LHD SPECIFIC SECTIONS 101, 102, and 103

101: Air Conditioning and Refrigeration Fundamentals

101.1 State the type and locations of the Air Conditioning (AC) Plants and refrigeration units onboard.

AC Plants There are (6) six separate and independent air conditioning (AC) plants having an individual refrigeration capacity of 300 tons. They are designed to provide chilled water for the AC Chilled Water Circulating System. The AC plant has a centrifugal compressor and charged with 950 pounds of refrigerant R-114. A single AC plant is capable of chilling water to 44 F (regulated outlet temperature) at a rate of 1,350 gallons per minute (gpm) and discharging to the chilled water circulating pump that supplies the chilled water circulating loop.

LOCATIONS: #1 and #2 AC plants - 4-41-2-E (Fwd Diesel) #3 and #4 AC plants - 6-73-0-E (Auxiliary Machinery Room) #5 and #6 AC plants - 4-89-2-E (Aft Compressor Room)

Refrigeration Units The Ship Service Refrigeration (RSS) system provides the facilities for stowing and preserving the perishable foodstuff carried aboard ship. There are (5) five refrigerated spaces serviced by (3) three refrigeration plants. Each 5.5 ton refrigeration plant has a reciprocating compressor and 2 lbs of refrigerant R-12, seawater-cooled condenser, receiver, dehydrator, evaporator controls, suction controls, forced air unit coolers, gages, temperature indicators, switches and fittings for system integrity and interconnection.

LOCATION: #1,2 and 3 Reefer Units - 6-45-0-E (Reefer Decks/Fire pump Room)


#1 Chillroom - 4-45-0-A #2 Chillroom - 5-44-0-A Freeze Storeroom - 5-41-0-A (4?) Thaw Room - 1-49-2-A Supply Department Storeroom 4-47-2-A

101.2 State the function and location of the following Major Refrigeration components:

a. Compressor - each of the three compressors is a (4) four cylinder, reciprocating single action, oil lubricated, 5.5 ton R-12 unit. Compressor action draws heat-laden gas from the evaporator, compresses the gas and discharges it to the condenser.

b. Condenser - are shell and tube type heat exchanger. The function of the condenser is to change the state of the refrigerant gas to a liquid. Condensation of R-12 occurs as the hot gas travels down over the condenser tubes and is cooled by the seawater passing inside the tubes.

c. Receiver - Acts as a reservoir to provide for the storage of system charge of R-12.

d. Freeze Box - Used for meat and other products required to be stored from zero degrees and below temperatures.

e. Chill Box - Used for storing vegetables, fruits, milk and other perishable produce at 38 degrees F.

f. Evaporator/cooling coil - the function of forced-air unit coolers is to chill the air inside the refrigerated spaces so that transfer of heat may preserve food stores at a predetermined temperature. Components of the unit cooler are: - cooling coil with refrigerant distributor (evaporator), - fan and motor, - drain pan, - electric defrost heaters, - defrost termination thermostat, - and controls. The evaporator coils change the state of the R-12 from low temperature, low pressure liquid to low pressure, low temperature (-20 degrees F) gas, absorbing heat from the air and evaporating the R-12 in the coils as the air is blown over the coils by the fan. Located inside the refrigerated boxes.

g. Thermal Expansion Valve (TXV) - controls the R-12 flow to the evaporator (i.e. "meters" it). The thermal expansion valve changes the R-12 from high-pressure liquid to a low pressure, low temperature (-20 F) liquid. The valve senses pressure and temperature of the suction gas leaving the evaporator. Located near the cooling coil inside the refrigerated boxes.

101.3 State the function and location of the following major AC components:

a. Compressor - Each of the (6) six compressors is a centrifugal, 300-ton R-114 unit. It is a variable displacement machine. It has an impeller that spins in a specially formed housing to impart centrifugal force to the refrigerant gas. Low pressure, low velocity vapor from the suction line is drawn into the inlet cavity or eye of the impeller wheel along the axis of the rotor shaft. On entering the impeller wheel, the vapor is forced out between the impeller blades by the centrifugal force developed by the rotating wheel. The vapor discharges from the blade tips into the compressor housing at a high velocity and thru specially designed passages in the housing where its energy is converted to pressure. The resulting high pressure, high-temperature refrigerant vapor is discharged to the condenser.

b. Condenser - are shell and tube heat exchangers. The function of the condenser is to change the state of refrigerant gas to a liquid. Gas travels outside the condenser tubes and is cooled by the seawater passing inside the tubes. c. Chiller - A shell and tube heat exchanger. Chill water flows outside the tubes and R-114 inside the tubes. The heat from the water in the chiller causes the liquid refrigerant to boil lowering the temperature of the chill water.

