Cascade Fill Systems
Learn How a Typical Cascade Fill Systems Operates
A cascade fill system is an air system that works simply by transferring a gas from one cylinder into another cylinder that contains less pressure. The best that can be accomplished in this transfer process is the equalization of the pressure in the two cylinders. In a cascade fill system, you have a number of bulk air storage banks with varying pressures of gas in each. Lets assume the bulk banks contain the pressures as described below:
Bank 1 1850 PSI Bank 2 2700 PSI Bank 3 4260 PSI
A customer brings a scuba cylinder into the shop that contains 500 PSI of air pressure, the recommended minimum amount of air you would ever have in a scuba cylinder. It is a high pressure steel cylinder, so the customer desires a fill to 3500 PSI. To maximize the number of cylinders we could fill with the banks described above, we would fill as follows:
We would first open Bank 1 and allow the bank and the customer's scuba cylinder to equalize, that is, reach a pressure that is equal in both the bank and the scuba cylinder. We might, depending on the size of the bank, arrive at an equalized pressure of 1620 PSI. We can't get all the way to 1850, which is the starting pressure of Bank 1 because as air moves into the customer's scuba cylinder, the pressure of the air in Bank 1 is reduced. We would close Bank 1 and open Bank 2, and allow that bank and the scuba cylinder to equalize. Again, we might reach an equalized pressure of 2530 PSI. Again, as we deplete air from Bank 2, it's pressure drops. We would then close Bank 2 and open Bank 3. We would fill from Bank 3 until the scuba cylinder reaches a pressure of 3500 PSI, our desired fill pressure.
Of course, we could have just opened Bank 3 to begin with and filled the scuba cylinder from Bank 3 only. When we reach a scuba cylinder pressure of 3500 PSI, the fill would be completed. But by taking all of the volume of air from Bank 3, the pressure reduction in that bank would have been large, maybe down to 3600 PSI, depending on the bank size. If we attempted to do that with a second scuba cylinder, we probably could not get a full fill to 3500 PSI. We would then be forced to run the air compressor and refill Bank 3 to it's full pressure again.
The secret of the cascade system is to maintain a bank at very high pressure, using that bank only to top a cylinder to it's final fill pressure. Other banks are used to transfer the bulk of the volume to the scuba cylinder. This cuts down on compressor operating time, reducing the cost of producing breathing air. The management of compressor run time is a critical variable in a scuba store. The cascade system allows us to manage that run time.
Diagram of the Dive Sports Cascade System
The Dive Sports air fill system includes separate air fill panels for standard breathing air and Enriched Air Nitrox. The core of the system is our North American Hypres breathing air compressor. The air compressor (shown below in green) takes air conditioned air from inside of our building and compresses is in three progressive steps up to a pressure of approximately 5000 PSI. The compresses air is then sent through two hyper-filter cartridges, where moisture, oil, and other contaminants are removed. The cleaned air is routed to the air fill panel (shown below in blue panel on the right) where various valves are manipulated to store it in one of three 1800 cubic foot storage banks (shown below in yellow). The air fill panel provides capability to fill up to four scuba, SCBA, paint ball, or commercial cylinders at a time. Filling is accomplished by manipulating various valves on the panel to remove air from the three cascade air banks. Enriched Air Nitrox is filled from the EAN fill panel (shown below in the blue panel on the left). Enriched Air Nitrox is manufactured by combining pure aviation oxygen from cascaded oxygen banks (shown below in yellow) with standard breathing air from the air cascade banks. The flow of clean air to the Enriched Air Nitrox fill panel is controlled by the breathing air panel and can be taken from any of the clean air banks. Both gases (clean air and oxygen) are placed directly in the customer's cylinder based upon a mixture formula for the particular mixture desired. We invite you to drop by and let us show you this system up close. We think you will agree that the Dive Sports system is second to none in Alabama.
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