# Commercial diving/Dive from a wet bell and diving stage

Relevance: Scuba diving (none), Surface supplied diving (none), Surface oriented wet bell diving (full).
Required outcomes:
* Demonstrate the ability to dive from a wet bell or diving stage
* Demonstrate the ability to carry out wet bell panel operations
* Demonstrate the ability to complete the emergency on-board gas access procedure
* Demonstrate the ability to carry out bell emergency procedures

## Dive from a wet bell

Specific skills:

### Dive as bellman

    Wet bell pre-dive inspection and checks
    Prepare umbilicals and tie off as required
    Dress in with pre-dive checks
    Enter bell and rack umbilical
    (Diver enters bell and racks umbilical)
    Check safety chains and report secure and ready for launch
    Hold on to handholds during transit
    Report bell in water and canopy under
    Operate blowdown to keep canopy filled
    Equalise as required, and call stop if there is an equalising problem
    Release safety chain once submerged to allow emergency exit if bell does not stop in time for equalising
    Report progress until bell at working depth
    Monitor:
       Voice communications
       Main gas supply pressure
       Diver and bellman supply pressure
       On-board emergency gas supply pressures
       Bell lights for emergency light signals
       Diver's umbilical for line signals
    Report when diver leaves and returns to bell
    Tend diver's umbilical while diver is out of the bell
    Remain available for action in an emergency
    Switch over to onboard gas before leaving the bell in an emergency
    Check bell ready for ascent
    Report when bell is ready to leave bottom
       Umbilicals stowed
       Chains secured
       Bell ready to leave bottom

### Dive as bell diver

    Complete bell pre-dive checks
    Measure off and tie back umbilicals to suit job and hazards; at least 2m shorter than bellman's umbilical, 5m less than shortest distance to major hazards, taking into account possible underwater tending points.
    Dress in and prepare for dive with pre-dive checks.
    Enter bell after bellman and rack umbilical
    Notify bellman when ready
    Hold handholds during transit
    Remain ready to take over from bellman if bellman incapacitated
    Equalise as needed during descent
    Call stop if descent too fast to equalise or other problem
    Report any problem not noticed by bellman
    Lock out of bell when instructed from surface:
       Lock out of type 1 bell or stage on opposite side to entry so that umbilical passes through frame.
       Take off a couple of coils of umbilical, lock out and report locked out.
       Complete bell integrity check and report back to surface on status:
          Main lift wire secure
          Umbilicals secure
          Guide wires clear
    Proceed to worksite
    Monitor umbilical for:
       line signals
       snags
       excess slack
    Keep watch for light signals
    Report progress of work as appropriate, inform surface of contingencies, incidents or emergencies
    In the event of main gas failure, open bailout and report to surface, request pneumo air, start return to bell
    Return to bell on instructions or emergency signals or if not feeling well
    Follow umbilical back, bellman to take up slack
    Report return to bell, when locked in and when umbilical secure
    Check on bellman on return to bell
    If bellman not responsive, switch over to onboard gas and report to surface, prepare for ascent

## Operate the wet bell gas panel

Specific skills

### Monitor gas pressures
## Access emergency on-board gas
## Perform wet bell emergency exercises

Specific skills:

### Emergency signals

Loss of voice communications is not an emergency, but it compromises the ability of the diving team to effectively manage an emergency, if one should occur.
If voice communication to the diver is lost, the supervisor may establish communications by flashing helmet lights, or the bellman can be asked to establish contact using line signals.
If contact cannot be established, or there is any doubt about the diver’s condition, the bellman should recover the diver to the bell.
If voice communication to the bellman is lost, the supervisor will instruct the diver to return to the bell.
If there is a complete loss of voice communications to the bell, contact can be established using an agreed procedure and signalling methods. Typically, the supervisor will signal the bell by flashing the bell lights and the divers will signal by operating the blow-down valve to provide a large flow of gas.
If these methods fail, it may be possible for the supervisor to assess the situation using on-board video or an ROV, if these are available. The supervisor will also consider sending the standby diver in.

#### Signal to the surface that voice communications has failed

    The bellman or diver can indicate to the surface that they are unable to hear voice communications from the surface by releasing a distinct blast of air from the bell blow-down valve or a helmet free-flow valve.
    and other emergency signals

#### Respond to a signal of failure of voice communications to the surface.

    (The supervisor may signal that they are not receiving voice communication from diver or bellman by flashing the bell lights and if necessary the diver’s helmet light.)
    The bellman acknowledges this by signalling the surface with two distinct blasts of air from the blow-down valve.
    The bellman then gives the diver 4 pulls on the umbilical to signal to return to the bell.
    The diver will acknowledge this by replying with 4 pulls and return to the bell.
    Bellman and diver will stow the umbilical and prepare the bell for ascent
    Bellman will signal with 4 distinct blasts of air from the blow-down valve that the bell is ready to ascend
    (The bell will be hoisted slowly while the supervisor monitors depth on the pneumofathometer.)
    If there is any need to stop the ascent the bellman will signal with a long continuous blast of air from the blow-down valve
    The supervisor will deploy the standby diver provided that he still has voice communications.