d. Orifice Plate - A type of metering device. The refrigerant drains from the condenser through an orifice or restrictor located in the chamber to the bottom of the chiller. Provides a seal between the gas and liquid sides of the system and maintains condensing pressure.

e. Chill Water Pump - Pumps chill water from the chiller to the supply header of the chilled water loop at the rate of 1,350 gpm and back to the chiller.

f. Expansion Tanks - (2) two tanks located in the return line of the chilled water loop serves to keep the loop filled to capacity. The pair of expansion tanks receives or discharges water to maintain the correct quantity of water in the loop if variations in water volume should occur. Also maintains positive pressure on the pump so it doesnt lose suction. Pressurized with 60 psi air, volume is 400 gallons a pair.

g. Cooling Coils -Types; - Fan Coil Assemblies (FCA)- consist of: - a fan and motor, - a chilled water cooling coil, - air filters, - internal bypass dampers, - thermal insulation, and - noise attenuation. The FCA draws air downward from the inlet, through the filters. The air is then ducted through the chilled water cooling coil, upward through the fan and motor section, and discharged to the supply outlet.

- Fan Coil Units (FCU) consist of: - a fan and a (2) two speed motor, - motor controller, - air filters, - inlet and outlet openings, - electric heater, - heater contactor, - thermal and acoustic insulation, - thermostat, and - chilled water cooling coil. Ductwork may be connected to the inlet and outlet openings. The cabinet is designed to permit ready connection of a power supply, chilled water supply and return lines and drainage lines. The fan coil draws air from the inlet through the air filters, through heater and discharges to the supply outlet.

- Cooling Coils (CC) Vent duct assembly supply-type unit, cooling coils are installed with the filters in vent system ductwork down stream of the supply vent fan.


Reefers: (3) 5.5 ton Carrier reciprocation units located in the Fire Pump Reefer Machinery Room (6-45-0-E)

A/C Units: (5) 300 ton York centrifical units are located: #1 Forward Diesel and A/C Machinery Room (4-41-2-E) #2 Auxiliary Machinery Room (6-73-0-E) #3 Auxiliary Machinery Room (6-73-0-E) #4 Forward Diesel and A/C Machinery Room (4-41-2-E) #5 Forward Diesel and A/C Machinery Room (4-41-2-E)

Refrigerator boxes: #1 Freezer (-4 to 0 F) #2 Chill Box (33 to 36 F) #3 Chill Box (33 to 36 F) #4 Thaw (37 to 40 F) #5 Battery locker (6 to 10 F)

Refrigerant: Reefers use R-12 A/C Units use R-114


103.1 State the type and location of the boilers onboard:


USS Boxer has (1) one boiler per main machinery space (two total). They are classified as 2 drum, natural circulation, D type boilers, manufactured by Combustion Engineering, Inc. 600 psi type, V2M (Vertical tube, 2 drum, Marine), LHD-1 CLASS.


NR 1 Boiler located in the Aft Main Machinery Room (6-81-0-E)
NR 2 Boiler is located in the Fwd Main Machinery Room (6-65-0-E)

103.2 Describe the function of the following major components:

a. Superheater - Used to raise the temperature of the saturated steam leaving the steam drum from 600 to 900 F (but not to exceed 950 F).

b. Economizer - A heat transfer device that uses the gases of combustion to preheat the feedwater in the boiler before it enters the steam drum for fuel economy (from 250 to 350 F). Secondary use is to cool the stack gasses (prevents unburned fuel ignition). Located above the generating bank.

c. Steam Drum - Located on top of the boiler. Collects all the steam before it passes to the superheater, distributes feedwater to the downcomers, and maintains water level at +7 to -6 (what???).

d. Water Drum - Located on the bottom part of the boiler, sometimes called the MUD-DRUM. Equalizes the distribution of water to the generating tubes, also contains the desuperheater (Auxiliary Steam).

e. Furnace - The enclosed space in the middle of the boiler where fuel and air are mixed together (by burners and air registers (what is an air register?)) for combustion. This heats the water in the headers (around the bottom, outside) and flashes it into steam.

f. Soot Blowers - A device that removes soot accumulation (unburned fuel) built up on the tubes during boiler operations, (5) five soot blowers per boiler. How does it do this?

g. Forced Draft Blower - Provides pressurized air for proper combustion in the furnace during all steaming conditions.

- There are 2 per Main Space.
- Manufactured by Elliot.
- Horizontally-mounted turbine-driven type.
- Driven by Main or Hotel (150 psi) steam

h. Port Use Fan (PUF) - Provides pressurized air for combustion in the furnace during light off.

