What exactly is the cause of air leakage in non-metallic compensators? - -Troubleshooting from installation to maintenance
Non-metallic compensator air leakage, to put it bluntly, means which string in the system is not correctly adjusted. Friends who are engaged in desulfurization, dust removal, power stations and cement all know that once this thing leaks, the efficiency will drop, the energy consumption will rise, and the environmental protection data will suffer. Today, let's go through it from beginning to end, breaking up the six most common causes of air leakage and crumbling them into pieces. What is not false is all the pits stepped on at the scene.
1. Inadequate installation: the root cause of artificial air leakage, accounting for more than half of on-site faults
Many non-metallic compensators leak air. To put it bluntly, they are mines buried to save trouble during installation. A typical scene: the flange surface is not cleaned, and the residual welding slag and rust are directly pressed on the sealing surface; The bolt tightening sequence is at will, one side is tight and the other side is still loose; What's even more outrageous is that some workers installed the guide tube of non-metallic expansion joint (fabric fiber expansion joint) backwards-two days ago, a desulfurization project, tossed all day to find the leakage point, and finally found that the guide tube was installed backwards, and the airflow directly washed the fabric layer, so it was strange that it didn't leak.
Especially when you use rectangular non-metallic expansion joints with circular baffle doors (double seals), the installation deviation is one millimeter, and the thermal expansion and contraction during operation can rip out cracks in the fabric layer. Remember: The flange bolts must be pre-tightened diagonally multiple times, and the torque value is according to the design requirements. Don't believe "almost OK", it's almost the air leakage point.
2. Aging or damage of the fabric layer: the material should be changed when it arrives, don't carry it hard
The core of the non-metallic compensator is a fibrous fabric and a rubber/fluoroplastic composite layer. High-temperature smoke, acid-alkali corrosion, ultraviolet irradiation-these environments are the natural enemies of the fabric layer. Over time, it will brittle, delaminate, and even appear micropores that are invisible to the naked eye. If the actual temperature of the medium is not considered when selecting the rubber compensator or rubber PTFE compensator, the rubber layer will crack in one year, and the air leakage will be a piece of leakage.
Then how to check? Don't just look by your eyes. Teach you a trick: the water drizzle method. Spray water on the surface of the compensator, and stick it with a paper towel on the other side. If there are wet marks, there are micropores. A hundred times more reliable than visual inspection.
3. Seal failure at flange connection: gaskets and bolts, no matter how small they are, must be taken seriously
Many air leaks actually leak out of the flange seams, but unfortunately most people look for the fabric layer at first. There are only three reasons for leakage: the wrong material of the gasket is chosen (you should use asbestos if you should use PTFE, and it will be crisp when baked at high temperature); The bolt pre-tightening force is not enough (it is loose after several times of thermal expansion and contraction); Or the flange itself has been deformed.
They used a non-metal compensator next to the metal corrugated expansion joint in the cement industry, which kept leaking air. I changed the non-metallic compensator three times before and after, but the problem was not solved. Finally, it turned out that the flange weld was cracked, and it wasn't the fabric at all. Tens of thousands of dollars were spent in vain and the construction period was delayed. Therefore, when checking, don't just stare at the compensator body, but the flange joints and welds have to be checked.
4. Mismatch between system design and working conditions: pressure, temperature and displacement, which exceeds the standard is a pit
Each non-metallic compensator has its own boundaries of use. The actual displacement of the pipe exceeds the design value, or the medium pressure exceeds the pressure bearing limit, and the fabric layer is either burst or overcompressed. For example, in the power station industry, the pipe system with corrugated expansion joint and high-temperature axial expansion joint is matched. If the cold and hot displacement calculation is less than 20%, the non-metallic section will be repeatedly wrinkled until perforated.
Has the pipeline direction, support mode and actual operating temperature changed? In some projects, non-metallic expansion joints are installed behind the flue gas baffle door, but the seal of the baffle door itself is not tight, and the high-temperature flue gas scurries to the compensator, which has long exceeded the design temperature. In this case, the leakage of the baffle door has to be taken into account when designing and selecting.
5. Media corrosion and dust accumulation: chronic killer, most easily overlooked
The non-metallic compensator behind the desulfurization flue gas baffle door is the hardest hit area. The flue gas after wet desulfurization contains condensed acid, and the pH value is as low as 2~3. Ordinary fabrics will rot after a few months. There is also the problem of dust accumulation-it is only a matter of time before the dust piles up in the compensator trough, expands and contracts repeatedly, and the fabric is worn out.
For the convenience of maintenance, some projects will install manual plug-in insulation doors or electric plug-in insulation doors to isolate them. But here's the problem: if the isolation door itself is not tightly sealed, the smoke will flow back, which will aggravate the corrosion. It becomes a vicious circle. Therefore, when selecting, acid-resistant rubber or PTFE compensator must be used for acid corrosion environment; If the dust accumulation is serious, consider installing a purging device or choosing a model with a larger wave distance.
6. Routine maintenance and inspection: Don't wait until smoke and fire come out before starting
Wait until the air leak and smoke are emitted before going for emergency repairs, and the cost will at least triple. Check the bolt torque regularly and observe the fabric surface for bulging or discoloration-bulging indicates that the layers are detached, and discoloration indicates that the aging has reached a critical point. Conditionally, the upper ultrasonic leak detector scans the flange joint, which is much more accurate than the human eye.
Once a trace leak is found, quickly change the sealing gasket or repair it locally. Don't drag, drag until the whole non-metallic expansion joint is scrapped, the replacement cost is high, and the loss of shutdown is greater. Remember, the national standard JB/T 12235-2015 for non-metallic compensators has clear requirements for leakage rate, and the implementation can save a lot of trouble. Standards are not decorations, but the bottom line of life-saving.
There are thousands of reasons for air leakage of non-metallic compensators, but more than 70% of them are in the two links of installation and maintenance. Get these six points thoroughly, and your on-site air leakage rate can be reduced by at least half. What are you waiting for? Hurry up and check the compensator on your site.