是所有用金属钢材料浇铸成铸件加工的闸阀统称铸钢闸阀。 Cast steel gate valve: All gate valves that are cast with metal steel materials for casting are collectively referred to as cast steel gate valves. Corresponding to cast steel gate valves are cast iron gate valves, forged steel gate valves, and malleable cast iron gate valves.
Cast steel gate valve: 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 and so on.
There are various specific steel grades commonly used under various cast steel gate valves as follows:
1. Casting grades of carbon steel gate valve are: WCA, WCB, WCC, LCB, etc .; applicable temperature -46 ° ~ 425 °.
2. Stainless steel gate valve casting grades: 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 high-strength low-alloy steel, of which high-temperature alloy steel is often referred to as chromium-molybdenum steel.
Casting grades of chrome molybdenum steel gate valve: ZG1Cr5Mo, ZG15Cr1MoV, ZG20CrMoV, WC6, WC9, C12A, etc. Applicable temperature: 550 degrees to 750 degrees.
The applicable temperature of each specific grade material is different, and it is selected according to the actual working conditions.
When talking about cast steel gate valves in valve procurement, they usually refer to carbon steel gate valves of the WCB brand, because in the early days, steel castings were not as abundant as they are now. When it comes to cast steel gate valves, only WCB is a good choice. The cast steel gate valve is the WCB carbon steel gate valve. The WCB carbon steel gate valve is also one of the oldest and most widely used valve structure forms.
Test the leak by fully pressing the gas pressure of 0.5Mpa ~ 0.7Mpa.
Test execution standard: GB / T 13927-2008 Name General Valve Pressure Test
Design standard: GB / T12234-2007 Name: Steel gate valve with stud connection bonnet for oil and gas industry
Flange connection: JB / T 79-94 flange standard of the Ministry of Machinery, GB / T 9113-2000 national recommended flange standard, HG / T 20592-2009 flange of the Ministry of Chemical Industry
Structure length: GB12221-2005 Name: Structure length of metal valve
Nominal diameter: DN15 ~ DN1200mm
Nominal pressure: PN10 ~ PN320, 1.0Mpa ~ 32.0Mpa
1. Carbon steel gate valve material code "C": water, oil, steam (temperature ≤425 ℃)
2. 304 stainless steel gate valve material code "P": nitric acid (temperature ≤200 ℃)
3. Material code of 316 stainless steel gate valve "R": Acetic acid (temperature ≤200 ℃)
4, WC6, WC9 chromium-molybdenum steel gate valve material code "I": water, oil, steam (temperature ≤ 595 ℃)
Install and use
1. Before installation, check the valve cavity, sealing surface and other parts. No dirt or sand particles are allowed to attach. 2. The bolts of each connection part must be tightened evenly. 3. Check the packing parts to be compacted to ensure the sealing of the packing It is also necessary to ensure that the shutter can be opened flexibly. 4. Before installing the valve, the user must check the valve model, connection size and media flow direction to ensure consistency with the valve requirements. 5. When installing the valve, the user must reserve the valve drive Necessary space; 6. Wiring of the driving device must be carried out according to the wiring diagram; 7. The gate valve must be regularly maintained, and must not be bumped or squeezed at will, so as not to affect the seal.
1) The installation position, height, and import and export directions must meet the design requirements, and the connections should be firm and tight.
2) The handles of all kinds of manual valves installed on insulation pipes must not be downward.
3) Visual inspection must be carried out before the valve is installed. The nameplate of the valve should comply with the current national standard "General Valve Mark" GB 12220. For valves with a working pressure greater than 1.0 MPa and a cut-off function on the main pipe, strength and tight performance tests should be carried out before installation, and only approved after use. In the strength test, the test pressure is 1.5 times the nominal pressure, and the duration is not less than 5min. The valve housing and packing should be qualified without leakage. During the tightness test, the test pressure is 1.1 times the nominal pressure; the test pressure shall meet the requirements of the GB 50243 standard for the duration of the test, and the leakage of the sealing surface of the valve disc is qualified.
