First, I will answer you first: Non-metallic expansion joints do have glass filaments, and they are very critical
Let's get straight to the point – there are indeed glass filaments in the non-metallic expansion joints. If you take one apartNon-metallic expansion joint (fabric fiber expansion joint)The ring belt, you can feel the sticky glass fiber when you touch it with your hand. It's no secret, it's part of the design to begin with.
But many people panic when they hear "glass filament": Will this thing blow off at high temperature? Will it corrode? Is it durable?
Tsk, you're right worried.Glass filament plays the same role in non-metallic expansion joints as steel in concrete-Responsible for carrying the pull force and maintaining the shape. Without this skeleton, the soft materials of silicone cloth and polytetrafluoroethylene simply can't hold up the thermal displacement and pressure of the pipe system.
So don't just hear glass filament and think it's cheap. On the contrary,It is precisely one of the core materials that determine the life of the expansion joint。
Second, the "sandwich" structure of non-metallic expansion joint: glass filament is only one layer
Let's draw a picture for you first (think about it): The circle of non-metal expansion joints is actually a multi-layer sandwich.
- The outermost is silicone cloth or fluororubber coated cloth, which is used to resist aging, oxidation and wind and sand.
- The middle layer is glass silk cloth, and some will lay several layers of reinforcing net.
- The inner layer is usually pasted with polytetrafluoroethylene (PTFE) film to prevent corrosion and adhesion.
You see, glass filament cloth does not exist alone, it is pressed between two layers of flexible material. Take a real case: Last year, there was a cement plant project, which used the one in our stationMetal Corrugated Expansion Joints in Cement IndustryReplacement scheme, but the customer's flue gas pipe temperature fluctuates greatly, and finally selected a non-metallic expansion joint. When the manufacturer sends the sample, take the blade to cut the section of the circle belt, and the naked eye can see three layers of glass filament checkered cloth sandwiched in the middle.
The weaving density, yarn thickness and temperature resistance grade of glass filament directly determine how many kilograms of tensile force this loop can carry. Do you think it's not critical?
Third, what is the effect of matching glass filament with silicone cloth and polytetrafluoroethylene?
This set of combination boxing is actually very sophisticated. Glass filament is responsible for strength, silicone cloth for sealing and weather resistance, and PTFE for corrosion resistance. Each performs his duty.
The thermal expansion coefficients of glass filament and silicone gel cloth are different。 When the temperature is high, the silicone cloth expands greatly, while the glass filament expands less, and the layers are easily detached. Therefore, regular manufacturers (such as us) will do pretreatment in the process-impregnating a layer of coupling agent on the surface of the glass filament cloth, so that the glue and glass filament can "bite" tighter.
So what exactly is the matching effect? I'll tell you directly about the data:
In the flue gas pipeline below 350℃, this composite belt has been running continuously for 2 years, and the interlayer adhesion is still above 80% when it is torn apart. If the medium contains sulfur or acid, the inner layer must be replaced with PTFE film, and the glass filament should be used correctly.
Then why not just make a whole with pure PTFE? The answer is very simple: pure PTFE is too soft, and it creeps after a few pulls, which can't replace the skeleton function of glass filament at all.
4. Don't just look at whether there is glass filament when selecting the type. These three points are more critical
Many purchases ask "Is there any glass filament" as soon as they come, as if they can't do without glass filament. But I'm telling you,When choosing non-metallic expansion joints, these three points are ten times more important than whether there is glass filament：
First, the medium temperature and composition.Glass filaments are divided into two kinds: medium alkali and non-alkali. Ordinary medium-alkali glass filament is temperature resistant to 550℃, and alkali-free glass filament is temperature resistant to 650℃, but it is immediately scrapped when it encounters hydrofluoric acid. If there is fluoride in your smoke, the inner layer must be PTFE, and the glass filament must be covered with a fluorine-resistant coating. Many people ignore this detail.
Second, the displacement amount and direction.Non-metal expansion energy saving absorbs multi-directional displacement, but the number of layers of the loop band is designed ≠ thick to be durable. Large displacement on rectangular pipe, it is necessary to calculate the warp and weft strength of each layer of glass filament cloth. From our stationRectangular non-metallic expansion jointOften, an extra layer of reinforcing strips is added in the corners, because the stress of the four corners of the rectangle is concentrated.
Third, the installation environment.Open air plumbing? Coastal high salt spray? There is a dust explosion risk? These directly determine whether flame retardant coating or UV protection coating should be added to the outer layer. Glass filament itself is not UV-proof, and it will brittle when exposed to the sun for a long time. This is protected by an outer silicone cloth.
You see, model selection is a systematic project. Just staring at the glass filament is equivalent to buying tires only looking at the rubber but not the depth of the pattern.
5. Two days ago, a customer asked me: Is rectangular non-metallic expansion energy-saving glass filament used?
Two days ago, a buddy who was doing desulfurization engineering called and asked, "That guyRectangular non-metallic expansion jointIs there any glass filament in the belt?”
I said yes, the standard is three layers of alkali-free glass filament cloth and two layers of PTFE film. He immediately asked, "Then there is sulfuric acid condensate in our smoke, so the glass filament will not be broken by corrosion?"
I understand this concern. But the point is,The glass filament cloth is wrapped between that PTFE inner layer and the silicone cloth outer layerThe condensate does not contact the glass filament at all. Our salt spray experiment also proved that the strength of glass filament decreased by less than 5% when sprayed continuously for 720 hours under acid mist environment at PH =2.
After he listened, he dropped eight rectangular non-metal expansion joints on the same day. Tsk, sometimes as long as customers understand the structure, their worries will naturally disappear.
Do non-metallic expansion joints have glass filaments?The answer is yes, but it's not a weakness, it's a skeleton. What really determines whether the product is good or not is the matching process of this layer of skeleton and inner and outer materials.