Non-metallic compensator leaking? Don't be in a hurry to change, try these steps to fix the leak first
I answered a phone call two days ago, and the customer said that the non-metallic expansion joint of their dust removal system began to smoke after half a year. When disassembled, the particulate matter in the smoke grinds a hole in the skin-this kind of thing is too common in cement and electric power industries. The non-metallic compensator (also called fabric fiber expansion joint) is leaking. Your first reaction is to replace it with a new one? Don't worry. Find out the leak point first. 80% of the cases can be fixed on site.
Where's the leak? Three common locations
Non-metallic compensator is used in flue gas pipeline and desulfurization system. The medium temperature is high and corrosiveness is strong, and the leakage is basically in three positions: one is the overlap joint between layers, the other is the sealing surface at the connection of flange, and the third is the riveting point or weld between the guide tube and the skin. And guess what? Many times it is not the skin itself that is broken at all, but the bolts are loose-the flange surface leaks, which can be solved by tightening. So the first step is not to rush to buy new pieces. First, take a flashlight and brush it with soapy water to see where the bubbles come from.
The medium contains sulfur or strong acid and alkali, and the sealing gasket becomes brittle after aging, and it will break when touched. At this time, you have to judge the type of leak: is it pitting perforation (small hole), sealing surface failure, or overall fatigue cracking? The countermeasures are completely different in different situations.
Preparation before mending leaks: Wrong material selection is equal to dry for nothing
Don't put any glue on it. This site hasrubber compensator、Rubber PTFE compensator、Non-metallic expansion jointAnd other products, leak repair materials must match the working conditions. High-temperature flue gas pipeline uses high-temperature resistant silicone rubber or fluororubber sealant, and ceramic fiber repair materials have to be replaced when the temperature exceeds 300℃. If the medium contains acid and alkali, use PTFE sealing tape, refer to this sitePTFE-lined hoseCorrosion resistance ideas.
Be sure to clean up before repairing the leak. Oil, dust accumulation and old glue layer have to be shoveled off to expose fresh substrate. Wipe it with acetone or alcohol, and wait until it is completely dry before starting. Otherwise, if you make it up, it will drop in two days.
By the way, if the flange surface leaks, check the bolts first-in many cases, it's just thermal expansion and contraction that causes loosening. Just take a torque wrench and re-tighten it according to the original torque. Don't get major surgery right up there.
Three Methods of Leakage Mending in Actual Combat
Method 1: Small perforations or cracks are patched with temperature-resistant cement + glass fiber cloth in multiple layers.Apply the glue to the break first, stick the cut fiberglass cloth, and then scrape it flat with a scraper to ensure that there are no bubbles. Apply one layer until it dries (usually 4-6 hours), then apply a second layer, at least three layers. Finally, brush a layer of temperature-resistant sealant on the outer surface to form a protective film. This method is suitable for perforations less than 20 mm in diameter.
Method 2: The local damage area is large, and the skin of the same material is cut and replaced.This site has ready-madeNon-metallic expansion jointSkin material, cut according to the damaged area, overlap width at least 50mm. Apply high-temperature-resistant adhesive to the overlap surface, and rivet and fix it with stainless steel press strips and self-tapping screws after pasting. Note that the spacing of the pressing strips should not exceed 150mm, and the riveting points should be staggered out of the original structural holes to avoid stress concentration.
Method 3: Total Outsourcing? Don't mess around.Someone asked if you could just wrap a metal compensator on the outside? No way. This site hasHigh temperature axial expansion joint、Universal corrugated expansion jointHowever, these metal parts are used for pipe displacement compensation, and their structure is completely different from that of non-metallic skin. Hard wrapping will limit thermal displacement, but accelerate damage. A more reliable way is to customize a short-joint non-metallic expansion joint to replace the damaged section. The size should match the original pipeline. Just provide the diameter, temperature, pressure and displacement when ordering.
Testing and routine maintenance after leak repair
It can't be put into operation directly after repairing, so do the airtightness test first. Brush soapy water or foaming agent on the repair area, introduce 0.05~0.1MPa compressed air (the design pressure of non-metallic compensator is low, so don't overpressure), and observe whether there are bubbles. If there is no air source, feel the air leak point with your hands after running, or use infrared thermal imaging to see the temperature abnormality-the temperature at the leak will be significantly lower.
Check the skin surface quarterly for blistering, delamination, and hardening. Especially in cement plants,Metal Corrugated Expansion Joints in Cement IndustryNext to the non-metal segment, dust wear is fatal. It is recommended to establish a ledger, record the location of each leak and the number of repairs, and accumulate data to judge when to completely replace it.
When should I give up patching and replace it with a new one?
If the same part is repaired more than twice, or the leakage area exceeds 30% of the total area, don't worry about it. The design life of non-metallic compensator is generally 3~5 years, and the aging will be accelerated by temperature, corrosion and mechanical fatigue. Also note that if the leak occurs in connection with this siteFlue gas baffle door、Electric plug-in insulation doorWhen connecting, consider whether the system vibrates too much. Vibration will cause fatigue cracking of the skin, which is useless. You have to install damping or switch to non-metallic expansion joints with reinforcing nets.
Don't save hundreds of dollars to make up for the leakage. As a result, the leakage expands and leads to the shutdown of production-the loss starts with tens of thousands of dollars. If you need to change, you will not lose money in the general ledger.