CMC Rescue MPD User Manual page 15

10 m [33 ft] of the descent), it is recommended to convert from hand-tight
Belay Line tension to shared tension between the Main Line and Belay
Line. Should the Main Line system fail from this point on, a Shared Tension
system will minimize rope stretch and provide a considerably reduced
arresting distance as compared to a conventional untensioned belay. It
will also help mitigate other hazards, such as an inadvertently slack Belay
Line or rope-induced rockfall, since the now-tensioned Belay Line will be
suspended above the terrain between contact points, just like the Main Line.
SHARED TENSION SYSTEMS
Shared Tension Systems are essentially two lowering systems in place of
one lowering system and a belay, with each line supporting approximately
half the load. If either system should fail, the increased load on the other
descent control device will cause an increase in rate of descent. While the
MPD is an effective belay device capable of safely arresting a falling load,
when used as a descent control device you are manually overriding the
belay function. This could result in increased stopping distances
if not using proper technique.
Therefore, in a Shared Tension lower it is imperative that the running end
rope of the Belay Line be held back toward the anchor, maintaining the
"S-shaped" bend as the rope runs through the MPD. If there is a sudden
change in speed or tension on the rope running through the MPD,
the belayer must immediately let go of the Release Handle
(disengage) while maintaining a firm grip on the running end of the
rope to ensure the braking mechanism activates and arrests the load
in the shortest distance possible.
YOU MUST LET GO OF THE RELEASE HANDLE WHILE MAINTAINING A FIRM
!
GRIP ON THE RUNNING END OF THE ROPE TO ACTIVATE THE BELAY!
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