single bellows and gimbal hardware designed to resist pressure thrust. The gimbal expansion joint hardware operates like the universal joint on a drive shaft to accommodate angular movements in any plane.
Universal Gimbaled Expansion Joints are similar to the hinged universals except that the two expansion joints are gimbal type. The advantage of this arrangement is the ability of the expansion joint to accept large lateral movements and independent angular movements in any plane.
It contains two hinge pins, the axis of each being perpendicular to the other. Each set of pins is connected to each other with a central gimbal ring. It provides similar restraint and resistance to axial forces such as the pressure thrust and to shear forces as the hinge type apart from having other features like absorbing angular rotation, preventing torsion on bellows and no main anchors required.
Rectangular joints are most commonly used in low pressure ducting to absorb thermal growth, the addition of flexibility in short runs, and as vibration absorbers adjacent to fans, blowers and other mechanical equipment. In general, they are used in the same manner as the corresponding circular joint.
Rectangular Expansion Joints have applications in the cement, power, petrochemical, refining, chemical and steel industries.
The main features of these expansion joints are that they absorb axial and lateral movements, absorb displacements due to thermal expansion, balance pressure thrust remains constant and they eliminate main anchors.
Materials:
The bellows can be manufactured in a variety of materials (the same as for Circular expansion joints), including CS, MS, Austenitic Stainless Steels (300 series), High-nickel alloys such as Inconel, Incoloy, Hastelloy.
Insulation of Rectangular Expansion Joints.
To withstand conditions that have a high internal temperature (e.g.1000°C) and low external temperature (e.g. 90°C), a special flow liner can be fitted (for example made from SA 240 Gr. 310S). The liner is made with expansion gaps to enable it to expand at the operating temperature without generating unacceptable buckling at the hot face of the liner. As part of the installation, the void in the flow liner is filled with an insulation bolster comprising high-temperature insulating materials. This reduces the temperature across the insulation to provide a lower “skin” temperature, for example, 90°C.
Additional options for Rectangular expansion joints.
- Single Miter Rectangular (90° Corner) Expansion Joints.
- Double Miter Rectangular (90° Corner) Expansion Joints.
- Round Corner Rectangular Expansion Joints.
- Camera Corner Rectangular Expansion Joints.
- The intermediate pipe and the bellows can be supplied as one single piece, segmental Joints.
- Loose Bellows elements /Flanges.
Oval type Expansion Joints are also most commonly used in low pressure ducting to absorb thermal growth, the addition of flexibility in short runs, and as vibration absorbers adjacent to fans, blowers and other mechanical equipment. In general, they are used in the same manner as the corresponding circular joint.
Oval type Expansion Joints Application: Turbine exhaust made for M/s HNL Kottayam through M/s BHEL under third party inspection by M/s Lloyd’s Register Asia. Size : 1160mm x 800mm x 1000mm long.
The designs of the hot blast mains along with the bustle pipe are to address system movements and residual expansions to give trouble free operation. The expansion joint system must be designed to accommodate thermal movements in the X, Y and Z directions of the stove branch connections, main and bustle.
Hot Blast Main Bellows Temp. 1400° C made from Incoloy 825 (SB424 UNS NO8825) made first time in India for steel plants, Size : 2200 NB X 1600 mm Long.
We regularly manufacture & supply to major steel plants in India.
Tuyere stocks are generally designed for blast Furnace Stove to minimize joints and bends for improving the life of the refractory lining and minimizing pressure loss. The use of a horizontal jointing system, connected by means of quick release tapered wedges, facilitates quick and easy removal of blowpipe and elbow.
Blast Furnace Stove Bellows with refractory lining, Temp. 1400° C, Size: 350 NB to 550 NB for Steel Plants since 1984.
We regularly manufacture & supply to major steel plants in India.
The speciality of the gimbal expansion joints is that they are fundamentally designed to perform the function of accepting angular movement in any plane. They are quite similar to hinged expansion joints except for the fact that unlike hinged expansion joints, gimbal expansion joints are not restricted to deflection in only one plane and allow bending and angulations in any plane, This Gimbal type of Expansion Joints are used to absorb multiplane thermal growth to complex piping and pressure thrust.
- Absorbs angular rotation
- Eliminates pressure thrust forces
- Transmits shear and wind loads
- Supports dead weight
- Prevents torsion on bellows
- No main anchors required
- Minimum guiding required
- Low forces on piping system
This type of Expansion Joints is normally used where a change of direction occurs in a run of piping and pressure thrust to be absorbed.
Pressure Balanced Expansion Joints are devices which produce no pressure thrust forces in the piping system on the main anchors. In addition to eliminating the pressure thrust, the expansion joint can accept axial compression, axial extension, lateral and angular movements. The balancing thrust is created by using balancing bellows.
Pressure Balanced Elbows are metal expansion joints which can consist of a single or double bellows in the flow section, and a balancing bellows of equal area on the backside of the elbow. Tie rods attach the outboard end of the balancing bellows to the outboard end of the flow bellows. Under pressure, the tie rods are loaded with the pressure thrust force. If the flow bellows compresses in service, the balancing bellows extend the same amount without exposing the adjacent anchors to pressure thrust forces. However, the spring forces associated with bellows movements are imposed on the adjacent equipment. A pressure balanced elbow type expansion joint can accept axial compression, axial extension, lateral movements and very limited angular motion.
In-Line Pressure Balanced Metal Expansion Joints consist of single or double (universal) bellows to accept the piping induced axial compression, extension and lateral movements. An oversize bellows with approximately two times the area of the flow bellows is used to create an annular pressure chamber that produces a balancing pressure thrust force. Tie rods are used to link the bellows elements and contain the pressure thrust force. In-Line pressure balanced expansion joints are typically used in straight pipe runs between intermediate anchors (non pressure thrust resistant) or adjacent to rotating.
