Electronics Material Officer Course
MODULE NUMBER FOUR
LESSON TOPIC FIVE
ELECTRONIC SUPPORT SYSTEMS AND MISCELLANEOUS EQUIPMENTMODULE FOUR LESSON TOPIC FIVE
LESSON TOPIC OVERVIEW
LESSON TOPIC FIVE
ELECTRONIC SUPPORT SYSTEMS AND MISCELLANEOUS EQUIPMENT
As a shipboard EMO, you must be thoroughly familiar with the support systems for your equipment. In this lesson, we will discuss those systems. We will also discuss other types of equipment for which you may be responsible, including closed circuit television systems,
electronic warfare systems, and infrared equipment.
The LEARNING OBJECTIVES of this LESSON TOPIC are as follows:
4.13 Describe shipboard electronic support systems to include:
b. Physical properties
j. Other electronic subsystems
k. Technical documentation
l. Material condition
4.14 Describe the following aspects of electronic systems:
a. Cooling supply
b. Electrical supply
c. Dry air supply
d. Various distribution switchboards
4.15 Describe the purpose and use of Ship's Information, Training, and Entertainment TV (SITE-TV).
The student should review the "LIST OF STUDY RESOURCES" and read the Lesson Topic LEARNING OBJECTIVES before beginning the lesson topic.MODULE FOUR LESSON TOPIC FIVE
LIST OF STUDY RESOURCES
ELECTRONIC SUPPORT SYSTEMS AND MISCELLANEOUS EQUIPMENT
To learn the material in this LESSON TOPIC, you will use the following study resources:
Written Lesson Topic presentations in the Module Booklet:
1. Lesson Topic Summary
2. Narrative Form of Lesson Topic
3. Lesson Topic Progress Check
1. Assignment Sheet
2. Answer Booklet
1. Shipboard Electronics Material Officer, NAVEDTRA 12969
2. Electronic Technician 3 & 2, NAVEDTRA 10197
3. Electronic Technician Supervisor, NAVEDTRA 12411
4. NSTM Chapter 532
5. System Manual for Central Dry Air Systems - Surface Ships, NAVSEA 0949-LP-056-8010
LESSON TOPIC SUMMARY
ELECTRONIC SUPPORT SYSTEMS AND MISCELLANEOUS EQUIPMENT
This lesson topic will introduce you to various support systems that are necessary for your electronic equipment to function properly. The lesson narrative is organized as follows:
Electronic Support Systems and Miscellaneous Equipment
A. Introduction to Support Systems
B. Air Cooling Systems
C. Liquid Cooling Systems
D. Dry Air Systems
E. Electrical Power
F. Maintenance of Support Systems
G. Closed-Circuit Television
F. Infrared Equipment
ELECTRONIC SUPPORT SYSTEMS AND MISCELLANEOUS EQUIPMENT
LESSON TOPIC 4.5
INTRODUCTION TO SUPPORT SYSTEMS
Support systems include electrical power, ventilation, dry air, and liquid cooling systems. Without support systems, our combat systems could not function. As the EMO, you need to be aware of these support systems and understand their impact on your electronic equipment.
AIR COOLING SYSTEMS
Cooling systems safeguard the expensive electronic systems that your technicians maintain. Electronic equipment generates heat and must be cooled. Critical waveguide systems require dry air pressurization to purge them of moisture and to prevent internal corrosion. These systems require a thorough knowledge of cooling and dry air systems, as multimillion dollar electronics depend on them. We will begin with a discussion of air cooling systems. There are four methods of air cooling: convection, forced air, air to air, and air to liquid.
Cooling by the convection principle is shown in Figure 4.5-1. As equipment generates heat and warms the air in its vicinity, the warm air, being lighter, rises through the outlet openings. The cooler air is drawn in through the inlet openings to replace the warm air. This method is limited in its cooling effect because it relies on natural airflow and requires that the equipment
Figure 4.5-1 Convection Cooling
enclosure be of open construction without air filters. To increase heat dissipation, a finned heat sink can be added to the heat producing part or section of the equipment, e.g. the power supply, as shown in Figure 4.5-2. Fins increase the effective surface area of the part, allowing more heat to be transferred to the air. For the maximum transfer of heat, the part must be in contact with the heat sink. Silicone compound is usually applied between the heat source and the heat sink for better thermal transfer. The heat sink must be kept free of any dirt or dust, which would act as an insulator. This is one reason why electronic spaces must be kept clean.
Figure 4.5-2 Finned Heat Sink
To increase the cooling effect over that provided by convection cooling, forced air cooling (Figure 4.5-3) uses a blower instead of natural convection currents to provide air movement. Cool air is drawn into the equipment enclosure and flows past the heat producing part, picking up the heat. The air is then exhausted from the equipment. An air filter is provided at the air inlet to remove dust and dirt that otherwise would settle on the internal parts of the equipment. The air filter must be kept clean according to the equipment's maintenance requirements to ensure maximum air movement and cooling.
