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Uses of large diameter valves
- Categories:Industry Knowledge
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- Time of issue:2016-01-13 14:33
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(Summary description)1.Purpose Large-diametergatevalveissuitableforsmall-diameterpipelinesofClass150～2500,workingtemperatureof-29～425℃(carbonsteel)or-29～500℃(stainlesssteel).Itisusedtocutofforconnectthemediuminthepipeline
Uses of large diameter valves
(Summary description)1.Purpose Large-diametergatevalveissuitableforsmall-diameterpipelinesofClass150～2500,workingtemperatureof-29～425℃(carbonsteel)or-29～500℃(stainlesssteel).Itisusedtocutofforconnectthemediuminthepipeline
- Categories:Industry Knowledge
- Author:
- Origin:
- Time of issue:2016-01-13 14:33
- Views:
Information
1. Purpose
Large-diameter gate valve is suitable for small-diameter pipelines of Class150～2500, working temperature of -29～425℃ (carbon steel) or -29～500℃ (stainless steel). It is used to cut off or connect the medium in the pipeline. Choose different ones. The material is suitable for various media such as water, steam, oil, nitric acid, acetic acid, oxidizing medium, urea, etc. It is widely used in petroleum pipelines.
2. Installation points
1. The installation position, height, and direction of import and export must meet the design requirements, and the connection should be firm and tight.
2. The handles of all kinds of manual valves installed on the thermal insulation pipeline must not be downward.
3. The valve must be visually inspected before installation. The nameplate of the valve should comply with the current national standard "General Valve Marking" GB 12220. For valves with a working pressure greater than 1.0 MPa and a cut-off function on the main pipe, the strength and tightness performance test shall be carried out before installation, and the valve shall be used only after it is qualified. During 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 should meet the requirements of the GB 50243 standard during the test duration, and no leakage on the ram sealing surface is qualified.
3. Working principle
According to the sealing surface configuration, it can be divided into wedge gate valve and parallel gate valve. Wedge gate valve can be divided into: single gate, double gate and elastic gate; parallel gate valve can be divided into single gate Plate type and double gate type. Divided according to the thread position of the valve stem, it can be divided into two types: open stem gate valve and dark stem gate valve.
1. When the large-diameter gate valve is closed
The sealing surface can be sealed only by the pressure of the medium, that is, relying on the pressure of the medium to press the sealing surface of the gate against the valve seat on the other side to ensure the sealing of the sealing surface, which is self-sealing. Most gate valves adopt forced sealing, that is, when the valve is closed, the gate must be forced against the seat by external force to ensure the sealing performance of the sealing surface. The gate valve of the gate valve moves linearly with the valve stem, which is called the lifting stem gate valve (also called the rising stem gate valve). Usually there is a trapezoidal thread on the lifting rod, through the nut on the top of the valve and the guide groove on the valve body, the rotary motion is changed into linear motion, that is, the operating torque is changed into operating thrust.
2. When the large-diameter gate valve is opened
When the lifting height of the gate is equal to 1:1 times the valve diameter, the fluid passage is completely unblocked, but this position cannot be monitored during operation. In actual use, the apex of the valve stem is used as the mark, that is, the unmovable position, as its fully open position. In order to take into account the lock-up phenomenon caused by temperature changes, it is usually opened to the top position, and then rewind 1/2-1 circle, 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).
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