The International Maritime Organization first created the International Convention for the Prevention of Pollution from Ships (MARPOL) in 1973. Since its introduction a number of modifications, improvements, and enhancements have been implemented. This has resulted in a variety of new technologies being implemented across all types of ships. One such technology is the FGS (Fuel Gas System) – double wall pipe.
Applicable International Maritime Organization Air Pollution Rules
The most recent is Annex VI Prevent of Air Pollution from Ships which entered into force in 2005. This particular regulation set limits on sulfur oxide and nitrogen oxide emissions from ship exhausts. It also prohibits the deliberate omission of ozone-depleting substances. Designated emission control areas were also created to enforce more stringent standards for a variety of particulate matter. In 2011 the IMO adopted new groundbreaking mandatory technical and operational energy efficiency measures which will further reduce the amount of greenhouse gas emissions from ships.
How Have These Rules Affected Ships?
Under the revised MARPOL Annex VI the global sulfur cap was reduced to 3.5% effective 2012. The goal is to progressively decrease the amount of sulfur 2.5% by 2020. The limits in ECAs force over oxide and particular matter were reduced to 1% beginning in 2010. It will continue to be further reduced to.1%, effective 2015.
Progressive reductions in nitrogen oxide emissions from marine diesel engines were included in the revision of MARPOL as well. A Tier II omission limit was created for engines installed on or after 1 January 2011. More stringent Tier III omission limits will be in place for any engines installed on or after January 1, 2016.
In order to meet these new omission limitations many ships are moving from Bunker C fuel to natural gas or gas. Bunker C fuel is essentially the residual oil left over after the lighter, more volatile products are distilled out of crude oil. These molecules are significantly larger and heavier which results in a significant amount of energy per unit of fuel. Unfortunately, since it is the final oil left over from the distilling process it has many more impurities including the sulfur and heavy metals. This leads to a notably higher rate of air particulate creation during combustion.
Why Quality FGS-Double Wall Pipes Are Critical:
Fire / Explosion Prevention and Leak Detection
To ensure ships meet fire safety regulations and engine rooms FGS-double wall pipes are used in ships utilizing natural gas. The double wall is necessary because pipe fractures would cause fuel to spray in a fine aerosol mist. It would then ignite on contact with any hot surrounding surface such as the exhaust pipe or turbocharger casing. The double-walled pipe is designed to ensure fuel will be contained in the annular space between the inner and outer wall which provides more time for leak detection. It will then drain into a collecting tank fitted with a high-level fuel leakage alarm.
Another benefit of FGS-double wall pipe is corrosion protection. There are numerous elements which are highly corrosive that pipes are constantly exposed to when at sea. By utilizing a double wall design, the internal pipe garners an additional layer of protection against corrosion. While corrosion in the outer wall must be prevented, the corrosion will not lead to immediate leakage.
Lower Lifecycle Cost
An underrated benefit of FGS-double wall pipe is it has potentially a lower lifecycle cost for containment failure relative to single wall pipes. Containment failure costs include loss product, service interruption, lost production, cost of repair, environmental restoration, recommissioning, and potential intangible costs.