Figure 4.5-3 Forced-Air Cooling
In some equipment, a honeycomb RF interference filter is installed on both the inlet and the outlet to prevent stray RF from entering or leaving the equipment cabinet. These filters can also collect dirt that can reduce the airflow. Ensure that they are checked periodically.
Blower motor bearings must also be checked periodically. Because these bearings operate under severe conditions, they have a shorter service life than they might under normal service conditions. A general rule is: if the bearings fail, the entire motor must be replaced. If there is not a spare aboard, your technicians could disassemble the motor and see if they can make temporary repairs. In the meantime, your supply petty officer must order a new motor via CASREP. Do NOT risk damage to the equipment that the blower motor is designed to protect.
Some units of electronic equipment are hermetically sealed to prevent the entrance of moisture. For equipment of this type, an air-to-air heat exchanger (Figure 4.5-4) is used to prevent the air inside the equipment enclosure from mixing with the outside air and still allow cooling to take place. Air moving past the heat producing part absorbs heat and is forced through a heat exchanger by an internal blower. The heat in the internal air is absorbed by the heat exchanger. The cooled internal air is then returned to the equipment interior to continue the cycle. Heat is removed from the heat exchanger by forcing cool outside air through the heat exchanger by an external blower. There is no physical contact between the internal air and the external air. In some applications, the internal air is replaced by an inert gas such as nitrogen to prevent oxidation.
Figure 4.5-4 Air-to-Air Cooling
A more efficient heat transfer is possible when the air-to-air heat exchanger is replaced with an air-to-liquid heat exchanger (Figure 4.5-5). In this method, the internal air is also circulated past the heat producing part and through a heat exchanger, but the heat is removed from the heat exchanger by a liquid coolant circulating through the heat exchanger. Air-to-liquid cooling
systems usually use built-in safety devices to shut down the equipment to prevent overheating. The overheating could be caused by low or no liquid flow, liquid too hot, an inoperative circulating fan, or reduced heat exchanger efficiency because of improper maintenance. For proper operation, all of the air cooling systems depend on the condition of the ship's ventilation system. Proper maintenance and operation of shipboard ventilation systems is paramount to sufficient cooling of electronic equipment. This includes the cleaning of filters and maintaining of air conditioning boundaries. Additionally, "rigging" ventilation systems to resolve "cooling problems" is not authorized. Do not allow it.
Figure 4.5-5 Air-to-Liquid Cooling
Although air-cooling can protect heat-producing devices, liquid cooling, in which the liquid flows directly through the device to be cooled, provides better cooling efficiency. Figure 4.5-6 shows a basic liquid cooling system. This type of cooling system is normally found on large equipment installations where a large amount of heat is developed. Many radar transmitters, for example, require this type of cooling. Methods of cooling previously discussed cannot dissipate the heat that a high powered radar transmitter develops. A disadvantage of this type of cooling system is that it is large and complex. Because liquid cooling systems are complex and are common aboard ship, a typical system will be described to give you a better understanding of the how the individual components function within the system and the basic maintenance required to keep the system at a high state of readiness.
For an electronic water cooling system to operate satisfactorily, the temperature, quality, purity, flow, and pressure of the water must be controlled. This control is provided by various valves, regulators, sensors, meters, and instruments that measure the necessary characteristics and either directly or indirectly regulate the system. The liquid cooling system consists of a seawater or a chilled (fresh) water section that cools the distilled water circulating through the electronic equipment. The main components of the system are the piping, valves, regulators, heat exchangers, strainer, circulating pumps, expansion tank, gauges, and demineralizer. Other specialized components are sometimes necessary to monitor the cooling water to the electronic equipment.
Figure 4.5-6 Basic Liquid Cooling System
A typical liquid cooling system is composed of a primary loop (system) and a secondary loop (system). The primary loop provides the initial source of cooling water, either seawater or chilled water from the ship's air conditioning plant, or a combination of both. The secondary loop transfers the heat from the electronic equipment to the primary loop. The coolant normally used in the secondary loop is double-distilled water, obtained from the Naval Supply System. This distilled water is ultrapure and is maintained in that state by a demineralizer. However, in emergency situations, untreated boiler feed water can be used.
CAUTION - The use of standard distilled water could cause premature system degradation. In some secondary systems, ethylene glycol is added to the water to prevent freezing when the system is exposed to freezing weather.
PRIMARY LIQUID COOLING SYSTEM
The cooling water for the primary cooling system is either seawater or chilled water. The chilled water is from the ship's air conditioning plant.
Seawater from a sea connection is pumped by a seawater circulating pump in one of the ship's engineering spaces (this pump could just as well be in an electronics space) through a duplex strainer to remove all debris and then through the tubes of a heat exchanger. Finally, it is discharged back into the sea at an overboard discharge. The seawater loop can have either one or several branches. Multiple-branch loops supply primary cooling water to a number of heat exchangers for electronic equipment. To regulate the proper amount of seawater to each cooling branch, an orifice plate is installed in the line between each heat exchanger and the duplex strainer. The heat exchangers are referred to as seawater-to-distilled-water heat exchangers.
