The difference between ductile iron Valve and cast steel gate Valve classification threatening the sealing surface of stainless steel valve several “evils”

The difference between ductile iron Valve and cast steel gate Valve classification threatening the sealing surface of stainless steel valve several “evils”

The opening and closing part of the cast steel gate valve is the gate plate. The direction of the motion of the gate plate is perpendicular to the direction of the fluid. The gate valve can only be fully opened and fully closed, but cannot be adjusted and throttled. The two sealing faces of the gate valve are wedge-shaped. The Angle of the wedge varies with the valve parameters, usually 50, and 2�ã52 ‘when the medium temperature is not high. The wedge gate valve can be made into a whole, called the rigid gate; It can also be made into a gate that can produce trace deformation in order to improve its technology and make up for the deviation of the sealing surface Angle in the process of processing. This kind of gate is called elastic gate.
The opening and closing part of the cast steel gate valve is the gate plate. The direction of the motion of the gate plate is perpendicular to the direction of the fluid. The gate valve can only be fully opened and fully closed, but cannot be adjusted and throttled. The two sealing faces of the gate valve are formed into a wedge. The wedge Angle varies with the valve parameters, usually 50, and 2¡ã52 ‘when the medium temperature is not high. The wedge gate valve can be made into a whole, called the rigid gate; It can also be made into a gate that can produce trace deformation in order to improve its technology and make up for the deviation of the sealing surface Angle in the process of processing. This kind of gate is called elastic gate.
Classification of cast steel gate valves
Cast steel gate valve: according to the material, there are carbon steel gate valve, stainless steel gate valve, low alloy steel gate valve (high temperature resistant chromium molybdenum steel belongs to this category), low temperature steel gate valve, etc.
Various types of cast steel gate valves have various specific steel grades commonly used as follows:
1. Carbon steel gate valve casting grades are: WCA, WCB, WCC, LCB, etc. Applicable temperature -46 degrees ~425 degrees.
2. Stainless steel gate valve castings: 301 stainless steel, CF8 stainless steel (corresponding to forging 304 stainless steel), CF8M stainless steel (corresponding to forging 316 stainless steel), etc. Applicable temperature -198 degrees ~816 degrees.
3, low alloy steel is divided into high temperature alloy steel and perfect low alloy steel, among which high temperature alloy steel is often said chromium molybdenum steel.
Chromium molybdenum steel gate valve casting grades: ZG1Cr5Mo, ZG15Cr1MoV, ZG20CrMoV, WC6, WC9, C12A and so on. Applicable temperature 550 degrees to 750 degrees.
The temperature applicable to each specific grade of material is different, depending on the actual working conditions.
Gb nominal pressure (MPa)
American standard pound class (>
Nominal pressure of valve
1.62.54.06.410.015030040060090010 K20K
2.43.86.09.615.03.17.810.215.323.13.17.8 body strength test pressure (Mpa)
High pressure water sealing test 1.82.84.07.011.02.15.67.511.216.82.15.6 (Mpa)
Low pressure gas seal test (Mpa) according to 0.5Mpa~0.7Mpa gas medium pressure test leak detection.
Test performance standard: GB/T13927-2008 name general valve pressure test
Design standard: GB/T12234-2007 Name: Steel gate valves with stud caps for the petroleum and natural gas industry
Flange connection: JB/T79-94 Mechanical Ministry flange standard, GB/T9113-2000 National recommended flange standard, HG/T20592-2009 Chemical Ministry flange
Structure length: GB12221-2005 Name: metal valve structure length
Nominal diameter: DN15~DN1200mm
Nominal pressure: PN10~PN320, 1.0Mpa~32.0Mpa
Handwheel, handle and transmission mechanism are not allowed to be used for lifting, and collision is strictly prohibited.
Double gate valves should be mounted vertically (i.e. stem in vertical position with handwheel on top).
Gate valves with bypass valves should be opened before opening (to balance the pressure difference between inlet and outlet and reduce the opening force).
