Positive pressure air respirator is mainly composed of high pressure air cylinder and cylinder switch, pressure reducer, quick connector, positive pressure air supply valve, positive pressure full face mask, gas source pressure gauge, gas cylinder residual gas alarm, and medium pressure It consists of safety valve, positive pressure exhalation valve, back support, shoulder strap, waist belt and other components.
1.High pressure gas cylinder and bottle valve
(1) High pressure gas cylinder material
High-pressure gas cylinder materials include high-strength steel, ultra-high-strength steel, carbon fiber and Kevlar fiber.
(2) Structure of carbon fiber cylinder
Carbon fiber composite gas cylinders are made of high-strength fibers such as aluminum alloy liners, external carbon fibers, glass fibers, and epoxy resin layers.
The aluminum alloy liner is manufactured according to the US Department of Transportation's CFR178.463, AL manufacturing standard, 100% inspection, inspection items: wall thickness, straightness, coaxiality, smoothness and hardness. The main winding layer is filament carbon fiber, and the outer layer uses glass fiber and epoxy resin layers to increase impact resistance and wear resistance.
(3) Damage
Level 1: shallow depth to resin layer;
Level 2: Scratch to glass fiber, depth <0.25mm (white) resin for repair.
Three levels (discarded): 1,> 0.25mm (dark gray);
2. Strong acid and alkali corrosion places
3.The horizontal projection length of the scratch is 3/4 of the bottle
(4) Cylinder valve
The rotation of the handwheel opens or closes the valve of the high-pressure gas cylinder.
The EN-137 and GA-124 standards require that the cylinder valve handwheel has a structure to prevent false closing. Cylinder valve outlet G5 / 8 female thread.
At present, various cylinder valves can be divided into three types according to their appearance: vertical, horizontal, and horizontal with a meter. The cylinder valve is equipped with a safety diaphragm. When the pressure in the cylinder rises to 40-42 MPa, the pressure is automatically released, which can prevent the cylinder from bursting due to the high pressure in the cylinder and avoid personal injury.
2.Integrated pressure reducer
Reducer assembly
The pressure reducer assembly includes a pressure reducer, a medium pressure safety valve, an air source residual gas alarm, a pressure display device, and an air output duct (medium pressure pipe). The function is to reduce the pressure of high pressure gas to 0.7 MPa, and continuously Supply the right amount of air to meet the breathing needs of the human body. When the pressure of the air source is between 3-30MPa, the pressure of the pressure reducer chamber is 0.7 ± 0.15MPa. At this time, the maximum output flow rate is not less than 3001 / min.
â‘ Reducer
The pressure reducer is generally made of brass or aluminum alloy as the material of the shell, and its internal structure can be divided into two types: piston type and diaphragm type. Regardless of piston type or diaphragm type, it can be divided into two types: constant pressure output and non-constant pressure output, so the pressure reducer can be divided into four types: constant pressure piston type, non-constant pressure piston type, and constant pressure diaphragm type. 2. Non-constant pressure diaphragm type.
The structure and principle of non-constant pressure piston are introduced.
The working principle of the reducer is shown in the figure. The principle of the piston pressure reducer is to control the piston to move up and down through the pressure adjustment of the spring pressure and the gas pressure balance of the intermediate pressure chamber B, thereby driving the valve stem to make the gap between the valve stem and the valve seat reduce or increase, and control the The amount of air in the medium pressure chamber guarantees an output pressure of 0.7 MPa. When the wearer stops breathing, when the pressure reducer gas output is zero,
As the pressure of the gas in the medium pressure chamber B rises, the piston 1 will move upwards, and the high pressure gas will enter the medium pressure chamber, and the pressure in the medium pressure chamber will rise accordingly, pushing the piston to close the high pressure valve until between the valve stem 10 and the valve 11. The gap was reduced and Zui finally closed completely. When the wearer inhales, the air pressure in the medium pressure chamber will decrease, and the pressure regulating spring will push the piston to open the high pressure valve to achieve a new balance.
When the wearer inhales, the air pressure in the medium pressure cavity will decrease, and the diaphragm will bend inward under the elastic force of the main balance spring, which will push the ejector rod, open the high pressure valve, and high pressure gas enters the medium pressure cavity. When the wearer stops inhaling, the air pressure in the medium pressure chamber rises accordingly, pushing the diaphragm to reset and closing the high pressure valve to achieve a new balance.
The non-constant pressure output pressure reducer's high-pressure valve head directly bears on the high-pressure gas. As the high pressure changes, the force on the valve head changes accordingly. Therefore, the output pressure is not constant pressure. It has a simple structure and is easier to maintain than a pressure reducer with a constant pressure output. Therefore, there are still some air breathing apparatus pressure reducers that use a non-constant pressure reducer.
