First, the definition of the valve:

"Valve" is defined in the fluid system, used to control the direction of flow, pressure, flow rate of the device. Valve is to make the piping and equipment inside the medium (liquid, gas, powder) or stop the flow, and can control the flow of the device.

Second, according to the role of different open and close the valve, the valve of the classification of many, here are the following.

1 according to the role and use classification

(1) cut-off valve: the valve shut-off valve, also known as closed-circuit, its role is to connect or disconnect the pipeline media. Cut-off valve category include gate valves, globe valves, plug valves, ball valves, butterfly valves and divide.

(2) Check valves: Check valves, also known as a one-way valve or Stove Valve and its role is to prevent the media back in the pipeline. Pump water off the bottom valve check valve category also belong.

(3) safety valve: the role of safety valve to prevent the pipe class or device in the medium pressure exceeds the set value, so as to achieve security objectives.

(4) control valve: valve types including control valve, throttle valve and the valve, and its role in the regulation of media pressure, flow, and other triple numbers.

(5) shunt valve: shunt valve includes a variety of distribution valves and steam traps, etc., whose role is assigned, separation or mixed media in the pipeline.

Valve introduces the basic knowledge, use and maintenance

Valve and its use
The first chapter the basics of the valve
Basic knowledge about the valve section
Overview: The valve is a control device for fluid piping. Its basic function is to connect or disconnect the flow of the pipeline medium, changing the direction of medium flow, medium pressure and flow regulation, piping and equipment to protect the normal operation.
First, the classification of the valve:
Can be divided according to purpose and role:
1, the cut-off valve: truncated or connected media channels. Such as: gate valve, globe valve, ball valve, butterfly valves, diaphragm valves, plug valves.
2, check valve: to prevent a pipeline in the media back.
3, the distribution valve: to change the flow of media, distribution, separation or mixed media effect. Such as the distribution of valves, steam traps, ball valves.
4, the control valve: regulation of media pressure and flow. Such as valves, control valve, throttle valve.
5, the safety valve: the pressure to prevent the device exceeds the specified value in the media, to provide over-pressure safety protection.
Second, the basic parameters of the valve
1) the valve nominal diameter (DN) 2) the valve of the nominal pressure (PN)
3) valve pressure and temperature levels: when the valve temperatures in excess of the nominal pressure of the base temperature, the maximum working pressure must be reduced accordingly.
4) the pressure of the valve unit conversion:
According GB1.1-83 provides that the original use of Kgf/mm2, Kgf/cm2 abolished in favor of MPa. The conversion relationship is:
1 Kgf/cm2 = 0.0980665MPa 1 MPa = 10.135Kgf/cm2
5) valve Applicable medium:
Industrial valves used in petroleum, chemical industry, metallurgy, electricity, nuclear and other industries, through the medium of gas (air, steam, ammonia, nitrogen, hydrogen, coal gas, liquefied petroleum gas, natural gas, etc.); liquid (water, ammonia, oils, acids, bases, etc.). Some have a strong corrosive, as well as the strong-radiation.
Third, the nominal pressure classification:
1) vacuum valve: pressure less than standard atmospheric pressure. 2) low-pressure valve: nominal pressure PN ≤ 1.6MPa. 3) valve: nominal pressure PN is 2.5 ~ 6.4 MPa. 4) high-pressure valve: nominal pressure PN is 10 ~ 80.0 MPa. 5) high pressure valves: nominal pressure PN ≥ 100 MPa.
Fourth, the operating temperature:
1) at room temperature valve: for medium temperature -40 ℃ ≤ t ≤ 120 ℃ 2) in the temperature valve: for medium temperature 120 ℃ <t≤450℃ 3)高温阀:用于介质工作温度t> 450 ℃ 4 ) cryogenic valve: for medium temperature -100 ℃ ≤ t ≤ -40 ℃ 5) cryogenic valve: for medium temperature t <-100 ℃
Fifth, connection method:
1) Threaded valves: valve with internal or external thread and pipe thread connections. 2) Flanged valves: valve with flange, with the pipe flange connection. 3) Welding valves: valve with welding groove, and soldered pipe connections. 4) Clamp valves: valve with clip mouth, and the pipe clamp connections. 5) The sleeve valves: the use of card sets and pipeline connections. 6) connecting the valve to the folder: bolt directly to the valve and two pipes are connected together through the folder.
Section II, the valve model methodology
First, the composition of the valve type the following order:
   
