| Partial Pressure Blending |
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|
 Overview
 Partial pressure blending
Constant flow blending
Membranes
IT College seminars
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| Partial Pressure Blending
is a technique in which a receiving cylinder (or bank) is
used as a blending container on high pressure. There are no
limits in the possibilities – any Nitrox, Heliox or Trimix
blend can be made with this technique, which makes it very
popular for “technical diving”, where a single dive can require
different blends.
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| For providing Nitrox services for
recreational diving, the technique has disadvantages: |
| High staff cost due to the
long time to fill the cylinders – depending on the
recommendations you follow, the filling speed is between 3 and
5 bar per minute. |
 High
staff cost due to the need to oxygen clean equipment on a regular
basis – almost the entire system and the cylinders
and cylinder valves get in contact with pure oxygen at elevated
pressures. All such equipment must be oxygen serviced on a regular
basis. A recently cleaned valve or cylinder is never a problem,
but each time a cylinder is filled, small contaminations enter
the cylinder, which accumulate over time and thus increasing
the risk. |
| High safety risk (fire and
explosion) when the system is handled incorrectly –
working with pure oxygen at elevated pressures is always a risk.
The risk can be handled with proper procedures. Not knowing
or ignoring the procedures increases the risk immediately. |
| High risk combined with high workload
(cost) make this technique inadequate for filling bigger quantities
of Nitrox cylinders. The technique easily triples the cost of
a fill, compared to filling a cylinder with compressed air,
which would make the option of diving with Enriched Air unattractive
for the average recreational diver. The indicated disadvantages
can be reduced by first filling in banks and then cascade into
the diving cylinder, but will not be eliminated. |
| Because of the advantages of the
system, many dive operations keep a filling whip around for
special needs, such as filling cylinders for Semi-closed rebreathers,
oxygen cylinders for emergencies and closed system rebreathers
and to fill certain mixes for “technical diving”. |
| Required training: |
- Mathematics to calculate the required blend, without
venting residual gas from the cylinder.
- Compressor know-how to prepare and maintain the compressor
to deliver oxygen compatible air.
- Oxygen servicing the equipment that comes in contact
with pure oxygen at elevated pressure.
- Knowledge of the features of the system to increase safety.
- Knowledge of the environment requirements for the filling
system.
- Knowledge of the filling procedures and administration.
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| All these aspects are covered in
the special IT College seminar |
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