Your questions answered: How to Choose Oil-Free or Oil-Lubricated Rotary Screw Air Compressors for Your Application

This webinar provides a comprehensive comparison between oil-free and oil-lubricated rotary screw air compressors to aid professionals in selecting the optimal compressor for their specific needs. Additional questions from this live webcast are addressed here.

By Plant Engineering May 10, 2024
Courtesy: Kaishan

During this April 18 webcast, the presenters left questions unanswered. Watch, “How to Choose Oil-Free or Oil-Lubricated Rotary Screw Air Compressors for Your Application,” and read this Q&A. Webcast presenter Brandon Dial, director of industrial sales for Kaishan, answered additional questions not addressed during this webcast.

Question: Foaming on oil lubricated machine usually causes what?

Answer: Mixing of non-compatible lubricants is a common cause. Always check with your supplier on mixing lubricants. Usually, it’s best to fluid the system and change all the filters. Then use new lubricant and filters when changing.

Question: For water cooled compressors, do you publish the supply water temp and resulting delta T based on the minimum water flow?

Answer: Yes, this information will be on the original equipment manufacuter’s (OEM’s) technical data sheets.

Question: What is the influence of extremely high or low temperatures on the functioning of the system (oil-free or not)?

Answer: Both can cause premature failure on many components, and often, the compressors will operate (shutdown) due to overheating or freezing the control lines.

Question: Why wouldn’t you always use a desiccant-type air dryer?

Answer: Desiccant dryers give you an excellent dew point but consume a great deal of energy. Due to the high cost of ownership, you should only consider where needed.

Question: Is it necessary to use a discharge check valve? What is the best type?

Answer: Most air compressors will have their own built in check valve, so it is not needed. But always check with the OEM.

Question: What changes on the oil injected compressor when using a food grade lubricant versus a standard lubricant?

Answer: Typically, the lubricant doesn’t last as long and you’ll have more frequent maintenance.

Question: What are the benefits of the two-stage vs single-stage rotary compressor?

Answer: Energy efficiency. Learn more here.

Question: What are recommendations for cooling air temperature for air-cooled units?

Answer: Learn more in this article.

Question: What are the more important maintenance items to keep locally for these air compressors?

Answer: You definitely want to keep the critical components like filters, oil, transducers, sensors and even a service kit for each valve.

Question: How long do the inline filters and oil-water separators last?

Answer: We typically size them to be replaced annually.

Question: Which air compressor is best for industries?

Answer: This is a hard question to answer in general, there are so many possibilities. We recommend you work with a local expert to see what would be best for your application.

Question: What makes a tank wet?

Answer: Tanks before the dryer are known as wet tanks—much more condensate to deal with.

Question: Curious about the comment about food grade lubricant lasting 2x as long in an oil injected machine.

Answer: It’s the other way around—usually OEM lubricants are rated for 8,000 hours while food grade lubes are commonly replaced at 4,000 hours.

Question: Did Kaishan produce a 50 Hz machine, as well?

Answer: Yes, Kaishan makes all models in 50 and 60 Hz.

Question: I believe you said care needs to taken when considering a variable speed drive (VSD). Can you expand on that again?

Answer: Ambient conditions should always be considered when choosing a VSD. Many compressors get put in harsh conditions (too hot, dirty, wet, etc.) and this can lead to a premature VSD failure.

Question: Can you give me some examples of insights you’ve discovered in an air sampling?

Answer: Numerous types of contaminates that we can address—from issues internal to the compressor to the atmospheric air these units ingest.

Question: What are some of the industries where oil-free use is becoming more common?

Answer: Food and beverage, pharma and electronics are the most common.

Question: Where are your oil-free compressors manufactured?

Answer: We engineer, manufacture and assemble in Loxley, Ala.

Question: Do you have a sales company here in Middle East?

Answer: Yes. You can contact us here.