Let's make one thing clear first: Although non-metallic compensators and metallic compensators are both called compensators, their installation locations are very different
Metals can carry high temperatures and high pressures, such as power station steam pipelines and refinery pipelines, but the strengths of non-metals are low pressure, large displacement and corrosion resistance. The typical scene is smoke duct. Two days ago, a customer called me and asked me if I could install a non-metallic compensator on the steam main pipe. As soon as I heard it, I asked him to stop quickly-the temperature of the steam main pipe started at least 300℃, the pressure was above 0.5MPa, and the non-metallic fabric layer was directly carbonized. I asked him to look at the "high temperature axial expansion joint" on our website, and that was the right answer. Therefore, if the location is not selected correctly, no matter how good the product is, it will be for nothing.
Where is the main battlefield of non-metallic compensators?
The chimney entrance of the power station, the inlet and outlet of the desulfurization tower, the inlet and outlet pipelines of the dust collector, and the kiln head and tail of the cement industry-in these places, the medium temperature is generally below 200℃, the pressure is slightly positive or negative, and the pipeline displacement is large (both lateral and angular). The metal compensator either can't bear the corrosion or the cost is ridiculously high. You go to the 'Non-Metallic Expansion Joints (Fabric Fiber Expansion Joints)' and 'Rectangular Non-Metallic Expansion Joints' on our site, which are specifically designed for these scenarios. For another example, the flue gas baffle door of desulfurization system (such as our 'desulfurization flue gas baffle door') is often equipped with a non-metallic compensator next to it. Why? Because there are sulfur dioxide and water vapor in the flue gas, the metal bellows will rust out in half a year, but the non-metallic fabric layer plus PTFE film can last for three to five years.
Many people think that non-metallic compensators are soft, just find a place to stuff them in. Wrong! It is most afraid of high temperature and high pressure. If the pressure exceeds 0.1MPa, don't put it hard. The non-metallic fabric layer can't bear the high-pressure bulge. We have encountered a customer who installed a non-metallic compensator on a blast furnace gas pipeline with a pressure of 0.2MPa. As a result, it leaked in half a year-the wrong position was selected, and no one could save it.
Rectangular pipes and shaped pipes: What nonmetallic compensators do best
Bellows can be used for round pipes, but rectangular air ducts-such as the rectangular flue of the sintering machine head of a steel mill or the rectangular flue duct of a power plant-metal bellows either can't be made or the price is sky-high. At this time, only non-metallic fabric compensators can be used. Our 'rectangular non-metallic expansion joint' specializes in this, and the installation position is usually in front and behind the fan inlet and outlet, and the baffle door, which is used to absorb thermal expansion and installation deviation. Note: Rectangular pipes are often limited in space, so the installation position of non-metallic compensators should reserve enough maintenance space, otherwise it will be troublesome to die when replaced in the future. I have seen a desulfurization tower renovation project. The compensator is installed close to the wall, and even the wrench can't reach in during maintenance. In the end, it can only smash the wall-tsk, can you die if you leave 30 centimeters more in the design?
Three Forbidden Areas of Non-Metallic Compensators
First, if the medium temperature exceeds 300℃, you don't think about it.Even high-temperature-resistant silicone cloth can't hold it, and the temperature resistance is about 260℃. If it exceeds this number, you have to use 'high-temperature axial expansion joint' or metal products with heat insulation layer. Some customers have to take non-metals to test the export of flue gas heat exchangers, and as a result, they smoke in a month.
Second, there are pipelines with serious accumulation of condensate or dust.Non-metallic compensators are prone to dust accumulation and corrosion. If the location is selected on a horizontal pipe, be sure to consider drainage or ash discharge measures. For example, in the horizontal flue behind the dust collector, there is a lot of dust in the flue gas, and the bottom of the non-metallic compensator will accumulate hard lumps and then wear the fabric layer. What to do? Either install it vertically or open an ash discharge port at the bottom.
Third, the pressure exceeding 0.1 MPa is the red line.Don't believe that "it's okay to exceed it a little". The design pressure of non-metallic compensators is slightly positive pressure. If the system pressure fluctuates greatly, it is necessary to install a pressure relief valve. Remember: the metal can carry 0.5MPa, and the non-metal exceeds 0.1MPa, just wait for the bulge to leak.
Actual Combat Misunderstanding: Non-metallic Compensators Can't Bear Thrust
Some people think that the non-metallic compensator is soft and easy to install, so they install it where it needs to withstand the blind plate force (thrust) of the pipe. Wrong! Non-metallic compensators can only absorb displacement and cannot withstand thrust. For example, at the corner of the pipe or when the valve is closed, the blind plate force will act directly on the compensator, and the non-metallic one can't bear it at all-the fabric layer will be torn apart. At this time, the fixing bracket should be added, or replaced with 'universal corrugated expansion joint' or 'large tie rod expansion joint'. Before selecting the position, calculate the pipe thrust. How does that count? Find the pipeline diagram of the design institute to see the thrust value between the fixed brackets. If it exceeds 0.1MPa, decisively give up the non-metallic scheme.
Final step: three steps to get the installation position
On-site working conditions vary widely. How to locate them specifically? Three simple steps: First, look at the pipeline diagram and find the pipe section between the two fixed brackets with the largest thermal displacement-that place is the candidate location for the non-metallic compensator. Second, confirm that the medium temperature and pressure fall within the parameters of the non-metallic compensator (refer to JB/T 12235-2015 standard). Third, avoid positions where condensation, dust accumulation and mechanical collision are prone to occur. If you are unsure, just ask us about the drawings for sales. The article on our website 'National Standard for Non-Metallic Expansion Joints' has detailed parameters.
By the way, when installing, be sure to align the direction of the arrow with the flow direction of the medium, otherwise the force direction of the fabric layer will be reversed, and it will collapse in less than three months. Alas, this kind of low-level mistake happens several times a year.