Two days ago, the equipment supervisor of a power plant called and asked as soon as he opened his mouth, "How many years will your non-metallic compensator be changed? Give me an accurate number." I said you don't worry, it would be a lie to give the year directly. In the same factory, the life of the flue and the desulfurization tower export can be two or three times different. Today's article will break this matter apart and make it clear.
Why are there no uniform fixed replacement years for non-metallic compensators? — — First distinguish the working conditions and materials
Non-metallic compensators (that is, we often call fabric fiber expansion joints and non-metallic expansion joints) are different from metal bellows. The fatigue life of metal parts can be considered almost inseparable, but non-metals are composite materials-fluororubber, silicone rubber, polytetrafluoroethylene, glass fiber cloth, ceramic fiber... The temperature resistance, corrosion resistance and pressure resistance of each material are far from different. Such asrubber compensatorAndPTFE compensatorOne is afraid of high temperature and the other is afraid of strong alkali. Together, it is meaningless than life.
Is the medium flue gas or steam? Is there any particulate scour? Is the temperature stable or fluctuates frequently? Is there any vibration at the installation location? If these problems are not clear, giving a suggestion of "changing every three years" is no different from playing rogue.
Reference table of replacement cycle under common working conditions: flue gas, high temperature, corrosion and wear scenarios have their own living methods
The following table is based on the actual statistics of our on-site maintenance projects in the past ten years, and only lists the mainstream scenarios. Note: This is a reference value, not that it must be thrown in the year. For details, it depends on the "five-step check method" below.
| Application Scenario | Typical temperature range | Main Material Suggestions | Reference Replacement Cycle |
|---|---|---|---|
| Ordinary flue gas pipe (low sulfur content) | ≤200℃ | Fluorine rubber + glass fiber | 4-6 years |
| Desulfurization/wet flue gas (containing a large amount of SO2, water vapor) | 50~120℃ | Butyl rubber + PTFE lining | 2-3 years |
| High temperature flue gas (boiler outlet, kiln) | 400~800℃ | Ceramic fiber + stainless steel wire mesh reinforcement | 1-2 years (regular inspection required) |
| Scour with particles (cement/plant ash transport) | ≤150℃ | Wear-resistant rubber + outer sheath | 1-2 years |
| Clean gas/air ducts | ≤100℃ | Nylon fabric + rubber | 6-8 years |
You see the pattern? The higher the temperature, the stronger the corrosion, the more particles, the shorter the life. So don't take itReplacement periodic table of non-metallic compensatorWhen dead commands, it is only the starting point.
How to judge whether you should change? Five on-site inspection steps are more reliable than watching the watch
- Step 1: Look at the appearance. Can you spot bulging, delamination or surface cracking at a glance?Especially the sealing surface at the connection of the flange, once delamination occurs, it is basically over. We came across aRectangular non-metallic expansion jointThe exterior looks okay, but when it is removed, it is found that the internal fiber has been carbonized and shattered when touched. The exterior is just the threshold.
- Step 2: Measure the leak.Apply to welds, flange corners with soapy water or smoking agent. If there is a leak, it will not only waste media, but also accelerate the corrosion of internal materials. If the leak point is in the middle of the fabric layer, it can't be repaired, but it can only be replaced.
- Step 3: Feel the stiffness.Press the surface of the compensator by hand in the shutdown state. Be wary if it feels particularly hard (the material ages and becomes brittle) or particularly soft (the fibers break and lose their strength). Normal non-metallic compensators should have some elasticity, which can rebound quickly after pressing.
- Step 4: Check the displacement margin.Use a steel ruler to measure the current actual displacement against the designed displacement at the time of installation. If the compensator has been pulled to the limit or compressed to the limit, it means that it has been overloaded and is not far from being scrapped.
- Step 5: Look inside.If possible, take a look at the internal situation from the manhole or disassemble one end when shutting down for maintenance. Any scaling, corrosion pits, loose fibers? This step is the most straightforward, but it is also the easiest to overlook.
These five steps are more accurate than the "suggested replacement cycle" given by any manufacturer. You might say: How do we have time to do a full set of inspections every quarter? Then do a look + leak test at least every six months and a full set once a year. If you really have to wait until the smoke comes out before shutting down the furnace, the loss will not be the money of a compensator.
Common reasons for early scrapping: improper installation, excessive media, structural design defects
To be honest, many non-metallic compensators are not aged normally, but are "killed".
Improper installationIs the most common case of wrongdoing. For example, the pre-stretching/compression amount is not adjusted properly, and it deviates from the design neutral point when installed; Or the flange bolts are unevenly screwed, resulting in excessive local stress. EspeciallyDesulfurization flue gas baffle doorThe matching non-metallic compensator, due to the limited space on site, often has to be adjusted back and forth during installation. If you don't pay attention, you will work hard, and your life will be directly halved.
Media exceeds standardIt's also easy to understand. The design temperature is 250℃, but the actual operation occasionally rushes to 350℃. At this moment, the fluororubber is completely wasted. In addition, the chloride ions and sulfate radicals in the medium exceed expectations, and the PTFE layer will be attacked. Don't expect a compensator to carry everything-it needs design margin, but it also has limited margin.
Structural design defectsIt is more hidden. For example, the axial/transverse/angular displacement is not calculated enough during model selection, resulting in the compensator being hard-pulled; Or there are no protective measures such as guide tubes and baffles, and the dust-containing gas directly washes the fabric layer. These things can be avoided in the design stage, but many buyers only pay attention to the price and don't ask the manufacturer for a detailed displacement calculation book.
Proper maintenance can extend life: the key action for routine inspection and regular maintenance
If you want to make the nonmetallic compensator last for another year or two, just follow the following suggestions.
- A weekly glimpse.During the inspection, take a look at the surface of the compensator to see if there is any abnormal discoloration (whitening or yellowing indicates accelerated aging), whether it is scratched by foreign objects, and whether there is any debris and dust around it. Clean it up when you see it.
- Displacement was recorded monthly.Draw a scale line on the pipes on both sides of the compensator and measure the relative displacement change every month. If the displacement suddenly increases, it means that there is something wrong with the pipe support. Don't just stare at the compensator.
- Fastening is done once per overhaul cycle.The flange bolts will slowly loosen due to thermal expansion and contraction. When tightening, the torque value should be reached in diagonal order in 2-3 times. Don't try to save trouble and screw it in place at once.
- It is prohibited to put foot rods, hang cables and put tools on the compensator.It looks like a trivial matter, but local pressure will destroy the uniformity of the fiber layer and quietly bury hidden dangers.
- Spare parts should be stored in the right place.Spare in the warehouserubber compensatorOrRubber PTFE compensatorDon't be exposed to the sun or near the radiator. Normal temperature, protection from light and dryness are the minimum requirements.
Alas, in fact, many people understand this common sense, but once production and progress are under pressure, these "small things" are left behind. Waiting until the non-metallic expansion joint leaks before buying goods urgently and rushing to install them overnight costs more than twice as much as regular replacement.
If you don't know the working conditions of your site, or want to know how much life is left of the currently used compensator, you can send us the specifications and parameters and give us an evaluation suggestion directly. Don't wait for the smoke to ask "what to do"-then the answer is only one word: change.