Since the instrument air has been dehumidified by a refrigerated dryer, is a pneumatic triple unit still necessary?
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As the title says, thank you
A pneumatic triple unit is necessary; firstly, it serves to filter out impurities that may enter the air supply during transmission； The second is voltage stabilization ； Third is to apply lubricant to the cylinder.
Instrument air ensures a dew point of -35 degrees Celsius or lower! I have both two-piece and three-piece units available, depending on the situation.
It must be added; what if the cold dryer fails? Our process gas comes from the air separation cryogenic tank, and it is equipped with filters and pressure reducers – one of these serves to prevent water from entering, another is for filtering, and yet another is for reducing and stabilizing pressure; all of these are very necessary. Also, after each stop for maintenance, it’s a good idea to take photos of all the filters and pressure reducers before starting the vehicle again; take photos of them at the end of the official website as well. Just in case, in some processes other gas sources may be connected to the instrument air supply for temporary use, or instrument air might be used as a substitute; in operations such as stamping, backflow can occur. Although the likelihood is low, it still needs to be prevented, as any problems that arise could increase the workload on the instruments.
The key is to understand the functions of the triple unit: filtering and dust removal, pressure reduction and stabilization, and lubrication; this shows that simply dehumidifying is not sufficient to ensure the quality of the air supply
It must be added; there are profound lessons to be learned from this
Should one set be added per pneumatic valve, or for the entire pipeline?
For valves, a pneumatic pressure reducing valve is still necessary; no petrochemical company would install pneumatic triple units on a large scale.
In addition to dehumidification, cold dryers also have functions of filtration and oil removal; therefore, a filter-pressure reducing valve integrated with the instrument air supply is sufficient, and a three-piece unit is not necessary. The places with high requirements are those where two cold dryers are connected in series; our factory is one such place. The second dryer has a lower power rating and is used solely for supplying air to instruments. After all, no one would allow both dryers to stop working without taking any action :D, furthermore, another drawback is that the three-piece unit breaks down more easily than the filter pressure valve.
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