- Only one per Main Space.
- A single-vane axial fan, horizontally mounted, motor driven

i. Boiler Safeties - (3) three safety valves that relieve excess pressure when the boiler drum reaches a set point.

- 750 psi at the Superheater,

- 765 psi at the 1st drum and

- 775 psi at the 2nd drum.

103.3 Discuss the following methods of Combustion Control:

a. Automatic -

The system is in complete automatic when it operates without human assistance, controlled by the ACC (Automatic Combustion Control) system. (Operates via a 15 psi pneumatic signal

b. Remote Manual -

All systems or individual components are operated in remote manual at the boiler console by shifting the A/M Control Station from automatic to remote manual and manually generating a pneumatic signal to the final control element as required. Used during light off and when operating at a slow speed

c. Local Manual -

A method for operating the boiler and machinery from the respective operating stations by hand without the assistance of the automatic systems. A casualty configuration.

130.4 State the function of the Chelant Boiler Water Treatment System.

- Prevents scale formation, minimize corrosion (oxidation) and minimize chemical carry over.

- Accomplished by an automatic and continuous injection of a solution of trisodium EDTA and hydrazine into the DFT at a rate proportional to the feed water flow.

- Can also be accomplished by manually injecting trisodium phosphate (TSP) directly into the boiler.

The following are the Boiler operating Chemical Limits:

Conductivity: 500 mW/cm

Alkalinity: 0.100 - 1.000 EPM (Equal Parts per Million)

Phosphates: 10 - 40 PPM (Parts Per Million)

Chloride: 1.0 EPM (Equal Parts per Million)

103.5 State the location and function of the following Feedwater components:

a. Deareated Feed Tank (DFT)

- One per Main Space.

- Serves (3) three purposes:

(1) De-aerates - removes oxygen and non-condensable gases from the feedwater;

(2) Pre-heats the Feedwater (operates as a direct contact heat exchanger);

(3) Stores Feedwater.

b. Main Feed Pumps (MFP)

- (2) two per Main Space.

- Turbine-driven (Auxiliary Turbine), 2-stage, centrifugal type.

- Provides sufficient discharge pressure to force feedwater into the steam drum at a discharge pressure of 850 - 900 psi and a temperature of 250 F.

c. Main Feed Booster Pump (MFBP)

- (2) two per Main Space.

- Electrically driven.

- Takes suction from the DFT and provides a positive suction head to the MFPS at a discharge pressure 60 psi and a temperature of 250 F.

d. Feedwater Control Valve (FWCV)

- (1) one per Main Space.

- The final control element of the Feedwater Control System.

- Supplies the right amount of Feedwater in order to maintain normal water level in the boiler (+/- 1 (what??) set point).

103.6 State the purpose and normal operating pressures of the boilers onboard USS Boxer?

The boilers onboard BOXER are designed to produce superheated steam (700 psi at 900 F.). The temperature/pressure is measured at the Superheater outlet header under full power condition.

a. Main Steam - is used to operate the following equipment:

- HP (High Pressure) & LP (Low Pressure) Turbines - (1) one set located in each Main Space (main propulsion);

- #1 & 2 SSTGs (Ships Service Turbo Generators) - located in the Fwd Main Machinery Room (main electricity forward);

- #3 SSTG - located in the Auxiliary Machinery Room (6-73-0-E) (makeup/standby electrical generator for forward/aft);

- #4 & 5 SSTGs - located in the Aft Main Machinery Room (main electricity aft).

b. Desuperheated Steam -

Used to drive all the auxiliary turbines (MFPs (Main Feed Pump), FDBs (Forced Draft Blowers), FFPs (Fire Fighting Pumps)) in both main spaces along with all the services requiring steam throughout the ship. This is accomplished by taking steam from the Superheater outlet through the desuperheater located in the water drum. Resultant steam is at 700 psi, 600 F.

103.7 Discuss the purpose of the following automatic boiler controls:

a. Feedwater Control:

Supplies the required amount of feedwater to the boiler under all conditions of operation, maintaining normal water levels.

b. Fuel Oil Control/Combustion Air Control -

Both work together and maintain the fuel oil and combustion air input to the boiler proper for the steam demand. They maintain steam pressure at the set point of 700 psi.

c. Airlock -

Isolates vital air to the final control elements on the Forced Draft Blowers (FDBS), Fuel Oil Cutout Valve (FOCV), Feed Water Control Valve (FWCV) and Main Feed Pumps (MFPS) at the values that existed the instant of supply air failure. Master air lock is set at 65 psi and all components are individually set to 40 psi. This allows a time delay to perform a controlled plant shutdown in the event of the loss of supply air.

AZC(AW/NAC) Kimberly King