In the field of industrial pipe compensation equipment, what is the difference between fabric expansion joints and non-metallic expansion joints is a question that many engineers and technicians often confuse when purchasing. Some people think that "different names, things must be different", while others think that "fabric expansion joints are a kind of non-metallic expansion joints". What is the relationship between the two? This article will systematically sort out the differences in definitions, classifications and applications to help you thoroughly understand these two concepts.
1. Looking at relationships by definition: Actually the same thing
To understand the difference between fabric expansion joints and non-metallic expansion joints, we first need to clarify the definition of both.
Non-metallic expansion joint-also known as non-metallic compensator, non-metallic expansion joint, refers to the pipeline compensation device made of non-metallic material with the elastic element constituting its working body。
Fabric expansion joint-also known as non-metallic fabric compensator and fiber fabric compensator, is a pipeline compensator with non-metallic materials such as fiber fabric as the core elastic element。
As can be seen from the definition, fabric expansion joints and non-metallic expansion joints are highly overlapping in core concepts. The elastic elements of non-metallic expansion joints are typically fibrous fabric, so fabric expansion joints are the prevailing form of non-metallic expansion joints. In fact, these two names are often mixed in the industry。
| Device Name | Core Definition | Relationship Description |
|---|---|---|
| Non-metallic expansion joint | The elastic element is made of non-metallic material | Cover a wider range |
| fabric expansion joint | The elastic element is a fibrous fabric | Is the main form of non-metallic expansion joint |
Conclusions: Both are essentially the same product, with non-metallic expansion joints being a larger category, while fabric expansion joints being the most dominant and common form of non-metallic expansion joints.
2. Two main types of non-metallic expansion joints
Although fabric expansion joints and non-metallic expansion joints point to the same kind of products in most occasions, from the strict classification point of view, non-metallic expansion joints are mainly divided into two types according to the different materials of elastic elements：
1. Fiber fabric expansion joint
This is the most common type. The elastic element of the fiber fabric expansion joint is composed of fiber fabric composite material, and the core elastic element is made of high temperature and corrosion resistant materials such as fluorine rubber, silicone rubber or polyester cord。
Applicable working conditions: It is widely used in high-temperature hot air ducts, flue gas ducts and dust removal ducts. The working temperature can reach above 400 ℃. Special materials such as ceramic fiber cloth can withstand instantaneous high temperatures up to 1770 ℃。
2. Rubber air duct expansion joint
Another non-metallic expansion joint is a rubber expansion joint. Rubber expansion joints are divided into FDZ, FVB, FUB, XB and other models, which are composed of rubber and rubber-fiber fabric composite materials, steel flanges, sleeves, etc., and are mainly used for flexible connection between various fans and air ducts。
Difference from fabric expansion joints: Besides the basic characteristics of non-metallic expansion joints, rubber expansion joints also have better sealing performance (adopting large flanged structure, without gasket sealing), better shock absorption effect and higher compressive strength。
3. Core characteristics of fabric expansion joints
As the main form of non-metallic expansion joints, fabric expansion joints have the following core characteristics：
| peculiarity | Specific Description |
|---|---|
| Compensate for multidimensional directions | The axial, transverse and angular displacement can be compensated simultaneously, while the metal expansion joint can only compensate a single direction |
| No reverse thrust | The main body is made of fiber fabric, which does not produce reaction force on the equipment, and can simplify the design of the bracket |
| Noise and vibration isolation | The fiber fabric and heat insulation cotton have the functions of sound absorption and vibration isolation to reduce system noise and vibration |
| High temperature and corrosion resistance | Fluoroplastics and silicone materials have excellent high temperature and corrosion resistance |
| Good sealing | Complete production and assembly system to ensure basically no leakage |
| Lightweight and low price | Weighs about 1/3-1/2 of metal expansion joints and costs less than metal compensators |
4. Unique advantages of rubber non-metallic expansion joints
Although rubber expansion joints also belong to the category of non-metallic expansion joints, they have their unique advantages over fabric expansion joints：
Good shock absorption effect: The elasticity of rubber material is better than that of fiber fabric, and the shock absorption effect is better in the import and export of vibration source equipment such as fans and water pumps.
Excellent Sealing: With large flanged structure, good sealing can be achieved without additional gaskets, and installation is more convenient.
High compressive strength: It has higher pressure bearing capacity than fiber fabric expansion joint, suitable for medium and low pressure pipeline.
Use limitation: Rubber expansion joints cannot meet the use conditions under ultra-high temperature (above 400℃), and fiber fabric expansion joints still need to be selected under high temperature conditions。
V. Suggestions on Selection in Practical Application
In actual engineering selection, the following strategies are recommended:
| Operating condition | Type of recommendation | reason |
|---|---|---|
| High temperature flue gas (> 400℃) | Expansion joint of fibrous fabric | The temperature resistance is better and can reach more than 1000℃ |
| Hot air duct (200-400℃) | Expansion joint of fibrous fabric | High cost performance, obvious overall advantage |
| Fan/water pump inlet and outlet | rubber expansion joint | Good shock absorption effect and excellent sealing property |
| Acid-base medium | Fibrous fabric expansion joint (fluororubber) | Better corrosion resistance |
| Medium and low temperature pipeline ( | Both can be done | Select according to specific working conditions |
Core selection principle: Select the most suitable type comprehensively according to working temperature, medium corrosiveness, displacement requirements, installation space and budget. Fiber fabric expansion joints are preferentially recommended for conventional high temperature working conditions; Rubber expansion joints can be considered in cases where vibration is severe and high sealing performance is required; Special material of ceramic fiber fabric must be selected for extreme high temperature (> 1000℃)。
VI. SUMMARY
The core conclusion of what is the difference between fabric expansion joints and non-metallic expansion joints is as follows:
| Dimension | Core Conclusion |
|---|---|
| Essential relationship | "Fabric expansion joint" is approximately equal to "non-metallic expansion joint", which belongs to the same object and synonyms |
| Official Definition | Non-metallic expansion joint is the official name, and the core feature is "the elastic element is made of non-metallic material" |
| fabric expansion joint | The elastic element is "fiber fabric", which is the most mainstream form of non-metallic expansion joint |
| Another type | The non-metallic expansion joint also includes rubber material type, which is suitable for low-temperature and high shock absorption occasions |
| Core Strengths | Multi-dimensional compensation, no reverse thrust, noise and vibration isolation, temperature and corrosion resistance, good sealing performance, light body and low price |
Summary in one sentence: Fabric expansion joints and non-metallic expansion joints refer to the same product in the vast majority of cases – non-metallic expansion joints are the formal name, and fabric expansion joints are their core and most common type. The two are essentially the same, except the name angle is different. When selecting the model, focus on the working condition parameters instead of obsessing over the name difference.