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Ballasting Flow Rates: The True Cost of Delays & How to Avoid Them

In today’s maritime industry, ship owners and operators are required to make new, costly investments to ensure that vessels comply with the latest environmental regulations. This includes the Ballast Water Management Convention (BWMC), which requires most vessel owners to install and operate an effective ballast water management system (BWMS). Typical BWMSs have a primary treatment component, in most cases a filter, then a secondary treatment component to neutralize the organism found in the ballast water. With profit margins under pressure, and numerous products to choose from, many shipowners see BWMS and filter selection as a weighty decision with long-term CAPEX and OPEX implications.

To make a smart decision, it is essential that shipowners understand both the regulatory and technical benefits of specifying a BWMS that includes a suitable filter – one that promotes proper filtration to avoid ballasting delays and non-compliance with the BWMC.


Regulation and non-compliance

In order to comply with the International Maritime Organization (IMO) Ballast Water Management Convention and the additional US Coast Guard (USCG) ballast water regulation, it is essential to select and operate a high-performing BWMS to ensure long-term and reliable treatment of invasive aquatic species. In practical terms, most ships ballast in port or river estuary waters, where sediment is significantly higher than out at sea. This can significantly impact flow rates if a low-quality filter is installed, which can then extend ballasting times.


Flow rates impact finances

Ballasting rates for a vessel are designed alongside the rates of cargo loading and discharge. For vessels to safely load and unload cargo, the ballast pumps must be able to either load ballast water or discharge ballast water to maintain the stability of the vessel. The slowing of the flow during ballasting can have dangerous consequences for vessels during cargo discharge if the stability of the vessel becomes compromised, such as listing.

A decreased flow rate occurs for two primary reasons: firstly, during heavy loading, when filling the tanks to maximum capacity as quickly as possible, the filter will often go into continuous backflush and a significant portion of the water will be diverted through the backflush line. Secondly, filter loading and increased differential pressure across the mesh places a larger discharge head on the ballast pump, causing the pump to flow less water to the tank.

In reality, the time it takes to move ballast can range from 12 hours to nearly 90 if the filter is not designed for heavy loading. In comparison, a filter appropriately designed for a vessel’s loads and the waters where it will be ballasting may be able to move more than three times as much water than a filter that slows or clogs.

The exact amount of money that can be lost will depend on the market, the type of vessel, whether the vessel is in port, how busy the crew is, and what the costs may be for additional time alongside. However, as an example, a VLCC tanker earning a typical $36,000/day, every hour of delay can cost $1,500 plus any port charges. These costs can rapidly add up and should be kept in mind when considering CAPEX and OPEX for a BWMS installation.


The challenge of sediment

An additional factor that can decrease flow rates is the level of sediment being collected while ballasting. Two particular locations, the Mississippi River Delta and the Yangtze River, show exceptionally high Total Suspended Solids levels and present a particular challenge to many BWMS technologies.

Sediment is one of the critical factors in filter clogging but allowing sediments to accumulate has further implications to the vessel. The buildup in the ballast tanks between drydocking periods can create an unpumpable, permanent ballast that, if not removed, reduces the vessel’s cargo capacity over time.

For vessels contracted in the bulk and oil trades, this may affect the charter agreement and cause vessels to carry less than the obligatory cargo amounts as per the voyage plan, with potentially significant implications for a ship’s earning ability. Vessels are designed to carry a specific amount of cargo based on weight and displacement, so vessels ferrying around even a few inches of sediment over the entire bottom of ballast tanks can quickly see tonnes of additional weight added to their dead weight. This additional dead weight may offset cargo loads.

The choice of a BWMS and its filter is critical for shipowners and operators to avoid non-compliance and expensive ballasting repercussions. It must be economically sound, both from a CAPEX and long-term OPEX standpoint. The filter within a system has a big effect on its ability to perform effectively, efficiently and within the regulatory parameters. As such, it is an investment with potential implications for many company departments, including technical, operations and finance. This makes BWMS and filter selection a business critical issue.

For more information on this topic, please download our whitepaper on the cost of compliance here:

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