Another means of providing seawater is through the ship's firemain. The seawater is taken from the firemain through a duplex strainer and a flow regulator (orifice plate) to and through the heat
exchanger. It is then discharged overboard. The connection to the firemain is permanent. The
ship's fire pump is used to pump seawater into the firemain. The fire pump is similar in design to the previously mentioned seawater circulating pump, except that it has a much larger capacity.
Yet another means of getting seawater as a primary coolant is by an emergency connection. This method is used if the normal seawater supply is lost. The connection is usually by means of a 1½-inch fire hose. The emergency supply comes from an alternate portion of the ship's firemain or a portable pump rigged by the ship's damage control party. The portable emergency hose is normally stored in the liquid coolant machinery room. You, as EMO, should be able to rig the emergency cooling fire hose yourself, if necessary. There may not be time to locate trained individuals to save a multimillion dollar radar. Thoroughly familiarize yourself and all your ETs in emergency procedures. Seawater systems are referred to as open loop or one pass systems because the seawater flows through the system only once.
Chilled Water Coolant
Chilled water is taken from the supply main of the air conditioning-chilled water systems. It can be used as either the primary source of coolant or as a backup source for seawater or other primary chilled water. The chilled water flows through the tubes of the heat exchanger (chilled water-to-distilled water), a flow regulator, and back to the chilled water system. A temperature regulating valve at the inlet of the heat exchanger regulates the flow of chilled water through the heat exchanger to maintain the required water temperature in the secondary loop (distilled water). The ship's air conditioning-chilled water circulating pump is used to pump the chilled water through the heat exchanger. The chilled water system is a closed loop water system because the water is recirculated. It must be kept tight and free from leaks to assure satisfactory operation.
SECONDARY LIQUID COOLING SYSTEM
The secondary cooling system is designed to transfer heat from the electronic equipment being cooled to the primary cooling system. This system is usually composed of a distilled-water circulating pump, a compression or gravity-feed expansion tank, the electronic equipment being cooled, a demineralizer, a temperature control valve, monitoring equipment with its associated alarms, and the heat exchanger, which is shared with the primary loop. The secondary system is a closed loop water system, compared to the seawater system, which is a one-pass or open loop system.
TYPES OF LIQUID COOLING SYSTEMS
In the U.S. Navy there are three basic configurations of liquid cooling systems. You could conceivably have all three aborad. The three types of systems are:
lType I - Seawater/distilled water (SW/DW) heat exchanger with SW/DW heat exchanger standby
lType II - SW/DW heat exchanger with a chilled water/distilled water (CW/DW) heat exchanger standby
lType III - CW/DW heat exchanger with a CW/DW heat exchanger standby
The specifications for the type of system (or systems) installed on your equipment will depend on the operational requirements of the equipment. Some electronic equipment requires the temperature of the distilled water to be regulated very closely; others do not.
Type I Liquid Cooling Systems
SW/DW systems are used for electronic system installations that can be operated satisfactorily with seawater temperature as high as 95°F. This should result in a distilled water supply temperature to the electronics of approximately 104°F. Operation of a Type 1 system will be discussed on the following paragraphs, illustrated by Figure 4.5-7.
Figure 4.5-7 Type I Liquid-Cooling System
Starting with the distilled water pumps, pressurized distilled water flows to the temperature regulating valve. The temperature regulating valve is installed to partially bypass distilled water around the sea water-to-distilled water heat exchanger so that a constant water temperature can be supplied to the electronic equipment. As the temperature in the distilled water increases, more water is directed to the heat exchanger and less to the bypass line. This maintains the output water temperature constant. The standby heat exchanger is usually of the same design and is used when the on-line heat exchanger is inoperable or is undergoing maintenance. The heat exchanger is sized to handle the full cooling load of the electronic equipment plus a 20% margin.
From the heat exchanger, the water goes through various monitoring devices, which check the water temperature and flow. Water temperature and flow depend upon the requirements of the electronic equipment being cooled. After the water moves through the equipment, it is drawn back to the pump on the suction side. In this way, a continuous flow of coolant is maintained in the closed-loop system. An expansion tank is provided in the distilled water system to compensate for changes in the coolant volume, and to provide a source of makeup water in the event of a secondary system leak. When the expansion tank is located above the highest point in the secondary system and vented to the atmosphere, it is called a gravity tank. If it is below the highest point in the secondary cooling system, it is called a compression tank, because it requires an air charge on the tank for proper operation. The demineralizer is designed to remove dissolved metals, carbon dioxide, and oxygen. In addition, a submicron filter (submicron meaning less than one millionth of a meter) is installed at the output of the demineralizer to prevent the carry over of chemicals into the system and to remove existing solids.
