CARB requires bypass systems on DPFs for commercial harbor craft vessels
14 September 2024
The California Air Resources Board’s (CARB) Executive Officer signed Executive Order DE-24-003, establishing the requirements for safety systems (a.k.a. bypass or override systems) for future Executive Orders issued to manufacturers of CARB-Verified Diesel Particulate Filters (DPFs) for Commercial Harbor Craft (CHC) vessels. These requirements have been adopted to satisfy the safety concerns of the US Coast Guard in regards to DPF installations on certain harbor craft vessels such as tug boats.
The CARB CHC Regulation establishes performance standards for main propulsion and auxiliary engines on regulated in-use vessels that are equivalent to the cleanest available engine and a DPF. The engine standards include Tier 4 Marine Emission Standards or Tier 4 final off-road emission standards, or Tier 3 marine or off-road emission standards (for engines under 600 kW where no Tier 4 engine is commercially available). The DPF requirement is for a CARB-verified Level 3 DPF (i.e., Tier 3 + DPF or Tier 4 + DPF), if a verified DPF system is available.
The DPF requirements are phased-in from 2024 to 2031, depending on the type and model year of the vessel. The first DPF compliance deadline for certain categories of tugs and ferries is December 31, 2024.
The DPF requirements of the CHC Regulation, approved in March 2022, have been opposed by the California marine industry, which argues that the DPFs have not been approved by the US Coast Guard or by a marine certification society and may present a safety hazard for marine crews—such as by disabling the engine if the DPF becomes clogged by soot. These concerns have been supported by the Eleventh Coast Guard District, which has jurisdiction over California.
CARB generally disallows DPF bypass devices in verified emission control systems to ensure exhaust gases are filtered at all time. After an exchange of letters with the Coast Guard, CARB first allowed the installation of DPF bypass systems and now such safety systems are mandatory on all affected CHC engines.
Under Executive Order DE-24-003, the DPF manufacturer must design and install the safety system on the DPF as part of the verified system. Among several conditions, the DPF manufacturer must equip the safety system with sequentially-numbered security seals as well as an electronic monitoring and tracking system to track each time the safety system is used; the vessel owner/operator must only use the safety system during an emergency situation; and the system must be designed to allow the DPF’s operation to resume immediately after the emergency situation is resolved.
Source: CARB