Small diameter globe valve, mostly using external thread connection or ferrule connection, larger diameter globe valve can also use flange connection. Most of the globe valves are driven by a handwheel or handle, a few high-pressure larger diameter globe valves that need an automatic operation can also be driven by electricity.
The flow resistance of the globe valve is large, and the closing torque is also large, which affects its application on large-diameter occasions. In order to expand the scope of application of the globe valve, at home and abroad are currently researching to improve the structure of the globe valve, in order to reduce the flow resistance and closing torque. For example, in recent years the emergence of internal pressure self-balancing globe valve. This article briefly describes the application of various types of globe valves.
1. Needle globe valve
Needle globe valves are used for precise flow control. The valve flap is usually made integral with the valve stem, and it has a needle-like head that fits the valve seat with very high precision. Also, the thread pitch of the needle globe valve stem thread is smaller than that of a normal globe valve stem thread. In general, the size of the needle globe valve seat hole is smaller than the pipe size. Therefore, it is usually limited to the use in pipelines with a small nominal size and is more often used for sampling valves.
The stem and the channel of the DC globe valve are at a certain angle, and the sealing surface of its seat is also at a certain angle with the import and export channels, and the valve body can be made integral or separate. DC globe valve almost does not change the flow direction of the fluid, the minimum flow resistance in the globe valve. The seat and valve sealing surface can be welded carbide, making the whole valve more resistant to scouring and corrosion, ideal for pipeline control in alumina systems, but also suitable for coking and solid particles in the pipeline.
3. Angular globe valve
The biggest advantage of the angle shut-off valve is that the valve can be installed in the corner of the pipeline system, which not only saves 90 ° elbow but also facilitates the operation, most suitable for application in the ammonia production system of fertilizer plants and refrigeration systems. Such as J44H-160 and J44H-320 are completely designed for a synthetic ammonia production system.
4. Steel ball or ceramic ball sealed globe valve
The structure of the valve is characterized by the valve body being divided into one-piece and split type, the valve flap is STL hard alloy steel ball or amorphous powder material by pressing the forming, high-temperature sintering, fine research made of porcelain ball. The ball is rolled and enveloped at the lower end of the valve stem in the ball hole of the stem, and the ball can produce numerous sealing lines when doing a three-dimensional rotation in the ball hole of the stem, which greatly increases the service life of the sealing surface and also ensures reliable sealing. The valve is generally used for a smaller nominal size, about DN6~25, due to the limitation of the ball size, and is suitable for high temperature and high-pressure steam pipelines in nuclear power plants and thermal power plants, instrument pipeline of sampling and drainage systems, as well as temperature, pressure, wear and corrosion resistant pipelines in petrochemical and chemical systems.
5. High temperature and high-pressure power station disconnecting the valve
High-temperature and high-pressure power station disconnecting valve body and cover are connected with pressure self-sealing or clamp type, the connection between the valve body and pipeline in the form of butt welding connection, the valve body material is mostly chromium-molybdenum steel or chromium-molybdenum-vanadium steel, sealing surface welded carbide. Therefore, high temperature and high-pressure resistance, good thermal resistance; sealing surface wear resistance, abrasion resistance, corrosion resistance, good sealing performance, and long life. Most suitable for thermal power industrial systems, petrochemical systems, and metallurgical industries, such as high temperature and high-pressure water, steam, oil, and superheated steam pipeline.
6. Oxygen pipeline disconnecting the valve
The oxygen pipeline disconnecting valve is designed strictly according to the requirements of the oxygen pipeline, and the outside of the stuffing box is strictly sealed to prevent external dirt from entering the stuffing box. Valve body flanges at both ends of the grounding device, after installation in the pipeline, should be grounded to prevent static fire. The shell material is usually selected as austenitic stainless steel or copper alloy, with good electrical conductivity, not easy to electrostatic fire. The sealing sub-material is Teflon to the valve body material, good sealing performance, gas inspection leakage is zero. The parts before assembly and the whole machine after the completion of the assembly test must be degreased to prevent causing an electrostatic fire. Mainly applicable to the oxygen pipeline of metallurgical system, in other industries oxygen pipeline is also applicable.
7. LPG globe valve
The LPG shut-off valve is specially designed for LPG pipelines or devices. The structure pays attention to the fire prevention requirements. The packing is made of PTFE, with reliable sealing and no external leakage. The sealing sub-material is selected from PTFE or nylon to the body material of the valve, with reliable sealing. Suitable for LPG pipeline system, as an opening and closing device. Also suitable for other pipeline temperatures is not higher than 80 ℃ for cut-off valve use.
8. Screwed stem globe valve
The upper threaded stem shut-off valve stem is not in direct contact with the medium. According to the different configurations of the shell and inner parts materials, applicable to different working conditions. If the shell material is carbon steel, the sealing sub-material is alloy steel, the packing is flexible graphite, and the stem material is Cr13 stainless steel, suitable for water, steam, and oil pipeline; if the shell material is 12Cr18Ni9 or 06Cr19Ni10, the sealing sub-material is the valve body itself or hard alloy, the packing is PTFE, the stem material is 14Cr17Ni2, suitable for Nitric acid-based corrosive media pipeline or device.
If the shell material is 1Cr18Ni12Mo2Ti or 0Cr18Ni12Mo2Ti, the sealing sub-material is the body material or hard alloy, and the packing is PTFE, and the valve stem material is 1Cr18Ni12Mo2Ti, it is suitable for corrosive medium pipeline or device mainly based on acetic acid. The maximum nominal size of the upper threaded stem shut-off valve is generally DN200, and it is best to set the internal bypass or external bypass valve above DN200, and change the media flow direction to “high in and low out” to reduce the valve operating torque.
9. Lower threaded stem globe valve
Lower threaded stem shut-off valve stem threads are directly in contact with the working medium, directly subject to media corrosion, so that the stem threads are easy to rust, resulting in opening and closing efforts. Its structure is also only suitable for smaller nominal size specifications, generally between DN6 ~ 150, for clean media as instrumentation valves and sampling valves.
10. API 602 forged steel globe valve
The valve body and cover are made of carbon steel or stainless steel forgings, and the connection between the valve body and cover has various forms such as bolted connection, threaded connection, and welding. There are upper threaded stem and lower threaded stem, sealing sub-materials are Cr13 stainless steel, stainless acid-resistant steel, STL hard alloy, etc., packing can be selected from flexible graphite or PTFE, connection methods are flange, threaded, socket welding, and butt welding, pressure class 150 ~ 1500, nominal size of NPS 1/4 ~ 4.
Widely used in petrochemical, electric power, chemical, and other departments of the device and pipeline, the working medium is steam, oil, and corrosive media. Structure length according to the manufacturer’s standard, partly in line with ASME B16.10; flange connection size according to ASME B16.5; welding size in line with ASME B16.25; socket welding hole size in line with ASME B16.11; threaded connection end size in line with ASME B1.20.1.
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