How to choose the right valve in pipeline design?

How to choose the right valve in pipeline design?

Low intensity mechanical vibration is inevitable in the rotating equipment and flowing media of the unit. The mechanical vibration of the rotating equipment is transmitted to the system pipeline through the connecting parts and media of the system, thus posing a great threat to the safe operation of the unit. The hazards of pipeline vibration mainly include the following points:
Hazards of pipeline vibration

Low intensity mechanical vibration is inevitable in the rotating equipment and flowing media of the unit. The mechanical vibration of the rotating equipment is transmitted to the system pipeline through the connecting parts and media of the system, thus posing a great threat to the safe operation of the unit. The hazards of pipeline vibration mainly include the following points:
1. Harm to staff
Interference of staff’s vision, reduce the construction efficiency; Staff feeling tired; Leading to quality accidents and even safety accidents; Working in the vibration environment with considerable intensity for a long time may cause great harm or influence to the body of the construction personnel.
2. Hazard to buildings
Due to the different intensity and frequency of pipeline vibration, the building structure of some buildings will be damaged (common damage phenomenon is the foundation and wall cracking, wall peeling, stone sliding, heavy can make the building foundation deformation, etc.).
3. Harm to precision instruments
Pipeline vibration will affect the normal operation of precision instruments and instruments of the system, affect the accuracy and reading speed of the calibration of instruments and instruments, and even the reading can not be done. If the vibration is too large, it will directly affect the service life of instruments and instruments, and even be damaged; For some sensitive electrical appliances, such as sensitive relays, vibration will even cause its misoperation, which may cause some major accidents.
4. Damage to the system main device
Long-term pipeline vibration back will cause uneven output of the main equipment of the system, which will affect the mechanical properties and normal operation of the main equipment.
Causes of pipeline vibration and its elimination measures