The high-pressure valve head of the constant-pressure regulator does not rest on the high-pressure gas, and its output pressure does not change with the change of the air source pressure, so that the air supply valve maintains constant pressure input, the suction resistance is relatively stable, and the wearer breathes for a long time. It is not easy to fatigue, and is currently a pressure reducer popular with wearers.
â‘¡Medium pressure safety valve
The function of the medium pressure safety valve is that when the pressure reducer loses the pressure reducing effect on the high pressure air (such as the pressure reducing spring or the diaphragm, the valve is damaged), the medium pressure safety valve is opened, and the high pressure air is released after the pressure of the safety valve is maintained. Low pressure output, avoiding high pressure air output directly, accidents occur. It is required that when the pressure in the pressure reducing chamber is (1 ± 0.2) MPa, the medium pressure safety valve should be opened.
The working principle of the pressure safety valve is shown in the figure. The spring force of the medium pressure safety valve spring 4 has been adjusted according to technical requirements to ensure that when the pressure in the pressure reducer chamber is normal, the medium pressure safety valve is closed and airtight. When the pressure in the pressure reducer chamber is out of control, the pressure acting on the valve The force is greater than the force acting on the valve by the spring 4. The valve opens, and the gas in the decompression chamber enters the medium pressure safety valve, and is discharged through the small hole in the adjustment cap. When the pressure in the decompression chamber returns to normal, the valve is closed and kept airtight.
â‘¢Air source residual gas alarm
The function of the air source residual gas alarm is to send an alarm sound when the pressure in the cylinder drops to 5 ± 1MPa to remind the wearer to quickly evacuate the fire.
The gas pressure PA in the high-pressure chamber A acts on the opening *, which causes the compression alarm adjustment spring to move to the right, so that the opening * and the valve pad are in contact with each other to ensure gas tightness. When the gas pressure in the high-pressure chamber A drops to a certain value, the force of the PA on the opening * is smaller than the force of the alarm adjustment spring on the opening *, and the opening * moves to the left; the opening * comes out of contact with the valve pad, The high-pressure chamber gas will emit an alarm sound when the residual gas alarm is turned on * and flows into the gas source.
From the sound of the alarm to the complete exhaustion of the gas in the cylinder, it is calculated at a medium labor intensity of 30L / min. If a 5L cylinder is used, it can continue to be used for 6 to 10 minutes. When the wearer hears the alarm sound, he should evacuate the scene immediately.
The nominal use time is calculated according to the following formula.
Gas cylinder volume (L) X cylinder working pressure (MPa)
Nominal use time = ---------------------------------
30 (L / min) X0.098 (MPa)
In the formula:
30 (L / min) refers to the amount of air consumed per minute by the medium labor intensity of related industries in China.
The use time is affected by various factors and is different from the nominal use time. The gas consumption for different users and use conditions is different. The greater the work intensity, the faster the gas consumption in the cylinder.
3.Air source pressure indicating device
The gas source pressure indicating device is composed of a high-pressure conduit and a pressure gauge, which is used to indicate the gas storage pressure in the gas cylinder. Estimate the remaining operation time. The high-pressure conduit and pressure gauge housing are provided with a protective cover to prevent damage during impact.
4.Medium pressure pipe and quick connector
The medium-pressure tube is a rubber-clamped rubber tube. It forms a flexible air output duct with a quick connector. One end is connected to the air supply valve and the other end is connected to the pressure reducer.
The quick connector consists of two parts, the connector and the connector seat. When the two parts are not connected, the flexible catheter connector seat connected to the pressure reducer is locked, and even if the cylinder is opened, it will not leak air. When the quick connector connected to the gas supply valve is inserted into the connector seat, the locking mechanism is opened to allow gas to enter the gas supply valve.
Alarm
The technical indicators of audible alarm have the following three requirements:
a) Raising pressure
b) sound level and frequency range
c) Air consumption by alarm
The sound level of the alarm shall be greater than or equal to 90dB (A) within a range of 1 meter, and the frequency shall be maintained between 2000 and 4000HZ.
5. Air supply valve assembly The air supply valve assembly (air supply valve) is to reduce the medium-pressure gas output by the pressure reducer to the pressure that the human body can breathe again according to the inhalation of the wearer, for the wearer to breathe. Device, which is a key component of positive pressure air respirator, is composed of high-strength plastic casing, rubber diaphragm, rocker valve, positive pressure spring lever mechanism, etc., and its output port is connected with a full-face air input soft duct. With a gas supply capacity of more than 2001 / min. The structure diagram is shown in the figure.
