BG4 Parts And Functions Summary Flashcards
What is the BG4?
A self-contained closed-circuit, oxygen (O2) breathing apparatus that allows the wearer to work in an irrespirable atmosphere for up to four hours.
What type of pressure does the BG4 use?
Positive pressure apparatus.
How long can the BG4 allow a wearer to work in an irrespirable atmosphere?
Up to four hours.
What are the four major systems of the BG4?
- Pneumatics
- Breathing loop
- Electronics
- Backplate and harness assembly
What does the fully charged steel O2 cylinder provide?
400 litres of O2 at a pressure of 200 bar.
What is the purpose of the O2 pressure reducer?
Reduces high pressure O2 from the oxygen cylinder into medium pressure O2.
What is the constant dosage of O2 supplied to the breathing loop?
1.5 to 1.9 L/min.
What happens when excessive breathing demand occurs?
Additional medium pressure O2 is supplied to the breathing loop by the minimum (demand) valve.
What is the rate at which the manually operated by-pass valve injects O2 into the breathing loop?
50 L/min.
How is carbon dioxide (CO2) removed from exhaled air?
Using soda lime located in the refillable CO2 scrubber canister.
What effect does the scrubbing process have on inhaled air?
It produces heat which increases the temperature of inhaled air.
What is used to cool the heated air before inhalation?
An air cooler that uses ice.
What helps ensure low breathing resistance in the BG4?
- Cooled air
- Larger diameter breathing hoses
What occurs if the breathing loop becomes over pressurized?
A pressure relief valve vents exhaled air.
How is accumulated moisture released from the breathing loop?
Via the moisture relief valve.
What does the electronic monitoring system in the BG4 comprise?
- Sensor
- Switchbox
- Sentinel
What does the electronic monitoring system continuously measure?
The pressure in the O2 cylinder.
What happens when residual (low) pressure is reached in the BG4?
An alarm is generated.
What design aspect of the backplate and harness assembly enhances wearer comfort?
Ergonomic design.
What do quick connect latches and easy adjust straps reduce?
The amount of time and energy the wearer must expend in donning and doffing the apparatus.
What is the main function of the Sentinel?
To provide information to the wearer regarding O2 cylinder pressure, time until low pressure alarm, high pressure leak test results, battery test results, low pressure alarms, and no pressure warning.
What does the Sentinel indicate regarding O2 cylinder pressure?
It indicates the current O2 cylinder pressure.
What does the Sentinel display about time?
It displays the time remaining until the first low pressure alarm.
What does the Sentinel indicate about the high pressure leak test?
It indicates the results of the high pressure leak test.
What does the Sentinel provide information on regarding the battery?
It indicates the results of the battery test.
What type of alarms does the Sentinel provide?
It provides low pressure alarms and a no pressure warning.
At what pressure does the first low pressure alarm activate?
55 bar.
What occurs during the first low pressure alarm at 55 bar?
The Sentinel beeps intermittently for 30 seconds and red LEDs flash.
At what pressure does the second low pressure alarm activate?
10 bar.
What happens during the second low pressure alarm at 10 bar?
The Sentinel beeps continuously and the red LEDs flash until it switches off.
What does the no pressure warning indicate?
It indicates that the O2 cylinder is closed or empty.
What pressure level triggers the no pressure warning?
<1.40 mbar.
What sound does the Sentinel make for the no pressure warning?
It beeps once.
What visual indication accompanies the no pressure warning?
The red LEDs flash.
What is the function of the pressure relief valve?
Prevents over-pressurization of the breathing loop.
Where is the pressure relief valve mounted?
Physically mounted to the frame of the BG4 at the breathing bag.
How does excess air exit the breathing loop?
Routed from the breathing loop at the scrubber canister along a clear tube to the valve.
What happens when there is too much air in the breathing loop?
The breathing bag over-inflates, pushing the pressure plate against the relief valve tappet.
At what pressure range does the pressure relief valve open?
Between 2.0 and 5.0 millibars (mbar).
What is the consequence of the pressure relief valve opening?
Expels the excess air into the atmosphere.
Which components of the pressure relief valve are interchangeable?
Internal components with those of the moisture relief valve.
What connects the Pressure Relief Valve to the Switchbox?
A blue line.
Fill in the blank: The pressure relief valve is part of the _______.
[breathing loop]
What is the function of the O2 pressure reducer?
Distributes high and medium pressure O2 to the breathing loop
The O2 pressure reducer is crucial for regulating oxygen flow and pressure in breathing apparatus.
What activates the electronics of the O2 pressure reducer?
High pressure from the O2 cylinder
This activation is essential for the proper functioning of the breathing system.
What is the medium pressure output range of the O2 pressure reducer?
4.0 bar to 4.4 bar
This range is vital for maintaining safe and effective oxygen delivery.
At what pressure does the relief valve activate in the O2 pressure reducer?
6.0 bar
This prevents over pressurization, ensuring safety during operation.
What is the flow rate of O2 replaced from the breathing loop under normal operation?
1.5 to 1.9 L/min
This constant dosage is important for maintaining adequate oxygen levels.
What happens when the minimum (demand) valve is activated?