Type code (1), transmission mode code (2), connection type code (3), structure type code (4), valve seat sealing surface material code (5), nominal value (6), body material code (7 .)
(1) the type of code (with Pinyin letters): gate Z, plug valves X, trap S, globe valve J, check valve H, valve Y, throttle L, valve A, the plunger valve U, ball Q, control valve T, diaphragm G, valve D, sewage valve P
Note: The low temperature (below -40 ℃) front valve Code D; insulation front of the valve code B; with the front bellows valve code W; anti-sulfur front of the valve symbol K.
(2) Transmission Code (Arabic numerals): electromagnetic moving 0, spur gear 4, the gas - hydraulic 8, electromagnetic - hydraulic 1, bevel gear 5, 9 electric, electric - 2 hydraulic, pneumatic 6, Worm 3 , hydraulic 7.
Note: The manual and the safety valve, pressure reducing valve, trap the code is omitted.
(3) connection type (Arabic numerals): 1 female, 2 male, 4 flange, weld 6, 7 on the clip, clamp 8, 9 sets of cards.
Note: including butt weld and socket weld

Knowledge of valve performance
Sealing performance
Valve sealing performance is part of the valve seal to prevent leakage of the medium of the ability of the valve it is the most important technical performance indicators. Sealing valve has three parts: opening and closing parts and the valve seat sealing surface between the two contact points; packing and the valve stem and stuffing box with the Department; body and bonnet of the connection.
Mobile media
Medium flow through the valve will generate pressure loss (both before and after the valve pressure difference), that is, the flow valve on the media have a certain resistance, medium to overcome the resistance of the valve will consume some energy. From energy conservation considerations, the design and manufacture of valves, valve to minimize the flow resistance of the medium.
Gate opening and closing force and torque
Opening and closing force and the valve opening and closing torque is turned on or off the force or torque to be applied. Close the valve, you need to make opening and closing parts and the valve seat sealing surface between the two seal than a certain pressure, but also to overcome between the stem and packing, between the stem and the nut threads, bearing at the stem end and other friction parts of the friction force, which must exert a certain force and closing torque off valve in the opening and closing process, the need to open and close the opening and closing force and moment of change, and its maximum is the ultimate in off transient or on the initial transient. Should strive to design and manufacture of valve closing force and closing to reduce the torque.
Opening and closing speed
Complete with valve opening and closing speed is a movement on or off the time required to represent. Generally open and close the valve speed is not critical, but in some cases there are special requirements for opening and closing speed, if requested on or off quickly, to prevent accidents, and some require the slow shut down to prevent water hammer, etc., which in the selection of valve type should be considered.
Sensitivity and reliability of the action
This refers to changes in the valve for the medium parameters, the sensitivity of the response accordingly. For the Pilot Safety Valve, reducing valve, regulating valve, the valve used to adjust the medium parameters and the safety valve, steam trap with a specific function such as valves, its function is very important to the sensitivity and reliability of the technical performance indicators.
Life
It indicates the durability of the valve, the valve key performance indicators and has great economic significance. Requirements to ensure the seal is usually expressed as the number of open and close, can also be used to indicate the use of time.
Valve Basics:
Nominal diameter: is valve with nominal diameter pipe connection channel. DN said.
Nominal pressure: is the mechanical strength of the valve design pressure. With the PN said.
Valve: used to connect or cut off the pipeline medium, not for regulating media flow. It is suitable for pressure, temperature, and a large diameter range, especially for large, medium diameter pipes.
Advantages: A fluid resistance. B open and close more effort. C medium flow direction is generally unrestricted.
Disadvantages: height of a large, open and close for a long time. Scratch the sealing surface is easy to produce. Valve stem by the structure and movement pattern: the next shot and the dark bar. Wedge and parallel.
Ram: rigid single gate, flexible single gate, double plate and so on.
Butterfly: With the valve stem with a circular rotating disc for opening and closing pieces, in order to achieve the opening and closing movement of the valve. It is mainly used to do cut-off valve can also be designed to regulate or cut and conditioning.
