Valve is a fluid delivery system in the control unit, with diversion, closure, regulation, throttle, to prevent backflow, diversion or overflow relief and other functions. Valve as an important control element of the pipeline. Pipeline system to select the most suitable valve is very important, related to the safety of the pipeline, flow loss, cost, etc., must be familiar with the characteristics of the valve and the selection of the valve and the basis for the.
At present, China's valve industry has been able to produce the full range of gate valve, globe valve, check valve, ball valve, butterfly valve, throttle valve, plug valves, diaphragm valves, safety valves, regulating valves, steam traps and special valves in 12 categories; the maximum working pressure is 600MPa, the maximum nominal diameter of 5350mm, the highest the working temperature is 1200 DEG C, the lowest working temperature of -196, it is used to water, steam, oil, natural gas, corrosive media (such as the concentration of sulfuric acid, nitric acid, etc.) combustible materials (such as benzene, ethylene), toxic medium (such as hydrogen sulfide), and radioactive and explosive medium, medium (sodium metal, water loop etc.). Pieces of material bearing bronze valve, cast iron, ductile iron, high silicon cast iron, cast steel, forged steel, low-alloy steel, stainless steel, Hastelloy, Inconel Seoul, Monel alloy, duplex stainless steel, titanium alloy. And be able to support the production of a variety of hydraulic, pneumatic, electric valve drive device. The valve face of so many varieties and complexity of various conditions, to choose the most suitable for installation of piping system valve product, I think (Bret valve), should first understand the characteristics of the valve; second should master the steps and the basis for selection of the valve; the valve should follow the principle of choice.
First, the characteristics of the valve has the use of characteristics and structural characteristics
To determine the use characteristics of the main valve and the use of performance, is using the characteristics of the valve are: valve type (closed valves, regulating valves, safety valves etc.); product type (gate valve, globe valve, butterfly valve, ball valve etc.); valve main parts (valve body, valve cover, valve stem, valve, seal surface) material; valve drive pattern.
It identified the structural characteristics of the structure characteristics of the valve installation, repair, maintenance and other methods, there are structural characteristics: the connection structure of the valve length and overall height, and pipeline (flange connection, threaded connections, clamp connections, threaded connections, welded connections etc.); the sealing surface of the form (insert ring, thread ring, welding, spray welding, valve body); stem structure (rotating rod and the lifting rod).
Two, select the valve step
Clear the valve in the device or device, the use of the valve to determine the working conditions: the application of media, working pressure, working temperature and so on;
Determine the nominal diameter of the valve connection pipe and connection way: flange, thread, welding, etc.;
Determine the way to operate the valve: manual, electric, electromagnetic, pneumatic or hydraulic, electro-hydraulic linkage, etc.;
According to determine the selection of the valve housing and the inner parts of the material working temperature of pipeline transmission medium, working pressure: steel, carbon steel, stainless steel, alloy steel, stainless steel, cast iron, malleable cast iron, ductile iron, copper alloy etc.;
Select the type of valve: closed valves, regulating valves, safety valves, etc.;
Determine the type of valve: gate valve, globe valve, ball valve, butterfly valve, throttle valve, safety valve, pressure reducing valve, steam trap, etc.;
Determine the parameters of the valve: for the automatic valve, according to different needs to determine the flow resistance, discharge capacity, back pressure, etc., and then determine the nominal diameter of the pipe and the diameter of the valve seat;
Determine the geometric parameters of the valve: structure length, flange connection form and size, open and close the valve in the direction of the size of the height of the connection of the bolt hole size and quantity, the entire valve size and so on;
The use of existing information: valve product catalog, valve product samples, such as the selection of appropriate valve products.
Three, the choice of the basis of the valve
The use of the valve, the use of operating conditions and control methods;
The nature of the working medium: working pressure, working temperature, corrosion performance, whether it contains solid particles, the medium is toxic, whether it is flammable, explosive medium, medium viscosity, etc.;
Requirements for valve fluid characteristics: flow resistance, discharge capacity, flow characteristics, sealing grade, etc.;
Installation dimensions and dimensions requirements: nominal diameter, and pipe connections and connection size, size or weight restrictions, etc.;
Additional requirements for valve reliability, service life and performance of explosion-proof electrical equipment such as (in the selected parameters should pay attention: if the valve is to be used for control purposes, additional parameters must be determined as follows: the pressure operation method, maximum and minimum flow requirements, the normal flow down, shut down when the pressure drop, the largest valve and the minimum inlet pressure).
Bret suggested that according to the above options and steps of the valve, must also be the internal structure of various types of valves to a detailed understanding of rational and correct selection of the valve, so as to make the right choice of preferred valve.
The final control of the pipe is the valve. Valve opening and closing parts to control the flow of media in the pipeline, the shape of the valve flow channel with a certain flow characteristics, in the selection of the most suitable for the installation of the valve pipe system must take into account this point.