#### Respond to emergency signals from surface

    See bell emergency signals

#### Respond to loss of main air supply to the diver

    If the main air supply fails the diver will immediately open the bail-out valve and report the situation to the supervisor
    The bellman will switch the diver to onboard gas.
    If this does not restore main air supply, the diver will request air on the pneumo line and insert the end into the helmet.
    If pneumo air supply works the diver will then close the bailout valve and instruct the surface to adjust pneumo flow to a comfortable level
    If the cause of the failure is known and is likely to be rectified easily and quickly the supervisor may advise the diver to stand by while it is fixed, otherwise the diver will return to the bell. If pneumo air is not available, the diver will return to the bell without undue delay.

#### Respond to loss of main air supply to the bellman. (Is the onboard gas normally on?)

    The bellman should observe that the onboard air has cut in and report to the supervisor.
    The diver will be recalled to the bell, The bellman will help recover the diver and make the bell ready to leave bottom.
    If the surface air supply cannot be restored, the dive will be aborted and the ascent made on on-board air supply
    Surface decompression may be necessary.

#### Respond to failure of main air supply to the bell

    The bellman will immediately switch over to on-board gas and inform the supervisor.

### Bell abandonment

It is possible for a bell to be disabled in a way that prevents it from being lifted by any immediately available method. Surface oriented divers cannot remain under pressure indefinitely, and the escalating decompression obligation caused by delays in starting the ascent increase risk of decompression sickness. Abandonment of a type 1 wet ball or diving stage is relatively straightforward provided the umbilicals are clear of obstructions. Type 2 bells provide a greater challenge. The divers can ascend part or all of the way by deploying their umbilicals and ascending following the main lift wire, the umbilical, the anti-spin rope or other convenient line to the surface. If voice communications remain functional, the emergency ascent can be coordinated from the surface. If not the standby diver should be deployed to assist in the rescue and provide information to the supervisor.

#### Abandon type 1 bell or stage

* Divers follow their own umbilicals out of the bell/stage and surface where best practicable
** It may be appropriate to surface on the lifting cable
** Otherwise divers can surface in mid-water controlled by tenders

#### Abandon type 2 bell, method 1

    (This method gets the divers ascending with minimum delay and thereby minimises their decompression obligation. It will usually be best option when a cable or bell umbilical is continuous to the surface.)
* Diver exits bell with bight of bellman's umbilical in hand to keep it clear of snagging on the bottom
* Diver ascends on whichever of bell cables or umbilical seems best, carrying the bellman's umbilical as far as it will go and stops, supported by the chosen cable.
* If tied off the bellman unties the umbilicals to allow their full length to be used
* Bellman pays out the rest of the diver's umbilical, which the diver takes up and drapes the slack over his arm to prevent it snagging at depth.
* If not already on on-board gas, bellman switches over to on-board gas, leaving main gas on.
* Bellman leaves bell and follows his umbilical up until reaching the diver, then both continue ascent along the chosen cable as far as their umbilicals allow, stopping to decompress as may be required.
** If there are tools on the bell suitable for disconnecting umbilicals from helmets they should be taken in case it is necessary to disconnect each other and continue ascent on bailout.
* If the umbilicals are not long enough to reach the surface, the stand-by diver will come down to meet them and may do a change-out to a spare umbilical from the surface. Even if only one spare umbilical is available, pneumo breathing air supply can be provided. The standby diver can also provide a swimline/jackstay to the exit point where appropriate.
* Once at the surface, diver, bellman and standby diver establish positive buoyancy and exit water by an expedient route.
* Surface decompression may be necessary or advisable, depending on the actual dive profile.

#### Abandon type 2 bell method 2

    (This method relies entirely on bailout gas during ascent, and delays the divers at the bell depth, which may increase decompression obligation significantly. It also puts the divers out of communication during the ascent. The risk is relatively high, but it is possible that no other workable option exists - this is the method of last resort. The risk will usually be greater than method 1 where method 1 is practicable.}
* Diver and bellman switch to bailout gas
* Bellman and diver disconnect umbilicals from each other while at the bell and ascend whichever one of the bell cables or bell umbilical seems best on bailout gas, with surface decompression as necessary. There may be unavoidable delays at the surface before the divers are back under pressure in the chamber.
* If possible the standby diver would be sent in to meet the divers and provide some communications, an alternative breathing gas supply, and a secure route to the exit area.

#### Abandon type 2 bell method 3

    (Only possible if another bell or stage is immediately available. Divers will be exposed to pressure for longer than the other methods, so decompression will be increased, but breathing gas security, ascent rate control and communications are better. )
* Send standby diver down on a second bell or stage with spare umbilical.
* Bring diver and bellman over to the rescue stage, and swap out umbilical/s as practicable, or switch to onboard gas by the best available method, then surface on the rescue stage.
Variations may be possible depending on the equipment available and the dive plan. The preferred method based on the risk assessment should take such factors into account.

## Surface standby for bell operations

Specific skill:

### Deploy as standby diver for a bell diver rescue

    Enter water on instruction from supervisor
    Provide running commentary on progress
    Follow lift wire or bell umbilical to bell
    Pass through? bell to guide umbilical
    Check on-board gas is open
    Follow divers umbilical to diver
    Flush hats and open bailouts as divers are found
    Recover one at a time to bell, following umbilical to avoid snags.
    Suspend first diver in lifting tackle
    Follow other umbilical to recover second diver to the bell by the same procedure
    Recover and stow umbilicals in the bell
    Secure safety chains, report to surface that bell is ready to leave bottom
    Support casualties in bell during ascent