What is good about the boiler inlet non-metallic compensator? Find out the working conditions first
Everyone who has worked at the boiler entrance knows how bad the working conditions are: the high-temperature flue gas rushes straight, and the temperature is often three or four hundred degrees; The boiler starts and stops frequently, and the thermal displacement is large and miscellaneous; There is still dust in the smoke, and it is ground like sandpaper. If a metal expansion joint is installed in such a place, it will almost be a matter of time before fatigue cracks. I have seen many power plants, and the metal bellows cracked in half a year. When I removed it, I saw that the welds were full of cracks. What about that?Boiler inlet non-metallic compensatorDesigned for this scenario-fabric fibers plus temperature-resistant coatings, the flexible structure can absorb axial, lateral and angular displacements simultaneously without transmitting thrust to the boiler body. To put it bluntly, it is like a soft joint, dissolving the stress of head-to-head.
Don't just look at the nominal temperature when selecting a model. These three dimensions are the key
Many purchases ask "how much is the temperature resistance" as soon as they come, as if everything will be fine if the temperature is enough. But when things go wrong, they die somewhere else. I took it apart for you and said:
- Media composition:Does the flue gas contain sulfur? Does it contain moisture? Sulfur-containing flue gas will form sulfurous acid when it meets water, which is extremely corrosive. At this time, you have to choose a composite structure with corrosion-resistant coating, such as silicone cloth + ceramic fiber. If there is only hot and dry smoke, ordinary fiberglass cloth can carry it.
- Pressure fluctuation range:The boiler inlet pressure is generally not high, but fluctuates greatly. The withstand voltage of the non-metallic compensator is naturally weak. If it exceeds 50kPa, don't put it hard. It should be replacedCorrugated expansion joint for power station industryOrExternal pressure single axial expansion joint。
- Direction of displacement:Pipe strike determines whether the displacement is axially stretched, transversely misaligned, or angularly deflected. Rectangular entrance commonly usedRectangular non-metallic expansion jointThe circular pipe is equipped withCircular non-metallic compensator。 Note: If the pipeline has a compound displacement in multiple directions, the flexibility advantage of the non-metallic compensator is fully reflected.
In addition, under low and medium temperature operating conditions (rubber compensatorAndRubber PTFE compensatorIt can also be competent, and the cost is lower. However, when it exceeds 300℃, the composite structure of silicone cloth + ceramic fiber is honestly used. Don't be cheap, it's more expensive to replace after burning it out.
The pits in the installation process, six of the ten failures are here
Two days ago, I met a customer. The non-metallic compensator leaked smoke after three months of use. When I removed it, I found that the guide tube was installed backwards. The direction of the arrow points to the direction of the medium, and as a result, the high-temperature smoke blows directly on the fabric layer and wears out in a few minutes. Remember:The guide tube must be directed toward that direction of the medium flowThe function is to block the straight blowing and let the airflow go along.
Cold-tight pre-stretching。 Steam boiler pipe from cold state to hot state, the temperature difference is large, the pipe elongation is considerable. If the non-metallic compensator is not pre-stretched when installed, the fabric will be pulled to the limit in the hot state, and the life span will be greatly reduced. How to calculate the specific stretch amount? Refer to the question and answer on how to adjust the expansion joint tie rod nut, which has detailed steps.
uneven bolt tightening torque。 The flange surface is often warped because workers use ordinary wrenches to twist by feel, some tight and some loose. It is recommended to use a torque wrench and tighten it in three times in diagonal order. Check the manufacturer's manual for torque values, don't pat your head.
Operation and maintenance: Nonmetallic compensators fear these two things the most
One is sharp object scratching. Once the welding slag and metal sheets left by the air duct construction are embedded in the fabric fiber, a hole can be ground out in a few minutes once the equipment runs. Therefore, be sure to thoroughly clean the inside of the pipe after installation, and it is best to confirm it with an endoscope.
The second is local overheating. When the boiler load suddenly changes, the local temperature may exceed the design value and burn out the liner. For example, at the entrance of a rotary kiln in a cement plant, the non-metallic compensator bubbles and hardens in less than half a year, because the temperature of the kiln head occasionally soars to 450℃. In this case, either change to a material with a higher temperature resistance grade or install insulation. It is recommended to check the fabric surface once a quarter: illuminate it with a bright flashlight to see if it is blackened, blistered, and hardened. Once you find it, replace it immediately-don't wait until the smoke leaks before shutting down, that will be a big loss.
Advantages and disadvantages of non-metallic compensators compared to metal schemes
Low cost, light installation and good vibration isolation-these are the three advantages of non-metallic compensators. a set ofRectangular non-metallic expansion jointThe weight is only 1/5 of the metal expansion joint of the same size, and no large hoisting equipment is needed during installation. And it does not transmit thrust and is friendly to the boiler body and pipe rack.
Weak pressure resistance。 Therefore, the boiler inlet is generally only used in the low pressure section of Corrugated expansion joint for power station industryOrExternal pressure single axial expansion joint。 In addition, if there is wet flue gas behind the desulfurization tower on site, don't forget to considerDouble-sealed flapper doorAndDesulfurization flue gas baffle doorLinkage seal-wet flue gas is highly corrosive, and the non-metallic layer needs additional protection.
In general,Boiler inlet non-metallic compensatorIt is a very cost-effective choice, but the premise is to choose the right model, install the right direction and manage the maintenance. Follow the above steps, and it will last for three to five years.