Two days ago, a friend who was doing a desulfurization project called and said that the non-metallic expansion joint on their pipeline bulged and torn in less than half a year. After removing it, it was found that the internal pressure compensation structure was not designed in place at all. This sounds quite troubling, but if you think about it, there is one fundamental reason: the non-metallic expansion joint is regarded as a "soft persimmon" to save money, ignoring its core ability-resisting internal pressure.
To put it bluntly, this thing is used to absorb the internal pressure of the pipe to generate axial thrust. The metal relies on bellows to carry hard, while the non-metal relies on fabric and rubber composite layer to "soften and solve". The one in our stationNon-metallic expansion joint (fabric fiber expansion joint)Andrubber compensatorIn essence, they all rely on this flexible structure to eat internal pressure. However, the problem is that many people think that non-metals must save money and worry than metals. As a result, the internal pressure compensation ability is ignored when selecting the model, and the car is directly overturned.
What exactly does the internal pressure compensator compensate for? Don't be confused by the name
Many people ask, are expansion joints and compensators the same thing? Yes, in the context of industrial pipelines, both words are common. But the term "internal pressure compensator" emphasizes its ability to counter the axial thrust generated by the pressure inside the pipeline.
A hot air duct of DN600, medium temperature 350℃, pressure 0.2MPa. You have to compute the metal expansion joint, and choose the right wave number to withstand it; What about non-metallic expansion joints? Through the composite structure of multi-layer fabric sandwiched with rubber, the thrust generated by internal pressure is dispersed to the support and the pipeline by cooperating with the flow guide tube and the reinforcing ring arranged inside. If you don't count it right, the pipe itself will twist around like a noodle. Inside our stationRubber PTFE compensatorAndRectangular non-metallic expansion jointEach has its own emphasis on corrosion resistance and temperature resistance, but the logic of internal pressure compensation is the same-flexible absorption and rigid conduction.
The three most pits in type selection: temperature, medium and compensation amount
Pit 1: Temperature.The upper temperature resistance limit of non-metallic expansion joints depends on the fiber and rubber materials. Our commonNon-metallic expansion jointUsing PTFE/silicone rubber coated fabric, the long-term temperature resistance is 200-300℃; But if you encounter the high temperature section behind the smoke baffle door, and the temperature rushes above 400℃, you have to considerHigh temperature axial expansion jointOr simply goMetal Corrugated Expansion Joints in Cement IndustryYeah. Don't expect a layer of fabric to withstand high-temperature exhaust gases. That's a joke about equipment life.
Pit 2: Medium.Desulfurization flue gas contains sulfide and chloride ions, which is extremely corrosive, and ordinary rubber is quickly finished. This is the time to chooseRubber PTFE compensatorOr lined with PTFE, like the one in our stationPTFE-lined hoseThat idea-use a PTFE layer to separate the corrosive medium from the rubber. Otherwise? Three months of corrosion and perforation, and then all the work of plugging leaks.
The third pit: the amount of compensation.Many people only look at the amount of axial compression and ignore the lateral and angular displacement. The advantage of non-metallic expansion joint is that it can absorb multi-directional displacement at the same time, but if there is not enough margin in design, a dozen internal pressures will directly collapse the flange connection. For example, a rectangular air duct of DN1000 has a lateral displacement of 20mm and an angular direction of 3°. If you give a 50mm axial compensation amount, it is equivalent to giving it for nothing. WeRectangular non-metallic expansion jointIn the selection table, the horizontal and angular compensation amounts are indicated separately-don't bother, check when you need to check.
Installation and Maintenance: Those Overlooked Details
A customer bought oursNon-metallic expansion jointIt saves trouble when installing, and no guide tube is installed. As a result, the high-speed air flow directly washed the fabric layer, and it wore out in three months. The role of the guide tube is not only to guide the flow of the medium, but also to protect the flexible body from direct erosion-this is repeatedly mentioned in the FAQ (refer toSpecific Function of Expansion Joint Guide Tube）。
In addition, do not remove the tie rod or limit screw during transportation and installation-this is mentioned repeatedly in our FAQ (refer toDo you need to remove the screw of the expansion jointAndHow to adjust the tie rod nut of expansion joint）。 Many people thought that was redundant, but as soon as they debugged, they pushed the compensator to the limit. The function of the tie rod is to prevent the damage of the flexible body caused by unexpected displacement before installation, and it is the correct solution to adjust it in place and then loosen it.
For maintenance, check the outer fabric regularly for bulging and cracking, especially the flange sealing surface. From our stationSleeve type pipe expansion jointAndRotary compensatorAlthough the structure is different, the logic of seal inspection is the same-if you find a leak, don't delay it and deal with it immediately.
Do you choose non-metal or metal? It depends on the work condition. Don't pat your head
Metal expansion joints (e.g.Universal corrugated expansion joint、External pressure single axial expansion joint) Strong pressure capacity, long life, suitable for high temperature and high pressure steam pipeline; What about non-metallic expansion joints? It is cheap, corrosion-resistant and absorbs large displacement, especially suitable for low-pressure and large displacement scenarios such as flue gas, air duct and desulfurization system.
For example, in power station industry and cement industry, the diameter of flue gas pipeline is always more than 3 meters, and the cost of metal is frightening, and the installation space is limited. At this time, the internal pressure compensator of non-metallic expansion joint is the optimal solution. Such asCorrugated expansion joint for power station industryAlthough it can also be used, the price is doubled and maintenance is troublesome. Another example is that in the desulfurization systemDesulfurization flue gas baffle doorFront and rear, low pressure, strong corrosion, non-metal is standard.
There is no best product, only the best matching working conditions. Our station's product line coversMetal hoseToPTFE compensatorFinding the right people and asking the right questions saves ten times more money than choosing blindly. Before the next selection, take the working condition table first. Don't drop the temperature, pressure, medium composition and displacement-this job is not lazy.