Advantages: A simple structure, small size and light weight. B: fluid resistance. CUHK diameter butterfly valve, fully open when the effective flow area larger. C to enable the rapid and relatively easy effort. D to achieve a good low pressure sealing. E adjusted performance.
Disadvantages: limited by the sealing material, the use of butterfly valves smaller range of pressure and temperature, most of the butterfly valve with rubber seals, rubber materials under temperature limit.
A, cut-off valve category: mainly used for streaming media, cut off or turned on. Including gate valve, globe valves, diaphragm valves, plug valves, ball valves, butterfly valves, etc.
B, control valve: primarily for regulating the medium flow and pressure. Include: control valve, throttle valve, reducing valve and so on.
C, non-return valve: used to prevent the media back, including the structure of the valve. Divided into: Lift, Swing, disc and diaphragm and other types.
D, shunt valve: for allocation, separation or mixed media. Including the distribution of various structures such as valves and steam traps.
E, relief valve category: security for overpressure protection. Including all types of safety valve.
Valves generally have the properties: sealing performance, strength properties, regulation, operation performance and circulation performance.
Valve consists of: a drive, sports organizations, the closure of parts, seals, fasteners and shell composition.
Valve: straight-through, DC-and right-angle type. Straight-through is the most common. But its maximum fluid resistance. DC-like fluid resistance, used for containing solid particles or the viscosity of the fluid.
Advantages: relatively simple valve structure, manufacturing and maintenance more convenient. ◎ sealing surface is not easy to wear, abrasion, seal better, longer life expectancy. ◎ When the valve closing stroke from smaller, shorter time from the closed valve height smaller. Disadvantages: ◎ large flow resistance. ◎ torque from the closed, open and close more laborious. ◎ flow direction is limited.
Cut-off valve structure: 1. Straight-through: a common structure, the maximum fluid resistance. 2 DC-style: fluid resistance, used for containing solid particles or the viscosity of the fluid. 3 Right Angle: The smaller diameter, higher pressure.
Throttle: by changing the flow channel cross-section to control the fluid pressure and flow are adjusted class, but because of its structural constraints, there is no valve adjustment feature, it can not replace the regulator valve.
Throttle valve opening and closing pieces of mostly conical streamlined. Its structure is simple, easy to manufacture and maintenance, and low cost. Regulation accuracy is not high, can not replace the valve. Can not be used as a cut-off valve, non-sealing performance requirements.
Ball: is the sphere with a circular hole made hoist parts, with the stem rotating sphere, in order to achieve the opening and closing movement of the valve.
Advantages 1 fluid resistance when fully open ball channel, body channel and connecting pipe cross-sectional area equal to, and connected into a straight line, the medium flow through the valve, rather with a straight pipe flow, the ball valves in various types of valve fluid path of least resistance. (2) open and close rapidly open and close when the ball just turn 90 °, easily and quickly. 3 structure is relatively simple, small, light weight. In particular, it is far less than the height of gate and globe valves. 4 good sealing performance. Valve commonly used flexible soft seals.
Disadvantage smaller temperature range. Generally soft seal ball valve, the use of temperature limited by the material. The development of sealing materials and metal seal valve ball valve to expand the application temperature range.
Valve structure: According to the structure of the sealing mechanism can be divided into a floating ball valve and ball valve fixed. The former mainly by medium pressure ball pressed on the seat in the export side, the use of pressure and diameter limited. The latter sphere installed in the valve body on the upper and lower bearing support, the location of the fixed sphere, the role is sealed by spring pressure and media pressure to seat the ball and achieve. Thus a smaller opening and closing torque, for use in high pressure and large diameter applications.
Safety valve selection
A distinctive feature of high-quality safety valve:
1, the valve mounting dimensions meet the national standards.
2, security. Valve is carried out according to relevant national standards and seal strength test trial to ensure that the mechanical properties of the valve in line with national standards
Requirements.
3, the sensitivity. Pressure off of the valve, the pressure back seat in the national standards and user requirements within the take-off pressure is accurate, rapid take-off
, Back seat pressure stable.
4, sealing. After sealing the valve back seat performance, no leakage.
