Improving the safety of watertight doors
Gard News 207, August/October 2012
Some suggestions concerning the problems of power-operated watertight doors.
Photo courtesy of IMS, Norway.
In Gard's view it is necessary for designers of ships and institutions responsible for approving the designs (flag states and class societies) to observe the basic requirement of the SOLAS Convention to keep the number of watertight doors in subdivision bulkheads of ships to a minimum. That requirement, valid for both cargo ships and passenger ships, appears to have been overlooked.
It is also confusing to have different requirements for watertight doors depending on whether a ship is built before or after 1st February 1992. If flag states do not re-examine the systems on board older vessels and adjust them to the principles of the new regulations, shipowners must do that voluntarily in the interest of the safety of their crews. On the bridge, the remote control of the watertight doors should only be able to close the doors, not to open them, and the important requirement for vessels built after 1st February 1992, that the operating mode of the doors must always be set on the bridge to "local control", should preferably be respected by all. The bridge control in "doors closed" mode should only be used in emergencies and for testing purposes. When testing the doors everyone must be warned.
Because it is so important not to place the switch in "doors closed" mode on the bridge, Gard would suggest a physical protection to the switch, a device which would have to be removed before the switch can be placed in that position. This would force personnel on the bridge to think twice before activating the switch.
Levers for operating the doors locally should conform with the SOLAS regulations for ships built after 1st February 1992: they must be positioned as described by the regulations and their movement must correspond to the direction of the movement of the door. Also, there are doors operated by push buttons, which do not appear to comply with SOLAS regulations. Levers should have three positions: open, neutral and close, and should always return to neutral position when the operator releases it. Old systems, where the operating lever can be locked in closing position, are dangerous. There is, however, one aspect of current regulations regarding the location of the local levers which may require further consideration: the fact that when a body is trapped by the door, the lever may be obstructed by the body and cannot be placed in position to open the door.
SOLAS requires indicator lamps on the bridge panel for all watertight doors, and they must be red for open and green for closed. If older systems have the opposite colours, they should be adjusted and proper information posted at the panel. Considering that an open door in a subdivision bulkhead represents a risk to the ship in case of water ingress, red is the natural colour choice for an open door warning.
There must be clear instructions on board as to how to operate and make use of the doors. Procedures must be consistent, there must be no difference between the procedures in the vessel's ISM manuals, instructions from management, Master's orders, postings at the doors and on the bridge, etc.
Crew members must be trained and special attention should be paid to how the doors will close if in bridge control "doors closed". There should be clear understanding that, when the alarm is sounding and the light is flashing when opening a door on location, the door is in bridge control and the door will then close automatically when the operating handle is released. To distinguish this dangerous situation, it is not recommended to also have an alarm for door movements in "local control" mode. It should also be noted that, should a fault to the door systems occur, the door will close as if it were in bridge control. The requirement that no person shall transit a power-operated door when it is moving must be strictly enforced: "If it moves, you don't!"
watertight doors on three decks, and all locations are shown on the panel. The "master mode"
switch can be seen in the upper left-hand corner.
Speed of door movement should not be tampered with by personnel on board thinking it closes too slowly. That is difficult to do for electrical doors, but can be easily done on hydraulically-operated doors. In order to prevent that, it may be a good idea to seal the setting of the hydraulic flow valve. It is also worth noting that the requirement for a door to close in a minimum of 20 seconds is the same as for a door of 1200 mm width as for a door of 600 mm width. Larger doors may therefore close with double the speed of smaller doors. If larger doors are not fully open when somebody tries to pass through them, there may be little time available if they close.
The correct working of watertight doors is essential to the vessel's survivability in case of water ingress. Doors are an important element of a vessel's subdivision and as such a part of the safety system. Such doors must therefore be seen as important for the classification certificate, the safety construction certificate and the loadline certificate. The surveyors inspecting a ship for the issuance and maintenance of these certificates must therefore have the necessary knowledge of how watertight doors are to function.
Following the accident on board the offshore installation KRISTIN in Norway in 2005, the manufacturer of the door developed an anti-crush protection called the "IMS safety strip", using laser beam sensors. Doors using this device will open if any object is within the door frame. On the bridge there will be a provision to override this safety device and close the door to save the ship. After the accident this "safety strip" was fitted to the doors of the KRISTIN and to some other Statoil-operated rigs in the North Sea, reducing the risk of injury to personnel. As far as is known the "IMS safety strip" has not been fitted on board any ships, and it would be up to the IMO and flag authorities to consider and approve that.
Finally, power-operated watertight doors must be considered an important piece of machinery. There are mechanical, hydraulic, electric parts, parts to be replaced and settings to be controlled in accordance with the maker's instructions. It is not unusual for a door to have 100 movements a day, for instance in accesses to laundries of cruise ships, and up to 500 movements have been recorded. Wheels of doors will be worn, with subsequent wear of the packing at the bottom, resulting in loss of tightness.
At investigations following accidents, it is not uncommon to discover unauthorised modifications or total lack of maintenance of the doors. For regular service of power- operated watertight doors, a requirement for periodic service by the manufacturer should be introduced.
Power-operated watertight doors should be considered "hazardous machinery" and, so that they are safe to use, all aspects of the door mechanisms must be reviewed as required by European Standard "Safety of machinery", EN 292-1 and EN 292-2.
Any comments on this article can be e-mailed to the Gard News Editorial Team.
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