What are the types of pneumatic mechanical valves? Detailed explanation of working principle

Types of pneumatic mechanical valves

In mechanical engineering, a mechanical valve is a device used to control the flow of fluids (liquids, gases, slurries) in pipes or other enclosures;controlled by a movable element that opens, closes or partially blocks an opening in a channel . There are seven main types of mechanical valves: ball, gate, needle, plug (cock), butterfly, poppet and spool.
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In a stop valve, the movable element M can be a conical plug or a disc mounted on a seat on the valve body;the disc can have a replaceable rubber or leather gasket, as in a domestic faucet. In a gate valve, the movable element is a wedge-shaped disc that rests against two tapered faces in the valve body. Needle valves have a long tapered needle in a tapered seat.
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A plug valve or stopcock is a conical plug with a hole perpendicular to its axis that fits into a conical seat in a mechanical valve body at right angles to the pipe. By rotating the plug, the hole is aligned with the pipe to allow flow or set at right angles to block the passage.
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A butterfly valve is a disc that pivots along one diameter;in the fully open position, the disc is parallel to the direction of flow. This type of damper in chimneys or warm air heating systems is also used for the air intake of carburetors on gasoline engines. passage;on hydroelectric turbines, such mechanical valves may be 20 feet in diameter or larger.



How pneumatic mechanical valves work

Compressed air is used to promote the movement of multiple groups of combined pneumatic pistons in the actuator, and the force is transmitted to the characteristics of the cross beam and the inner curved track to drive the hollow spindle to rotate. The compressed air disc is transmitted to each cylinder, and the position of the air inlet and outlet is changed to change the rotation of the spindle. direction, according to the requirements of the rotation torque required by the load (valve), the number of cylinder combinations can be adjusted to drive the load (valve) to work.

The two-position five-way mechanical valve is usually used with a double-acting pneumatic actuator. The two-position position is controllable in two positions: on-off. The five-way valve has five channels for ventilation, one of which is connected to the air source, and two are connected to the double-acting actuator. The air inlet and outlet of the outer air chamber of the action cylinder are connected, and the two air inlets and outlets of the inner air chamber are connected. The specific working principle can be referred to the working principle of the double-acting pneumatic actuator.

Precautions for daily maintenance of mechanical valves:

1. The valve should be stored in a dry and ventilated room, and both ends of the passage must be blocked.

2. Valves stored for a long time should be inspected regularly, dirt should be removed, and anti-rust oil should be applied to the processing surface.

3. After installation, regular inspections should be carried out. The main inspection items are: (1) Wear of the sealing surface. (2) Wear of the trapezoidal thread of the valve stem and valve stem nut. (3) Whether the packing is out of date and ineffective. If it is damaged, it should be replaced in time. (4) After the valve is repaired and assembled, a sealing performance test should be carried out.

Precautions for use and maintenance of mechanical valves:

1. The purpose of use and maintenance is to extend the service life of the valve and ensure reliable opening and closing.

2. The valve stem thread often rubs against the valve stem nut. Apply a little yellow dry oil, molybdenum disulfide or graphite powder for lubrication.

3. For valves that are not frequently opened and closed, the handwheel should be turned regularly and lubricant should be added to the valve stem thread to prevent seizure.

4. For outdoor valves, a protective cover should be added to the valve stem to prevent rain, snow, dust, and rust.

5. If the valve is mechanically inactive, lubricating oil must be added to the gearbox on time.

6. Always keep the valve clean.

7. Always check and maintain the integrity of other parts of the valve. If the fixing nut of the handwheel falls off, it must be matched and cannot be used randomly. Otherwise, the upper part of the valve stem will be worn in all directions, gradually losing the reliability of the fit, and even being unable to operate.

8. Do not rely on the valve to support other heavy objects, and do not stand on the valve.

9. The mechanical valve stem, especially the threaded part, should be wiped frequently, and the lubricant that has been soiled by dust should be replaced with new one, because the dust contains hard debris, which is easy to wear the thread and valve stem surface, affecting the service life. .