[Air Systems and Controls] Flashcards
Compressors may be either single-acting (compression on one stroke per revolution) or double-acting (compression on both strokes per revolution) NOTE: This means that compression is taking place on both sides of the piston and that each end of the cylinder is fitted with suction and discharge valves.
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What is high pressure PSI?
1,000 PSI to 5,000 PSI
What air distribution system is used for different purposes such as TLI systems and air hose connections?
Nonvital air
Which type of control system regulates the pressure in the air receiver by controlling the output of the compressor without stopping or changing the speed of the unit?
Constant-speed control
What are the two types of valves commonly used in high-pressure air compressors
1) Strip or feather valve
2) Disk-type valve
Describe the W-type low-pressure reciprocating air compressor
3-cylinder and 2-stage (2 first-stage and 1 second-stage)
What does the compressing element of a reciprocating air compressor consist of?
1) Cylinder
2) Piston
3) Air valves
What type of driving unit connection is it when flexible couplings are used to join the driving unit to the compressor when the speed of the compressor and the speed of the driving unit are the same?
Direct-couple drive
What are installed on air compressors for the removal of all but the friction loads on the compressors?
Unloading systems
What is low pressure PSI?
150 PSI or less
What keeps the compressed air from forcing oil back into a lubricator?
Check valve
What type of bottoms do vertically-mounted receivers have and why?
Convex, to permit proper draining of accumulated moisture, oil, and foreign matter
How are compressors classified?
1) Capacity (high or low) of compressing element
2) Source or driving power
3) Method by which the driving unit is connected to the compressor (belt-driven, direct-connected)
4) Whether air delivered is oil-free or non-oil-free
What is the heart of any compressed air system?
Air compressor
How are most medium-pressure and high-pressure compressors cooled?
By the ship’s auxiliary freshwater supply or by seawater pulled from the ship’s fire main or machinery cooling water service mains
What are air receivers called in high-pressure air systems? What are multiple connected ones called?
Air flasks
Air banks
What are the classifications of air compressors?
1) Duplex
2) Single-stage
3) Multi-stage
4) Horizontal
5) Angle
6) Vertical
What is the reservoir of oil that the oil pump draws from?
Oil sump
What are the characteristics of a high-pressure reciprocating compressor?
1) Motor-driven
2) Liquid-cooled
3) 3- to 6-stage (most are 4)
4) Single-acting
5) Vertical
What is the first thing that should be done before starting maintenance on an air compressor system?
Ensure it’s secured
In which type of compression is air compressed in two or more compression elements to reach final discharge pressure?
Multi-stage
What type of driving unit connection is used with small, low-pressure, motor-driven compressors and with some medium-pressure compressors?
V-belt drive
What is medium pressure PSI?
151 PSI to 1,000 PSI
What air distribution system is primarily used for engineering purposes and is supplied to electronics systems?
Vital air
What does the amount of oil that must be fed to the cylinder depend on?
1) Cylinder diameter
2) Cylinder wall temperature
3) Viscosity of the oil
What percent above normal working pressure of the receiver are the relief valves set?
12%
What remove heat generated during compression and promote condensation of any vapor that is present in an air compressor?
Intercoolers and aftercoolers
Where is the type and grade of oil used in a compressor specified?
Equipment technical manual (TM)
How are most high-pressure air compressor cylinders lubricated?
Adjustable mechanical force-feed lubricator
Which type of control system stops the compressor if the cooling water temperature rises above a safe limit, and does not automatically restart?
Automatic high-temperature shutdown
In which type of compressor do the two pistons travel together (parallel)?
Duplex
What are the characteristics of a low-pressure reciprocating compressor?
1) 2-stage
2) Vertical “V” or “W” cylinders
What type of driving unit connection is it when the compressor and the driving unit are mounted on the same shaft?
Close-coupled
What are the two types of pistons?
1) Trunk - driven directly by the connecting rods
2) Differential - modified trunk pistons having two or more different diameters
When operating a manual valve, slowly crack it open until flow is noted and pressures on both sides have equalized. What rate of pressure rise should it be kept under?
200 PSI per second
In which type of compression is the compression of air from suction pressure to final discharge pressure completed in a single compression element (one cylinder)?
Single-stage
What is the top of a piston called?
Piston crown
Lubrication begins automatically as the compressor starts up
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What air distribution system is the most widely used air system aboard ship?
Low-pressure air (LP ship’s service air)
What is an air storage tank installed in each space that houses air compressors, and functions to minimize pressure variations in the system and to supply air during peak demand?
Air receiver
What are the characteristics of a medium-pressure reciprocating compressor?
1) 2-stage
2) Vertical
3) Duplex
4) Single-acting
5) Usually have differential pistons
What type of motor do the shipboard compressors have?
Electric
Describe the V-type low-pressure reciprocating air compressor
2-cylinder and 2-stage (1 first-stage and 1 second-stage)
How is the running gear lubricated?
Oil pump
What air distribution system is used for emergencies or abnormal situations to provide air to the low-pressure air system?
High-pressure air system
3,000/150 PSI reducing station
Which type of control system starts and stops the compressor automatically as the receiver pressure falls or rises within predetermined setpoints?
Start-stop control
What are the two basic types of air dehydrators?
1) Desiccant - drying agent
2) Refrigerator - cooling coils
What are the three types of shipboard air compressors and their PSI?
1) Rotary - 20 PSI or less
2) Centrifugal - 125 PSI or less
3) Reciprocating - 100-5,000 PSI
Army watercraft use RECIPROCATING (compressed in one or more cylinders)
