By Dez Duran-Lamanilao
Watertight doors (WTDs) are installed to prevent the ingress of water from one compartment to another during flooding. They are usually located at the bottom part of the ship where the engines and shaft tunnel are found. They may be kept close especially when the ship is underway or may be left open except during an emergency.
Image source: NAVINT
Ships are built with WTDs for the following purposes:
- For the effective utilization of space
- As an optional means of escape
- To avoid dead-end corridors
- To transport goods
- For the maintenance and transport of spare parts
For passenger ships, for example, Meyer Werft uses different types of watertight doors designed to meet each ship’s unique specifications.
- Normal WTD below bulkhead deck
- Light WTD with reduced scantlings,
- Semi-watertight doors that are meant for GZ (righting lever) range only and not below immersion line
- Fire doors
Companies and manufacturers must observe the regulations set by the International Convention for the Safety of Life at Sea (SOLAS) regarding closure of watertight doors:
- All the power-operated doors must close simultaneously from bridge and Ship Control Center (SCC) within a minute when the ship is in upright condition.
- The door must have an estimated uniform rate of closure (should be within 20 seconds or 40 seconds with the ship in upright condition) under power.
- During power failure where a hand operation is needed, the door must be closed within 90 seconds.
Watertight hatches allow access and provide protection to watertight compartments. They can be in the form of clip handles, toggle clamps, flush hatches, or those that feature central operation, providing a safe, quick escape from any compartment.
Companies should undergo a feasibility study to identify which particular types of watertight doors and hatches would fit a ship’s specific requirements. In addition, engineers should take particular attention to evacuation in designing WTDs to minimize possible injuries in cases of emergencies and increase chances of survivability.