User manual

Poseidon MKVI User Manual
Appendix 2
Page 87
WARNING:
Planned decompression diving requires additional training and
support equipment. NO NOT attempt to use a MKVI rebreather for
decompression diving without proper training and equipment! In
particular, when diving with a MKVI enabled for decompression
diving, it is the DIVER’S RESPONSIBILITY to ensure access
to an adequate supply of breathing gas to effect a safe and
controlled bailout to the surface, including full decompression
requirements!
Setpoint
A MKVI enabled for decompression diving uses a different PO
2
setpoint algorithm. The intent
of the algorithm is to keep the setpoint higher for longer when a decompression ceiling has
been encountered during a dive. This comes at the cost of making buoyancy control more
difcult in shallow water. The algorithm will always use the highest setpoint (typically 1.3 bar),
subject to the following limitations:
1. The FO
2
is limited to 75%. Thus at the surface the setpoint would be 0.75 bar. At 3m the
setpoint would be 0.98 bar, and at 6m and greater the setpoint would be 1.3 bar (for a rig
with a 1.3 high setpoint value).
2. The hyperoxic linearity test still applies. Thus a rig that fails the hyperoxic linearity test will
not be allowed to use a setpoint > 1 bar. (See chapter 3, hyperoxic linearity test in the
MKVI manual).
Open-Circuit Bailout
On a MKVI that is not enabled for decompression diving, the system monitors the amount of
gas remaining in the diluent cylinder, and warns the diver when the calculated amount of
6. Decompression Diving with the MKVI
A MKVI enabled for decompression diving will behave differently compared to a MKVI that is
not congured for decompression diving. Important changes in the functionality when a diver
approaches and enters decompression are:
• The ceiling indicator will not ash. It will just be on and not ashing. When the ceiling indi-
cator is on, the alert triangle will not be on.
• The rig will not issue an alarm (HUD & Buddy lights, Audio Alarm) when decompression is
entered.” There is no audio alarm when decompression is entered on a non-decompres-
sion conguration.
• When the mouthpiece is found to be in an indeterminate state (neither in Open-Circuit nor
Closed-Circuit position) a different audio alarm signal will alert the diver to correct the
mouthpiece position. The reason for this is that when the mouthpiece is in an indetermi-
nate position, decompression is calculated as though the diver is breathing in open-circuit
mode. The alarm helps prevent the diver from being penalized from a decompression
point of view.
Controlling Resource Algorithm (CRA)
A decompression enabled MKVI has a different controlling resource algorithm (CRA).
In a standard MkVI, the remaining dive time is the minimum of remaining no-decompression
dive time (RNDT), Oxygen supply, Battery supply or OTU’s. What this means in practice for
most divers on most dives is that the remaining dive time is the RNDT.
For a decompression-enabled MKVI, an RNDT of zero is permissible and will not generate an
alarm. Thus, after the RNDT reaches zero (i.e., when a decompression ceiling exists), the CRA
instead only takes into account the Oxygen Supply, Battery Supply, and OTU value when cal-
culating the remaining dive time.
While a decompression ceiling exists, the CRA is not displayed on the LCD screen, because
this part of the screen is used for the total decompression time (see chapter 3, dive proce-
dures in the MkVI manual). However, the CRA is still calculated (excluding the RNDT value) and
used to generate alarms, if needed. Also, whenever a decompression ceiling exists, if the TTS
exceeds 80% of the CRA time (for any of the CRA values other than RNDT), an alarm will alert
the diver that the dive must be terminated.
diluent is insufcient to reach the surface. When using a MKVI enabled for decompression
diving, the system assumes that the diver is carrying additional gas supplies for open-circuit
bailout, and therefore no warnings are given to the diver when the standad diluent supply is
insufcient to allow a safe open-circuit bailout to the surface.
Planning your CC Dive and OC bailout
For more comprehensive planning tool use the “WeDive” application which can be
used with iPhone and iPad. See AppStore for further information.