The air compressor pipe is not an ordinary pipe, and the rubber compensator can't bear it at all
How ruthless is the air compressor outlet pipe? The temperature always goes up at 120℃, the pressure starts at 0.8MPa, the vibration frequency is tens of Hz, and the thermal expansion and contraction starts and stops once a day-under this working condition, the rubber compensator will age and crack after half a year, and the non-metallic expansion joint (the kind of fabric fiber) has insufficient compression resistance, so an explosion is an accident. Therefore, it is necessary to put on metal expansion joints, to be precise, bellows metal expansion joints. It can absorb axial displacement, lateral displacement and angular displacement at the same time, while the rubber compensator can only cope with small displacement and become soft at high temperature. To put it bluntly, the metal expansion joint of air compressor is the only choice to carry high temperature, high pressure and vibration.
Two days ago, I met a customer who thought the metal expansion joint was expensive, so I used a rubber compensator for the cheap picture. And the result? After three months of air leakage, I changed it three times in half a year. Finally, the cost is higher than buying a better expansion joint. This is not new.
The easiest pit to step on in model selection: only look at the diameter, regardless of fatigue life
Many people choose the metal expansion joint of air compressor. When they come up, they ask how big the diameter is. When they get the universal corrugated expansion joint, they install it. Wrong! The air compressor pipeline starts and stops once a day, which is 365 thermal cycles a year. Coupled with pressure fluctuation and vibration, if the wave pitch and wall thickness of the universal corrugated expansion joint are not designed according to the number of cycles, it will start to crack after hundreds of times. The correct method is: calculate the actual cycle times first, and determine the design parameters according to the required fatigue life. For example, this site'sUniversal corrugated expansion jointAndHigh temperature axial expansion jointAll have clear fatigue life grades. When selecting the model, compare the table "Expansion Joint Model and Dimension" of this site to match the wall thickness, number of layers and wave number.
Leaked? Eighty percent is the wrong type
The air compressor pipeline often has to turn, and at this time, the straight pipe pressure balance expansion joint is not very effective-it only absorbs axial displacement, and it can't handle the multi-dimensional displacement and blind plate force at the turn. What to do? Upper compound hinge transverse expansion joint or curved tube pressure balance expansion joint, these two can absorb axial, transverse and angular displacement at the same time, and do not produce blind plate force, so the requirements for pipe support are low. If the pipeline layout space is really narrow, such as the section between the air compressor outlet and the aftercooler, which is narrow and curved, then using a metal hose with a universal corrugated expansion joint can also save the emergency, but note that the metal hose can't be used as an expansion joint, it is only suitable for compensating small displacement and vibration reduction.
Don't put the large-diameter thick-walled expansion joints used in the power station industry on the air compressor-they are all metal bellows, but the working conditions of the power station are high temperature and low pressure, while the air compressor is high pressure and medium temperature, and the design logic of wall thickness is completely different. Not to mention the cannon killing mosquitoes, but the cost has doubled, which is pure waste.
Real case: Chemical plant did not leak for three years because it changed metal expansion joints
Three centrifugal air compressors in a chemical plant are connected to the grid, and the outlet main pipe leaks once every six months. I used to change the rubber compensator, but I couldn't hold it; Later, it was replaced with a high-temperature axial expansion joint, the pipe wall material was upgraded to 316L (the original 304, which was not corrosion resistant enough), the number of bellows layers was changed from single layer to double layer (to improve fatigue life), and the limit tie rod and universal hinge structure were matched-so far there has been no incident in more than three years. To put it bluntly, the metal expansion joint of air compressor is not a standard part, and it has to be paired one by one according to the pipeline layout, medium temperature, pressure fluctuation and vibration frequency. Compare the table "Expansion Joint Model and Size" on this site, and then flip through the "Metal Hose Pressure Standard", and you can basically lock the model.