The "soft joint" of the boiler smoke duct: what exactly does the non-metallic skin compensator do?
Anyone who has been to the boiler room knows that the smoke duct is no joke when it expands and contracts with heat. The pipe stretches as soon as it is hot and shrinks as soon as it is cold. If nothing is buffered in the middle, the weld collapses and the equipment breaks down, it will all be a matter of minutes. At this time,Non-metallic skin compensator for boiler plantIt comes in handy-to put it bluntly, it is the "soft joint" of the smoke duct system, specifically designed to absorb axial displacement, lateral displacement and angular displacement, while also absorbing shock and noise. The manufacturer's term is "non-metallic expansion joint (fabric fiber expansion joint)", which is used to be called skin compensator by insiders. Don't underestimate this layer of cloth and several layers of glue, it carries real temperature difference and vibration in the operation of the boiler.
Two days ago, I met a customer, saying that their factory changed two skin compensators last year, but it leaked in half a year. As soon as I heard it, I guessed that 80% of the selection was a pit. The working conditions of the boiler smoke duct are complicated, the temperature ranges from normal temperature to 600 to 700 degrees Celsius, and there are sulfur oxides and dust sandwiched in the medium. If any parameter is wrong, the life span will be discounted.
First look at the working conditions: temperature, pressure and medium, none of them can be missed
chooseNon-metallic skin compensator for boiler plantThe first step is not to turn over the sample, but to find out the working conditions. The temperature determines the temperature resistance grade of the skin material-ordinary silicone cloth only carries 250℃. If the flue gas temperature exceeds 400℃, you have to confirm with the manufacturer whether to use fluororubber cloth or ceramic fiber layer. Not to mention the pressure, although the boiler smoke duct is mostly slightly negative pressure, the positive pressure impact at the moment of fan start can directly burst the weak compensator. The medium is the easiest to overlook-the condensed water in the flue gas is acidic, and the ordinary rubber compensator will rot if it can't last for three months, so it has to be lined with PTFE or corrosion-resistant formula.
An ordinary non-metallic expansion joint was used in the flue at the inlet of the desulfurization tower of a power plant. As a result, the skin was corroded by the acid dew point in less than half a year. Later replaced withNon-metallic expansion joint (fabric fiber expansion joint)With an anti-corrosion coating on the inner layer, it is still stable for more than two years now. When selecting a model, you also need to look at the pipe layout-is it a rectangular flue or a circular flue? This site has correspondingRectangular non-metallic expansion jointAndNon-metallic expansion joint (fabric fiber expansion joint)Different structures have different compensation capabilities. Don't try to save trouble. Take a round, hard and square one. It's as uncomfortable as wearing small shoes.
The three most common mistakes to make when installing, how many have you stepped on?
The installation looks simple, but the rollover rate is the highest. First mistake: not removing the transport screw. When the non-metallic skin compensator leaves the factory, several screws will be installed in order to fix its shape. This thing must be dismantled after installation, otherwise the compensator can't move, which is equivalent to welding a section of pipe. Last year, because of this, the thermal expansion of the pipeline in a chemical plant directly cracked the compensator flange.
The flange surface is uneven. The flue flange of the boiler is either deformed by welding, or the lining is not shoveled clean. When the skin compensator is installed and screwed, the local compression force is not enough, and smoke leaks from the gap after two days of operation. Be sure to check with a level ruler before installation, and uneven areas should be leveled or polished.
The guide tube direction is ignored. a great manyNon-metallic skin compensator for boiler plantThere is a guide inside, and the arrow is clearly marked-it must point to the direction of the medium flow. If it is installed backwards, the smoke directly washes the inner wall of the skin, the temperature exceeds the limit and the wear, and the life is directly cut in half. in the stationSpecific Function of Expansion Joint Guide TubeThat FAQ is very thorough, so you can turn it out and read it before installing it.
