Safety at sea
More than meets the eye
– by Mark van Tamelen, 16 February 2017
Anyone who has ever stayed in a hotel knows the story: green exit signs, fire extinguishers in the corridors, smoke detectors and evacuation plans hanging next to the door in every hallway. These are all visual safety features designed to help ensure guests get to safety as quickly as possible in an emergency. One can also imagine that hotels have numerous other adaptations to the installed systems which are designed to guarantee the safety of guests and staff.
Things are no different on vessels at sea. The major difference is in the impact these security features have on the construction of the vessel and the equipment on board. And that is the subject of this this blog.
SOLAS as a starting point
When engineers determine the basis of a HVAC system, we always start by applying the rules laid down in SOLAS (the International Convention for the Safety of Life at Sea). They contain the minimum requirements a vessel and its equipment must meet in order to make sailing at sea as safe as possible.
In addition to SOLAS, classification societies have their own views and interpretations with which the vessel and equipment must comply to ensure the safety of those on board. This brings with it major challenges: HVAC systems are designed to respect all the rules while having the least possible impact on the design of the vessel and its components & systems. An installation on a container vessel is subject to different requirements than on a navy ship or cruise vessel. In addition, the rules of various classification societies can be interpreted in different ways, which may result in different realisations of the same system.
Safe Return to Port
The six-star cruise vessel Scenic Eclipse is one of the projects on which we are currently working. This vessel is subject to Safe Return to Port (SRtP) requirements. The overall intentions with the SRtP regulations are to increase the vessels’ robustness and ability to safely return to port unsupported after an incident of fire or flooding, and thus reduce the likelihood of evacuation.
The systems required to be available to support habitability- such as air conditioning and ventilation – must be arranged to be simultaneously available in the assigned Main Fires Zones (MFZ) should an incident occur in any other compartment. For any given case of fire within the casualty threshold, a safe area must be available in other main vertical zones than the one exposed to the incident. This requirement has a fairly large impact on the HVAC system, which is normally installed centrally.
The consequences of SRtP for HVAC
What is the impact of the SRtP requirement on the HVAC system on board this cruise vessel?
- The cooling/freezing equipment is divided into two separate systems.
- The chilled water system consists of two smaller chillers instead of one large one. This means that one chiller can always keep running if a MFZ is closed. By laying the pipe system with bypass pipes, we can seal off entire zones of the vessel on the water side and always continue to operate at least two zones.
- The heating systems feature double heat exchangers as well as bypass pipes, just like the chilled water system.
- The automation is completely redundant and comprises two servers in different zones. In addition to air handling units (AHUs) and chillers, this system contains all other disciplines, such as valves for bypass pipes and fire damper operation. The network is laid in a loop through the vessel, and consists of fireproof data cable made of glass fibre. If central control is no longer possible, each individual AHU can be operated separately at all times.
- The capacity of the AHUs should be set so that all persons in the safe areas receive sufficient fresh air from the outside. This reduces the possibility of recirculation and requires the use of a rotary heat exchange wheel.
- At the same time, the size of the system must be kept within bounds.
While these considerations only refer to the impact of SRtP on the HVAC, they affect the design of many more systems on board. This requires a more multi-disciplinary/system-based approach throughout the new build project. For example, this cruise vessel also features a second wheelhouse and the possibility of setting up an emergency hospital. Furthermore, several other classifications which would impose different requirements on the vessel may also apply. For instance, Scenic Eclipse also has a polar code and a clean ship classification.
While the regulations of classification societies make our work extra challenging, applying inventive technologies allows us to guarantee the safety of passengers and crew.
Mark van Tamelen | Senior project engineer
Mark van Tamelen joined Heinen & Hopman in 2000. He started as a drafter in the Dutch yacht division and expanded his field of operation over the years to the export department. He now takes care of specific unique projects with enthusiasm and devotion, key characteristics for which all H&H’s employees are known.