Picking the right type of expansion joint, sometimes it can be a difficult task. With so many types and the materials and features associated with each of them, it’s not an easy choice trying to decide which one will work best for your needs.
Different types of bellows include:
- Axial bellows: This is one of the simplest forms of bellows and one of most economical to use. In manufacturing, axial bellows can absorb movement through pipes and it is also ideal for both angular and lateral movement.
- Expansion bellows: These are designed to absorb heat that forms as a result of expansion that occurs during construction processes.
- Exhaust bellows: These are used commonly in diesel engines and exhaust both noise and air from machines. Exhaust bellows are used for railways and several other modes of transportation. This is because a running engine vibrates and exhaust bellows help compensate for movements caused by the vibration as well as differences in temperatures, which result in thermal expansion.
- Hinged expansion bellows: These are common used for application in thermal power plants since they are used to absorb heat during thermal expansion or contraction.
- Non-metallic bellows: These are commonly used in the food industry since they are made of materials such as rubber, leather and plastic.
Metal bellows, fabric bellows and expansion joints are commonly used and as with most things, there are advantages and disadvantages to using any of them. If you are trying to decide between fabric expansion joints and metal expansion joints, here are some pros and cons of each:
Fabric expansion joints are best used in applications that involve low temperatures. By using them, there are no restraints on size and fabric expansion joints are often chosen for their cost-effectiveness. This is because they are easier to produce and can be delivered quickly.
While expansion joints are affordable and easy to prepare, they don’t have the ability to handle higher temperatures like metal expansion joints do. They also aren’t quite as durable and may need occasional replacement.
What are metal expansion joints used for? Simply put, they’re assemblies designed to absorb the temperature-induced expansion and contraction of construction materials which is usually due to extreme hot or extreme cold. They’re also used to absorb vibration, hold parts together and allow movement due to shifting earth.
Metal expansion joints are stronger and are known for being more rugged than fabric and other materials. While fabric expansion joints may need occasional replacement, metal expansion joints are typically maintenance free. They are also non-combustible, meaning they handle extreme temperatures whether they’re being exposed to high heat or freezing cold. Forged steel 150# flanges are rated for pressures up to 285 psig at 100 degrees Fahrenheit, according to ASME B-16.5 flange specifications. The allowable pressure is reduced to 65 psig at 850 degrees.
Another benefit of metal expansion joints is that they can be used in various press conditions, including air, liquid and cryogenic. In addition to their versatility, metal expansion joints also ensure that gas and liquids won’t leak. This is a benefit because it eliminates the need for risk prevention in this area.
A custom bellows design requires focus on 12 vital attributes:
- Stress modes
- Pressure differential
- Rigid stops
- Spring rate
- Life cycles
- Temperature extremes
- Assembly Method
- End Configuration
- Geometric Constraints
Metal expansion joints are a superior choice to other types of material in many respects. But understanding what are metal expansion joints used for compared to the features of other materials such as fabric will help you find exactly what you’re looking for.
It will also help you understand what sort of materials work best and what bellow type works best for your needs whether you want to know about standard bellows, metal bellows, stainless steel bellows, exhaust bellows for engines for bellows for other applications.