Handwheels, handles and transmission mechanisms are not allowed for lifting, and collision is strictly prohibited.
The double-gate gate valve should be installed vertically (that is, the valve stem is in the vertical position and the handwheel is at the top).
The gate valve with the bypass valve should be opened before opening (to balance the pressure difference between the inlet and outlet and reduce the opening force).
The gate valve with transmission mechanism shall be installed in accordance with the instructions of the product instruction manual.
If the valve is used frequently, lubricate at least once a month.
Pros and cons
1. The advantages of cast steel gate valve: small fluid resistance, little sealing and erosion by medium. Less effort to open and close. The medium flow direction is not restricted, does not disturb the flow, does not reduce the pressure. The structure is simple, the structure length is short, the manufacturing process is good, there are many optional materials for high temperature and high pressure resistance, and the scope of application is wide.
2. Disadvantages of cast steel gate valve: It is easy to cause erosion and abrasion between sealing surfaces, and it is difficult to maintain. The external dimensions are relatively large, a certain amount of space is required for opening, and the opening and closing time is long.
Gate valve classification
Divided by the form of the ram
Gate valves are divided into gate types: wedge gate valves and parallel gate valves, wedge gate valves can be divided into: single gate type, double gate type and flexible gate type; parallel gate type gate valves can be divided into single gate Plate type and double gate type.
Lifting points by valve stem
The gate valve can be divided into bright stem gate valve and dark stem gate valve according to whether the stem is raised or lowered. While the valve stem rotates, it lifts the bright-stem gate valve; the valve stem only rotates and does not lift the dark-stem gate valve.
The riser gate valve is called linear lift valve (also called riser gate valve) if the ram of the riser valve moves linearly with the valve stem. Usually there is a trapezoidal thread on the lifting rod, and the rotary motion is changed to linear motion through the nut on the top of the valve and the guide groove on the valve body, that is, the operating torque is changed to the operating thrust. When the valve is opened, when the lift height of the gate is equal to 1: 1 of the valve diameter, the fluid channel is completely clear, but this position cannot be monitored during operation. In actual use, the apex of the valve stem is used as a mark, that is, the position where it cannot be opened, as its fully open position. In order to consider the lock-up phenomenon caused by temperature changes, it is usually opened to the top position, and then back to 1 / 2-1 turn, as the position of the fully open valve. Therefore, the fully open position of the valve is determined by the position of the gate (ie, stroke>).
In some gate valves, the stem nut is located on the gate plate. The stem does not rise and fall when the light is rotated. The handwheel rotates to drive the stem to raise the gate. This valve is called a rotary stem gate valve or a dark stem gate valve. The switch is the same as the open gate valve. It will be fully open when it is turned off and fully closed when it is turned off. Compared with the open lever gate valve, the opening of the gate cannot be seen with the naked eye, it is more difficult to grasp, and an opening degree indicator bar needs to be installed.
Wedge gate valve is widely used in petrochemical, thermal power plants and other oil, water vapor pipelines as the opening or closing device to connect or cut off the medium in the pipeline
1.Compact structure, reasonable design, good valve rigidity, smooth passage and small flow coefficient
2. The sealing surface is made of stainless steel and hard alloy, which has a long service life.
3. Flexible graphite packing, reliable sealing, light and flexible operation
4.The driving method is manual, pneumatic, electric, gear transmission
5.Structural form: elastic wedge type single gate, rigid wedge type single gate and double gate type
Design specification: GB / T 12234
Structure length: GB / T 12221
Connecting flange: JB / T 79
Test and inspection: JB / T 9092
Pressure-temperature: GB / T 9131
Product identification: GB / T 12220
[Applicable medium and applicable temperature]
[Major parts material]
The main connection size of the gate valve