A pipe bellow, also known as a flexible bellow, is necessary for pipeline systems because of high temperatures. And to absorb movement and vibration. We can make a pipe joint from metal
into a metallic bellow
, plastic (such as PTFE
, or an elastomer such as rubber joints.
Moreover, pipe bellows have convolutions. Additionally, the shape of the convolution helps withstand the internal pressures of the pipe. But they are flexible enough to accept axial, lateral, and angular deflections. Expansion joints
help with other criteria: noise absorption, anti-vibration, earthquake movement, and building settlement. Also, pipe bellow joints
should be designed according to rules laid out by EJMA
; for fabric expansion joints
, there are guidelines and a state-of-the-art description by the quality association. Finally, pipe expansion joints
are also known as “compensators
,” as they compensate for thermal movement. Contact Dannenbaum LLC for more information or a quote on a metal bellow.
Flexible bellows, also known as pipe bellows, are flexible elements that absorb movements in the pipe system. These movements absorbed are axial, lateral, angular, and universal movements. The flexible bellows can absorb one of these movements more in combination.
Metal pipe joints can handle higher temperatures than rubber joints.
As a result, they reduce stress, vibration,
and noise in piping systems by providing a point of flexibility to absorb movement.
You can make flexible joints from steel. The flanged ends rotate for easy bolt-hole alignment during installation.
Flanges mate with the same-size flat surface. Bellow pump connectors
or metal hose pump connectors
Axial Movement Pipe Bellows
Axial movement is the movement of the flexible bellows in the direction of the longitudinal axis. This movement can be compressive, where the laminated bellows
shorten in length, or extensive, where the bellows extend in length. In most applications, flexible bellows are deemed necessary because of the increasing temperature of the pipe system.
Typically cryogenic and chilled water services, the pipe system contracts in service, causing the expansion joint to extend in length. In addition, thermal expansion of the pipe system results in axial compression of the installed flexible bellow. Therefore, the specifications for flexible bellows should always state the movements as they affect the flexible bellows and not those generated by the pipe system.
Industrial bellow angular motion is the rotation or angulation of the end planes relative to each other, which results in the longitudinal centerline becoming an arc. The convolutions are extended along the outer radius of the arch and compressed along the inside radius. Torsion or twisting is rotation around the longitudinal centerline of the pipe expansion join
t and is sometimes confused with angular motion. Industrial bellows do not absorb torsional displacement, and although a industrial bellow can react to torsional moments, avoid if possible.
Industrial bellows can absorb these movements as individual motions or in any combination and multiple planes. Aside from the physical limitations of deflecting a industrial bellow without damaging it, the design is usually based on specified cyclic movements for a given fatigue life at the operating pressure and temperature.
The accepted method for equating axial, lateral, and angular motions is outlined in the Standards of the Expansion Joint Manufacturers Association, Inc. The following equations are based on this method but are for complete pipe bellows – not per convolution described by the standards. A typical industrial bellows design over a range of diameters has 12 inches convoluted (L) length and is rated for 3 inches compression (Ec) with zero lateral and angular movements. The correct specification of industrial bellows movement requirements is one of the essential factors in the successful application of this product. Therefore, the axial, lateral, and angular movements must be realistically stated and the corresponding cycle life.
One of the most common mistakes is to overstate these values to obtain a conservative design. However, over-emphasis of any parameter can jeopardize other design elements and result in unnecessary costs. Several good rules to remember when specifying motions of the industrial bellow include:
- Separate the cyclic and noncyclic motions, such as installation displacements.
- Distinguish between regular operating movements and upset conditions.
- When comparisons to the manufacturer’s rated motions, be sure to distinguish between concurrent and nonconcurrent values.
- Realistically state fatigue life requirements for the industrial bellow. Cycle life is not proportional to rated travel. Small displacement changes can result in substantial cycle life changes and vice versa.
- Avoid large lateral offset requirements for single industrial bellows – particularly for large diameter bellows.
Running engines cause self vibration. Therefore, you can use the bellows to connect the exhaust gas pipes. Thus compensates for those movements and temperature differences resulting in thermal expansion. Piping expansion joint: In this application, bellows are formed in series to absorb thermal movement and vibration in piping systems that transport high-temperature media such as exhaust gases or steam. Other products and market segments use metal bellows are also used in, including medical applications like implantable drug pumps, industrial actuators, aerospace applications such as altitude sensors, and fluid management devices (accumulators, surge arresters, volume compensators, and liquid storage). Pipe bellows
are also found in space applications, providing reservoirs with potable water and accumulators to collect wastewater.
Read more on pump bellow connectors
Lateral Movement Flexible Bellows
Lateral movement moves perpendicular to the bellow’s longitudinal axis; it is a shearing movement of the flexible bellows with one end offset from the other, usually with the ends of the bellows remaining parallel.
Thus, a single formed metal bellow expansion joint
, working with shearing action, can accept a relatively limited amount of lateral movement, especially when the flow characteristics of the system demand that an inner sleeve is necessary.
It is usual for more extensive lateral movement to utilize a twin bellows arrangement with an intermediate pipe between the bellows. The flexible bellows’ lateral action is taken up by an angle of the bellows in opposite directions.
The amount of lateral movement available depends on the rotational movement capacity of each bellows and the distance between them. Thus, increasing the distance between the bellows increases the lateral movement capability of the flexible bellows proportionally.
In particular, pinned units used in 2-pin or 3-pin arrangements can convert pipe growth into the angular rotation and control the expansion from 2 directions and in 2 planes.
It is important not to confuse angular rotation with torsion. Torsion is a twisting rotational movement around the longitudinal axis; it generates undesirable shear forces within the bellows, and anyone should always avoid putting torsion on the bellows. Instead, please refer to the section about torsion.
Such units usually require a lot of flexibility to absorb significant amounts of combined movements. However, this often leads to a limited pressure-containing capacity due to considerations towards the bellows’ stability.
Important to know about flexible metallic bellows and movements
You can help by telling the properties of the flexible bellow when sending an RFQ. STAMP (Size, Temperature, Application, Movement and Pressure).