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Jotun 09/11/2016

Bentley Systems 10/11/16

A case for common sense

The Naval architect: January 2016

Ice and the extreme cold are formidable forces for those who routinely operate in polar and sub-polar conditions. The “work warm-up schedule” developed by the Saskatchewan Department of Labour, and adopted by The American Conference of Governmental Industrial Hygienists (ACGIH) in 2013, exemplifies this reality. It states that in even what could be considered normal Arctic weather conditions there must be four breaks in a four hour work period, and that in temperatures below -32˚C in 20knot winds ­ not unusual in the Arctic ­ only emergency work should be undertaken. Such conditions can be alleviated by the design of a vessel’s work areas, providing heat and shelter. However, despite their clear necessity, their arrangement is often not considered in collaboration with those who work on vessels sailed in ice; a fact that presents something of a growing problem.

As the gradual melt of the Arctic ice continues and the advance of technology enables more ships to enter the Arctic Ocean it is obvious that progress will dictate that the exploitation of the Arctic for mineral wealth will grow. In 2009, the US Geological Survey estimated that the Arctic may be home to 30% of the planet’s undiscovered natural gas reserves and 13% of its undiscovered oil. Further recent surveys such as that by Woods Mackenzie have shown this could be on the low side with some going as high as 30%.

Owing to the lack of port facilities in the region and the cost of work ships designed for the region, it makes sense that any work ship destined for the region must have a fully utilised multi-capability that is optimised for those working in the extreme cold.

Designs should combine ice class suitability for the area of operation, taking into account the necessary ice breaking capability, with wider functionalities and features. These should include supply capabilities, anchor handling and towing, search and rescue, pollution control, helicopter landing and carrying, and prolonged operational sustainability. Vessels should also be manned by crews with ice experience.

While ice classification, supply capabilities and anchor handling and towing functions are obvious and little different from that required for standard winter operations in the North Sea (except for the limitations that the ice will impose), the remaining operations, from search and rescue to sustainability, are a cause for concern and desperately require further attention in design.

Stern launch and recovery
Search and rescue requires the launch and recovery of Fast Rescue Craft (FRC). If the ship is operating in sheet ice conditions there is little point in lowering boats, but for conditions where there is broken ice or open water the launch of boats and their maintenance must be considered.

Presently, these boats are stowed and launched from single point launch davits on the sides of the vessel. The problem here is that in ice conditions the ice will be alongside the ship, hampering the launch and recovery of FRCs. The one area that will be free from ice, even if only temporarily, is the stern, which is kept free by the progress of the ship through the water and the action of the propeller. With this in mind, it makes sense that a stern launch ramp arrangement should be used; the boats would still be able to be used from their side davits positions, but they would also be able to be transferred to the stern area when required.

The naval architecture branch of the US Coast Guard’s Engineering Logistics Centre carried out an assessment of vessels with stern launch capability ­ presented at the World Maritime Technology Conference in 2003 ­ to develop criteria for the design and evaluation of stern launch and recovery systems for small boats from ships of up to 400 feet in length.

The overall tests involved eight ships of different nationalities but the results determined that the average launch times were 14.25 seconds and the recovery times 14.3 seconds, while figures of 5 seconds were achieved. These times are far better than any I managed during my four years in command of such ships with side davits. The whole launch and recovery process is what can be determined as the transition phase, which is the launch and then the approach and recovery. It is this last part that is the most difficult and time consuming. A boat being recovered on the side davit has to slow down on the approach and match speed with the mother ship to catch the davit wire and hook on before recovery. On a ramp recovery this is not required. Obviously this is very dependent on weather, the FRC used and the ability of the crews both on the boat and on the ship. It is essential that any FRC using ramps have water jet propulsion and certainly dry start diesel engines will enable the boat to be started on the ramp.     

The main problem of a stern ramp position is the limitation in a seaway caused by the pitch of the vessel while heading into the sea. The average vertical lift limits referred to are 2 metres at an average speed of 5 knots. To those inexperienced in ice water conditions this might seem a major problem but ice has a considerable damping effect on the sea conditions. The vertical lift does not interfere with the launch but only the recovery and if the ship is still equipped with the side davits the boats can be recovered there.

I am not suggesting that the davits should be abandoned. They should be present for normal operation and to offer a choice to the command for launch, recovery or both. The stern ramp availability is driven by sill depth and pitch motions, whilst a davit needs to consider a range of constraints associated with the environment, including pendulum effects, hoisting speed and the safety of deck crew.

None of the tested ships featured extendable hydraulic ramps that would be capable of increasing the sill depth of the ramp, but such an idea is certainly not beyond the bounds of ship design. If these ramps were to be used the operational ability of the stern ramp recovery would be considerably extended.

