Take it apart: What exactly is the flue gas flange non-metallic compensator?
To put it bluntly, this is what we always sayNon-metallic expansion joints (fabric fiber expansion joints)A variant of-specially equipped with flange interface, used on flue gas pipes. The structure is not complicated: the outermost layer is temperature-resistant fabric fibers, such as silicone cloth and fluorine tape; Thermal insulation cotton sandwiched between; There are also deflectors or anti-corrosion coatings inside. The flange end plate is welded directly to the nozzle and sealed by bolts.
Compared with ordinary non-metallic expansion joints, flue gas flange models emphasize corrosion resistance and high temperature resistance. Why? Because the smoke often carries sulfide and dust, the temperature is always two or three hundred degrees. If you take a regular civilian compensator up there, a month will suck.
How did it catch fire?
In desulfurization, dust removal, power stations and cement industries, the demand for non-metallic compensators has risen fiercely in recent years. The reason is simple: the metal expansion joint can't bear under the conditions of sulfur-containing wet flue gas. Electrochemical corrosion plus dust wear, two or three years to leak. Do you calculate, how much does a power station lose in one day for maintenance and shutdown? Hundreds of thousands or even millions.
Non-metallic fabric fibers are naturally not afraid of acid and alkali, and can absorb multi-directional displacement-axial, transverse and angular, without metal fatigue. Two days ago, I met a power plant customer.Metal rectangular expansion jointThree times in two years. Replace it with oursNon-metallic expansion joints (fabric fiber expansion joints)— Notice that we're usingRectangular non-metallic expansion joint— Four years old and still in good condition. Do you say it's a good deal or not?
Don't step on pits in model selection: temperature, pressure and medium are three hurdles
Conventional silica gel cloth can withstand the temperature of about 260℃, and fluorine tape can reach the beginning of 300℃. No matter how high it is, ceramic fiber composite structure must be used. Don't think that all non-metals are the same. If the temperature exceeds, the skin will directly carbonize and be as brittle as paper.
The pressure thing,Flue gas flange non-metallic compensatorGenerally used in low positive or negative pressure systems. The design pressure usually does not exceed 0.1MPa. Don't use it under overpressure-otherwise, the fabric layer will bulge and tear, so wait for the furnace to be stopped.
Media is more critical. The acid dew point of the flue gas after wet desulfurization is low, and the pH value of the condensate is as low as 2~3. At this time, you must choose the model with PTFE lining or acid-resistant coating, otherwise it will rot for half a year. We have encountered a customer who bought an ordinary model cheaply, but the flange was rusty and worn out in three months.
Compared with metal compensator, the advantage is not only corrosion resistance
Many people think that non-metallic compensators are just "bargains", but they are actually wrong. For flue gas pipelines of the same diameter, the metal compensator can only absorb a small amount of displacement by bellows, and the large displacement needs to add a compound structure, which doubles the cost. However, a single-layer non-metallic expansion joint can absorb the axial displacement of more than 50mm and the angular displacement of ±5°, and the price may only be half that of metal.
In addition, the non-metal has good heat insulation performance. The surface temperature of the pipeline can drop a lot, which is to protect the adjacent equipment. However, the disadvantages are also obvious: the pressure bearing capacity is weak and cannot be used in high-pressure pipelines; Impact resistance is poor, and it may break directly when it encounters water hammer or pipe burst airflow. Therefore, you have to weigh the working conditions clearly when selecting the model-don't expect it to be a universal plaster.
Installation and routine maintenance Several easy-to-overlook details
First, the flange connection surface must be flat. Otherwise, once the bolts are tightened, the local force of the fabric layer is uneven, and it is easy to tear during operation. Second, the direction of the guide tube should be aligned with the flow direction of the medium-the arrow mark cannot be installed backwards, and the guide tube will become a resistance member if it is installed backwards. Third, the thickness of the insulation layer should be calculated well. Insufficient external insulation can lead to excessive temperature on the outer surface of the skin, accelerating aging.
Whether the flange bolts are loose (thermal expansion and contraction will drop the preload), and whether there are any bulging or leakage marks on the skin surface. Once you find wear or small holes in the fabric layer, repair or replace it quickly. Don't wait until air leaks before stopping the furnace.
Common Myth: Don't worry about the flue gas flange non-metallic compensator after installation?
Wrong! While it is less maintenance than a metal compensator, it is by no means "once and for all". Especially in wet flue gas conditions, the internal condensate accumulates at the bottom of the corrugation for a long time (despite the drainage holes), which will slowly corrode the flange and skeleton. It is recommended to open the drain valve every six months to drain the condensate.
In addition,rubber compensatorRarely used in flue gas systems-because rubber is not resistant to high temperatures and acids and bases. If mistakenlyRubber PTFE compensatorWhen used on flue gas pipes, it is basically scrapped in half a month. When selecting the model, look for the serious name of "non-metallic expansion joint (fabric fiber expansion joint)", and don't be fooled by low-priced counterfeit goods.