The root cause of pipe vibration in unit system is the design, installation, operation and operation of the unit, and the pipe vibration directly reflects the mechanical properties and operation of the rotating equipment. When the system equipment and pipeline vibration, should be according to the specific situation, one by one analysis of the possible causes of vibration, find out the crux of the problem, and then through serious discussion and analysis to formulate feasible and effective measures to eliminate, reduce the vibration hazard to a relatively low limit.
The reasons for vibration of rotating equipment and pipeline and its elimination measures are analyzed as follows, which can be used as a reference for preventing and eliminating pipeline vibration in field construction.
1. Motor vibration causes pipeline vibration
2. Vibration of pump body leads to pipeline vibration
3. Pipe vibration is caused by other reasons in the water supply system
4. Other reasons of compressed air system lead to pipeline vibration
How to choose the right valve in pipeline design? In fluid piping systems, valves are control elements whose main role is to isolate equipment and piping systems, regulate flow, prevent backflow, regulate and discharge pressure. Because the piping system to choose the most suitable valve is very important, so, to understand the characteristics of the valve and the selection of valve steps and basis is very important.
In fluid piping systems, valves are control elements whose main role is to isolate equipment and piping systems, regulate flow, prevent backflow, regulate and discharge pressure. Because the pipeline system to choose the right valve is very important, so, to understand the characteristics of the valve and the selection of valve steps and basis is very important.
First, the characteristics of the valve
Use characteristics: it determines the main use of the valve performance and range of use, belong to the valve use characteristics are: valve category (closed circuit valve, regulating valve, safety valve, etc.); Product type (gate valve, globe valve, butterfly valve, ball valve, etc.); The main parts of the valve (valve body, cover, stem, disc, sealing surface) material; Valve transmission mode, etc.
Structural characteristics: it determines the installation of the valve, repair, maintenance and other methods of some structural characteristics, belonging to the structural characteristics are: the structural length of the valve and the overall height, and the pipe connection form (flange connection, thread connection, hoop connection, external thread connection, welding end connection, etc.); The form of sealing surface (insert ring, thread ring, surfacing, spray welding, body body); Valve stem structure form (rotating rod, lifting rod), etc.
Two, valve selection steps
Clear valve in equipment or device use, determine the working conditions of the valve: applicable medium, working pressure, working temperature and so on. (2) Determine the nominal size and connection method of the pipe connecting with the valve: flange, thread, welding, etc. (3) Determine the way to operate the valve: manual, electric, electromagnetic, pneumatic or hydraulic, electrical linkage or electro-hydraulic linkage. ¢Ü According to the pipeline transmission medium, working pressure, working temperature to determine the selected valve shell and inner parts of the material: gray cast iron, malleable cast iron, ductile iron, carbon steel, alloy steel, stainless acid-resistant steel, copper alloy, etc. ¢Ý Choose the type of valve: closed-circuit valve, regulating valve, safety valve, etc. ¢Þ 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 automatic valve, according to different needs to determine the flow resistance, discharge capacity, back pressure, and then determine the nominal diameter of the pipeline and the diameter of the seat hole. ¢à to determine the selected geometric parameters of the valve: structure length, flange connection form and size, open and close after the valve height direction of size, connection of the bolt hole size and number, the size of the entire valve shape. ¢á Use the available information: valve product catalog, valve product samples, etc., to select the appropriate valve products.
Three, valve selection basis
(1) the use of the selected valve, operating conditions and control mode. (2) The nature of the working medium: working pressure, working temperature, corrosion performance, whether it contains solid particles, whether the medium is toxic, whether it is flammable, explosive medium, medium viscosity and so on. ¢Û Requirements for valve fluid characteristics: flow resistance, discharge capacity, flow characteristics, sealing grade and so on. (4) Installation size and appearance size requirements: nominal diameter, connection with the pipe and connection size, appearance size or weight limit. ¢Ý Additional requirements for the reliability of valve products, service life and explosion-proof performance of electric devices.
According to the above selection of valve basis and steps, reasonable and correct selection of the valve must also be a detailed understanding of the internal structure of various types of valves, in order to be able to preferentially choose the valve to make a correct choice. The ultimate control of the pipeline is the valve. Valve opening and closing parts control the flow of media in the pipeline, the shape of the valve flow channel enables the valve to have a certain flow characteristics, which must be taken into account when selecting the valve suitable for installation in the pipeline system.
Four, the selection of valve should follow the principle
Valves for closing and opening media
The flow channel is a straight-through valve, the flow resistance is small, usually selected as a cut-off and open medium with the valve. Downward closed valve (globe valve, plunger valve) because of its tortuous flow path, flow resistance is higher than other valves, so less selected. Closed valves may be used where high flow resistance is permitted.
Valves for flow control usually choose valves that are easy to adjust flow as flow control. Downward CLOSING valves (such AS GLOBE valves) ARE SUITABLE FOR THIS PURPOSE BECAUSE THE SEAT size IS PROPORTIONAL TO THE STROKE OF THE SHUTOFF. Rotary VALVES (PLUG, butterfly, BALL valves) and FLEXURE BODY VALVES (PINCH, DIAPHRAGM) ARE ALSO AVAILABLE FOR THROTTLING CONTROL, but USUALLY ONLY IN a limited range of valve DIAMETERS. Gate VALVE IS A disc shaped gate to the circular seat port to do transverse motion, it only in close to the closed position, can better control the flow, so usually not used for flow control.
Valve for reversing shunt According to the needs of reversing shunt, this valve may have three or more channels. Plug and ball valves are more suitable for this purpose, and therefore, most valves used for reversing and diverting are selected as one of these valves. However, IN SOME CASES, other TYPES OF VALVES MAY ALSO BE USED AS commutATION diverTERS, PROVIDED THAT TWO or MORE VALVES ARE properly connected to EACH other.
Valve for medium with suspended particles when medium with suspended particles, suitable to use the closing part along the sealing surface of the sliding valve with wiping action. If THE SHUTOFF IS VERTICAL TO THE BACK AND FORTH MOVEMENT OF THE SEAT, PARTICLES MAY BE TRAPPED, SO THIS VALVE IS ONLY SUITABLE FOR BASICALLY CLEAN MEDIA UNLESS THE SEALING MATERIAL ALLOWS FOR PARTICLES TO BE EMBEDDED. Ball valves and plug valves wipe the sealing surface during opening and closing, so they are suitable for use in media with suspended particles.
At present, whether in petroleum, chemical industry, or in other industries of the pipeline system, valve application, frequency of operation and service are changing, to control or eliminate even low leakage, the most important, the most critical equipment is the valve. The ultimate control of the pipeline is the valve, the valve in all fields of service and reliable performance is.