1. What is a "split" large-diameter nonmetallic compensator? — Starting with the embarrassment of a pipe
The inner diameter of their flue is 3 meters, and they ordered an integral non-metallic compensator (that is, what we often call a non-metallic expansion joint, the kind of fabric fiber). As a result, when the goods arrived at the scene, the crane couldn't reach them, and the entrance of the factory building was narrow. It took three days to get such a soft big guy in. What's worse is that I accidentally scratched the skin during installation, and I tear the skin back and forth for a month.
Anyone who has done big pipelines understands this embarrassment. So-calledLarge diameter non-metallic compensator splitThat is, the traditional integral compensator is disassembled into several independent modules-usually the frame (metal flange frame) and ring belt (non-metal skin + insulation layer) are manufactured and transported separately, and then assembled and installed at the site. You can understand it as a "Lego-style" expansion joint: the frame is in place first, and the loop tape is closed last. The structure is not essentially different from the integral one. Both rely on flexible bands to absorb thermal displacement, but the manufacturing and delivery forms are completely different.
2. What on-site headaches does the split structure solve? — — Three major pain points of transportation, hoisting and maintenance
Transportation. The integral non-metallic compensator above DN3000 can easily exceed 2 meters in height and 3 meters in width, and ordinary trucks can't pull it at all-if it exceeds the limit, you have to break your leg just to get a permit. The split design disassembles the frame into 2~4 petals (rectangular or circular), and the width of each module is controlled within 1.5 meters, which can be done by standard flatbed trucks, saving more than 30% freight.
Hoisting. The integral compensator is lighter in weight (compared with the metal expansion joint), but the 3-meter diameter ring belt and frame are also one ton smaller, and the center of gravity is unstable. If there is no large crane on the site or the space in the factory is limited, the split modules can be put in place one by one with hand-pulled hoists or forklifts, and then assembled at the flange. Two days ago, a buddy from a cement factory said that their hot air duct was split, and three people installed it in half a day. At least eight people had to add cranes to change the integral type.
Maintenance. This kind of non-metallic skin has a life span (generally 3~5 years), and it must be replaced if it is broken. In one piece, you have to disassemble it with the frame-but the frame is welded to the pipe, and you have to cut it and then weld a new one on it. What about the split? Loosen the pressure plate screw, pull out the old loop tape, stick the new loop tape in, and press it tightly. Halving maintenance costs is not an exaggeration.
3. Split vs monolithic: Don't just focus on the price when choosing a model, these points are more important
If the split style is so good, should the monolithic style be eliminated? Don't hurry. In terms of price, the split type is usually 10% ~15% more expensive than the integral type because it has an extra set of connectors and sealing structure. Therefore, it is only cheap, and it is completely enough to choose the integral type in the case of small caliber (below DN1000).
But large calibers (especially above DN2000) must not just look at price. There are also a few hard indicators:
- Pressure resistance: There is one more compression structure between the split ring belt and the frame. If the sealing surface is not well treated, the low pressure is OK, but the positive pressure exceeds 0.1MPa, which is dangerous. The split non-metallic expansion joint of our factory has stepped groove + double sealing strip on the flange surface, and the measured pressure is 0.3MPa without leakage.
- Thermal displacement compensation amount: The split type and the integral type can be completely consistent in the design of ring belt materials and layers, and the compensation amount is not lost. However, it should be noted that if the joints of the split frame are deformed by welding, the ring band will be wrinkled, and the actual compensation amount will be discounted. Therefore, manufacturers must be required to do a good job in welding process evaluation.
- Site installation conditions: If the pipe is already in place and the space on both sides is narrow, the split is almost the only solution. For example, the flue at the outlet of the desulfurization tower can't be stuffed in the integral type, and the split type is installed with the frame first and then the ring belt, which is perfect.
Small-caliber drawings save trouble and buy monolithic; For scenes with large diameter, limited space and frequent maintenance, you can bite your teeth and split it, which will be worry-free in the later stage.
4. Install the split compensator. If you make these steps wrong, you will install them for nothing
Split installation looks simple, but there are quite a few pits. The most outrageous thing I have ever seen is that the customer installed the upper and lower lobe frames backwards, and as a result, the bolt holes didn't match up, and the site had to be repaired. Keep these four key points in mind:
Step 1: Frame pre-assembly.First, transport the parts to the site, lay them flat on the ground, pre-screw them with bolts, and check the diagonal error. The roundness deviation of the circular frame does not exceed 5mm, and the diagonal difference of the rectangular frame does not exceed 3mm. No problem to weld the seam to death again (Note: the grade of the welding rod is consistent with the base metal, and it is polished smoothly after welding).
Step 2: The frame is in place.Use a sling or forklift to feed the assembled frame between the flanges on both sides of the pipeline, and adjust the position to ensure that the center line of the frame coincides with the axis of the pipeline. There is a "nonsense" here, but it must be said: Don't use wire rope to strangle the frame directly, it will easily scratch the sealing surface.
Step 3: Install the loop belt.This is the easiest link to go awry. The band (i.e. the non-metallic skin) must be threaded out from the inside of the frame, allowing the strip to press the edge of the band. When screwing on the pressure plate, tighten it alternately according to the diagonal line, and the torque value refers to the torque given by the manufacturer (generally 80~120N·m). Don't screw to death once-first pre-tighten to 50%, and then apply the force evenly in two times, otherwise the band will wrinkle.
Step 4: Check the seal.After installation, do the air pressure test, the pressure is 1.5 times of the working pressure, and the pressure is kept for 15 minutes. Brush all the splicing seams and pressing plates with soapy water. Bubbling is leakage. You have to readjust the pressing plates or replenish the sealing plaster. This step is saved, and smoke leakage is found when it is put into operation later, and the shutdown loss can be more than the money of one compensator.
5. Case talk: the real performance of split non-metallic compensator on desulfurization flue and cement hot air pipe
Case 1: Exit flue of desulfurization tower of a coal-fired power plant.The flue diameter is DN3200, the medium is saturated wet flue gas, the temperature is 50~70℃, and the pressure is ±3kPa. The original design used integral non-metallic expansion joints (fabric fibers), but the on-site hoisting space was blocked by towers and concrete columns, and large cranes could not enter. Later, the split type is used-the frame is divided into four petals, each petal is 1.2 meters wide, and it is sent in by a forklift through the manhole door for assembly. The loop belt adopts four-layer structure: silicone cloth + glass fiber cloth + PTFE membrane + stainless steel wire mesh, which is both acid-resistant and negative pressure-resistant. It has been in operation for two and a half years so far, and there has been no record of downtime due to leaks. The owner's posting: the transportation + hoisting cost saves 42,000 yuan compared with the overall scheme.
Case 2: Hot air duct at kiln tail of a cement plant.Large temperature fluctuation (normal temperature ~400℃), pipe diameter DN2400. The integral compensator ring belt ages fast at high temperature for a long time, so it has to be replaced every two years. However, when the integral replacement is done, it is necessary to cut the frame and build scaffolding, and it takes 3 days for an overhaul. After switching to split type, you only need to loosen the pressure plate to replace the loop belt, pull out the old loop belt and plug in the new loop belt, and two people can do it in half a day. Maintenance workers say, "This stuff is called humanization".
To put it bluntly,Large diameter non-metallic compensator splitIt is not a new technology, but a practical solution to solve the three old problems of "can't be installed, transported and repaired" on the spot. Don't look down on this structural splitting-people who can figure out simple problems in engineering often save the most money.