JFD COBRA Manuel d'exploitation et d'entretien
ISSUE
Water ingress to COBRA scrubber
A client reported water ingress to the scrubber on a COBRA set. JFD inititally replaced the
Hot Water Housing (as it was thought the fault occurred in this component) but the clients own
investigations revealed an incorrectly set hot water PRV. The incorrectly set PRV failed to protect
the COBRA set from excessive hot water pressure and this caused the inner liner of the hot water
housing to deform and lose contact with the sealing o-ring. As a result hot water leaked into the
scrubber housing.
SOLUTION
Following a thorough review and investigation of the hot water PRV, JFD recommend
resetting the relief valve to open at 3 psi (rather than 4 psi as previously advised in the manual) and
checking the setting fortnightly thereafter.
Please see following pages for procedure.
COBRA Bailout System
23 May 2019
Page 1 of 3
ADVISORY NOTICE
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Background
A client reported water ingress
to the COBRA scrubber. Their
own investigations discovered the
cause to be excessive hot water
pressure due to an incorrectly
set relief valve in the COBRA hot
water system.
Copyright © JFD Limited 2019
DB500-PGN-2
Procedure to set Hot Water PRV
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Copyright © JFD Limited 2019
DB500-PGN-2
COBRA Bailout System
23 May 2019
Page 2 of 3
Figure 1 - Test equipment
See figure 1.
Fit the test plug (DB5003843), test nut (DB5003844) and o-ring (E13330) to the hot water relief valve DB5002335
as shown in figure 1. These items are contained in the COBRA Tool and Test Kit. Fit a 3/8” UNF plug to the
outlet of the relief valve.
Connect an LP air supply and a calibrated LP gauge. Care should be taken when applying the pressure if a very
low range gauge is used until it is confirmed that the PRV will vent correctly.
NOTE: Ensure that the 3/8” plug does not interfere with the spring inside the PRV. It may be preferable to fit
the Hot Water Inlet Hose from the COBRA set (which has a specially shortened 3/8” fitting) and fit a 9/16” UNF
blank to the other end of this hose.
Immerse the hot water relief valve in water (minimum depth to cover relief outlet).
Gently apply air pressure to the relief valve inlet and note the pressure reading when bubbles start to form in the
water
NOTE: The reading is taken when the first bubbles begin to form. Any appreciable flow through the PRV will
cause a higher reading on the gauge due to the port size on the test fitting.
Figure 2 - Cross section of Hot Water Relief Valve
See figure 2.
Slacken the locknut (item 5), hold the stem (item 2) and turn the adjuster (item 3) clockwise to increase the set
pressure or anticlockwise to decrease the set pressure, then retest.
When 3psi +/- 0.2 psi has been achieved, tighten the locknut (item 5) against the adjuster, ensuring components
are locked together.
Confirm set pressure has not changed.
Remove test equipment and re-fit relief valve to set.
ADDITIONAL
JFD recommend that the scrubber canister is removed and inspected at the end of every dive, irrespective of
whether it is intended to change the sodalime at that time. Any moisture detected should be investigated. This
ensures that the set is serviceable for the next diver.
ONGOING WORK
JFD are currently undertaking work to improve the flow capacity of the relief valve. This will ensure that the
COBRA set is protected from overpressure, even if the COBRA set hot water outlet is totally blocked for any
reason. A further guidance note and replacement parts will be issued in the near future to allow clients to carry
out this modification.
COBRA Bailout System
23 May 2019
Page 3 of 3
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Copyright © JFD Limited 2019
DB500-PGN-2
Table des matières
Autres manuels JFD Instrument de plongée
