1. Read the figure before assembly: What does the structure of the non-metallic compensator look like?
Don't have a headache at the drawings as soon as you get up. The core components of non-metallic compensators (also called fabric fiber expansion joints or rectangular non-metallic expansion joints) are nothing more than three: a metal frame (usually carbon steel or stainless steel), a non-metallic loop (multi-layer fabric + fluororubber/silicone coating), and strips and fasteners. The common "guide tube" on the drawings is not necessarily standard-depending on the working conditions, if it is a high-temperature flue gas pipe, we generally install it on the inside. Keep one thing in mind:Non-metallic compensator assembly flow chartInstead of decoration, every line corresponds to a part position, especially the marking of flange bolt holes and loop band overlap seams. If you are wrong, all the follow-up will be in vain. You asked how to see the overlap direction? Drawings usually have arrows or inlets on them, don't take it for granted.
2. Pre-installation of flange and frame: If this step is not done well, sealing is a joke
Don't be in a hurry to put the tape on after the frame is welded. First check the flatness of the flange surface. According to the national standard JB/T 12235-2015, the flange flatness error of non-metallic compensator cannot exceed 1.5mm/m. We have encountered a lot of on-site feedback on air leakage. When we disassembled it, we found that the frame was deformed by welding, and the strips could not be compressed no matter how they were twisted. Correct practice: After the frame is welded, go to the platform for correction first, and then pre-tighten the upper and lower flanges once with bolts to see if there are any gaps. If it is a rectangular non-metallic expansion joint, the four-corner weld is most likely to warp, so it has to be smoothed after repair welding. You save time in this step, and you have to rework the pressure test later.
3. Cutting and overlapping of fabric bands: the size is 3mm wrong, and the life is less than two years
The loop belt is the "soft core" of the entire compensator. When cutting, be sure to leave an overlap margin according to the drawing-the conventional is 50-80mm, depending on the thickness and number of layers. The overlap direction should follow the flow direction of the medium to avoid the direct impact of air flow on the seam. Two days ago, I met a customer who cut it himself, and reversed the warp and weft directions. As a result, the ring band tore during thermal expansion. Also, the edge of the band must be edged, otherwise the fiber burr will become an air leakage channel. The non-metallic ring tape we use is usually a composite layer of silicone cloth + fluororubber cloth + glass fiber felt, and the laying order can't be messy: the outermost layer is weather-resistant, the middle layer is insulated, and the inner layer is corrosion-resistant. Align layer by layer when assembled and use a dedicated press roller to drive away air bubbles. Alas, this step tests patience the most, but it is also the link that best reflects the value of non-metallic compensator assembly flow chart.
4. String and bolt tightening: the tighter the torque is not tightened, the better
After the loop tape is laid, press the strip. The strips are divided into continuous strips and segmented strips, and the rectangular non-metallic expansion joints are often used for segmented strips, which are convenient for adjustment. Bolt tightening should be divided into three steps: first pre-tighten to 50% torque, and check whether the ring belt is evenly pressed into the groove; Then screw to 80% in diagonal order; Finally cycle through to 100%. The torque value is determined according to the bolt specification and flange material. M16 bolts are generally screwed to 80-100N·m, which will squeeze the ring belt or deform the bead. After installation, check the gap between the press bar and the flange with a gauge, and it is considered qualified if the 0.1mm plug is not inserted. Why is it so troublesome, you ask? Because once the ring belt is biased, the stress is uneven during hot operation, and it will crack in a few months. Think about it, is it a loss if a piece of equipment is scrapped because a few bolts are not tightened properly?
5. Factory inspection and pre-compression: Smart engineers will stop losses at this step
Assembly does not mean delivery. Air tightness test must be performed-hold pressure at 1.5 times the design pressure for 15 minutes according to JB/T 12235-2015. But what is more important is pre-compression: the non-metallic compensator should be pre-compressed to 50-70% of the designed displacement according to the working conditions before leaving the factory, so that the fibers and coatings inside the ring belt can fully adapt to the stress distribution. We have seen some people put the loop belt loosely, but as a result, when the temperature heats up at the scene, the compensation amount is not enough and it is directly broken. Conversely, preloading too much will not work, and the band folds will wear out. So,Non-metallic compensator assembly flow chartThe last step should be marked with "pre-compression amount" and "cold tightening value", which are the lifeline before installation.