The air supply valve assembly is directly installed on the mask, and a hose is connected to the medium pressure air pipe on the pressure reducer through a quick joint. The convex interface of the air supply valve is equipped with a ring washer. After connecting with the double loop line of the air supply valve interface on the mask, it forms a double seal, which is reliable.
The convex interface of the air supply valve is provided with a row of air supply holes. When in use, the gas is sprayed from the air supply holes to the inner surface of the window, which can quickly remove the mist or frost in the window.
Protected by a rubber cover on the air supply valve is a throttle switch. When the mask is removed from the face, press the middle part of the rubber cover with your thumb and press it completely, there will be a "click" sound, you can close the air supply valve, stop the air supply, and avoid wasting air in the bottle. When the mask is put on the face again to keep it sealed and inhale, the air supply valve will automatically open to supply air.
The air supply valve assembly is directly installed on the mask, and a hose is connected to the medium pressure air pipe on the pressure reducer through a quick joint. The convex interface of the air supply valve is equipped with a ring washer. After connecting with the double loop line of the air supply valve interface on the mask, it forms a double seal, which is reliable.
The convex interface of the air supply valve is provided with a row of air supply holes. When in use, the gas is sprayed from the air supply holes to the inner surface of the window, which can quickly remove the mist or frost in the window.
Protected by a rubber cover on the air supply valve is a throttle switch. When the mask is removed from the face, press the middle part of the rubber cover with your thumb and press it completely, there will be a "click" sound, you can close the air supply valve, stop the air supply, and avoid wasting air in the bottle. When the mask is put on the face again to keep it sealed and inhale, the air supply valve will automatically open to supply air.
The red knob on the air supply valve is an emergency flush valve, which has three functions:
â‘ When the air supply valve fails unexpectedly, through the manual knob, turn one-half turn in the direction indicated on the emergency flush valve, which can provide a constant air flow of at least 225L per minute, allowing air to flow directly into the mask;
â‘¡ In addition to emergency air supply, you can also use the outflow air to directly flush the dust and dirt inside the mask and air supply valve to avoid inhalation;
â‘¢ After closing the bottle valve, you can also drain the remaining air in the system pipe through the flush valve knob.
The supply valve has two states, one is the working state, and the other is the non-working state. The non-working state is changed to the working state by inhaling or manually pressing the lever.
In the non-operating state of the positive pressure air supply valve, the lever 11 and the diaphragm 10 are in a substantially parallel position, but inclined slightly upward. The lever 11 drives the diaphragm 10 to separate from the rocker contact 12 through the link 9. Under the action of the spring 5, the rocker valve 6 and the input valve 4 are stuck together.
During operation, medium pressure air P1 enters the input port. Under the action of pressure P1 and spring 5, valve 4 is kept airtight. Under the action of the starting force, the diaphragm is pushed by the atmospheric pressure PH to move toward the output port, and the lever 11 is used to drive the lever 11 to move in the same direction, so that the tension spring 2 exerts pressure on the diaphragm 10 and accelerates the movement of the diaphragm. Pressing the rocker head 12 swings the rocker 8 and compresses the spring 5 so that a gap is formed between the rocker valve and the valve seat, and the medium pressure gas enters under the diaphragm to generate air pressure P2. The diaphragm is in equilibrium under the action of atmospheric pressure, spring 2 tension, contact 12 thrust, and output pressure P2, maintaining a certain gap. At this time, the output flow is equal to the input flow.
When the output flow is increased or decreased, the air pressure P2 under the diaphragm will decrease or increase, the diaphragm will move down or up to make the rocker valve gap larger or smaller, and the air flow entering the supply valve will be automatically adjusted To make its output and input flow equal.
When the output flow rate is zero (ie, exhaled or holding state), the pressure of the diaphragm rises, the diaphragm moves up, the rocker valve is closed, and the air no longer enters below the diaphragm, leaving the diaphragm in the zero-output equilibrium position.
From the above analysis, it can be known that the diaphragm is balanced under the action of atmospheric pressure, spring 2 tension, output pressure P2, and thrust force. As long as an appropriate tension spring 2 is selected, the purpose of air pressure P2 under the diaphragm can always be greater than atmospheric pressure.
6.Mask assembly
The mask assembly (mask) is a device used to cover the face and isolate toxic and harmful gases from entering the human respiratory system (see figure). In order to ensure an effective seal with the human face, the mask assembly has three specifications: small, large, and extra large. it includes:
â‘ Front window: single eye, curved surface, injection molded from high-strength polycarbonate material, impact resistance, surface coated with wear-resistant layer, good light transmittance, no distortion. When in use, the air is sprayed to the inner surface of the window through a row of small holes on the air supply valve, which flushes out the fog generated by the window due to the temperature difference.
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