The length of life depends on these points-don't wait for a leak to replace
Some people say that the skin compensator is a consumable, and it is normal to change it every three years. However, under the same working conditions, some factories can use it for five years, and some factories leak in one year. What's the difference? First, whether the number of skin layers is enough. The positive pressure pipeline must have at least five layers: the outer layer of weather-resistant fluorine adhesive tape, the middle layer of heat insulation cotton and the inner layer of anti-corrosion fluorine adhesive tape. Don't believe that "two floors are enough", it is cost-saving to fool people. Second, the insulation cotton should be compacted. During installation, the compression amount of the quilt is not enough, and when the high-temperature smoke flushes, the cotton layer becomes thin, and the local hot spots will be wasted once they are worn. Third, the flange pitch should not be too thin. According to JB/T 12235-2015 standard, it is recommended that the bolt spacing should not exceed 150mm. If the spacing is large, it will not be tightly pressed, and the sealing performance will collapse directly.
Don't change the pipe support near the expansion joint randomly. For the convenience of maintenance, some factories removed the guide bracket next to the compensator. As a result, the pipeline lost its constraint, and the lateral displacement was fully pressured on the skin, which tore the fabric layer in a few months. Remember, the compensator compensates for displacement, not the job of carrying the bracket for you.
Compared with metal expansion joints and rubber compensators, why does it win?
Why not just use metal expansion joints? Or a rubber compensator? We need to see the scene. Metal expansion joints such asMetal rectangular expansion joint、Universal corrugated expansion jointThe pressure and temperature resistance are really strong, but that thing has a great thrust on the pipeline, and it is heavy in weight and requires high installation space. The smoke duct of the boiler is often tens of meters long. If it is all made of metal, it will cost twice as much to fix the bracket. Moreover, when the flue gas contains acidic condensate, the metal bellows is prone to stress corrosion and cracking, and the replacement cost is painful.
What about the rubber compensator? Corrosion resistant, cheap, easy to install, but low temperature and pressure ceiling. Generally, the rubber compensator can't carry more than 150℃, and the flue temperature at the tail of the boiler can easily reach 300℃, so you don't think about it. WhileNon-metallic skin compensator for boiler plantCombines the advantages of both: fabric layer + thermal insulation cotton + anticorrosive coating, can withstand the high temperature of 600℃, the axial compensation can be ±50mm or even greater, the lateral angular displacement can also be absorbed, and the reaction force to the pipeline is minimal. In the stationrubber compensatorAndRubber PTFE compensatorIt is more suitable for low-temperature and low-pressure acid-alkali medium pipelines, and the smoke duct still has to be non-metallic.
To put it bluntly, which one to choose depends on the budget in your pocket and the life of the plumbing. You want to save money to the bone, then gamble with the rubber one; You want to use it safely and reliably for ten years, and the skin compensator is an old scalper verified by the boiler industry.
Maintenance formula: look diligently, wipe lightly, don't hold hard
Finally, a few words about maintenance. The non-metallic skin compensator is most afraid of "invisible problems". During daily inspection, take a flashlight to illuminate the skin surface. Is there any bulging, cracking and local blackening? Blackening means overheating and carbonization, so you have to check whether the temperature is exceeded. Fluid buildup on the surface? It could be a flange leak or condensate backwards. Don't be too troublesome, watch it once a week, for a minute, and save it from downtime before regretting it.
When cleaning, don't scrape with a hard brush, let alone flush the skin directly with steam-that layer of fabric looks strong, but it can't stand the tearing of high-pressure steam. Gently wipe with a soft cloth dipped in neutral cleaner to remove dust and oil. One more thing: don't wait until it leaks to change it. If you find a hole as big as a sesame seed on the surface of the skin, you have to prepare spare parts. Repair glue can only help emergencies, but can't manage for three months.
Do you ask if there is a new way? No. But remember one formula: watch diligently, rub lightly, and don't hold hard. Do these three things,Non-metallic skin compensator for boiler plantIt will give you at least two more years. If you don't believe me, try it.