Type II Liquid Cooling Systems
SW/DW, CW/DW systems are used in installations that cannot accept a DW temperature higher than 90°F. The secondary system of the Type II cooling system (Figure 4.5-8 on page 4-5-13) is similar to the secondary system of the Type I cooling system and uses many of the same components. The major difference is in the operation of the CW/DW heat exchanger. The secondary coolant is in series with the SW/DW heat exchanger and automatically supplements the cooling operation when the SW/DW heat exchanger is unable to lower the temperature of the distilled water to the normal operating temperature. The CW/DW temperature regulating valve allows more chilled water to flow in the primary cooling system to the CW/DW heat exchanger. This causes the temperature in the secondary system to go down. Normally, this action only occurs in the event of high seawater temperatures encountered in tropic waters. The CW/DW heat exchanger is also used in the event of an SW/DW heat exchanger malfunction.
Type III Liquid Cooling Systems
CW/DW systems are used in installations where the temperature range is critical. They require close regulation of the DW coolant to maintain temperatures between established limits. For example, the temperature limits might be 70° and 76°F. As you can see, Type III systems are used where tighter control is required. The Type III secondary cooling system (Figure 4.5-9 on page 4-5-13) also operates in a similar manner to that of the Type I secondary system. The major difference is in the way that the temperature of the secondary coolant is regulated. A three-way temperature regulating valve is not used. A two-way temperature regulating valve is used in the primary cooling loop to regulate the temperature of the secondary loop.
Figure 4.5-8 Type II Liquid-Cooling System
Figure 4.5-9 Type III Liquid-Cooling System
The duplicate CW/DW heat exchanger is installed parallel with the first heat exchanger and is used as a standby heat exchanger. In the event that a malfunction occurs requiring the first heat exchanger to be removed from service, the standby exchanger can be put into service by manipulating the isolation valves associated with the two heat exchangers.
LIQUID COOLING SYSTEM COMPONENTS
You should be able to identify the individual components of a typical cooling system and describe how they operate. This will aid you as EMO when you do periodic tours and inspections of your equipment.
In the liquid coolant heat exchangers, heat that has been absorbed by distilled water flowing through the electronic components is transferred to the primary cooling system, which contains either seawater or chilled water from an air conditioning plant. In both cases (Figures 4.5-10 and 4.5-11), the heat exchangers are of the shell and tube type in which the secondary coolant, distilled water, flows through the shell, while the primary coolant, seawater (SW) or chilled water, flows through the tubes. A single pass counterflow heat exchanger is more efficient than the double pass heat exchanger, because there is a more uniform gradient of temperature difference between the two fluids. In Figure 4.5-10, the primary coolant (SW/CW) flows through the tubes in the opposite direction to the flow of the secondary coolant (DW). Heat transfer occurs when the seawater flows through the tubes; extracting heat from the distilled water flowing through the shell side of the heat exchanger. The distilled water is directed by baffles to flow back and forth across the tubes as it progresses along the inside of the shell from inlet to outlet. In Figure 4.5-10, the preferred method of double tube sheet construction is shown. Single tube sheet construction is shown in Figure 4.5-11.
Figure 4.5-10 Single-Pass SW/DW Heat Exchanger with Double Tube Sheets
Figure 4.5-11 Double-Pass SW/DW Heat Exchanger with Single Tube Sheets
Double tube sheets are used at both ends of a tube bundle. A void space between the sheets prevents contamination of the distilled water and permits the monitoring of water loss due to tube leakage. You should be on the lookout to detect leakage at the "telltale drains," which indicates a failure of a tube joint. The type of water leaking out indicates whether the failure is in the primary or secondary system. The telltale drains should never be plugged or capped off. A leak in one of the tubes shows up as a loss of water in the secondary side of the liquid coolant system, because it operates at a higher pressure than the primary side. This is intentional and ensures that the distilled water is not contaminated with seawater when a leak develops in a heat exchanger.
The expansion tank serves a threefold purpose in a liquid cooling system:
lIt maintains a positive pressure required on the circulating pump for proper operation of the circulating pump
lIt compensates for changes in the coolant volume due to temperature changes
lIt vents air from the system and provides a source of makeup coolant to compensate for minor losses because of leakage or losses that occur during the replacement of radar equipment served by the system
The expansion tank may be either a gravity tank or a pressurized tank. See Figures 4.5-12 and 4.5-13.
Figure 4.5-12 Gravity Expansion Tank
Figure 4.5-13 Pressure Expansion Tank
Strainers are used in the seawater cooling system to remove debris and sea life, which could clog the pressure and flow control device (orifice) and the tubes of the heat exchanger. The two types of in-line seawater strainers most commonly used in shipboard liquid cooling systems are the simplex (single) and duplex (double) basket strainers. See Figures 4.5-14 and 4.5-15.
Figure 4.5-14 Seawater Simplex Strainer
Figure 4.5-15 Seawater Duplex Strainer
Temperature Regulating Valves
The temperature regulating valve regulates the amount of cooling water flowing through a heat exchanger to maintain a desire temperature of distilled water going through the electronic equipment. Temperature regulating is usually provided by either a three-way valve, a two-way valve, or a combination of both as shown in Figures 4.5-16 and 4.5-17. The three-way valve is
used where seawater is the primary cooling medium in the heat exchanger and the two-way valve is used where chilled water is the primary cooling medium.