5 emissions requirements with safety valve, the valve back off the heavy volume to the requirements of national standard mechanical characteristics of the valve sealing performance and
Other features remain stable, does not change.
Second, the selection of Chengde high pressure valve fitting Limited safety valve and reasonable price, good quality, prompt delivery, good after-sales service.
Third, the use of low lift type safety valve, all-Kai style, holding the safety valve. Pressure: PN1.60 ~ 32.00Mpa; diameter: DN15 ~ DN200mm.
Is a safety valve for pressure equipment, container or piping of automatic pressure release device. When the pressure rises within the protection system than allowed
Xu value, the valve automatically opens, and expel some of the excess media to prevent the system pressure continues to rise, when the system pressure is reduced to a specified value
, The valve automatically closed by the order to ensure system uptime. How to properly use the safety valve is directly related to the use and operation of the unit cost
For personnel and equipment safety, the safety valve of choice below briefly describes a few key points:
1, the working pressure level (pressure level) is determined.
Safety valve working pressure and working pressure and working pressure of the spring class has a different meaning, can not be confused. Working pressure is
Before the safety valve under normal operation the valve static pressure, it is protected with working pressure of the system or the same devices. The working pressure of the spring-level is
Is a spring that allows the use of a working pressure range, the pressure within the valve's opening pressure (ie, the set pressure) can pass
By changing the amount of compression spring preload adjust. The same nominal pressure of safety valve, according to the spring design requirements can be divided into different work
For the pressure level. Specific division of the table below, divided on the premise that work stress can be enough to ensure that all the pressure of the upper and lower level are able to meet the standard
Action under the standard performance.
Selection of safety valve should be determined according to the required valve opening pressure of work stress level.
2, the choice of conditions
(1) the selection of DN
The safety valve of nominal protection system should be required to determine emissions. Several whole-valve should be greater than the rated displacement and possible access
Near the necessary emissions. Is necessary to protect the emission system is abnormal overpressure system to prevent excessive overpressure when the quality of the intervention must be excluded, it is by the system or equipment operating conditions, capacity and may lead to over-pressure and other factors to determine the reasons for .
(2) to determine the material
Selection of valve material should be considered medium temperature, working pressure, dielectric properties and materials technology, economy and other factors. Under normal circumstances the user can provide the safety valve unit according to my list of different types of sample temperature relief valve, pressure range and type of media used for representative selection. There are special requirements for materials, it can be ordered in consultation with me to solve.
(3) the selection of the special structure of the safety valve
1) with the choice of radiator valve
This type of valve is generally higher for medium temperature applications, in order to reduce the temperature of the spring chamber. Normally closed valve when the temperature exceeds 300 ℃, and with an open valve using temperature exceeds 350 ℃, the safety valve should be used with a heat sink.
2) bellows valve
Withstand the additional pressure on the back of the safety valve, and its back pressure changes of more than 10% of set pressure should be used in this safety valve. In addition to the use of corrosive media, the safety valve, spring and guide mechanism to prevent corrosion by the media, it should be used bellows safety valve.
3, the general safety valve Ordering Information
Order general safety valve should be marked the following items:
1) The safety valve of the type, nominal diameter, nominal pressure
2) The level or working pressure safety valve opening pressure (set pressure) value
3) Body material and the sealing surface material
4, a special safety valve specifications Ordering Information
When ordering special safety valve, safety valve should be specified in addition to the model, the nominal outside diameter and the opening pressure, still need to specify the following:
(1) safety valve discharge pressure and the back seat of the highest value of pressure (or open and close pressure) the minimum value;
(2) The protection system or equipment must be installed valve displacement and the number;
(3) the use of medium and heavy (liquid) or molecular weight (gas);
(4) the valve inlet medium temperature;
(5) back pressure valve to withstand the type and value;
(6) other requirements.