INFORMATION SHEET

FUEL OIL SYSTEM

Information Sheet Number 62P-105

INTRODUCTION

The boiler needs a consistent fuel oil supply pressure to properly operate. This consistent pressure is provided through one of two means. In ships with electric fuel oil service pumps (FOSP), a mechanical unloader valve dumps excess fuel back to the tank on suction or the suction side of the pump to maintain the system pressure. In ships with steam turbine-driven FOSPs, the speed of the pump is regulated to provide the proper fuel oil system pressure. This regulating device is called a constant pressure regulator and controls the amount of steam which enters the turbine.

REFERENCES

(a) 600 psi Main Propulsion Boilers NAVSEA S9221-A3-MMO-010

(b) Petroleum Fuel Stowage, Use, and Testing NSTM Chapter 541

INFORMATION

A. FUEL OIL SERVICE SYSTEM

1. Ships with only turbine-driven main FOSPs have a small electric FOSP installed. This pump provides enough fuel flow for the low firing rates associated with steaming auxiliary or in port. Some ships with two large electric FOSPs may also have a small electric FOSP.

2. The amount of fuel entering the firebox through the atomizer is controlled by the fuel oil control valve (FOCV). By regulating the pressure of the fuel manifold or header, the flow of fuel entering the firebox can be regulated and coordinated with the steam demand. The FOCV is usually an air operated valve which is controlled by the ABC system in ships having such a system installed. In those without a closed loop ABC system, the same valve is usually installed but requires an external, manual input from the operator, just like remote manual operation.

3. Since the FOSPs are positive displacement, rotary screw pumps, they require a continuous flow or the system would become over-pressurized. To protect against that eventuality, relief valves are installed. Also, system operation occasionally requires that a flow be established before fires are lighted, such as light-off preparations, testing fuel oil root valves, SSD's and fuel oil strainers. To provide this flow, a recirculating valve is installed. More commonly referred to as the "recirc" valve, it provides a flow through the system when fuel is not flowing into the firebox.

a. Should the fuel system become contaminated, the recirc also provides the means of purging the system through the three-way valve to the fuel oil contaminated tank. Of course, suction is shifted to a satisfactory fuel oil service tank and the contaminated fuel oil service tank is stripped of the water. Proper fuel testing procedures should prevent fuel contamination from occurring.

b. When securing the burnerfront in a casualty, the recirc valve is opened to bleed any residual pressure from the burnerfront.

c. A variety of safety features are associated with FOSPs pumps based upon their mode of operation. Generally, motor-driven fuel oil pumps are designed to shut off automatically if system pressure drops too low. If electrical power is restored before the pressure drops too much, the pump is designed to re-start. This feature which prevents the pump from re-starting if fuel pressure drops too low when system pressure is interrupted helps prevent a boiler explosion. Also, power to electric fuel oil service pumps can be secured from the DC deck by a remote switch.

d. Turbine-driven FOSPs can be secured from a remote location, usually the BTOW's station.

4. FUEL OIL QUICK CLOSING VALVE. The fuel oil quick closing valve (FOQCV) provides a means of quickly securing fuel flow to the boiler in a casualty. This valve instantly secures fuel to the burnerfront and is the first step in the burnerfront casualty securing procedures. It can be activated from the burnerfront and alternative activation stations, the location of which depends upon the ship class. Generally speaking, these alternate locations are the BTOW station or fireroom operating station and the upper level above the burnerfront. There is a means on the DC deck of securing fuel flow, usually a mechanism for activating the FOQCV or stopping the FOSP.

5. FIRESAFE FUEL OIL STRAINERS. Particulate matter in the fuel system can cause a malfunction of many components of the fuel oil service system, including the unloader or regulator, FOCV, FOQCV, atomizer, sprayer plate, root valve or SSD. To eliminate particulate matter in the fuel system, a strainer is installed. In all steam ship classes except the AO-177, a Firesafe Fuel Oil Strainer is installed. This strainer does not require a spray proof enclosure and is designed to be shifted and cleaned with the system pressurized. They should be shifted and cleaned prior to system start-up and when the differential pressure is greater than 10 psi. The AO-177 class has a special NAVSEA-approved duplex strainer.

6. Each fireroom is equipped with two fuel oil service tanks. These are the sources of fuel for the boiler and can be placed under suction only by the fuel oil service pumps. Tank volumes vary from about 15,000 to 30,000 gals depending on ship class. The tanks must be sampled and tested for bottom sediment and water (BS&W) prior to being placed on suction. Service tanks are shifted when the tank level is at 50%. This provides a reserve in case there is a problem with the tank to which suction was shifted.

