The flanged structure makes the skin installation no longer "tear the skin"-find out what it really looks like first
The traditional non-metallic expansion joint skin is fixed by either gluing or flange clamping. The glue ages badly at high temperatures and degumms within a few months; As for flange clamping, the tightening force of the bolts is uneven, and the gap is large, and the air leak will come. The flange design is to preform a circle of flapped edges on the edge of the skin, which is directly embedded in the flange groove or pressure plate. Once the bolt is twisted, the flange is pressed to form a sealing preload force. This trick is borrowed from the flanging process of metal hoses, but the effect is more obvious when placed on fabric fiber skins-especially forRectangular non-metallic expansion jointThis type of large section flue. Think about it, a flange with a width of several hundred millimeters is uniformly stressed, which can be compared with point screw fixation?
Skin is not as simple as "a piece of cloth": the combination of materials determines how long it lasts
Non-metallic expansion joint (fabric fiber expansion joint)The skin is usually composed of multiple layers of composite: the outer layer is anti-corrosion (fluorine tape or silicone cloth), the middle is thermally insulated (ceramic fiber felt), and the inner layer is temperature resistant (glass fiber cloth). The flange is a stress concentration area and must be extra reinforced-such as a layer of high-strength fibers superimposed on the fold, or thickened. Referring to the national standard JB/T 12235-2015, the overall temperature resistance grade, fracture strength and sealing performance of the skin have hard indexes. When selecting, if you only look at the thickness and not the bond strength between layers, the flange will delaminate in three months. Do you believe it? I have seen many projects, and I bought the low-end skin cheaply. As a result, the flanges were layered like a thousand-layer cake. When I took it down, the ceramic fibers in the middle were scattered into slag.
On-site case: Why do cement plant kiln tail flue and power station desulfurization tower entrance prefer flanged skin?
Used in cement industryMetal Corrugated Expansion Joints in Cement IndustryIt mainly copes with solid particle wear, but the non-metallic skin has advantages in absorbing large displacements and damping vibrations. The temperature of the kiln tail flue fluctuates greatly, and the flanged skin can expand and contract with the flue, so it will not crack fatigue like metal parts. Used in power station industryCorrugated expansion joint for power station industryChang andDesulfurization flue gas baffle doorIn combination, the flanged skin can adapt to the drastic change of flue gas temperature from 200 ℃ to 800 ℃. Two days ago, I encountered a desulfurization project. The original skin was directly fixed to the angle steel with screws, and it leaked in half a year-the fibers of the screw holes were torn and leaked like a sieve. After changing to the flanged type, the pressure plate is fitted with the flange surface, and the leakage rate is reduced to below 0.5%. Why? Because the flange is a continuous sealing surface, the screw only plays a fixing role, and the seal is pressed by the whole circle.
Don't just focus on the price when selecting the model: compensation amount, compression force and bolt spacing are indispensable
The compensation ability of the flanged non-metallic compensator skin depends on the wave height and the number of layers, but the flange width and platen stiffness determine the seal reliability. Usually, the flange width is 40-60mm, the bolt spacing does not exceed 150mm, and the torque is implemented according to the flange material and gasket requirements. Mentioned in the FAQHow to adjust the tie rod nut of expansion jointWhen installing the flanged skin, it should also be tightened symmetrically step by step-first in the middle and then on both sides, and reach the target torque in three passes. Otherwise, one side is stressed and the other side is wrinkled, which is the same as not installing it. In addition, the corner stress concentration should be considered in the flange skin of rectangular non-metallic expansion joint-this position has the smallest flange bending radius and is most likely to break first. Manufacturers usually add curved plates or thickened reinforcing layers at the corners. You have to ask this detail when selecting the model.
Maintenance cycle and replacement judgment: not wait until leakage before replacement
Surface cracks, exposed fibers at flanges, and corrosion of platens lead to the decrease of preloading force. Refer to the FAQService life of expansion jointNon-metallic skin is generally replaced once every 2-5 years, depending on the working conditions. If the flue gas contains high sulfur or moisture content, the life of the outer layer of fluorine tape will be shortened to two or three years. Usually, check whether there is air leakage with a listening stick during inspection, or brush the flange gap with soapy water-if bubbles are found, they should be replaced. Don't feel bad about the tens of thousands of dollars. Gas pipeline leakage and shutdown loss are enough to buy ten sets of skins. Alas, some customers have to wait until the leak is whirring before replacing it. At that time, even the flange may be corroded, and the replacement cost doubles.