Figure 4.5-16 Three-Way Temperature Regulating Valve
Several types and sizes of flow regulating devices are used in both primary and secondary cooling systems to reduce the pressure or the flow of coolant through the cooling system. The basic types are as follows:
lOrifice plate - the simplest design, consisting of a steel plate with a hole in it. With a constant known seawater pressure and with a given hole size, the volume of water through the device can be determined easily.
Figure 4.5-17 Two-Way Temperature Regulating Valve
lConstant flow regulator (variable orifice) (Figure 4.5-18) - Used with chilled water systems, it is installed downstream from the heat exchanger. This restricts the flow from the heat exchanger and keeps the heat exchanger fully submerged for greater heat transfer.
Figure 4.5-18 Constant Flow Regulator
lEquipment Flow regulator - Used primarily with electronic equipment to regulate the flow of distilled water through the individual cabinets and components. See Figure
lPressure regulating valve - (Figure 4.5-20) used to regulate a major section of the cooling system. Because the cooling system can handle a large amount of coolant, it usually has a pressure-relief valve to protect the equipment from being over pressurized.
Figure 4.5-19 Equipment Flow Regulator
Figure 4.5-20 Pressure Regulator
Flow Monitoring Devices
Most systems incorporate one or more types of devices to monitor and ensure an adequate flow of distilled water through the electronic equipment. A low flow switch is normally found in the secondary cooling system to monitor the overall coolant flow. It is electrically connected to a common alarm circuit to warn personnel when the system flow rate drops below a specified minimum value. See Figures 4.5-21 and 4.5-22.
Figure 4.5-21 Cooling System Flow Switch Figure 4.5-22 Equipment Flow Switch
The secondary cooling system water is maintained in an ultrapure state by a demineralizer. By maintaining the coolant at a high degree of purity, you minimize corrosion and the formation of scale in the radar unit. Corrosion or scale on a high heat density component, such as waveguide dummy loads and klystrons, results in the formation of a thermal barrier. The thermal barrier reduces the effectiveness of heat transfer at normal operating temperatures. This leads to premature failure of the components. A demineralizer is shown in Figure 4.5-23. A purity meter is shown in Figure 4.5-24.
In some secondary cooling systems, an oxygen analyzer is installed to measure the amount of dissolved oxygen in the liquid coolant. The presence of oxygen causes oxidation that leads to the formation of scale in the cooling system. An oxygen analyzer has an oxygen sensor installed in the supply side of the cooling system. The sensor is an electrolytic cell in an electrolyte solution or gel. A thin synthetic membrane covers the end of the sensor, which is inserted in the coolant. The synthetic membrane is gas permeable to the dissolved oxygen in the secondary coolant. This allows the oxygen to pass through the membrane. The oxygen reacts with the electrolyte, which
Figure 4.5-23 Demineralizer
Figure 4.5-24 Purity Meter
causes a proportional change in the amount of current flow in the sensor. The sensor's electrical output is measured and displayed on the oxygen analyzer's meter. The meter is calibrated to read the oxygen content in parts per million or billion.
Coolant Alarm Switchboard
The cooling system alarm switchboard, located in either CIC or the coolant pump room, monitors various conditions to alert you to a problem that may develop in the cooling system. When an abnormal condition occurs, the alarm switchboard indicates the fault condition with both a visual and an audible alarm. The alarm switchboard usually has several remote bells and lights in CIC and other electronic spaces aboard ship to indicate that a fault condition has occurred. There are several standard types of alarm switchboards used throughout the navy. A common type is shown in Figure 4.5-25. An illustration of displays and audible alarms is shown in Figure
Figure 4.5-25 Cooling System Alarm Switchboard
Figure 4.5-26 Alarm Switchboard Visual Displays and Audible Outputs
COOLING SYSTEM PREVENTIVE MAINTENANCE
Your most important responsibility in extending the life of the cooling system components and increasing the reliability of the cooling system is scheduling preventive and corrective maintenance according to the Planned Maintenance System (PMS). Properly performed preventive maintenance drastically reduces the amount of corrective maintenance necessary. When cooling systems are neglected, they deteriorate very quickly. An important part of your salt water cooling system is the sacrificial zincs. These are zinc plates that are bolted to equipment in which salt water is used. Zinc is electrochemically more reactive to salt than the other metals. Corrosion "prefers" zinc to steel. Some of your zincs may have been lagged over during a recent shipyard overhaul. Ensure that your technicians locate and inspect each one (using EGLs).
DRY AIR SYSTEMS
For optimum operation, modern high-powered radars must have their waveguide systems, in both the low and high power sections, pressurized with dry air. In some waveguide systems, dry air is used primarily to increase the dielectric constant inside the waveguide to prevent RF energy from arcing inside the waveguide. Arcing causes damage to the inside of the waveguide. It also reflects a short circuit back to the power amplifier tube. Should this happen, the power amplifier could sustain major damage. Also, the use of pressurized dry air decreases the problems of corrosion, contamination, collection of moisture and oil droplets (which affect preservation). At the same time, the overall reliability of the waveguide system is increased.
