Non-metallic expansion joint bonding, sounds like a little job, but it's really overturned enough for you to drink a pot
Two days ago, a customer of a cement factory said that the rectangular non-metallic expansion joint they changed leaked after only one week of use. When they were disassembled, the adhesive layer was directly detached. You mean it sucks or not? This kind of thing is actually quite common-insufficient bonding strength, wrong material selection and sloppy surface treatment can make the equipment scrapped in advance. Today, let's make this matter clear. From material selection to construction, to inspection, don't fall behind.
Step 1: Select materials, don't fool yourself with all-purpose glue
Fabric fibers, rubber, fluororubber, silicone rubber... the corresponding adhesives have to change accordingly. For example, the rubber compensator in our station can be done with neoprene adhesive; However, when it comes to rubber PTFE compensator, the surface inertness of PTFE is extremely strong, and ordinary glue can't be attached at all, so a special surface treatment agent plus fluororubber adhesive has to be used. There is also a pit: don't think that the temperature resistance grade is randomly selected. The working condition of the high-temperature axial expansion joint can reach above 500℃, and the adhesive is not temperature resistant enough, which is equal to white stickiness. So the first step is to find out what material and working conditions your non-metallic expansion joint is made of, and then choose glue.
Surface treatment: 60% of the bonding quality, don't fool
Many people try to save trouble and wipe it with a rag, and the result is degumming. The correct practice is divided into three steps: de-oiling, polishing and cleaning. Especially on the surface of fabric fibers, the loose fibers must be removed to expose fresh layers; Rubber pieces should be sandpaper to increase physical bite. The flange contact surfaces of our rectangular non-metallic expansion joints are usually coated and must be thoroughly removed. And guess what? Experienced older workers will wipe it again with acetone to make sure there is no residue. If this step is saved, the rest is all in vain.
Construction environment: humidity, temperature, pressure, none can be less
Silicone rubber adhesives are sensitive to humidity. If the humidity is less than 40%, it will cure slowly, and if the humidity is more than 80%, air bubbles may be produced. What to do? Control workshop temperature and humidity, or use heating lamps to assist. In addition, after bonding, the pressure should be kept, the pressure should be uniform, and the time should be at least 24 hours-don't believe those gimmicks of "half-hour curing", that is laboratory data, and the actual environment is far different. The non-metallic expansion joints (fabric fiber expansion joints) in our station are naturally cured for 72 hours before leaving the factory, which is the reason.
Different working conditions are treated differently, and no one size fits all
The non-metallic expansion joint installed next to the desulfurization flue gas baffle door, long-term contact with acid gas, the adhesive must be acid corrosion-resistant, fluororubber-based glue is the first choice. If it is used near the corrugated expansion joint used in power station industry, the temperature fluctuates greatly, and thermal fatigue has to be considered. On the other hand, in low-pressure situations such as manual plug-in insulation doors, the bonding requirements can be appropriately relaxed, but they can't be sloppy-anyway, I haven't seen any project that saves money by bonding.
How to test after bonding? Don't just pick your nails
Pick it with your nails and forget it if you can't pick it? Wrong. The formal practice is to test the peeling strength. Referring to the national standard of non-metallic expansion joints JB/T 12235-2015, the peeling linear speed and angle are regulated. If there are no conditions on the spot, at least do a visual + tapping inspection: uniform, no bubbles, no lack of glue, and no tapping sound. Another trick: the sample test piece is cured with the product, and the destructive test is done in advance. Previously, there were micro-cracks in the adhesive layer of a project, which was because the curing time was insufficient and it was eager to install. As a result, the thermal stress caused the crack to propagate during operation-this is the same as cooking before it is cooked.
The last truth
90% of the problems in bonding non-metallic expansion joints lie in the details. Glue selection, treatment, construction and inspection, which link is lazy, you have to double it back later. If you happen to have a plan at hand and are unsure, don't push it, talk to us directly-we have touched all materials and working conditions in our product library, from rubber compensators to non-metallic expansion joints, and the bonding scheme is naturally no problem.