What are the Uses and Classifications of Valves?

The valve is the basic component in the piping system, a mechanical device used to control the flow, direction, pressure, temperature, etc. of the fluid medium in the flow.

The Purpose of the Valve:
The valve is the control device for the fluid line. It can cut off and connect the medium in the pipeline, prevent the backflow of the medium in the pipeline, adjust the pressure and flow of the medium in the pipeline, and change the direction of the medium flow in the pipeline. It is used for overpressure safety protection, discharge of excess medium, prevent pressure exceeding the specified value, gas-water separation, etc. Now the valve has been widely used as a general mechanical product.

The valve can be controlled by a variety of driving methods, such as manual, electric, pneumatic, hydraulic, electro-pneumatic, or electro-hydraulic linkage and electromagnetic drive, etc. It can be controlled by pressure, temperature, or other forms of sensing signals, required action, or not performing a simple on or off.

The Composition of the Valve:
The two important parts that make up the valve body are the valve body and the valve cover. The closed structure formed by them prevents the fluid from seeping out of the valve body.

Classification of Valves:

There are many types of valves. With the continuous improvement of the technological process and performance of various complete sets of equipment, the types of valves are still increasing, and there are many classification methods.

By automatic and drive:

1. Automatic valve: A valve that operates by itself depending on the ability of the medium (liquid, air, steam, etc.) itself. Such as safety valves, check valves, hydraulic valves, steam traps, air traps, and emergency shut-off valves.
2. Actuated valve: A valve is operated by hand, electricity, or hydraulic or pneumatic force. Such as gate valves, globe valves, throttle valves, butterfly valves, ball valves, plug valves, regulating valves, etc.

Classification by use and role:

1. Cut-off valve: Mainly used to cut off or connect the medium flow in the pipeline. Such as globe valve, gate valve, ball valve, plug valve, butterfly valve, diaphragm valve, etc.
2. Check valve type: Used to prevent the backflow of the medium. Such as various check valves of different structures.
3. Regulating valve: Mainly used to adjust the pressure and flow of the medium in the pipeline. Such as regulating valves, throttle valves and pressure reducing valves, etc.
4. Diverter valve: It is used to change the direction of the medium flow in the pipeline, and play the role of distributing, diverting, or mixing the medium. Distributing valves of various structures, three-way or four-way plug valves, three-way or four-way ball valves, and various types of steam traps, etc.
5. Safety valve: Used for overpressure safety protection, discharges excess medium and prevents the pressure from exceeding the specified value. Such as various types of safety valves.
6. Multi-purpose valve type: Used to replace two, three, or even more various types of valves. Such as the cut-off check valve, check ball valve, and cut-off check safety valve.
7. Other special valves: Such as blowdown valve, vent valve, coke cleaning valve, pigging valve, emergency shut-off valve, etc.

Classified by technical parameters:

1. Classification by nominal size:

• Small-diameter valve: Valve with nominal size DN≤40.
• Medium-diameter valve: Valve with nominal size DN50~300.
• Large diameter valve: Valve with nominal size DN350~DN1200.
• Extra-large diameter valve: Valve with nominal size DN ≥ 1400.

2. Classification by nominal pressure:

• Vacuum valve: A valve whose working pressure is lower than the standard atmospheric pressure.
• Low-pressure valve: Valve with PN≤16.
• Medium pressure valve: Valve with PN of 25~63.
• High-pressure valve: Valve with PN of 100~800.
• Ultra-high pressure valve: Valve with PN ≥ 1000.

3. According to the working temperature of the medium:

• High-temperature valve: T>450℃
• Medium temperature valve: 120℃≤T≤450℃
• Normal temperature valve: -29℃≤T＜120℃
• Low-temperature valve: -100℃≤T＜-29℃
• Ultra-low temperature valve: T＜-100℃

4. Classification by valve body material

• Non-metallic material valves: Such as ceramic valves, glass fiber reinforced plastic valves, and plastic valves.
• Metal material valves: Such as copper alloy valves, aluminum alloy valves, lead alloy flanges, titanium gold valves, Monel alloy valves, Hastelloy valves, cast iron valves, carbon cast steel valves, low alloy steel valves, and High alloy steel valve.
• Metal valve body lining valve: Such as lead-lined valve, plastic-lined valve, enamel-lined valve, rubber-lined valve, etc.

5. According to the connection method with the pipeline

• Flanged valve: A valve with a flange on the valve body and a flanged connection with the pipeline.
• Threaded valve: A valve with internal thread or external thread on the valve body and a threaded connection with the pipeline.
• Welded connection valve: The valve body has a welded joint and is connected to the pipeline by welding.
• Clamp-connected valve: A valve with a clamp port on the valve body and a clamp connection with the pipeline.
• Valves connected by ferrules: Valves used for connecting ferrules and pipes.