High power waveguide uses dry air pressure around 20-35 psig to reduce waveguide arcing. The increased air pressure increases the dielectric of the air. Low-power waveguide uses dry air at between 1 and 8 psig, primarily to prevent corrosion and contamination of the inside of the waveguide.
The number of electronic equipments requiring dry air for operation has increased drastically in recent years. Central dry-air systems have been installed in many ships to overcome the problems of individual maintenance, repair, and supply support required by individual air dehydrators. However, there are still a large number of individual equipment dehydrators in use as back-up systems, should a failure occur in the ship's central dry-air system. There are several methods that can be used to remove excess moisture from the air. One method is to freeze the moisture by means of a refrigerant and then remove the frozen moisture by a mechanical means. A second method is to pass the air through a desiccant which absorbs the moisture. Some dehydrators use a combination of the two methods to remove the moisture.
CENTRAL DRY-AIR SYSTEM
The ship's central dry-air system is usually located in one of the ship's main engineering spaces and can be composed of a low-pressure (100 psig) air compressor, a Type I dehydrator, and either a Type II or Type III dehydrator. The air compressor compresses the air and then sends it to the Type I dehydrator (refrigerant). The Type I dehydrator removes the majority of the water and oil in both liquid and gaseous vapor forms from the air. Next, the Type II (desiccant) or a Type III (combination of refrigeration and desiccant) dehydrator processes the air to remove the last traces of moisture. This last bit of processing causes the air to become electronically dry. See Figures 4.5-27 and 4.5-28.
Figure 4.5-27 Desiccant Air Dryer
Figure 4.5-28 Dehydrator
Nitrogen Pressurization Systems
Nitrogen is an inert gas used to purge dry air systems of moisture prior to their operation and as a primary form of pressurization in some communications and weapons systems. For system charging, the equipment is given an initial charge of nitrogen and then is monitored and recharged as required. Nitrogen is not used in a continuous feed such as in the dry air systems described earlier; however, it serves the same basic purpose in the equipment. Ensure that a sufficient supply of nitrogen is on board; only water-pumped nitrogen should be used. Ensure custody control of the MK-260/U recharging kit.
Part of the routine work of the electronics division is to energize electronic equipment. This may occur every morning for daily tests or after a lengthy period of shutdown time for maintenance. At times equipment cannot be energized due to a missing power input. Technicians must know where power is coming from in order to restore it. Specific equipment and casualty control training for ETs must include power distribution. Electronics technicians should check with electricians prior to trying to resolve any power source problem. Source power may be secured due to a tripped generator, misaligned switchboard, open circuit breaker, scheduled electrical maintenance, or shifting of the load. Ensure that your technicians contact the duty electrician for the status of the power supply before they assume the worst and begin troubleshooting their own equipment. Take advantage of shore power. This is the perfect time to accomplish PMS on
equipment. With shore power, you generally are not concerned with shifting loads, tripped generators, etc. The duty electrician should be notified of electronics maintenance requirements (specifying the equipment to be energized) to ensure that the switchboard can handle the additional load. Technicians should know the status of the electrical plant and the main power panel that supplies source power to the equipment. The following section presents a typical ship's power distribution system and discusses areas that are closely related to electronic equipment.
POWER DISTRIBUTION SYSTEM
Most AC power distribution systems in naval vessels are 440 volt, 60 Hz, 3 phase, 3 wire, ungrounded systems. Refer to the EIMB General Handbook, Chapter 3, for information regarding ungrounded electrical power distribution systems. The AC power distribution system consists of the power plant, the means to distribute the power, and the equipment that uses the power. See Figure 4.5-29. The power plant is either the ship's service turbine generator or the emergency diesel generator. The power is distributed through the ship's service distribution switchboards and power panels. Some large ships use load centers, which function as remote switchboards. Power is used by any equipment that requires electrical power for its operation.
Figure 4.5-29 60 Hz Distribution (Partial)
If the ship's service distribution system fails, the emergency power distribution system supplies an alternate source of electric power to a limited number of selected loads that are vital to the safety of the ship (vital loads). This system includes one or more emergency diesel generators and switchboards. The emergency generator starts automatically when a sensor detects the loss of normal power. The operation of the ship's service generators, the emergency generators, and the distribution switchboards is the responsibility of the ship's engineers. There will be times when you will be concerned with electrical plant status because your electrical power requirements are not being met. For that reason, you need to be able to communicate in terms with which engineering personnel are familiar.
BUS TRANSFER EQUIPMENT
Bus transfer equipment is installed on switchboards, at load centers, on power panels, or on loads that are fed by both normal and alternate or emergency feeders. Either the normal or alternate source of the ship's service power can be selected. Emergency power from the emergency distribution system can be used if an emergency feeder is provided. Automatic bus transfer (ABT) equipment is used to provide power to vital loads, while non-vital loads can be fed through manual bus transfer (MBT) equipment. For example, the interior communications (IC) switchboard is fed through an ABT, whose alternate input is from emergency power. A search radar might be fed through an MBT to prevent power fluctuations.
