Wet Bell Diving Operations and Emergency Procedures
Handling System
The handling system may consist of a crane, but a system framework and dedicated winching system are typical. The winch should be classified as “man-riding” and equipped with two brake types. It can be operated manually with a joystick (up/down). The braking system must be independently tested every six months. The cable must be of the non-rotating type and visually inspected every six months. The management system should also incorporate a secondary method of raising the bell to the surface so divers can recover safely. There must be voice communication between the supervisor and the winch operator, and only one person should be aware of these signals.
Maintenance
A Planned Maintenance System (PMS) should be in place to keep the wet bell and work equipment operating correctly and safely.
Emergency Procedures
Emergency procedures are detailed in the company’s operations manual, a copy of which should be available at every dive site. The diving contractor and supervisor are responsible for ensuring that emergency procedures are available and functional.
Loss of Communications
This plan could be initiated either from the surface or from the bell, depending on who discovers the problem first. It is crucial that divers continue talking if the supervisor can hear them. The following procedure should be used if the supervisor cannot contact the diver or bellman:
- Surface: Signal to the bell “a loss of comms” by flashing the bell lights.
- Bellman: Signal to the surface with two blasts on the blowdown valve to acknowledge the emergency. Each blast should be about 2 seconds long, with a 2-second gap in between.
- Bellman: Give the diver one pull on the umbilical, then four pulls to signal a return to the bell.
- Diver: Acknowledge all lifeline signals and return to the bell.
- Bellman: Take up the diver’s slack umbilical and assist in stowing it.
- Divers: Both enter the bell. When ready to leave the bottom, signal the surface by giving four blasts on the blowdown valve.
- Surface: Lift the bell slowly, monitoring the pneumo and air supply pressure gauges.
- Bellman: If there are any problems leaving the bottom or on the way up, stop the lift by giving a series of blasts on the blowdown valve.
- Surface: If there is a problem during the lift, be prepared to send in the standby diver to assist.
The divers must keep talking during this operation in case communications return. This could be attended comms or, if he is fouled, a succession of 2 bells.
Loss of Bell Lifting Wire
If the main hoist rope breaks, the bell will slide down on the weight guide. Divers should release their umbilicals, swim to the surface, and climb the ladder to exit the water. This limits the maximum depth to 20 meters.
Loss of Air Supply to the Wet Bell
- Surface: If the main LP air supply fails, inform the supervisor and, on his command, switch over to the HP backup. Inform the divers and abort the dive.
- Bellman: If during the dive you lose your main supply and have to go onto bailout, switch over to the bell’s on-board air supply. Inform the surface of your actions and ask them to recall the diver back to the bell (although the diver will already have gone onto bailout and probably returned). The bellman should confirm that both divers are on bell reserve and are OK; you will be able to see this by looking at the two reduced HP gauges, which should be fluctuating as you breathe. Assist the diver in stowing his umbilical, secure the safety chain, and inform the surface when you are ready to leave the bottom.
- Diver: If your air supply fails, go onto bailout, inform the surface, and return to the bell.