Medium pressure O2 is supplied to the valve at a flow rate of 80 L/min
This allows for increased oxygen delivery when needed.
What flow rate does the manually operated by-pass valve inject O2 into the breathing loop?
50 L/min
This feature provides an additional oxygen supply when required.
How is the O2 pressure reducer connected to the O2 cylinder?
By a hand-tightened connector
This ensures a secure and leak-free connection.
Where is the minimum valve located?
On the right side of the breathing bag
What triggers the activation of the minimum valve?
Breathing loop pressure drops to between 0.1 and 2.5 mbar
What happens when the minimum valve is activated?
Injects additional O2 into the breathing loop
What causes pressure drop in the breathing loop?
Excessive breathing demand or a leak in the system
How much O2 does the minimum valve provide to the breathing loop?
Approximately 80 L/min
What color is the medium pressure O2 line connecting the minimum valve to the O2 pressure reducer?
Yellow
Which component is connected to the constant dosage metering orifice via a blue medium pressure O2 line?
Air cooler
What does the clear line connect in the system?
Pressure Relief Valve to the Switchbox
Fill in the blank: A clear O2 line joins the manually operated bypass valve to the ______ in the O2 pressure reducer.
constant dosage metering orifice
What colors of lines carry O2 from the pressure reducer to various components of the BG4?
Yellow, blue, and clear
What is the function of the breathing bag assembly in the BG4?
Holds the breathing bag in place with a retaining bar
The breathing bag assembly includes essential components for maintaining a proper breathing environment.
What components are attached to the breathing bag?
- CO2 scrubber canister
- Air cooler
- Minimum valve
- Moisture relief valve
These components work together to regulate the air quality within the breathing loop.
What is the capacity of the breathing bag?
5.5 litres
The breathing bag is designed to accommodate a significant volume of air for breathing.
What material is the breathing bag made from?
Yellow puncture-resistant polyurethane
This material is chosen for its durability and resistance to punctures.
How does the breathing bag generate positive pressure?
With the aid of two large springs
The springs assist in maintaining airflow throughout the breathing loop.
What components make up the breathing bag assembly?
- Two springs
- Pressure plate
- Breathing bag
These components work together to ensure effective breathing mechanics.
Where is the pressure relief valve mounted?
Physically mounted to the frame of the BG4 at the breathing bag
Its location is critical for monitoring and controlling pressure within the breathing loop.
What is the purpose of the pressure relief valve?
Prevents over-pressurization of the breathing loop
This is vital to ensure the safety and functionality of the breathing system.
What happens when too much air enters the breathing loop?
The breathing bag over-inflates, pushing the pressure plate against the relief valve tappet
This action opens the valve to expel excess air into the atmosphere.
At what pressure does the pressure relief valve open?
Between 2.0 and 5.0 millibars (mbar)
This pressure range is crucial for maintaining optimal operation of the breathing bag.
Are the internal components of the pressure relief valve interchangeable with any other valve?
Yes, with those of the moisture relief valve
This interchangeability allows for easier maintenance and repairs.
What connects the Pressure Relief Valve to the Switchbox?
A blue line
This connection integrates the breathing loop with the electronic control system.
What is the function of the moisture relief valve?
Drains moisture that accumulates in the breathing bag
The valve activates when the pressure in the moisture trap is between 15 - 25 millibars (mbar) and drains moisture into the atmosphere.
Where is the moisture relief valve located?
At the bottom of the breathing bag
It is attached to the frame of the BG4 with a retaining clip.
What prevents soda lime particles from entering the moisture relief valve?
A sintering filter
The filter is located at the top of the valve housing.
True or False: The internal components of the moisture relief valve are interchangeable with those of the pressure relief valve.
True
What is the purpose of the air cooler in the breathing loop?
Lowers the temperature of the inhaled breathing air
This reduces the physical strain on the wearer.
Where is the air cooler located in relation to the breathing bag and inhalation hose?
Between the breathing bag and the inhalation hose
It is secured to the frame by a roller clamp.
What type of system enriches the breathing loop with O2 at the air cooler?
Constant dosage system
Fill in the blank: The air cooler is a simple _______ that helps regulate the temperature of inhaled air.
[heat exchanger]
What is the connection method between the air cooler and the inhalation hose?
Quarter turn bayonet ring
What feature of the ice chamber prevents condensate and melted ice from entering the body of the BG4?
Cover on the ice chamber
How is the air cooler attached to the breathing bag?
Sleeve and collar connection
What are the molding seams on the hose connection used for?
Ensure proper alignment with the inhalation hose during assembly
What happens to the air cooler when filled with preformed ice?
Lowers the temperature of the inhaled breathing air
What is the breathing rate mentioned in the text?
30 L/min
At what ambient temperature can the breathing air temperature be maintained below 37°C?
24°C (75°F)
For how long can the breathing air temperature be maintained below 37°C?
Up to 4 hours
What factors affect how long the ice lasts and the air cooler remains effective?
Air temperature and breathing rate
What will reduce available service time for the ice packs?
Ice packs which are small, broken up or not completely frozen
What temperature can the breathing air rise above if ice packs are not effective?
37°C (98°F)
What modification is required for the BG4 Plus air cooler?
Must be modified to fit into the older BG4
