Fuel Oil Handling System (FOHS) | HFO | LDO

Introduction of FOHS

The Fuel oil handling system (FOHS) shall broadly comprise of the following:

Heavy fuel oil (HFO) / Low Sulphur heavy stock (LSHS) system for start-up of the boiler, load carrying up to 30% BMCR and as secondary fuel for pulverized coal flame stabilization at start-up / low load operation.
LDO (Light Diesel Oil) system for initial start-up (cold start-up), warm-up, low load operation up to 7.5% BMCR and for flushing of HFO pipe lines.

Note:

BMCR: Boiler Maximum Continuous Rating (BMCR) is the maximum rating specified for the boiler.

Function of Fuel Oil Handling System

The purposes of the Fuel Oil Handling System are targeted to achieve the following:

HFO/LSHS unloading from railway wagons
LDO unloading from railway wagons
Storage of HFO/LSHS
Storage of LDO
Collection of pipes drain oil emanating from Equipment, Strainers etc. to Drain Oil Tank located in Fuel Oil Pump House and recycle back to HFO/LSHS Tanks.
Collection of open drains from unloading area, tank farm, Fuel Oil pump house (FOPH) to oily water sump (OWS) for further treatment, recovered oil from OWS send back to drain oil tank through gravity.
Pressurizing and heating of HFO/LSHS for supply to boiler Fuel Oil burner at required pressure temperature condition and return to HFO/LSHS tanks.
Pressurizing of LDO for supply to boiler Fuel Oil burner and return to LDO tanks.
Heating of entire HFO/LSHS system including HFO/LSHS wagons, storage tanks, pipe lines etc. to ensure HFO/LSHS flowability.

Fuel Oil Handling System (FOHS) Description

Fuel Oil Handling System is described as following sub-systems:

HFO/LSHS Unloading system
LDO unloading system
Fuel Oil Storage System
HFO heating and Pressurizing System
LDO pressurizing system
Steam and Condensate System
Drain Oil System
Return HFO Cooling System

Note: Each sub-system description includes its own specific design requirements and basis.

Fuel Oil Handling System (FOHS) Components

The major components of the fuel oil handling system are as follows:

Pumps (Pressurizing Pumps, Unloading Pumps, Oil water Sump Pumps, DOT Pumps)
Storage Tank
Strainers (Basket Strainer, Duplex Strainer)
Heaters & Cooler
Pipes (Fuel oil pipes, Water pipes, Air pipes)
Valves (Gate valves, Globe valves, Check valves, Ball valves, Motorized Operating Valve (MOV), Control Valves etc.)
Instruments (Pressure Gauge, Pressure Transmitter, Pressure Switch, Temperature Gauge, Temperature Transmitter, Flow meter, Differential Pressure Gauge, Differential Pressure Transmitter etc.)

Common Fuel Oil Handling System Problems and Solutions

The Fuel Oil Handling System (FOHS) must operate reliably to ensure proper boiler start-up, flame stabilization, and low-load operation. Common problems in the system can affect fuel supply, burner performance, and boiler availability.

Low fuel oil pressure: Check pump performance, suction conditions, strainer blockage, and leakage in the fuel oil pipeline.
High differential pressure across strainers: Inspect and clean the strainer elements to restore proper fuel flow.
HFO high viscosity: Check the heating system, steam supply, temperature control, and insulation of fuel oil pipelines.
Fuel oil pump not developing required pressure: Inspect the pump, coupling, suction line, valves, and possible air ingress.
HFO heater malfunction: Check steam supply, condensate drainage, temperature instruments, and control valves.
Fuel oil leakage: Inspect pipe joints, flanges, valve glands, pump seals, and associated connections.
Burner ignition failure: Check fuel oil pressure and temperature, atomizing medium, burner nozzle condition, and ignition system.
Drain oil tank high level: Check drain oil pump operation, level instrumentation, and the return oil line for blockage.

Preventive Maintenance of FOHS

Regular inspection of fuel oil pumps, heaters, strainers, valves, pipelines, and instruments helps prevent unexpected failures. Monitor fuel oil pressure, temperature, pump current, and strainer differential pressure during operation. Ensure that leakage, abnormal vibration, and heating-system problems are addressed promptly according to approved plant procedures.