Power distribution is directly from the ship's service switchboards to large and important loads, such as missile launchers and directors. Distribution to other loads is through power distribution panels and, if applicable, load centers.
The IC switchboard is the nerve center of the interior communications system. All interior communications circuits and some electronic circuits are energized through the IC switchboard. Relay supply voltages, synchro excitation, and some 400 Hz power pass through this switchboard. Some of these supply voltages may be routed from the IC switchboard directly to the combat systems equipment. Most of them, however, are also routed through the missile fire control switchboard. Larger ships usually have two IC switchboards (one forward and one aft), while smaller ships have one centrally located IC switchboard.
60 Hertz Power
Many of the bigger loads in the combat system use 440 volt, 60 Hz, 3 phase power as a power source. This supply is also sent to transformers for conversion to 115 volt, 60 Hz, 3 phase power for distribution where needed. Additionally, it is used as an input to the 50 volt DC rectifier at the IC switchboard. The 50 volt DC rectifier output is distributed throughout the combat system
as a relay supply voltage.
400 Hertz Power
The 440 volt, 400 Hz, 3 phase power is made up in motor generator (MG) sets that are fed by the 440 volt, 60 Hz power. (See Figure 4.5-30) The 400 Hz supply is the primary source of power for some combat systems equipment. Distribution is primarily through the equipment switchboard via the IC switchboard. Besides the 440 volt, 400 Hz signal, 115 volt, 400 Hz power from regulated and unregulated transformers is supplied when required. In some systems the 115 volt, 400 Hz power is used as the input to a voltage regulator for generation of a 115 volt, 400 Hz precision supply.
Many other supply voltages are used in the electronic systems and subsystems. They are usually used as reference voltages for specific functions. For example, 12 volts AC is used as a reference in some systems.
When the technicians are missing power inputs to their equipment, they work backward from the load to the source. Usually, the power panels and bus transfer units that feed the equipment are located in close proximity, possibly in the same space, or in an adjoining passageway. Bear in mind that many suspected casualties have been corrected merely by restoring an inconspicuous power input or signal reference, sometimes after hours of troubleshooting.
Figure 4.5-30 400 Hz Distribution (Partial)
MAINTENANCE OF SUPPORT SYSTEMS
The following are the CNO guidelines for support system maintenance responsibilities. These guidelines are very specific and have been reinforced by the type commanders:
lDry air system operation and preventive maintenance from the inlet coupling of the air control panel to the electronic equipment being served is the responsibility of the appropriate combat systems rating.
lCooling water system operation and preventive maintenance starting at the saltwater strainer and including all of the secondary loop is the maintenance responsibility of the appropriate combat systems rating.
lOperation and maintenance of all combat systems support systems not assigned to combat systems ratings is the responsibility of the appropriate engineering rating.
lEngineering ratings will perform all casualty maintenance on combat systems support systems.
Maintenance training for support systems comes in several forms. The most common are OJT and PQS. Remember that PQS is mandatory. Other training must be used to maintain support systems in a high state of readiness. Short courses are offered at the RSG, IMA, and FTSC. Additionally, there are U.S. Navy C schools that offer support systems training. Check the CANTRAC.
Shipboard closed-circuit television (CCTV) systems are used for entertainment and for the routine work of the ship. CCTV makes it possible for shipboard personnel at remote locations to view or monitor various operations, training, and movies. One CCTV system installed aboard ships is the Shipboard Information, Training, and Entertainment (SITE) II system. This system is shown in Figure 4.5-31. SITE-TV is used for entertainment, training, combat information, flight operations, and secure information purposes. Your ship may have a SITE I system, which is a larger version of the SITE II. When the system is used to transfer tactical information from the CIC to remote stations, the TV camera is fastened to the overhead in the CIC so that it overlooks the plotting board. The video output of the camera is sent to viewer units. From these video signals, the viewer units reproduce and display the data on the plotting board. Thus, cognizant personnel are instantaneously and accurately informed of any changes in the tactical situation. Television systems are also used aboard aircraft carriers for briefing pilots before a mission. When the system is used for this purpose, a viewer unit is installed in each ready room. The TV camera is arranged so that it picks up the briefing officer and any pertinent charts or displays. In this way, all pilots concerned are briefed in one session.
Another use for CCTV is port briefs and shipwide training. The most popular use of CCTV, however, is for crew entertainment. News, various television programs, and movies are distributed to activities with the SITE system installed. There are stringent guidelines that must be followed when handling these programs. Consult NMPCINST 1710.1 for specific information regarding custody and handling of SITE TV movie programs. Site-TV equipment is generally maintained by IC technicians.
