Triality: An innovative project of VLCC tanker 
 Accomplished by Det Norske Veritas (DNV)

In early December Classification Society DNV published a preliminary information on his new project, named Triality,  a VLCC size tanker (aprx. 300.000 TPM) embodying a number of features that show it as an innovative oil tanker, emphasizing its ecological character, non-polluting the environment, sea and air, all at a lower operating cost than a conventional tanker of same capacity.

Conceptual design

Data and pictures as summarized below are taken from the DNV publication in Ref.1 at the end. Countless websites of media related to the maritime world have published the news about this project and those interested on it remain waiting to further information and getting to know the shipping industry's response to this initiative, that, if successful, would represent a milestone in the shipbuilding development, not only in the VLCC segment but also in other vessel sizes and types.

The main declared objective of this project is the design of a VLCC with a lower environmental impact than  a conventional VLCC by reducing emissions of NOx, SOx, CO2, particles and volatile organic compounds (VOCs) from cargo tanks and, if possible, also trying to reduce the large amount of ballast water used in unloaded trips to avoid the problems inherent to it. And all this at a lower operating cost than a conventional VLCC of same capacity and autonomy.

The project was carried out in a record time of two months and with the participation of 40 specialists in all involved subjects, in Oslo and elsewhere, with wide intercom via video conference.

Below I will summarize the most significant points in  Triality project and present a comparison of its main features compared to a conventional VLCC of the same capacity. My comments are shown in italics.

Below I will summarize the most significant points in  Triality project and present a comparison of its main features compared to a conventional VLCC of the same capacity. My comments are shown in italics.

Fuel: Liquefied Natural Gas (LNG)

  a) LNG is used for propelling (MP)and auxiliary (MA) engines

  b) LNG is also used for:

     - MPs scavenging air cooling 
     - MPs Cooling
     - Air conditioners, refrigerators
     - Recovery of VOCs

   c) LNG fuel tanks

      Triality incorporates two large LNG fuel tanks sited aft on deck, of 6.750 m3, that allow a round trip between the Gulf and the U.S without refueling.

        Note: As pointed out by DNV, the use of LNG in propulsion engines is not new, it has been used for years in small vessels at coastal traffic, and in large LNG transport vessels to utilize the load's boil-off. But its use is new in VLCCs, which make long trips between terminals that not always have LNG supply stations. Therefore, Triality  incorporates two large LNG fuel tanks located aft on deck, of 6,750 m3, which allow for a round trip without refueling, between the Gulf and USA.

 
The ballast-free ship

 
A conventional VLCC use ballast water to get 3 goals: 
a) When navigating unloaded, ballast lets getting an aft draugth to completely immerse stern propeller(s) 
b) idem  a forward draugth enough to avoid bottom slamming 
c) During the cargo loading ballast water is used to reduce bending moments and to correct ship's list and trim.

But ballast water presents several drawbacks:
a) It contains organisms that can cause damage when released to foreign ecosystems and additional fuel is   needed to transport the ballast water
 b) Fuel is consumed to transport ballast
 c) Dedicated ballast tanks require a costly maintenance to keep them corrosion free

Triality’s tank arrangement and hull shape eliminate the need for ballast in her operations. The hull has V shape transverse  sections in its lower zone, so that their draugths increase to achieve the displacement in unloaded condition. The smaller diameter of twin propellers against conventional single propeller, reduces the necessary draugth aft. In this way both conditions a) and b) above get fulfilled.

In the herein figure it can be appreciated the hull's form, which in the unloaded navigation condition (without ballast) has a block coefficient CB of 0.53 at a mean draft (Tl) of 6.5 m. The corresponding values of a conventional VLCC are CB = 0.75 and Tl = 10 m. The diameter of Triality's twin propelleres is about 7,50 m (estimated), while the conventional single one is about 9,20 m.

At full load Triality has a maximum draugth of 23 m with a CB of 0.62, compared with conventional VLCC' values of 22.5 m and 0.80

DNV states that thanks to these hull forms Triality needs a power of 10 MW in unloaded condition, as compared to 18 MW in load condition.

Cargo tanks arrangement
 
To control the forces on the ship structure (bending moments and shear forces) as well as heel and trim during loading / unloading, the cargo tank area has been subdivided by 4 longitudinal and 4 transverse bulkheads, getting a total of 25 tanks. This allows for a great flexibility in the order and sequence of tanks filling / emptying, and keeps within their limits stresses, heel and trim.

This tanks arrangement causes a steel weight increment and a bigger complexity and cost of cargo piping system, as compared to the conventional VLCC.

I note with some surprise that in the unload navigating condition, permissible bending moments are got without using water ballast, whereas in the VLCC ballast water must be used not only to get navigable draugths but also to not exceeding the maximum allowed bending moments. DNV's article does not mention this issue specifically.

Recovery of cargo volatile organic compounds (VOC) 
 
The most volatile cargo elements partly evaporate during the passage and during crude oil washing (COW), and are ejected into the atmosphere in the conventional VLCC, causing an economic loss and air pollution when combined with the NOx to produce ozone, with greenhouse effect. A normal VLCC loses 500 to 600 tons of cargo in a laden voyage.  Triality has got a pipes and coolers installation to recover VOCs in liquid estate, to be used as fuel in the steam boilers. The useless part of VOCs is returned to the cargo tanks. No COV is emitted to the atmosphere.

Economy in Triality's operation

 After showing their technical analysis designers ask themselves this question: Is it possible to go green  and be profitable? And their answer is a short one: Yes, Triality is more profitable than the conventional VLCC.
The reasons for this answer are on the results of their economic analysis of Triality's operating costs in various scenarios of fuel-oil and LNG prices , a summary being this: With the reference fuel-oil price, over a period of 20 years, the Triality’s Net Present Value has a higher initial investment cost of 14 MUSD and a lower operating cost of 38 MUSD in respect to the conventional VLCC.
In Ref.1 they present a more detailed information of this economic analysis.

Comparison bet. Triality and Conventional

Data	Triality	Conventional
Lpp (m)	351	320
Bradth(m)	70	60
Depth(m)	27,52	30
Load draugth (m)	23	22,50
Unload draugt (m)	7	10
Load block coef.	0,60	0,80
Unload block coef.	0,52	0,75
Power(Kw) loaded	21.000	18.000
Power(Kw) unloaded	10.000	18.000
Deadweight(Tm)	291.300	300.000

Summary: The Triality project is really innovative, even with some revolutionary features. I do not know the reasons for having spent so little time to its development, as a so complex and novel project as this, seems to need more time. We'll look at its progress and the wellcome that markets afford it.

 

Ref.(1) Triality VLCC. DNV Tanker Update No.2 2010