I. Oxygen valve production conditions
GB16912-2008 "Technical Regulations for the Production of Oxygen and Related Gases by Deep Freezing Method" makes the following provisions for the selection of oxygen valves.
(1) Oxygen pipeline valves should use professional oxygen valves and should meet the following requirements:
a.Oxygen pipeline with working pressure greater than 0.1 MPa, it is forbidden to use gate valve;
b. Manual oxygen valves with a nominal pressure greater than or equal to l.OMPa and a nominal size greater than or equal to DN150, preferably with bypass valves;
c. The selection of valve materials should be in accordance with
Valve material selection requirements
Working pressure P/MPa Material P ≤ 0.6
1. The valve and valve cover adopt malleable cast iron, ball or cast steel
2. Stainless steel stem
3 valve stainless steel
2P10 uses copper alloy), nickel and nickel base alloys.
Note: 1. The material of pressure or flow control valve with working pressure above 0.1MPa should be made of stainless steel or copper alloy or a combination of the above two types.
2. The valve packing should be made of PTFE or flexible graphite material.
(2) Oxygen valves with a nominal pressure greater than or equal to 1.0 MPa and a nominal size greater than or equal to DN150 are often used.
Second, the type of oxygen valve
Oxygen Special Valve, Oxygen Dedicated Stop Valve, Bevel Gear Oxygen Dedicated Stop Valve, Oxygen Special Check Valve, Oxygen Special Ball Valve, Oxygen Special Butterfly Valve, Oxygen Dedicated Pressure Reducing Valve, Oxygen Flame Retardant, Oxygen Filter, Oxygen Pneumatic Shut-Off Valve, Oxygen Adjust the valve.
III. Structural Factors of Oxygen Valves
1 The shut-off valve's opening and closing parts move flat on the valve seat, and its sealing surface load can be reliably controlled by the valve stem with trapezoidal transmission thread. With the help of the design of the valve flap and the valve seat, the friction force of the valve seat on the valve seat during movement can be small or even absent. This solves the problem of the friction of the sealing pair during valve opening or closing.
2 In the structural design of the globe valve, the flow of the medium must be considered in order to make it flow smoothly and reduce the strong impact formed - the flow path of the flow path of the oxygen medium flow should be smooth, smooth, free from corners, sharp corners, uneven, There is no abrupt change, and the internal parts of the valve are rounded and blunt and round. The stem clearance of the valve stem must be rounded to ensure that there is no sudden pressure change in the flow of the medium. There is no sudden change in the direction of the flow rate, and there must be no solids in the body cavity of the valve. Prevent static electricity.
3 The design of the globe and valve seat geometry of the globe valve is spherical-taper. A spherical surface and a tapered surface contact are theoretically linear contacts. It is actually a very narrow sealing strip, which can be achieved at low loads. Design stress. The spherical-tapered structure, after the valve is closed, has a force component that prevents lateral movement due to vibration. The spherical valve flap can be rotated in a certain range on the conical valve seat and automatically corrected to ensure good sealing performance.
4 In order to achieve a good sealing performance of the cut-off valve, the structure of the valve is guided so that it can accurately fall on the valve seat. When the wide valve is guided in the valve body, the valve flap is pushed laterally by the flowing medium. The force, which is absorbed by the valve body and not by the valve stem, further increases the sealing performance and the possibility of packing seals.
5 The connection between the valve disc and the valve stem of the stop valve is a hinge type. Its biggest advantage is that it can automatically adjust the position of the valve flap centering, and also reduce the friction between the valve flap and the valve seat during movement, and the sealing performance is easily guaranteed.
6 The valve stem of the stop valve is designed as a lifting rod, ie when the valve stem moves up and down
If it does not rotate, the valve flap will move up and down with it, and once again, the friction force of the valve flap and the valve seat will be reduced to reduce the wear of the packing. At the same time, the wear of the upper seal may also be reduced to a minimum.
7 The stem nut of the stop valve is closed with a metal cover, so that the stem nut is isolated from the atmosphere to prevent the dust from sticking to the stem nut and enter the lower part of the stem through the trapezoidal thread, so that it enters the stuffing box during the lifting of the stem. Lubrication of bracket bearings should use fluorinated grease.
8 The grounding bolt is provided on the end flange of the valve body of the special oxygen valve and is connected with wire bolts to avoid the explosion caused by static electricity.
9 The exposed parts of the stems of special oxygen ball valves and globe valves should be protected against dirt and oil. The plexiglass cover is installed on the frame of the bracket and there is a clear “oil ban” mark to remind the site personnel to pay attention.
IV. Medium flow
The medium of the T-shaped stop valve flows into and out of the valve seat. The closing of the valve is achieved by using the valve flap to “cover” the valve seat. Since the closing or opening of the shut-off valve is achieved by the valve acting on the valve stem against the dynamic pressure and static pressure on the front (or back) of the medium, the shut-off valve closing and opening torque is greater than the same pressure level and the same nominal size Gate valve, valve stem force. Therefore, the medium flow direction of the T-shaped stop valve with a small nominal size mostly comes from below the valve flap and then flows out from above the valve flap, that is, the medium is in the direction of “low to high” flow. Medium and large size T-shaped globe valves, nominal pressure PN16 40 (or CL150 3001b), nominal size not less than DN100, or nominal pressure not less than PN64 (or CL 4001b), nominal size not less than DN80. The medium flow direction adopts from the valve seat and the valve flap of the cut-off valve and flows out from the seat and the valve flap, that is, the medium enters the high-low flow direction. Mark the valve's media flow in the obvious part of the valve body.
Oxygen pipeline dedicated valves must be safety-oriented, in the valve type selection, structural design, valve body material selection has special requirements, while requiring strict degreasing, anti-static, oil and related inspections.