Manual Version 19 / 01-2019 II Page 12 of 44
SF2 ECCR OPERATION MANUAL
2.1 Lime duration time
The lime life of a scrubber depends on many different factors. The absorption
capacity depends primarily on the type or manufacturer, but storage, filling of the
scrubber, immersion conditions, temperature, exertion etc. Many factors have a
major influence on the nominal values of soda lime durations determined under
standard conditions.
2.2 Storage
To start the calcium reaction, moisture is required (CO2 reacts with water to form
carbonic acid). Therefore soda lime contains between 14-20% water. Incorrect
storage leads to drying out and thus to a loss of reactivity of the lime. Fresh lime, if it
is not stored airtight, will have dried out after 4 weeks at the latest. In addition, the
lime would bind the CO2 from the air and thus lose its absorption capacity. A filled
scrubber should therefore not be left standing around for too long. This is okay for a
repetitive dive on the weekend, but it should be replaced after 2 weeks at the latest.
2.3 Influence of temperature on the soda lime output
The soda lime output is particularly temperature-dependent. The lower the ambient
temperature, the worse the calcium reaction. This means that the soda lime filter
performance is significantly lower in cold water than in hot water. A canister filled and
used in warm Mexico waters could be used for 6 hours. The same canister filled and
used in 37 degrees Fahrenheit (3°C) cold mountain lake would be enough for 3
hours.
At 20 ° C e.g. the lime filtration rate is 100%, at 15 ° C it drops to around 80%, at 10
° C to around 65% and at 4 ° C to less than 50%.
In terms of temperature-dependent filtering performance, it is essential to note that
the filter rate per unit of time is meant here. The lime is not consumed faster in the
cold, but only reacts more slowly or the reaction zone becomes larger.
2.4 Influence of exertion on standing time
Another important point for the lime service life is physical activity and thus CO2
production. This can increase by up to tenfold with exertion and stress! Deep CCR
dives in cold water with stress and exertion are therefore high risk factors for a CO2
breakthrough or for hypercapnia. At rest, a person consumes about 0.3 l / min of
oxygen and converts this (depending on the respiratory quotient) into CO2. When
exercising, the O2 consumption or CO2 production increases to around 3.0 l / min,
top athletes can do even more. An average scrubber holds around 2 kg of lime, so it
has an absorption capacity of around 300 l of CO2 (approx. 150 l / kg). Usually one
produces an average CO2 production of 1.0 - 1.5 l / min during one dive. This means
that a fresh scrubber filling lasts for about 200-300 minutes. If the oxygen
consumption or CO2 production doubles due to exertion, the dive time is halved
accordingly. Depending on your personal consumption rate, diving conditions
(temperature, exertion, stress, etc.) and safety margin, you reduce the dive times.
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