Let's first talk about what skin striping is used for
To put it bluntly, it is the key accessory that holds the layer of cloth for the non-metallic expansion joint. Have you seen the guy in our stationNon-metallic expansion joint (fabric fiber expansion joint)Right? What holds that skin down on? It all depends on the bead and bolts. If the strip is not selected properly, air leakage, delamination, or even the whole expansion joint may be scrapped.
Two days ago, a buddy who was engaged in desulfurization flue spat with me, saying that the strips on their project were not anticorrosive, and they were rusty and worn in three months, and the skin flew directly, which was a headache. He used theDesulfurization flue gas baffle doorThe nearby non-metallic expansion joint is heavy in moisture and corrosive, and ordinary galvanizing can't bear it at all. You said that if this is the right 316L strip in the early stage, how can it be tossed and reworked?
The material and structure of the press bar, don't underestimate these iron bars
Common ones are galvanized steel sheet, stainless steel 304 or 316L. Specifically, it depends on the flue gas temperature and environment-like the high-temperature dry flue gas at the boiler outlet of a power plant, 304 is enough; Once it reaches the entrance of the desulfurization tower, the acidic condensate of wet desulfurization will peel after three months of galvanization. 316L is the correct solution.
Structurally, it is divided into integral type and clip type. Rectangular expansion joints are commonly made of angle steel or channel steel, such as the one in our stationRectangular non-metallic expansion jointThe four sides are bent with a whole press bar, and the corners are welded and polished, which has high strength. On the other side of the circular baffle door, it uses more segmented arc-shaped pressing strips, such asDouble-sealed single-axis circular baffle doorOrRound Flap Door (Double Seal)The flange is round, and the bead has to be assembled in sections. The width and thickness of the strip directly affect the sealing effect-it is too narrow to be pressed, and the edge of the skin is easy to cock up; Too thin and easy to deform, the bolt will bend as soon as it is tightly pressed, and the sealing surface will have gaps instead.
By the way, there is another situation:Electric plug-in insulation doorOrManual plug-in insulation doorThe non-metallic expansion joints used on the strip often need to avoid the guide rail of the plug-in plate, and the structure has to be treated with special shape. Don't take the standard strip straight up, confirm the interference.
I will talk to you about the pits to pay attention to when choosing a model
First pit: hole spacing.The spacing of the bolt holes on the press bar should match the screw holes of the equipment flange. Don't buy it back and find that it is two millimeters different. Take an electric drill to expand the hole on the spot, which is called an embarrassment. What is more afraid is that iron chips fall into the skin interlayer during reaming, and the fabric layer will be worn out during operation. Check the flange drawings in advance, or simply let the manufacturer match the drill according to the actual flange, which is worry-free.
The second pit: the matching of the bead to the skin.The skin is usually a multi-layer structure-fluororubber cloth, fiberglass cloth, PTFE membrane, and thermal insulation cotton. After compacting the strip, it is necessary to ensure that all layers are uniformly stressed, so that a certain layer cannot be fractured. For example, the fluororubber cloth is relatively soft. If the edge of the bead is not chamfered, the fluororubber layer will be cut if it is cut directly at a right angle. Therefore, for a better strip, the contact surface will be R-angled or a layer of rubber gasket will be added.
The third pit: bolt material.It is recommended to match stainless steel bolts of the same grade. Don't try to save money with galvanized bolts-in a corrosive environment, galvanized bolts are finished first, and they can't be removed even if they are rusted. The anti-loosening washer also has to be fitted, which is easy to loosen if the running vibration is large. Especially at the outlet of the fan or the corner of the flue, the vibration frequency is high, and ordinary spring pads can't prevent it at all, so nylon anti-loosening nuts or spring washers with anaerobic glue have to be used.
How to press the press strip to prevent air leakage during installation? Practical experience sharing
In the first step, after the skin is paved, put the pressing strips first, don't tighten them all at once. Pre-tighten one by one from the middle to the diagonal lines on both sides, similar to the technique of changing screws in car tires. In this way, the skin is evenly stressed, and one side is not crushed to death and the other side is loose.
In the second step, after all the bolts are applied with force, they are gradually screwed to the specified torque in two or three times. Don't be too big of torque-if it is too fierce, the strip will deform, and the skin will be pressed out of dents, which will easily leak. What's the right size? Generally, for M12 bolts, the torque is enough to hit 40-50N·m, depending on the thickness of the strip. Take the torque wrench, don't trust the feel.
In the third step, check the sealing surface with a light or smoke cake after loading. Especially the large size of rectangular non-metallic expansion joint, the corner position is most likely to leak. You can take a flashlight from one side and see if there is any light leakage on the other side. Use a smoker if you have the conditions, and the smoke will come out clearly from the gaps. If you find a leak, don't rush to dismantle it. Try to tighten the bolts partially first. If it doesn't work, just add a sealant-silicone weather-resistant glue, which can withstand the temperature to 200℃.
What should I do if the strip is broken? Matching with non-metallic expansion joints and baffle doors
The bead itself is a wearable part, especially on the fan outlet with high frequency vibration or the flue gas pipeline with frequent start and stop. The fatigue fracture of the bead is not unusual. At this time, there is no need to change the whole expansion joint, just change the pressing strip and skin separately, which saves a lot of cost. But there is a detail: after the old press strip is removed, the residual glue and rust on the flange surface should be cleaned, otherwise the new press strip will be uneven and still leak.
Stringing andFlue gas baffle door、Double-sealed single-axis circular baffle doorThe connecting part between them, the pressing strip should avoid the flange or sealing surface of the baffle door to avoid interference. For example, the space between the two sealing surfaces of the double-sealed baffle door is limited, and too much protrusion of the pressing strip will push the door panel closing path.
If you are usingElectric plug-in insulation doorOperating space must be reserved for the installation position of the pressing strip. The plug-in door actuator is on the side, and if the strip bolt protrudes too much, you have to dismantle the strip when changing the actuator, which is troublesome. Communicate with the manufacturer in advance, let the strip bolts be countersunk for installation, or use hexagonal bolts.
Although the strip is small, it involves a lot. Choose the right and install it, and it can be used for three to five years without problems; If you choose the wrong one, you will have to rework it in half a year. Spend more time on the selection and installation in the early stage, which will save a lot of maintenance costs in the later stage.