"Does the non-metallic compensator do heat insulation? I see that the metal bellows next door are covered with a thick layer, so I'm afraid of something going wrong." This problem is actually quite typical-I have seen too many people want to insulate non-metallic compensators as soon as they come up, and as a result, they not only spend money in vain, but also destroy the compensators. Today, let's make it clear when to add it and when not to add it.
1. Find out what material the non-metallic compensator itself is made of first
Non-metallic compensator (also called non-metallic expansion joint, fabric fiber expansion joint), the main body is laminated by flexible composite materials such as silicone cloth, fluorine adhesive tape and glass fiber. To put it bluntly, it is itself a set of multi-layer insulation structures. The temperature resistance of ordinary silicone cloth can reach about 200℃, and that of fluorine tape can reach above 250℃. In many operating conditions, the temperature resistance margin of the skin itself is sufficient.
Then why do some people always think they need to add insulation? Because everyone's mind is all about metal corrugated expansion joints-such asCorrugated expansion joint for power station industryOrMetal Corrugated Expansion Joints in Cement IndustryThe metal shell conducts heat quickly and must be insulated to prevent scalding and save energy. However, the skin of the non-metallic compensator itself is a bad conductor of heat. If it is piled up blindly for heat preservation, it may flatten the ripples and hinder the displacement, and the compensator will be scrapped in advance.
2. Under what circumstances must non-metallic compensators be insulated?
You can't talk to death. Under some working conditions, it is really impossible not to do heat insulation. There are three scenarios:
- High temperature operating condition: The medium temperature exceeds the allowable long-term use temperature of the skin. For example, the temperature of flue gas pipe is 400℃, ordinary silicone cloth can only carry 200℃, and fluorine tape can only carry 250℃-at this time, an insulation layer must be added on the outside of the compensator to reduce the surface temperature of the skin.
- Low temperature operating condition: likeDouble hinge expansion joint for air-cooled island vacuum pipelineThe medium is cold, and the outer wall is prone to condensation or even ice. What is done at this time is to keep the cold, not keep the heat.
- Human body protection: likeDesulfurization flue gas baffle doorThe temperature of the nearby non-metallic compensator may be less than 100℃, but it is safer to add a detachable insulation sleeve to prevent scalding. The environmental inspection also recognizes this.
What is the medium temperature? How much is the skin material resistant to temperature? What is the ambient temperature? The difference is calculated before we do it.
3. If the insulation is not done correctly, the life of the compensator will be directly reduced by half
Tsk, I met a client two days ago.Rectangular non-metallic expansion jointIt was covered with a layer of hard rock wool and then reinforced with cement. And guess what? The compensator barely stretched freely and ripped in a few months. The core function of non-metallic compensator is to absorb displacement. What is the difference between wearing a hard shell on it and welding it to death?
The insulation material must be soft and compressible, such as aluminum silicate fiber blanket. And it can't be pressed too firmly, let alone the insulation material can be stuffed into the corrugated gap-that is equivalent to jamming all the movable joints of the compensator. Remember an iron rule: leave at least 10mm gap between the insulation layer and the compensator, or use a metal shell for movable connection.
4. Correct practice: layered design + detachable structure
The standard practice is divided into three steps, and one step less may overturn:
- Moisture-proof insulation layer: Wrap a layer of aluminum foil or Teflon cloth outside the skin of the non-metallic compensator to prevent moisture penetration.
- Flexible insulation layer: Lay aluminum silicate fiber blanket, the thickness is calculated according to the temperature difference, generally 50-100mm.
- Protective shell: Use stainless steel or galvanized iron sheet as the shell, but it must be made into the style of two-half buckle and fixed with buckle-convenient for disassembly and assembly during maintenance, otherwise the whole insulation layer will be smashed next time you change the skin.
Some high temperature operating conditions, such as we giveHigh temperature axial expansion jointThe plan is to directly customize the non-metallic compensator with thermal insulation interlayer-the thermal insulation cotton is pre-installed between the skin and the protective net when it leaves the factory, and only the butt flange is needed on the site, thus saving the trouble of on-site construction. Is it much less worry-free?
5. In the final analysis, heat preservation is not the end, temperature control is
Judge whether the non-metallic compensator should be insulated or not. Don't just look at the name. First calculate three sets of numbers: medium temperature, ambient temperature, and allowable heat loss. For example, the temperature of the flue gas pipe is 400℃, and the non-metallic skin can only carry 250℃, so insulation must be added to reduce the skin surface below 200℃. However, if the flue gas temperature is only 150℃, the skin itself can cope with it, and adding thermal insulation is a pure waste of money.
In addition, the overall insulation design of the pipeline system must be considered. Non-metallic compensators are often the weak points in the whole insulation link-many projects age and leak in advance because the insulation is not done well, and finally the whole system has to be reworked. So, when you are unsure, directly ask the manufacturer for the temperature-pressure curve, which is much more reliable than guessing.
If you are still unsure, welcome to inquire. Our sideNon-metallic expansion joint (fabric fiber expansion joint)、Double hinge expansion joint for air-cooled island vacuum pipelineThey are all with detailed technical parameters, and you can know whether you should do heat insulation or not.