7. Should contamination of the fuel oil service system occur from water or particulate matter, not only must the system be flushed or purged, the affected tanks must be stripped of the contaminants. The bilge and stripping pump is used to strip 150-300 gals from the bottom of the tank which is again sampled and tested. This is repeated until the tank is satisfactory. Every attempt should be made to strip to a contaminated holding or settling tank from which the water and contaminants subsequently are stripped and the good fuel recovered and returned to a fuel oil storage tank for use. Usually the tank is contaminated by only a minimal amount of sediment and water. Care is taken to prevent stripping too much good fuel by stopping the stripping process so frequently. This prevents good fuel oil from being lost to stripping by inattention of watchstanders and helps preclude a vortex from forming and removing good fuel instead of water or contaminants.

B. FUEL OIL STORAGE AND TRANSFER SYSTEM.

1. Fuel oil is stored in either storage tanks or storage/ballast tanks. Those designated as "ballast" tanks are designed to be used as ballast. In recent years, ships are more routinely operating at lower fuel levels than in the past. This creates greater concern over the stability of the ship and how it affects the hull structural members. Ballasting is slowly becoming more common and its impact on fuel quality cannot be ignored. A later section discusses ballast and deballast concerns.

2. Fuel oil storage tanks must be sampled and tested for BS&W before transferring fuel from them to service tanks. If they are contaminated, then stripping must be done. This is the same procedure as discussed above. Also, storage tanks are tested for water, using an indicating paste, the day after they are filled with new fuel. This allows the contents to settle and gives an accurate assessment of the tank contents. The storage tanks also get a water indicating paste test once per month to verify the contents are satisfactory.

3. To safely and easily transfer fuel through the system, valve manifolds are installed to distribute the fuel from a central piping system to the various tanks. When receiving fuel, the number of tanks which should be aligned for filling at any given time is a function of the receiving rate and pressure. Too often, not enough tanks are aligned for the given rate and a tank may be filled too rapidly causing a fuel spill. The procedures for filling tanks is established in the EOSS and Ship's Information Book.

4. To help preclude overfilling a fuel tank, they are never filled to 100% of their physical capacity. When determining tank capacities, 5% is allowed for expansion due to temperature. This 95% now becomes the tank's 100% rated full capacity. For all intents and purposes, that becomes the full mark of the tank.

5. Since the air in a tank needs to escape when it is being filled or allowed to enter when being pumped down, vents are installed in each tank. These vents have flash-proof screens installed and are usually found on the main deck. The flash screens help counter the explosive nature of the fumes and vapors.

6. When receiving fuel, it must be tested frequently to ensure it meets the prescribed quality requirements. There are two tests conducted, a bottom sediment and water test (BS&W) and a visual test. The BS&W test is done at the beginning, mid-point and end of the fueling evolution. Visual tests are conducted every fifteen minutes during the evolution. The visual criteria is simply that the fuel be "clear and bright" and the test is a quick and easy check of the fuel quality.

7. Prior to receiving or transferring fuel, the system alignment must be checked and verified to be correct. The oil king will make the initial alignment of the systems. The alignment must then be verified by two other persons, including an officer of the Engineering Department A thorough check of the system helps eliminate problems and prevents oil spills. The CNO directs only the best-trained personnel man the fueling detail.

8. There are other precautions to take when receiving fuel, whether at-sea or in port. Some of them are: spill watches posted, oil spill kits checked and ready, scuppers plugged (in port), firehoses broken out on deck (in port), deck department notified, communications established to all stations, quantities and tank levels verified, and the CO's permission given.

9. Each ship needs to establish its own policy for transferring fuel within the ship (internal transfers). Issues requiring addressal are: extent of system verification, permission-granting authority, any time restrictions, personnel manning requirements, etc. See the REFUELING Section below for details.

10. When fuel is being transferred or received, the control station must be in constant communication with the manifold operator, tank sounder and the pump operator for internal transfers, and the fueling station for external transfers. The typical fuel oil transfer pump discharges 100 gallons per minute which can create a sizable spill in short order. Tank levels must be monitored continuously when being filled. Either tank level indicators or sounding tapes can be used.

11. Tanks must be filled in the proper sequence to minimize the impact of stress and strain on the hull and structural members. The Tank Sequencing Tables establish the prescribed sequence in which tanks are filled and emptied. This table is often found in the EOSS but may be in the Ship's Information Book or Damage Control Book, also. Most of these documents require that a tank be ballasted when it is emptied. If the valves in those systems have leak-by, there may be problems with water contamination of the fuel systems.