Figure 4.5-31 SITE II Television System
INFRARED EQUIPMENT (NANCY GEAR)
Infrared equipment belongs to a family of devices that use electro-optics for communication, surveillance, detection, and navigation. Also included are image-intensifying night observation devices, low level television, and lasers. Infrared equipment is designed to create, control, or detect invisible infrared radiations. The equipment is of two types, transmitting and receiving. The transmitting (source) equipment produces and directs radiations. The receiving equipment detects and converts these radiations into visible light for viewing purposes, or into voice or code signals for audible presentation. Infrared devices can be used for weapon guidance, detection of enemy equipment and personnel, navigation, recognition, aircraft proximity warning, and communications. Depending on its application, the equipment is either passive or active. The active method uses both transmitting and receiving equipment, whereas the passive method requires only receiving equipment.
The infrared spectrum, which extends from the upper limits of the radio microwave region to the visible light region in the electromagnetic spectrum, is divided into three bands: near infrared, intermediate or middle infrared, and far infrared. Devices operating in the near and middle bands are used for ranging, recognition, and communications. They normally have a maximum usable range of 6.5 to 10 miles. Equipment that operates in the far infrared band is used for ranging, missile guidance, and the detection and location of personnel, tanks, ships, aircraft, etc. This equipment normally has a maximum usable range of 12 miles. Perhaps the most widely used infrared transmitting gear is the VS-18/SAT Infrared Hood, with filter lens. It is mounted on the standard navy 12-inch searchlight (Figure 4.5-32). It blocks most visible light so that the searchlight cannot be seen from a distance. The light is operated in the same manner as an ordinary communication searchlight. Design variations to the VS-18/SAT Hood are used on nonmagnetic minesweepers with an 8-inch signal light, and hand signal lamps.
Figure 4.5-32 VS-18/SAT
Another type of infrared transmitting equipment is a 360° light. These lights are generally installed in pairs on yardarms (Figure 4.5-33) and are used on most naval ships. These lights, designated AN/SAT, are operated in the same manner as yardarm blinkers. They can be used as a steady light source or for signaling and recognition.
Figure 4.5-33 AN/SAT
Voice-tone equipment units are not in general use at the present time. They work by modulation of a light beam, which is received and amplified by a photocell receiver. Electronic infrared viewers convert infrared rays to visible light. They must be used to detect signals from VS-18/SAT or AN/SAT equipment, or to observe a night scene illuminated by an infrared source. The AN/SAR-4 viewing set (Figure 4.5-34) is a old set that is still in use. It consists of two main units: a 115 volts AC to 20,000 volts DC power supply and a viewer unit that consists of a sealed housing and two interchangeable sets of lenses. The housing contains an image converter tube that produces an image of the infrared scene on a phosphorescent screen.
Figure 4.5-34 AN/SAR-4
The AN/SAR-6 viewing set (Figure 4.5-35) is similar to the AN/SAR-4 except that it has an internal battery power supply instead of a separate power unit. The AN/SAR-7 viewing set (Figure 4.5-36) is similar to the AN/SAR-6 but is smaller and lighter. The Type T-7 AN/PAS-6 Infrared Metascope is an active (light emitting) hand held, infrared-sensitive viewer for detection and general use. The metascope also has a built-in infrared illuminator (light source) to render it capable of viewing objects without being detected by the naked eye.
Thermal imaging is a process by which changes in temperature are visually displayed in the viewfinder as changes in color. The Mast Mounted Sight (MMS), Figure 4.5-37, is an all weather electro-optic system consisting of a low light television system, thermal imaging system, and laser rangefinder/target designator. Typical applications for the MMS are mine avoidance, target identification/acquisition, and navigation.
Figure 4.5-35 AN/SAR-6
Figure 4.5-36 AN/SAR-7
Figure 4.5-37 Mast-Mounted Sight (MMS)
The hand held thermal imager (HHTI) is primarily a damage control device used locate personnel in smoke filled compartments. It may be used elsewhere, e.g., small boat reconnaissance. Its range is 700 yards. The AN/KAS-1 thermal imager is a bridge mounted unit used for chemical detection. It has a range of 3200 yards.
Night Vision Devices
Passive night vision sights (NVS) are devices that emit no visible or infrared light. The MK 37 NVS and MK 36 NVS are primarily bridge mounted units. The NVS uses an image intensifier tube to amplify received light, thus enhancing or allowing vision under nighttime or similar conditions of low illumination.
Night Vision Devices Management
As EMO you probably would not direct your technicians repair any of these devices. They are highly reliable, however, ensure that there is an adequate supply of batteries. If one of these devices fails, treat it as you would any other electronic equipment that is sent out for repair. Have your technicians give it a cursory examination. They must not break any factory seals in the process. Night vision equipment is classified as ordnance equipage and allowances have been established for all fleet units. Each command or activity with a requirement for night vision devices should have an approved allowance for such equipment. Adequate safeguards must be
established for accountability and to prevent compromise, damage, or loss. Although unclassified, they have been designated as sensitive ordnance hardware. Therefore, strict control of these items is mandatory.
PROCEED TO ASSIGNMENT SHEET 4-5-1A IN THE ASSIGNMENT BOOKLET. UPON COMPLETION, TAKE THE ASSIGNMENT BOOKLET TO THE LEARNING CENTER INSTRUCTOR.