How Expansion Joint Systems Work
Expansion joint systems are an innovative alternative for pipes and pipelines. These joints can be used in the oil, paper, and petrochemical industries and in many others fields.
The diversity of expansion joints available for application is great. They are usually manufactured at standard dimensions and can reach from 1 to 200 inches in diameter; can withstand temperatures from minus 300 degrees F up to 4000 degrees F and can resist at full vacuum or 2000 psig.
The introduction of fabric expansion joints on the market completely revolutionized the way that engineers solve thermal expansion, corrosive and abrasive problems. These fabric joints can be used in different applications for turbines. With different fabric membranes and designs, extensions joints can easily be used for turbine exhaust applications (GTX). GTX are rather problematic applications that pose distinctive challenges concerning performance and resistance through time but which can now be more easily solved with the help of fabric joints.
Metal bellows are generally used in pipeline systems that connect pumps and vessels. The design of the folds in the metal bellow allows for greater axial, lateral, and angular movement. To increase the angular or lateral flexibility, ties, pivots and other trimmings can be added to a metal bellow. The life span of these devices is determined by the shape, material, degree to which the junction must be able to move, and of course, forces that are greater than the designed limits.
With the help of these bellows, flanged-end and fused-end expansion joints can be quite easily and quickly fabricated. Both universal and double expansion joints use two bellows.
Metal expansion joints are crucial components for pipeline technology. They are used to counterbalance length changes, which usually occur in pipelines from temperature changes. Besides this, they are capable of absorbing vibrations developed by pumps, engines, compressors or turbines. Depending on the situation, axial and lateral movement as well as angular movement can be compensated. Metal expansion joints offer a cost effective choice and enhance the productive life cycle of a pipeline system. Designed to last as long as the system; metal bellows reduce sealing problems and the large space needed with alternative expansion equipment.
Some of the most vital and complex categories of expansion joints manufactured are those used in FCCU (fluid catalytic cracking unit). The reason for the complexity is these expansion joints have to withstand extremely high temperatures (1400 degrees F) and pressures, extreme and aggressive environments and great movement conditions.
To ensure a good function of these systems, absolute attention and skill is mandatory in designing the bellows and hardware. All FCCU joints are specially designed for every application in which they are used because any failure during installation can be hazardous to personnel and extremely expensive to users. Accepted specifications offer the basis for the design of the bellows and joint hardware of the FCCU joints.
Expansion Joints Keep your Production Moving
Piping systems are the life blood of many heavy industrial markets. Any time air, gases, or liquids need to be moved, there is a heavy investment in the piping systems to get them from place to place.
Even in a food processing plant there is a need for specially heated piping systems to move corn syrup from its storage container to the processing area.
If you are trying to make a 2000 LB. batch of chocolate syrup and the pipe isn’t heated properly, then the corn syrup is not going to move in the pipes, and it may take 8 hours to start flowing.
Now, if you have hot and cold material handling lines in your plant, then you have expansion joints. You know your business, and you know that in order to be profitable, your system must run at maximum efficiency.
Metal expansion joints allow for both movement and containment in your plant so that stresses don’t built up and cause a problem at the wrong time. And even if you specifically set aside time for maintenance, problems seem to gravitate more toward the critical moments when you don’t need them.
Metal expansion joints allow for the flow of fluids or gases in your system under all the specified conditions they are designed for. Note I said “designed for.”
They won’t hold up to stress that is beyond rated capacity. Knowing the conditions and allowing for unforeseen conditions is the trick to a reliable system that will serve you consistently.
You can imagine that problems of a joint failure in a submarine, for example. Your situation may not be that “Mission Critical,” but hot oil spraying on the plant assembly area is no picnic either. It happens. I won’t go into the most efficient methods of cleaning up hot oil. That’s another story.
Metal expansion joints may experience one or a combination of lateral, axial, angular, or twisting movements. Your specs should take all these motions into account. Often an exterior restraining system will keep the joint itself from being over-stressed to the point of separating.
Every joint has its limits. There are engineering solutions for a number of inherent weaknesses in an expansion joint system. If a bellows is needed in a high pressure situation, an exterior chamber can be added to equalize the pressure both inside and out so that the weakness of the bellows structure is less of an issue.
In order to limit total movement, tie rods can form a limiting cage that keeps and expansion joint from going too far. Or a hinge can be added to one side of a joint which limits the motion to a very predictable plane of action that is easier to design for.
Rather than accommodate all motions at once, multiple expansion joints can be used in series either to add flexibility or to increase the total amount of motion tolerated. Sometime internal sleeves serve to protect the joint from materials that might interfere with its smooth operation.
Using Expansion Joint Systems
An expansion joint is a device that contains one or more bellows, which is used to assist with structural changes, such as those produced by the thermal expansion or tightening of a pipe, tube, or vessel.
An expansion joint can be used to allow movement in a pipeline system. The bellows is a flexible part of an expansion joint that normally consists of several folds. The expansion joint is the best solution when making a piping system more elastic. Flexibility is needed when there are different movements in a pipeline such as, frequent vibrations, pulsations and thermal growth.
There are three basic types of movement that can be applied to the bellows and these are: axial, a movement in a direction parallel to the longitudinal axis; lateral, a movement perpendicular to the longitudinal axis; and angular, a rotational movement of the longitudinal axis.
Metal expansion joints are widely used in pipeline systems. They are vital elements for these technologies. The main reason why these flexible expansion joints are used is because they compensate different variations that may appear in length. Changes in a pipeline’s length are usually the result of high temperature differences, which the metal joints are designed to withstand. They are designed with consideration for different factors, such as: temperature, pressure movement and environment.
Metal expansion joints are also required when it comes to absorbing different vibrations produced by motors, compressors or turbines; the various axial, angular and lateral movements can be easily stabilized in almost any situation.
The metal bellows is a cylindrical container or vessel that can be stretched or compressed on account of several circular folds. They are flexible and durable when they are properly used, meaning if they are used within the designed specifications.
Metal bellows are used in many different industries mainly because they can perform many distinctive functions from sealing environments to carrying gases, liquids and slurry. They have the following standard dimensions: inside/outside diameter, free length and spring rate (the spring force applied by the bellows).
There are four different ways to manufacture a metal bellows. The first of them is electroforming, which actually means to deposit several layers of metal on a mandrel of aluminum. Secondly, chemical deposition is very similar to electroforming done by electro-depositing different types of metal on a mandrel; mechanical forming, and the forth one is welding.
The common materials used in the construction of metal bellows are usually aluminum, stainless steel, tantalum, titanium or steel. However, the most common available on the market is the stainless steel expansion joint, which can be manufactured with both single and multi-walled bellows. These can be used in different applications such as turbine piping, engine exhausts, shaft propellers and many others. Metal expansion joints have been effectively used in a wide variety of situations since around the year 1940.