12. Fuel oil accountability is a major concern and accuracy is important. The Navy Energy Usage Reporting System (NEURS) tracks the fuel usage and inventory of the Navy's fuel and requires each ship to report fuel inventory and usage on a recurring basis updating this system. A formatted, computer read message is the mechanism used by the Fleet Commanders to account for fuel usage. This accounts for usage only and has nothing to do with allocations which are controlled by the ISIC. Third Fleet has a separate fuel accountability system which manages allocation and usage, in addition to the NEURS report. Ships are required to submit NEURS reports:

a. Within three working days from the end of each month

b. When chopping to a new operational commander.

c. When changing operational status (enter/depart from a major availability).

d. When directed. On occasion, ships may be directed to submit NEURS reports more frequently as was the standard practice in 7TH Fleet for many years and was required for Operation Desert Shield.

C. BALLAST AND DEBALLAST SYSTEM

1. This system provides the capability to ballast, deballast and strip fuel oil tanks. This system maintains the ship's ballast in a stable condition when the fuel oil percentages are low, removes the ballast water after ballasting, and strips bottom sediment and water from fuel oil tanks. Tanks are ballasted, filled with seawater, via the firemain system through ballast manifolds. Tanks are stripped using the bilge and stripping pump or the main drain eductor as an alternative. Normally, tanks are deballasted using the eductor but can use the bilge and stripping pump. Some large oilers or amphibious ships can use their fuel oil transfer pumps to deballast.

2. Contaminated Fuel Oil Settling Tanks hold the effluent after stripping until it can be disposed of properly. If at sea, effluent may be discharged overboard. These tanks should be sampled and tested so that any good fuel in them may be recovered. Stripping manifold valves which discharge overboard are required to be locked.

3. Bilge and stripping pumps are installed in all ships. Some are electric motor driven and others are reciprocating steam pumps. Steam pumps often can be operated by low pressure air if no steam is available. This pump can also be used to transfer fuel from storage to service, storage to storage and for defueling operations if the transfer pump is OOC.

4. Fuel oil storage and service tanks may need to be stripped if fuel oil tests so indicate. Once per month and the day after receiving fuel, tanks must be sampled using water indicating paste. If this test indicates the presence of water above the lowest stripping suction line, the tanks must be stripped. When stripping a fuel tank, only 150-300 gallons at a time are stripped with sampling conducted after each 150-300 gallons. This prevents too much fuel from being stripped.

5. Bilges can be pumped using the bilge and stripping pump or the eductor. When pumping bilges in port, ship's force often uses a pneumatic bilge pump. Follow SOPA regulations when pumping bilges in port, particularly the posting of overflow watches. In port, bilges must be pumped to a barge or closed bottom doughnut. In most ports, the bilges must be tested by PWC to verify they contain no hazardous material. There is increasing emphasis on the use of oily water separators to eliminate the need for an oily waste barge or doughnut.

D. REFUELING PROCEDURES

1. The procedures below are prescribed for external refueling evolutions. For internal transfers, these procedures would need to be modified but the basic elements are the same.

2. Prior to refueling, the following actions must occur:

a. Post refueling bill. All personnel shall be well-trained and qualified for all assignments. Overflow watches are required when fueling in port.

b. Check out all refueling equipment, including special fittings which are often required and sometimes not readily available. In many foreign ports, special adapters may be needed.

c. Check out phone communications and circuits.

d. Pump up service tanks to 95% before refueling to ensure that the most fuel possible can be taken aboard.

e. Remove any ballast. Consolidate fuel into fewest number of tanks.

f. Align system in accordance with EOSS.

g. Plug scuppers and break out firehoses (in port). Check the oil spill containment kit.

h. Verify tank status by sounding all tanks and indicate levels on tank status diagram.

i. Station refueling detail. Should re-verify communications and equipment readiness.

j. Open as many tank fill valves as possible, speeding up refueling and minimizing time alongside.

3. When fueling has commenced:

a. Establish pumping pressure. Enough tanks must be aligned for fill at the established pumping pressure. This information is in the EOSS and SIB. As tanks get filled, the pumping pressure may need to be reduced.

b. Bring tank levels to 80% at full rate. Pressure is controlled to prevent fuel being blown out of sounding tubes and vents. Begin closing down on fill valves to slow fill rate and bring tank level to 95%. Never overfill tanks, 5% is needed for expansion.

c. Fuel analysis is furnished by the sending ship or station and the receiving ship should perform tests promptly and in accordance with NSTM 541. The receiving ship's Supply Department supplies the requisition data.

d. Sound all tanks and compute percentages.

e. Ensure fuel oil system is secured completely.

f. Make engineering smooth log entry indicating source, time started, product, amount received and time completed.