Find out what material the compensator ring belt is made of first, and the glue can be selected correctly
Nonmetallic compensators (also called fabric fiber expansion joints) are not a single piece of material. They are usually pressed together by several layers of composite materials-the inner layer is corrosion-resistant fluororubber or silicone cloth, the middle reinforcement layer is glass fiber or aramid fiber, and the outer layer is covered with a weather-resistant rubber coating. How much can the formula of different manufacturers differ? Just ask the supplier: some are mainly silicone rubber, some are fluororubber, and some are polytetrafluoroethylene (PTFE).
The glue doesn't match the substrate, and it is a fool to stick it on. For example, the surface energy of fluororubber is particularly low. Ordinary epoxy glue is coated with water, and it can't stick at all. It has to be coated with a special fluororubber treatment agent and then matched with special glue. So the first step, don't rush to buy rubber, ask your compensator supplier first: What rubber grade is used for the loop belt? They know best.
Common adhesives on the market, advantages and disadvantages are presented to speak human language
- Room temperature vulcanized silicone rubber (RTV silicone): Temperature resistance-60℃ to 250℃, good elasticity, suitable for low pressure, non-corrosive flue gas pipeline. Press the compensator body with your hand, which is soft, and RTV silicone is the most suitable. The disadvantage is that the intensity is not high, and it can't hold up in high-pressure situations.
- Neoprene adhesive (e.g. 801 glue): Initial adhesion is strong, the cost is low, and it will be firm once it sticks. However, the temperature resistance generally does not exceed 100℃, and it is easy to swell and soften when encountering oil. If you use it for temporary repair of room-temperature air ducts, it will work, but it won't work for a long time.
- Epoxy resins: High strength, resistance to chemical media, but hard after curing, no elasticity at all. The compensator itself needs displacement compensation, and the epoxy cracks as soon as it is stretched. If you really want to use it, you must make a flexible transition layer first.
There is also polyurethane glue, which is wear-resistant and oil-resistant, but it is afraid of ultraviolet aging, so it has to be covered outdoors. Before selecting glue, press the compensator body with your finger-silica gel is selected for soft, and epoxy can be considered for hard ones, but it must be fixed mechanically, otherwise it will crack when stretched.
Selecting glue according to working conditions is the core: temperature, medium and pressure must be missed
A few days ago, I dealt with a customer in a cement plant. Their non-metallic compensator was used in the high-temperature flue gas pipeline at the tail of the kiln, and the temperature was around 300℃ for a long time. I first used ordinary silicone gel, and it carbonized and fell off within two days. Later, it was replaced with high-temperature silicone sealant (temperature resistance 350℃), and then it was stabilized with mechanical striping.
If you are a desulfurization flue, the medium contains sulfuric acid and sulfurous acid. At this time, ordinary glue can't hold it at all, so you must use acid-resistant fluororubber special glue or PTFE lining special adhesive. Epoxy resin will slowly corrode away in this environment. Let's talk about pressure: low-pressure pipelines (less than 0.05MPa) can be wrapped with glue; In medium pressure (0.1-0.2MPa), it can't be held by glue alone, so it has to be matched with clamps or pressing strips.
Is that the truth? Glue is not a universal glue. If the working condition is wrong, no matter how expensive the glue is, it will be useless.
Construction details determine the success or failure of bonding. Don't ignore these steps
Surface finishing is a top priority. Wipe the adhesive surface clean with acetone or alcohol to remove release agent, oil and dust-if this step is not done properly, the rest will be for naught. Then sand it a little to add roughness. The surface of fluororubber has to be activated by a special primer, otherwise the glue can't hang.
The thickness of glue layer is controlled at 1-3mm. Too thick, slow to cure and easy to cohesive failure (the glue layer splits itself); Too thin, not enough adhesion, pull off. Don't be lazy about curing time: silica gel generally takes 24 hours to be completely vulcanized, and epoxy takes more than 8 hours, during which it can't be vibrated by force. If you encounter low-temperature weather (below 5℃), the performance of most glues is discounted, so you have to heat or change low-temperature products. If these details are not done, no matter how expensive the glue is, it will be useless.
Common causes of bonding failure and remedies, avoid detours
Interface detachment (the glue separates from the compensator), cohesive failure (the glue layer cracks itself), and the compensator body tears. Interface detachment is mostly due to poor surface treatment or wrong glue type selection; Cohesive failure indicates that the strength of the glue is insufficient or the cure is not thorough; The body is torn, that is, the compensator itself is aging and brittle, and no matter how good the glue is, it can't be saved.
If your compensator has been used for three or five years, and the ring belt has hardened and peeled, don't toss the viscose. It is more cost-effective to directly replace the whole non-metallic expansion joint (fabric fiber expansion joint). This station has ready-made rectangular non-metallic expansion joint and rubber compensator products, which are produced according to the standard JB/T 12235-2015, with supporting installation guidance, which saves worry and effort.
Before selecting glue, ask yourself-what temperature? What is the medium? How stressful? Once these three questions are clarified, the glue will naturally be chosen correctly.