Guidelines for preventing loss of propulsion after switch to low sulfur fuelNov 22, 2011 12:00 AM
The California Air Resources Board (ARB) created regulations for vessel emissions reductions for California waters as part of its continued mission to improve air quality around the state. These requirements came into effect in July 2009.
The regulations require that oceangoing vessels within 24 nautical miles of the California coast burn either marine gas oil (MGO) with a maximum of 1.5 percent sulfur or marine diesel oil (MDO) with a maximum of .5 percent sulfur in their main and auxiliary engines.
Following the implementation of the regulations, California witnessed a 100 percent increase in loss of propulsion (LOP) incidents within state waters during 2009. In 2010, California saw 54 LOP incidents compared with 24 in 2008 (the last full year before the regulations took effect.
The LOPs can be loosely categorized into six groups for ease of discussion:
In Group 1, engine failures resulting in the LOP result from the inability of the main engine, operating with MGO/MDO, to overcome the forces on the propeller from the forward momentum of the ship. The engine may turn over at higher rpm and initiate combustion; however, as the engine reduces speed to come to dead slow or slow astern, there are not enough BTUs in the fuel to maintain engine inertia. The engine stalls with the subsequent LOP.
In Group 2, failures resulting in the LOP result from problems controlling the temperature of the MGO/MDO. Each engine has specifications as to the temperature range required to operate using either heavy fuels or lighter fuels. For example, the optimal temperature range for an engine might be 135°C for a heavy fuel oil (HFO) and 40°C for the MGO. Because heavy fuels must be heated (for the right viscosity to burn) and lighter fuels may not need to be heated, there are problems associated during the fuel switchover in both heating and cooling the different systems since the fuel oil is supplied through the same auxiliary systems. Heating an MGO/MDO may cause "flashing" of the lighter fuel oil to vapor. The fuel injectors would not work when the fuel flashes, causing a loss of power in that cylinder. Multiple cylinder flashes could result in LOP.
In Group 3, failures resulting in a LOP are associated with the loss of fuel oil pressure to either the fuel pumps or fuel injectors. The loss of pressure could be a result of many factors, including wrong control set points, use of bypass valves, inoperable equipment, inattention to operating condition or excessive leakage through O-rings and seals.
Ships evolved to burn the heaviest and cheapest fuel available, HFO. To utilize the HFO on ships, the fuel is heated to as much as 150°C to get it to flow. In comparison, MGO/MDO is burned at ambient engine room temperature or 40°C and no heating is required. Once the cooler MGO is introduced into the fuel pumps and injectors, they contract, causing a loss of fuel pressure at the pump with marginal spray pattern and leaks at the injector.
Viscosity is another issue involving use of MGO in an engine that has successfully run HFO for some time. Typically the engine manufacturer's recommended minimum viscosity is two centistokes. When the temperature of the MGO is increased into an already warm engine that just ran on HFO, the heat lowers the viscosity, causing the fuel machinery parts to bind or break.
In Group 4, LOP is associated with the loss of fuel oil pressure or the loss of flow in sufficient quantities to maintain operation. Strainers and filters or the lack of a strainer and filter contribute to clogging or restrictions in the fuel oil supply system.
In Group 5, LOP appears to be associated with problems in either the starting air system or the control air systems. Problems with starting air systems are not fuel related and only need to be mentioned as a cause of LOPs.
In Group 6, LOP appears to be associated with mechanical failure not associated with other groups.
The intent of this guide is to reduce the LOP incidents occurring within the state of California's boundaries. The time to deal with problems aboard ship is either miles out at sea or alongside the dock, not in maneuvering/pilotage waters.
Many of the LOP incidents that occurred in 2010 involved 'first timers' — ships making their first entry into California waters since July 2009. Since California sees about one to two first timers per week, the Office of Spill Prevention and Response decided to provide suggestions for ships working with low sulfur distillate fuel oil (LSDFO).
For vessels intending to enter the California ARB Emissions Control Area for the first time since July 2009, I recommended and California advises the crew to conduct a "trial" — actual fuel switching within 45 days before entering California waters. The crew should run main and auxiliary engines no less than four hours on low sulfur distillate fuel. This will help identify any specific change-over or operational issues or problems.
The time period of 45 days was chosen based upon an understanding of containership operations where schedule is everything. Somewhere within that schedule, there is always time to perform a trial maneuvering and 45 days should allow the ship's personnel to experience the fuel switchover and document remedial fixes, if any, mitigating groups 1, 2, 3 and 4.
Ship engineers aboard both first timers and repeat visitors are strongly advised to carry out the following exercises within 45 days prior to entering the waters of California.
- Operate main engine from the engine control room.
- Operate main engine from engine side (local).
Crew should become familiar with "failure to start" procedures while maneuvering and establish corrective protocols for "failure to start" incidents.
The air and fuel in the start sequence can be adjusted in the engine control room and at engine side. These items cannot be adjusted from the bridge on most ships; hence, the provision of the advisory/guide establishes protocols for dealing with the "failure to start" scenario as outlined in LOP groups 1 and 2.
Too many ships have run out of "start air" because they continue to initiate starts from the bridge, where control of the fuel rack and amount of air for starting cannot be adjusted.
While underway after fuel switching is completed (HFO to LSDFO), ships should ensure that one of the senior engineering officers is in the engine control room while the ship is in pilotage waters. This engineering officer must be available to operate the ship main engine from the engine control room and to operate the ship main engine from engine side (local).
In following this recommendation concerning the presence of a senior engineering officer, special attention should be paid to the International Standards of Training, Certification and Watchkeeping (STCW) rest requirements. It has been proven too many times that fatigue can cause errors in judgment which could contribute to an LOP incident.
Some ships have the chief engineer down in the engine room for the fuel switchover. Then the chief engineer retires for rest while assigning the other senior engineer to stand by in the engine room, mitigating groups 1, 2, 3, 4, 5 and 6.
The following Engine Advisory Guidelines were taken from the U.S. Coast Guard MSA 03-09 with additions and clarifications from industry partners.
- Consult engine and boiler manufacturers for fuel switching guidance.
- Consult fuel suppliers for proper fuel selection. Exercise strict control when possible over the quality of the fuel oils received.
- Consult manufacturers to determine if system modifications or additional safeguards are necessary for intended fuels.
- Develop detailed fuel switching procedures.
- Establish a fuel system inspection and maintenance schedule.
- Ensure system pressure and temperature alarms, flow indicators, filter differential pressure transmitters, etc., are all operational.
- Ensure system purifiers, filters and strainers are maintained.
- Ensure system seals, gaskets, flanges, fittings, brackets and supports are maintained.
- Ensure that the steam isolation valves on fuel lines, filters, heaters, etc., are fully tight in closed position while running LSDFO.
- Ensure that the fuel oil viscosity and temperature control equipment is accurate and operational.
- Ensure detailed system diagrams are available and engineers are familiar with systems and troubleshooting techniques.
- Ensure senior engineers know the location and function of all automation components associated with starting the main engine.
Ships choosing to use these guidelines will alleviate some of the LOP incidents occurring within the waters of California.
Capt. Jeff Cowan works for California's Office of Spill Prevention and Response helping to make recommendations to the industry. Previously he spent 35 years at sea, including serving as master of various containerships.