Author:Site Editor Publish Time: 2018-10-11 Origin:Site
The valve is an important component of petroleum and chemical plants, and the successful operation of any device is inseparable from the correct selection of valves. Therefore, the valve selection is neither just considering the characteristics of the valve itself, nor just the professional design of pipes.
l How to choose the valve reasonably
l General Selection Principles of Valves
In reasonable selection of valves, not only professional design work of the pipeline and equipment layout including the chemical process, the process system, the chemical safety, environment protection and energy saving are supposed to be considered, other factors such as the fluid property, the operating condition, the external environment, economical efficiency and related laws and regulations should also be taken into account.
A valve as a relatively complex monomer pipeline component, involves a variety of properties and description parameters which include the valves' types, the basic parameters such as the application standard, the nominal diameter, the nominal pressure level, the main material, etc., structural parameters such as the valves' body structure, the type of the internal part, the type of the end connection, the bonnet type, the mode of operation, etc., the main parts' material such as the valve seats' sealing material, the valve sealing surfaces' material, the valve bonnets bolts' material, the gaskets' material, etc., and other special requirements including inspection, structural and manufacturing requirements.
Most of these attribute parameters are determined by the engineering designer in order to eventually get the valve to meet the application requirements of the industrial production plant. The general valve selection is based on the same process, or learning from the experience of selecting similar devices.
According to the characteristics of each product production process, the general requirements for valve selection for various media are as follows:
The first principle: the first principle of valve selection is that the sealing performance of the valve should meet the requirements of the medium. That is, the internal leakage should meet the standard
GB/T13927-1992 "General valve pressure test", external leakage is not allowed at all.
Article 2: Correct selection of the type of valve. The correct choice of valve type is based on the selector's flow to the entire production process
The comprehensive estimate of the required process is a prerequisite. When selecting the valve type, the selector should first understand the structural characteristics and performance of each valve. Generally, the type of valve is selected as the cut-off of the copper sealing surface for medium and low pressure steam.
Valve, steam gate valve above DN200; butterfly valve on circulating water main pipe, rubber gate valve on branch pipe; butterfly valve on low pressure air main pipe, cutting pipe on branch pipe
Stop valve; general ball valve for liquid materials, etc.
Article 3: Determine the end connection of the valve. The first two are most commonly used in threaded connections, flanged connections, and welded end connections, where the price of the threaded connection is more than the flange connection.
It is much lower, generally a smaller diameter valve, which should be used first.
Article 4: Selection of the material of the main parts of the valve. Select the material of the main part of the valve, first consider the physical properties (temperature, pressure) and
Learning performance (corrosive) and so on. You should also know how clean the media is (with or without solid particles). In addition to this, it is also necessary to refer to the requirements of the relevant regulations of the state and the use department. Correct and reasonable selection of the material of the valve can be obtained
Get the most economical life and best performance of the valve. The order of valve body material selection is roughly in accordance with cast iron-carbon steel-stainless steel, and the order of sealing material is selected: rubber-copper-alloy steel-F4.
For the valve applied to conditions with stringent requirements, just determining the above-mentioned valves' attribute parameters may not be enough. Sometimes, we should also take control of or have requirements on other factors which can affect the quality of the valve in accordance with the specific medium condition. These influence factors include the processing requirement such as the materials' smelting requirement, the forming method, the heat treatment, etc., and the inspection test requirement such as the non-destructive testing, the strength test, the seal test, the corrosion test, etc.
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