Why are natural gas pipelines inseparable from non-metallic compensators?
The answer to this question lies in the thermal expansion and contraction of pipes and the corrosiveness of the medium. During the process of natural gas transportation, the temperature changes greatly, with exposure to the sun in summer and low temperature in winter. In addition, the medium contains sulfur and water, so the metal bellows will be corroded and riddled with holes in a short time. We had a project before, and the metal bellows used by the customer leaked in two years. When we disassembled it, the corrugated surface was full of pitting pits. Replace it with a non-metallic compensator (such as the "non-metallic expansion joint (fabric fiber expansion joint)" or "rubber compensator" in our station), and the effect is immediate-corrosion resistance, good vibration reduction and low cost. Two days ago, a customer asked me: How long can the metal leak after two years of use. How long can it last if it is replaced with non-metal? Tsk, it depends on the selection and working conditions. Don't be in a hurry to pat your head. To put it conservatively, normal working conditions are fine for three to five years, but if you choose the wrong model, it will be scrapped in three months.
Non-metallic vs. metallic, who to choose is not a matter of patting the head
Some people shake their heads when they hear "non-metallic", feeling that it is not strong enough. In fact, the pressure of natural gas pipelines is usually not high (mostly medium and low pressure, 0.4~1.6MPa), and non-metallic compensators can completely withstand it. Moreover, natural gas pipelines often have vibration-compressors, pressure regulating stations and valves open and close, and the vibration is transmitted. The damping characteristics of non-metals are much better than those of metals, which can absorb vibration and protect pipeline welds. However, note that non-metals are not resistant to ultra-high temperatures (> 250℃ won't work). If your pipeline passes through the heating furnace area, you have to choose "high-temperature axial expansion joint", and don't take non-metals hard. In a word: room temperature, medium and low pressure, corrosion, close your eyes and choose non-metals; High temperature and high pressure, or metal is reliable-for example, our "universal corrugated expansion joint" or "corrugated expansion joint for power station industry" is suitable for high-pressure steam scenes. How to judge? Look at the design thermometer, don't feel it.
Three elements of type selection: temperature, pressure and medium corrosiveness, one cannot leak
Let's start with the temperature. Our "rubber PTFE compensator" has a wide temperature resistance range (-20℃ ~200℃), while "PTFE compensator" can resist strong corrosion but is slightly less flexible, so it is suitable for media containing hydrogen sulfide. In terms of pressure, natural gas pipelines are usually 0.4~1.6MPa, and the design pressure of non-metallic compensators is usually enough, but don't overpressure-some customers use 0.6MPa rubber compensators on 1.0MPa pipelines, and the result is bulging in three months. Media corrosiveness is more critical: natural gas contains hydrogen sulfide? Polytetrafluoroethylene or rubber tetrafluorine composite structure is selected. Remember: When selecting the model, compare with our product information. Don't take "non-metallic expansion joints (fabric fiber expansion joints)" to carry sulfur-containing media. Fabric fibers are afraid of corrosion and will be delaminated over time. Also, if the pipe has axial or angular displacement, calculate the compensation amount. Don't expect the non-metal to withstand axial thrust-it can only absorb lateral displacement and vibration.
It's no bullshit that installation details determine longevity
And guess what? Many construction sites hard screw the compensator directly to the flange, causing the fabric layer to tear. Correct practice: first install the pipe flange, adjust the coaxiality, then install the compensator, tighten the bolts symmetrically, and the torque is uniform. Nonmetallic compensators fear two things the most: twisting and straining. Forced twisting is absolutely not allowed during installation, and a compensator cannot be used to correct pipe misalignment. In addition, the non-metallic compensator cannot bear the axial thrust, so the guide bracket must be added. When our "rectangular non-metallic expansion joint" is used in the flue, we have to consider the dust accumulation problem and clean it regularly. If the pipeline needs to be overhauled and isolated, it can be used with "manual plug-in insulation door" or "circular baffle door (double seal)" to facilitate segmented operation. Also, don't forget to leave enough installation allowance-the non-metallic compensator is best at free length after installation, and don't pull too tight.
Maintenance is not about waiting for it to be broken before replacing it, but about looking at it regularly
Is there any bulge or crack on the surface of the non-metal compensator? Is the flange connection loose? Natural gas pipelines are generally inspected at least once a year. If you find that the rubber is aged and hardened, the surface is sticky or cracked, don't hesitate to change it directly. Under normal working conditions, the life of 3~5 years is no problem, but the environment is harsh (such as outdoor sun exposure, chemical splashing, frequent start-and-stop) may have to be changed in 2 years. Finally, don't buy small factory goods to save money-the key to non-metallic compensators lies in the composite layer process, and it is common for inferior products to degumm in layers. Our "rubber compensator" and "rubber PTFE compensator" have all been tested for pressure fatigue, and the data speaks for themselves, not fooling. Clean exterior surfaces regularly, especially for outdoor projects-UV rays accelerate rubber aging, and adding a shield can extend life. Keep maintenance records and know when to change the parts next time.