Friends who purchase or engage in equipment maintenance have asked this question nine times out of ten: Which non-metallic compensator is good? If you report the model directly, nine times out of ten are unreliable. There are several types of non-metallic compensators. The working conditions are different, and the things you choose can be a hundred and eighty thousand miles away.
First distinguish one thing: what kind of non-metallic compensator are you talking about?
Don't rush to compare the good with the bad, first see which type to install on your pipeline. There are roughly three types of non-metallic compensators common in industrial scenes: fabric fiber expansion joints, rectangular non-metallic expansion joints and rubber compensators. The name all sounds "non-metal", but the structure, material and scope of application are completely different things.
Fabric fiber expansion joint, also called non-metallic expansion joint, is mainly made of multi-layer fiber fabric, sealing material and heat insulation layer. It has good flexibility, can absorb multi-directional displacement, and is especially resistant to high temperatures. Rectangular non-metallic expansion joint, to put it bluntly, is a rectangular cross-section fabric fiber compensator, which is specially used on rectangular smoke duct. As for the rubber compensator, the main body is rubber and fiber reinforced layer, which relies on elastic deformation to reduce vibration and noise, and its temperature and pressure resistance are not as good as the first two.
Therefore, the premise of the question "which non-metallic compensator is good" is which category your working conditions are suitable for. If you choose the wrong type, no matter how good the product is, it will be useless. The rubber compensator is used on the flue gas pipe, and it burns in two months; Fabric fiber expansion joints are used on the water pump connection, and the vibration still cracks the pipe.
Select structure according to working conditions: temperature, pressure and medium determine life and death
Temperature and pressure are hard indicators. Fabric fiber expansion joints can usually hold hundreds or even thousands of degrees of smoke, but their pressure bearing capacity is general, which is suitable for low-pressure and large-diameter pipelines. The temperature resistance of rubber compensator generally does not exceed 100℃, and the pressure can be higher. However, there are oil, acid and alkali, ozone and so on in the medium, and the rubber will age soon.
Therefore, why do we recognize fabric fiber expansion joints in places such as flue gas pipelines, desulfurization systems and dust removal fan outlets? The flue gas temperature is high, the sulfur contains corrosion, and it is accompanied by vibration and displacement. Rubber can't do this work. On the other hand, the rubber compensator is the natural counterpart in places with low temperature but vibration, such as water pump inlet and outlet, chiller and diesel engine exhaust port. Its damping properties are there, and the vibration damping effect is far better than the fabric fiber layer.
Don't ignore installation position and displacement direction
The same equipment, installed at the outlet of the fan and installed at the inlet of the chimney, requires completely different compensators. The air flow at the outlet of the fan is unstable, with radial displacement and certain pressure pulsation; In the section of the chimney entrance, it is mainly axial thermal expansion, and may be accompanied by lateral wind load displacement. If you take a model that only does axial compensation and hard-mount it where you need lateral displacement, it won't take long to tear.
Rectangular non-metallic expansion joints are common in rectangular smoke ducts. At this time, it is not only necessary to look at the cross-sectional size, but also to understand the thermal expansion direction of the equipment. Wherever the pipe goes, the compensator has to be able to absorb displacement in which direction. Circular pipeline, axial or transverse compensation, when selecting a type, your mind should be clear. Is there enough space for installation? Flange connection or plug-in welding? These details must be clearly marked on the drawings.
Look closely at the skin material and the number of layers
The core of the fabric fiber expansion joint is not the metal frame on the outside, but the flexible skin in the middle. The skin is generally divided into several layers: the outermost layer is corrosion-resistant and aging-resistant fiber cloth, the middle layer is heat insulation layer, and the inner layer is sealing layer. How to match the number of layers and how to choose the material all depends on the working conditions.
For example, if the flue gas temperature is 600℃, it is necessary to choose silicon-titanium glass fiber cloth with high silicon fiber, and then reinforce it with stainless steel wire mesh. If the medium contains sulfur dioxide, polytetrafluoroethylene film should be considered as an anti-corrosion layer. Do you want to add the deflector? When there is high-speed dusty airflow inside, the guide tube can prevent the dust from directly washing the skin, but adding the guide tube will occupy a certain circulation area and may cause vibration. Only manufacturers who have done similar cases can get this balance accurately.
When selecting materials, don't just look at the temperature resistance meter. Some skins are marked with a temperature resistance of 800℃. In actual working conditions, the temperature fluctuates greatly, the material expands and contracts repeatedly, and the life span still drops from a cliff. So we have to ask clearly: What are the creep characteristics of this material at long operating temperatures? Have you ever had a fatigue test?
The last thing is to look at the manufacturer
After the first few steps, you already know which structure and material of non-metallic compensator you need. At this time, go to the manufacturer. It is not universal by marking "non-metallic expansion joint". It is the bottom line to make inspection according to JB/T 12235-2015 standard. This standard clearly writes the technical requirements, test methods and inspection rules of non-metallic expansion joints.
In addition to standards, it also depends on whether there are actual cases in the same industry. Those who have done the smoke duct of power station boilers and those who have done the tail of cement kilns have a completely different understanding of the working conditions. You ask him to take out two cases, the acceptance record, the running time and the replacement cycle, and you will know it when you ask.
The price of this thing, put it to the last comparison. The front structure is wrong, the material is low, and it is a hidden danger to buy it back and install it. Which non-metallic compensator is good, you ask? The answer is not the model, but the matching degree-working condition matching, structure matching, material matching, plus a manufacturer that does things according to standards. With all these four things together, the one in your hand is the best.