Improving the work environment
The stern ramp design also allows FRCs to be swiftly housed in a garage area built over the stern. Once the boats are on the ramp a winch could be used to drag the boats into the garage where, with a turntable arrangement, they can be quickly rotated. This speed is essential when a prolonged search and rescue operation is required and crews are replaced and an immediate launch is required.

The garage capability would also enable the frequent maintenance required for such boats operating in ice. In the davit position it is almost impossible to work on the boats in freezing conditions because of the time people can spend working outside and the limitations placed on ice covered equipment, as well as the inherent difficulty of working while wearing heavy weather clothing, especially gloves.

Further to this, positioning the workshop at the stern above the ramp means that the helicopter landing pad can be placed on the roof. I am frequently surprised by the continuing use of the bow for this pad as anyone who is familiar with arctic conditions knows that ice accretion is a very real threat.

For example, while operating in force 9 gale conditions with my engines reduced just to keep seaway, my ship accumulated around 300tonnes of ice on the bow area in one night. Any metal, especially if vertical, is a magnet for ice. This means that a helipad on the bow, which requires structural supports, will become ice covered and inoperable during any bad weather.
In contrast, a helipad that is located on the roof of the proposed stern workshop is not only out of the way of sea-spray, but benefits from the heated maintenance garage below, which would free the helipad from ice.

An integrated design solution
Pollution is probably the greatest problem of all in ice, firstly because of its impact on an increasingly fragile environment, and secondly because of the commercially crippling consequences such a spill would have for the unfortunate owner/operator. The US National Research Council states that we are far from ready to deal with any major incident. I would add that in the majority of cases, we are far from ready to deal with even a minor incident.

The use of chemicals to disperse the oil is still subject to considerable debate, especially in the Arctic. In July 2013 the Society for Experimental Biology stated: “A new study suggests that although chemical dispersants may reduce problems for surface animals, the increased contamination under the water reduces the ability for fish and other organisms to cope with subsequent environmental challenges.” It is also problematic as to whether the dispersant does more harm than the oil.

This then leads to the recovery of the oil. The current system of dealing with oil pollution on the seas is to utilise booms together with vessels equipped with skimmers. Sometimes the vessels are equipped with both and on other occasions two vessels have to be used.

In 1999 off the French coast, a spill of up to 7,000 tonnes occurred. Operating in bad weather over several days, five oil recovery vessels using booms and skimmers recovered just over 1,000 tonnes. There are several different types of oil skimmers, including vacuum, oleophilic, mechanical, weir and rope skimmers, but all designs depend on the laws of gravity. All of the mentioned skimmers, apart from the rope skimmer, act at the free water surface and are therefore susceptible to wave action. As the weather and wave action increases, the capability of these skimmers reduces dramatically.

However, the main reason for the overall poor performance of all of these types of oil recovery systems is that they are recovering from the side of the vessel. While this is not an efficient method in good weather, in poor weather it has an almost negligible capability. This is because of the action of the waves, current and wind. For recovery the vessels are stopped or just keeping steerage way. The ships then lie at an angle to the wind and seas. The winds and currents then cause the booms which are surrounding the oil alongside the side of the ship to elongate out of position, meaning that the oil is no longer being drawn into the suctions of the skimmers. In addition, once the wave height is over one metre the ability of the suctions to pick up the oil reduces, and the rolling of the ship adds to the problem.  It is regrettable to say that the whole concept of side recovery is not efficient.

With a stern recovery ship, booms can be deployed from the stern to encircle oil and by returning the end of the boom to the ship on the other side of the stern a catchment area is formed. The ship can then keep its head to sea and wind by using a slow centre thrust unit. By using a ramp tube pumping system with large suctions mounted behind grills that extend several feet below the water, the booms can be slowly reeled in, drawing the oil towards the ship. There is no wind sea or current effect on the boom as the ship is heading towards these effects with the boom directly astern.

The ship can also be backed into the oil. Several such suctions behind a grill running from side to side across the stern will take in far more oil than any side skimmer, transferring it to oily water separators that can then be pumped into separate tanks. With large quantities of oil a barge can be moored alongside the ship without any problems as the ship will have steerage way at all times. On top of this, it is also far easier cleaning the grill fronts than cleaning the side skimmers.

This is not rocket science, it is simply using good seamanship practice and common sense to solve a problem that presently the marine industry has been trying to solve by engineering alone.

When designing ships for the ice, account must be taken of those who have experience, not just in ice, but in the many varied tasks that such a work ship must undertake. Naval architects that work together with professional seamen can achieve the type of ship that will justify their high cost, and will ensure that the ships can meet the changes of the future. It is a given that the shipping movements in the Arctic are going to steadily increase. Apart from the normal hazards that the sea produces, the lack of adequate charts for the Arctic coupled with the ever-present dangers of ice will ensure the essential role of multi-functional ships, now and in the future.

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