Differences between process compressors and air compressors
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Clients often question why the price of process compressors is much higher than that of air compressors, and it’s not easy to convince them to accept such high costs. In fact, process compressors are primarily used to handle toxic, flammable, and explosive process gases in the petrochemical industry, and compared to air compressors, they have many special aspects in terms of design and manufacturing. Here are a few key points summarized; feel free to add more. (1) The unit shall have an uninterrupted continuous operation time of not less than 3 years, and a design life of not less than 20 years. (2) Under specified operating conditions, ensure that there is no negative deviation in the inlet volume (the air compressor allows a 5% negative deviation) ； Due to large fluctuations in operating conditions, the designed volumetric flow rate includes a substantial margin. (3) The shaft extension end is equipped with a mechanical seal (contact oil film seal or non-contact dry gas seal), a carbon ring seal (protected by nitrogen), or a combination of these; the cost of such seals is high. (4) The unit flow regulation is achieved through recirculation or frequency conversion. Intake throttling is used less frequently to prevent air from leaking in due to negative pressure at the inlet, or to avoid gas overheating when the pressure ratio becomes too high. (5) The main motor must be explosion-proof, with a power rating of at least 110% of the maximum power under any operating conditions, and not less than the shaft power at the time when the safety valve operates. (6) All instruments installed in hazardous areas are of the flameproof type; remote sensing instruments or control systems are mostly imported and expensive. (7) Under low load and low speed conditions, rolling bearings from well-known foreign brands are commonly used, while sliding bearings are employed under high load and high speed conditions; a vibration and temperature monitoring system for the bearings is required. (8) The lubricating oil system shall be designed in accordance with API614; oil pumps, filters, and coolers are typically provided in a redundant configuration, while separators and oil tanks require a sufficient volume for retention. (9) In environments with corrosive gases, the material for pressure vessels must be selected as stainless steel or a special material.
So there are many manufacturers that can produce air compressors, but few that can produce process compressors, as the complexity of the manufacturing processes differs greatly
I’m learning; I gain something new every day! Thanks
The author’s explanation is not clear. Hey, those who are interested in dancing-related topics: what you’re asking about is the difference between centrifugal process gas compressors and reciprocating air compressors. Of course, there’s a big difference between them. But if you try using a centrifugal air compressor, you’ll find that it’s definitely more expensive than a centrifugal process gas compressor.
From what the original poster means, it’s mainly because the transportation medium is different. Air compressors are mainly used to transport air. But other media are also transported using compressors, depending on the type of compressor used. For example, screw compressors can be used to transport air, but they cannot be used to transport oxygen, as they contain oil and could explode when in contact with oxygen. Rotary vane blowers can be used to transport air, but not gas, as sparks are inevitably generated during their operation. So, in essence, it comes down to the selection of compressors; different types of compressors can be used to transport various gas media. You can contact me for anything related to air compressors. We specialize in importing compressors of various types, haha.
It’s simply impossible to compare on the same platform.
To be honest, air compressors available on the market can also be used for conveying process gas at a slight positive pressure at the inlet, provided that the oil seal at the shaft extension end is reliable and does not leak. Such leaks often result in the medium gas being released directly into the atmosphere, leading to accidents. Without monitoring methods and countermeasures, if highly toxic gases leak into a factory, can on-site gas detectors suffice? It should be noted that when carbon ring seals are used for the shaft sealing of process centrifugal compressors, nitrogen isolation and venting are required, along with low-pressure alarms and interlocks for the nitrogen pressure or pressure difference ； Dry gas seals offer dual-end face or tandem double protection, along with low pressure difference alarms and shutdown functions; in the event of a seal failure, operators have ample time to respond. Large centrifugal air compressors used in PTA plants (which, strictly speaking, should also be classified as process compressors used in chemical processes; they require explosion protection and can operate continuously for long periods of time – whereas ordinary aerodynamic compressors generally don’t need to have capacities of hundreds of thousands of cubic feet per hour) come with various vibration monitoring systems due to their high cost, while small air compressors hardly ever have such monitoring mechanisms. Process compressors and air compressors, regardless of the layer on which they are placed, differ most significantly in terms of safety and reliability. For the same model and under the same operating conditions, it seems difficult for a process compressor to be less expensive than an air compressor.
I learned it! Are there also air compressors that don’t use oil seals? A mechanical seal will do.