The gate valve with driving mechanism shall be installed according to the instructions of the product.
Lubricate valves at least once a month if they are frequently used on and off.
Pipeline flow, pressure, temperature control of various industrial automation production. For example: electric power, metallurgy, petrochemical, environmental protection, energy management, fire protection system and so on. For a long time, the general gate valves used in the market are generally leaking or rusting. Some enterprises introduce the European high-tech rubber and valve manufacturing technology to produce the elastic seat seal gate valve, which overcomes the general gate valve poor sealing, rust and other defects. The elastic seat seal gate valve makes use of the elastic gate plate to produce a small amount of elastic deformation compensation to achieve a good sealing effect. The valve has the advantages of light switch, reliable seal, good elastic memory and service life.
Several “evils” that threaten the sealing surface of stainless steel valves
Stainless steel valve refers to the use of stainless steel materials made of valves. The valve is a control component in the pipeline fluid delivery system. It is used to change the channel section and the direction of the flow of the medium. It has the functions of diversion, cut-off, regulation, throttling, check, shunt or overflow pressure relief. Valves for fluid control range from simple globe valves to valves used in extremely complex automatic control systems in a wide variety of varieties and specifications.
Stainless steel valve and pipe or machine equipment connection is 304 stainless steel flange connection, commonly known as 304 stainless steel flange connection.
Stainless steel valve adopts stainless steel material with handle, turbine, pneumatic, electric transmission structure, switch flexible and light. Compact structure, light weight, easy to heat preservation, easy to install. Connection mode: welding, thread, flange for users to choose. It has excellent sealing performance and corrosion resistance. Stainless steel valves continue to absorb foreign advanced technology, combined with the actual situation of the domestic development, to domestic instead of imported. Used in natural gas, petroleum, heating, chemical and thermoelectric pipe network and other long distance transmission pipeline fields.
At present in the use of stainless steel valves, stainless steel ball valve, gate valve, globe valve in the market use more obvious.
Compared with traditional industries, due to the limitations of structural characteristics, it is not suitable for high temperature resistance, high pressure and corrosion resistance, wear resistance and other industries. The damage of all kinds of things is divided into two categories of man-made and natural damage, stainless steel valve is no exception, natural damage, is the wear of the valve under normal working conditions. It is the damage caused by the inevitable corrosion and erosion of the sealing surface by the medium, which is mainly divided into the following points:
1. Inadequate installation and maintenance
This factor leads to abnormal work of the sealing surface, and the valve runs with disease, resulting in forced friction and damage of the sealing surface. The main performance is that the valve is not selected according to the working condition, and the truncation valve is used as the throttle valve, which leads to the sealing pressure is too large and the sealing is too fast or the sealing is not strict, so that the sealing surface is eroded and worn.
2. Improper selection and improper operation
Mainly not according to the working conditions and choose the valve, such as the truncation valve when the throttle valve is used, resulting in the sealing pressure is too large and the sealing too fast or the sealing is not strict, so that the sealing surface by erosion and wear. Or the cast steel valve is used in corrosive media, or the non-temperature resistant valve is used in high temperature conditions. Or the general sealing surface material is used in a place with more impurities and higher temperature.
3. Medium erosion
It is the result of wear, washing and cavitation of the sealing surface when the medium is active. At a certain speed, the planktic fine particles in the medium violate the sealing surface, causing local damage. The high-speed moving medium directly washes the sealing surface, causing local damage. When the medium mixes and vaporizes, the indignant bubble blasting impacts the surface of the sealing surface, causing local damage. The erosion of the medium combined with the alternating action of chemical erosion will strongly erode the sealing surface.
4. Electrochemical erosion
The sealing surface is in contact with each other, the sealing surface is in contact with the sealing body and the valve body, as well as the concentration difference of the medium, the oxygen concentration difference and other reasons, will produce potential difference, electrochemical erosion, resulting in the erosion of the anode side of the sealing surface.