Compressed air system Buffer Vessel sizing

[remp]

Hi

I am installing a compressed air system that is made up of 4 air compressors approx 1400l/s in total.
What size buffer vessel should I install down stream of the compressor on the main line. Is there any rule of thumb.?

 

[racookpe1978]

What is your expected use rate? How will that use rate change with operations? (One very deep cycle, then a long pause? Many short cycles with a short delay between each? A more or less continuous use rate?)

What is the capacity of each of the four compressors? What is their advertised operating cycle?

What is your desired operating cycle of the compressors?

 

[remp]

racookpe1978

4 air compressors, 300l/s, 300l/s, 700l/s (on a VSD) & 1100L/s

The load is fairly consistant at 800L/s but can go to 1200L/s over the spate of an hour only or down to 500l/s over an hour also.

We have an existing buffer vessel that is about 4m3. Do you think this is enough?

 

[Duwe6]

Depends on your pipe volumn versus your normal and peak usage. I have seen a system that didn't even need a vessel, because the compressers were located several hundred yards/meters from the major users. The pipeline was the buffer.

 

[sheiko]

Use this spreadsheet after you understand it.

"We don't believe things because they are true, things are true because we believe them."

 

[racookpe1978]

With the compressors having significantly different capacities, you'll have at least two of the smaller ones running effectively continuously; or the largest plus a smaller one, running near continuously, under almost all "normal" useage.

Power surges (power costs) are highest at the starting surges, particularly when the surges start during a high-cost time of day from your provider. Running time and maintenance costs are proportional to each other and probably near equal between all 4 compressors. Unless you can tell that one unit seems to always start first, or another run longest when two are running - as if its setting were slightly higher start pressure. Worse case, you may find that one machine doesn't carry any load at all.

What are the current start-stop trips on the units? What are the running times and running costs? An automatic current data logger on each of the 4 power cables could be very effective, but would require maybe 2 weeks research time.