Atmospheric Control in Confined Environments (Diving)
The Customer Issue
A South African diving support company was running 6 and 18m3 decompression chambers and found that the smaller chamber was not performing satisfactorily.
The larger chamber easily controlled CO2 levels for 6-7 hours between Sofnolime filter changes whilst the same system in the smaller chamber required much more frequent changes.
Understanding the Issue
An analysis of the situation in the two chambers highlighted that both were being run identically. However because the smaller chamber was one third the volume, the gas in the smaller chamber was being re-circulated three times more frequently.
The net effect of this was to increase the cooling by the helium portion of the gas (reducing the absorption efficiency of the Sofnolime) and a short residence time within the scrubber.
The reduced residence time further reduced the absorption efficiency of the Sofnolime.
The Solution
The technical support team at Molecular Products created a complex model to simulate the conditions in the smaller chamber.
The model helped understand how to optimize the various trade-offs involved.
The analysis showed that the recirculation rate for the smaller chamber should be reduced from 120 m3/hr to 36 m3/hr for optimum performance.
The Results
As well as raising the performance of the smaller chamber to the level of the larger chamber the flow rate reduction also reduced the costs of running the re-circulating fan system.
The customer was delighted at the savings in Sofnolime required as well as the labour involved in managing the system.