6. Classification by manipulation:

• Manual valve: A valve operated by manpower with the help of a handwheel, handle, lever or sprocket, etc. When a large torque needs to be transmitted, reduction devices such as turbines and gears can be used.
• Electric valve: A valve operated by an electric motor, electromagnetic or other electrical devices.
• Hydraulic or pneumatic valve: A valve operated by the pressure of the liquid or air.

Classification by structure special:

1. Truncated gate: The closing member moves along the centerline of the valve seat.
2. Gate shape: The closing member moves in a direction perpendicular to the centerline of the valve seat.
3. Plugs and balls: The closures are plungers, cones, or balls that rotate around the axis of the province.
4. Swing: The closing member rotates around an axis outside the seat.
5. Butterfly: The structure in which the disc of the closing member rotates around the axis inside the valve seat or the axis outside the valve seat.
6. Spool type: The closing member slides in the direction perpendicular to the channel.

Classified by the structural principle:

Gate:

• Wedge gate valve.
• Lifting stem gate valve.
• Swing stem gate valve.
• Quickly open and close the gate valve.
• Shrink gate valve.
• Parallel gate valve.

Wedge gate valve:

• Single gate valve.
• Double gate valve.
• Resilient gate valve.

Parallel gate valve - single plate parallel / double plate parallel:

• The lift rod has a guide hole.
• The lift rod has no guide holes.
• The rotating rod has a guide hole.
• The swivel rod has no guide holes.

Butterfly valve:

• Centerline Butterfly Valve
• Eccentric butterfly valve

Eccentric butterfly valve:

• Single eccentric butterfly valve.
• Double eccentric butterfly valve.
• Triple eccentric butterfly valve.

Rotary valve:

• Ball valve.
• Spindle valve.
• Plug valve.

Ball valve:

• Floating ball valve.
• Secure the ball valve.
• Elastic ball valve.

Plug valve:

• Pressure-balanced plug valve.
• Tight-type plug valve.
• Block-type plug valve.
• Self-sealing plug valve.
• Oil-sealed plug valve.

Shut-off valve:

• Upper threaded stem.
• Lower threaded stem.
• Straight-through.
• Triangle.
• DC type.
• Plunger.
• Needle shape.

Throttle valve:

• Grooved disc.
• Window disc.
• Plug disc.

Check valve:

• Swing check valve (single/multiple).
• Lift check valve.
• Axial flow check valve.
• Butterfly check valve (single plate/multi-plate).
• In-line check valve.
• Nozzle check valve.
• Drain check valve.
• Slowly close the check valve.
• Diaphragm check valve (cone/ring).
• Ball check valve (single-ball/multi-ball).

Lift check valve:

• Foot valve.
• Spring load.
• Spring-loaded ring valve.
• Multiple annular flow rates.

Safety valve:

• Heavy hammer.
• Spring loaded.
• Pulse.
• Micro-start.
• Full start.
• Fully enclosed.
• Semi-closed.
• Open.

Pressure reducing valve

• Piston-type relief valve.
• Diaphragm pressure-reducing valve.
• Airbag type pressure-reducing valve.

Steam Traps:

• Mechanical steam traps.
• Thermostatic steam traps.
• Thermodynamic steam traps.

Mechanical steam traps:

• Free float.
• Lever float type.
• Free semi-floating ball type.
• Open down float type.
• Open up float type.

Thermostatic steam traps:

• Bellows type.
• Capsule type.
• Bimetallic sheet.

Thermodynamic steam traps:

• Disc type.
• Pulsed.
• Labyrinth or orifice plate type.

Diaphragm valve:

• Deadline.
• Roof style.
• Ram type.

Multipurpose valve:

• Shut off the check valve.
• Stop checking the safety valve.
• Check the ball valve.

Regulating valve:

• Pneumatic regulating valve.
• Electric regulating valve.
• Manual adjustment valve.

Pneumatic control valve:

• According to the pneumatic actuator structure: Membrane/piston/long stroke/rolling membrane actuator.
• According to the adjustment form: Adjustment type/cut-off type/adjustment cut-off type.
• According to the movement form: Straight stroke/angular stroke.
• According to the shape of the valve core: Flat plate / plunger / window / sleeve / multi-plate / eccentric / butterfly / spherical.
• According to the flow characteristics: Straight line / equal percentage / parabola / quick opening.
• According to the form of the upper bonnet: Ordinary type/heat dissipation (absorbing) type / long neck type/bellows sealing type.

Electric regulating valve:

• According to the form of electric actuator: Angular stroke/linear stroke/multi-turn type.
• According to the form of accessories: Servo amplifier/limit switch.
• According to the flow characteristics: Straight line / equal percentage / parabola / quick opening.
• According to the form of the upper cover: Ordinary type/heat dissipation (absorbing) type / long neck type/bellows sealing type.

Manual regulating valve - according to valve shape:

• Conical
• Cylindrical.

There are many types of valves, and they have different functions and applicable fields. You can choose the appropriate valve type according to your needs.

Reference: kknews