1. Why should non-metallic compensators emphasize "dust-proof and wear-resistant"? — — First the pain point, then the antidote
The dusty flue gas and powder transport in industrial pipelines will be worn out by ordinary compensators in two or three months, let alone leakage. Think about it, the dust concentration of the flue gas pipe at the tail of the kiln of the cement plant is always tens of grams per standard cubic meter. If the ordinary rubber compensator goes up, the coating will be beaten like a honeycomb by hard particles, and it will be done. The core advantage of dust-proof and wear-resistant non-metallic compensator (that is, fabric fiber expansion joint) is that it relies on multi-layer composite structure to keep hard particles out of the door. Two days ago, a cement factory customer told me that the metal corrugated expansion joint used in their flue gas pipeline cracked in half a year-the dust drilled into the groove of the corrugated pipe and repeatedly wore it, and the stress concentration directly cracked. After changing to non-metal, it is still running normally after more than a year. What's the difference? It lies in the anti-wear design of the skin material and the anti-dust penetration ability of the sealing layer. Don't underestimate that surface coating, PTFE or fluororubber pressed on, dust particles want to drill? There are no doors.
2. Structural disassembly: From the inside to the outside, every layer has a living
A typical dust-proof and wear-resistant non-metallic compensator is not as simple as a piece of cloth. The inner layer is temperature-resistant and corrosion-resistant polytetrafluoroethylene or silicone rubber coating, with reinforcing fibers-glass fiber and aramid fiber in the middle, and a layer of wear-resistant fluororubber or ceramic fiber cloth on the outside. If it is a high temperature working condition, you have to add insulation layer. Some designs will add a guide tube inside to reduce the direct scouring of the skin by the medium. This is not the same as this site'sNon-metallic expansion joint (fabric fiber expansion joint)as well asRectangular non-metallic expansion jointIt is the same technical route, but it is strengthened for the dust environment. The guide tube can directly allow the airflow to go along the pipeline, without directly impacting the inner wall of the compensator —Specific Function of Expansion Joint Guide TubeIt is discussed in detail in the question and answer, so I won't say much here.
3. Hard-on-hard: dust-proof and wear-resistant non-metallic compensator vs metal corrugated expansion joint
I think the metal ones are definitely stronger than the cloth ones. Not necessarily. In dusty flue gas, high-temperature flue gas, or acid-alkali corrosion, metal expansion joints (such as those used in power station industriesCorrugated expansion jointCement industryMetal corrugated expansion joint) corrugated pipes are easily abraded by dust particles, and even stress corrosion occurs. However, the non-metal compensator has no metal fatigue problem, and the overall weight is light and easy to install. However, non-metals also have shortcomings: weak pressure bearing capacity and intolerance to high negative pressure. Therefore, it is necessary to know the medium temperature, pressure and dust concentration when selecting the model. Don't replace the non-metal in the high-pressure steam systemSleeve type pipe expansion jointOrStraight pipe pressure balanced expansion joint— Those are two different things.
4. Which industries are used the most? — — Cement, steel, electric power, chemical industry
Take the cement industry as an example, the import and export of kiln head, kiln tail and dust collector have high temperature and large dust, and non-metallic expansion joints are standard. In the desulfurization flue gas system in the power industry, corrosion-resistant and dust-proof non-metallic compensators are also needed in front and behind the flue gas baffle door. Sintering machines and blast furnace gas pipelines in iron and steel plants are also inseparable. Even in waste incineration power plants, the flue gas contains acidic gas and particulate matter.Rubber PTFE compensatorOr the non-metallic expansion joint is instead the most cost-effective scheme. Under these scenarios, our siteRound Flap Door (Double Seal)AndDesulfurization flue gas baffle doorIt is often needed to be used together with non-metallic compensators to form a complete sealing scheme of pipeline system. Tsk, with a whole set, the leakage point can be reduced by two thirds.
5. Four-step selection method: temperature, pressure, displacement, medium
Neoprene rubber is used in ordinary working conditions, fluororubber or silicone rubber is used above 200℃, and ceramic fiber is obtained above 300℃. The second step is to look at the pressure: non-metallic compensators can generally only bear 0.1~0.5MPa, and the skeleton support should be specially strengthened under negative pressure conditions, such as stainless steel wire mesh. The third step is to calculate the displacement: the non-metal mainly compensates the axial and angular displacements, and a standard rectangular non-metal can expand and save energy to absorb the axial displacement of 50~100mm. The fourth step is to look at the medium: if it contains hard particles and alkaline dust, double-layer or even three-layer wear-resistant coating must be selected; If it contains acid corrosion, polytetrafluoroethylene or tetrafluororubber should be used. Don't buy the general-purpose model cheaply, otherwise you will have to change it in a few months, which is not worth the loss. Think about it, the labor cost of replacing the compensator plus the downtime loss is enough to buy several good goods.
6. Installation and maintenance: The key to saving money lies in the details
When installing the dust-proof and wear-resistant non-metallic compensator, the inlet and outlet flange surfaces must be parallel and the tightening moment is uniform, otherwise the skin will be folded and the life will be directly reduced by half. During operation, check the skin regularly for bulging, wear points and aging cracks. Especially if there is dust accumulation under the compensator, it should be cleaned in time, otherwise the dust accumulation will corrode the fabric layer after absorbing water. There's a trick: Install a protective layer (such as stainless steel guard plate) on the inside and outside of the compensator, which can double the life of dust washing. If site conditions allow, you can also refer toCorrect installation method of expansion joint of large tie rodHowever, the non-metallic expansion joint generally does not need a tie rod, and its displacement compensation depends on the expansion and contraction of the fabric. To put it bluntly, spending ten minutes getting the details in place is much more cost-effective than spending two hours repairing equipment.