Internal pressure self-sealing structure in the middle cavity
For slab gate valves with class over or equal to 900, a pressure self tightening sealing valve bonnet is adopted, which has a unique seal and is designed as a metal sealing ring. When the sealing ring is under pressure, as the pressure difference increases between the upper and lower sides, the sealing ring elastically deforms during the extrusion process to obtain a reliable seal. The sealing ring can be used repeatedly, and the inner wall of the valve body cavity that is often in contact with the sealing ring is build up welded with corrosion resistant hard alloys to increase the sealing performance of the middle port.
The seal design of the stem
When the sealing ring of the valve stem packing is disassembled under the action of the medium pressure, its structure should ensure that the valve stem does not come out. When the valve stem is raised to the highest position, the tapered sealing surface at the lower end of the packing box is attached to the tapered sealing surface of the valve stem to form an upper sealing structure. Metal wire, flexible graphite braided packing and flexible graphite forming rings are placed in the packing box to seal the valve stem. Incone1718 is adopted for the metal wire, which is suitable for sour gas environment and meets the requirements for anti sulfur erosion, ensuring the strength. A packing spacer with a seal ring is set in the middle of the packing. The self tightening packing can form an effective triple sealed structure to ensure zero leakage of the medium.
Being fireproof and antistatic
The flanges on both sides of the valve are equipped with grounding screw plugs and conductive springs between the wedge and the valve stem, so that a continuous circuit can be formed among the valve body, wedge, bracket, valve bonnet and valve stem to obtain the antistatic effect. The resistance value of the antistatic circuit should not exceed 10Ω. Valves must cover the full range of pressure ratings and nominal sizes in accordance with API 6FA standards, and conduct a fire test of physical valves. Such valve manufacturers should have fire test certificates.
Protection functions of valves
The slab gate valve adopts a full bore structure. When the valve is fully opened, the pressure loss of the medium through the valve is extremely small. There is a drain valve at the lower end of the valve body. The drain valve can be a plugged drain valve. It is necessary to consider the corrosion damage of the threaded connection by the medium and take protective measures. For the drain valve with a slightly larger nominal size, a flange integrally casted or forged with the valve body should be connected to the drain valve to eliminate the disadvantage of using a drain valve. The exposed stem is equipped with a good protective sleeve to prevent foreign objects from entering the stem seal. The valve is equipped with a valve position indicator on the dust cover or bracket, which is convenient to observe the valve switch position during operation. A movable limit device is set in the valve, and a locking device can be set between the valve and the operating device according to the requirements of use to lock the opening or closing device of the valve. Slab gate valves with a nominal size of DN over or equal to 100 are installed with lifting lugs and supports, which are convenient for valve maintenance, replacement, transportation or mechanical lifting during installation.
Valve test regulations
The test and inspection of the valve comply with the requirements of API6D. The leakage level of the metal hard sealed slab gate valve meets the requirements for Class B of ISO 15848-2. The stem seal of the high sulfur slab gate valve is tested for micro-leakage and meets the Class B leakage requirements of ISO 15848-2.
Conclusion
The special high-pressure slab gate valve for high sulfur and high acid resistance has the functions of good sealing performance, small opening torque, small flow resistance coefficient, great flow rate, easy clearing of the pig and long service life, and has the advantages of flexible opening and closing and labor saving operation. According to the needs of the project, there are manual transmission, bevel gear transmission and explosion proof electric transmission for high-pressure slab gate valves. The special high-pressure slab gate valve as a reliable device to control the flow and cut-off of the medium can be widely used in the mining and gathering of high sulfur oil and natural gas, oil and natural gas pipelines.
For slab gate valves with class over or equal to 900, a pressure self tightening sealing valve bonnet is adopted, which has a unique seal and is designed as a metal sealing ring. When the sealing ring is under pressure, as the pressure difference increases between the upper and lower sides, the sealing ring elastically deforms during the extrusion process to obtain a reliable seal. The sealing ring can be used repeatedly, and the inner wall of the valve body cavity that is often in contact with the sealing ring is build up welded with corrosion resistant hard alloys to increase the sealing performance of the middle port.
The seal design of the stem
When the sealing ring of the valve stem packing is disassembled under the action of the medium pressure, its structure should ensure that the valve stem does not come out. When the valve stem is raised to the highest position, the tapered sealing surface at the lower end of the packing box is attached to the tapered sealing surface of the valve stem to form an upper sealing structure. Metal wire, flexible graphite braided packing and flexible graphite forming rings are placed in the packing box to seal the valve stem. Incone1718 is adopted for the metal wire, which is suitable for sour gas environment and meets the requirements for anti sulfur erosion, ensuring the strength. A packing spacer with a seal ring is set in the middle of the packing. The self tightening packing can form an effective triple sealed structure to ensure zero leakage of the medium.
Being fireproof and antistatic
The flanges on both sides of the valve are equipped with grounding screw plugs and conductive springs between the wedge and the valve stem, so that a continuous circuit can be formed among the valve body, wedge, bracket, valve bonnet and valve stem to obtain the antistatic effect. The resistance value of the antistatic circuit should not exceed 10Ω. Valves must cover the full range of pressure ratings and nominal sizes in accordance with API 6FA standards, and conduct a fire test of physical valves. Such valve manufacturers should have fire test certificates.
Protection functions of valves
The slab gate valve adopts a full bore structure. When the valve is fully opened, the pressure loss of the medium through the valve is extremely small. There is a drain valve at the lower end of the valve body. The drain valve can be a plugged drain valve. It is necessary to consider the corrosion damage of the threaded connection by the medium and take protective measures. For the drain valve with a slightly larger nominal size, a flange integrally casted or forged with the valve body should be connected to the drain valve to eliminate the disadvantage of using a drain valve. The exposed stem is equipped with a good protective sleeve to prevent foreign objects from entering the stem seal. The valve is equipped with a valve position indicator on the dust cover or bracket, which is convenient to observe the valve switch position during operation. A movable limit device is set in the valve, and a locking device can be set between the valve and the operating device according to the requirements of use to lock the opening or closing device of the valve. Slab gate valves with a nominal size of DN over or equal to 100 are installed with lifting lugs and supports, which are convenient for valve maintenance, replacement, transportation or mechanical lifting during installation.
Valve test regulations
The test and inspection of the valve comply with the requirements of API6D. The leakage level of the metal hard sealed slab gate valve meets the requirements for Class B of ISO 15848-2. The stem seal of the high sulfur slab gate valve is tested for micro-leakage and meets the Class B leakage requirements of ISO 15848-2.
Conclusion
The special high-pressure slab gate valve for high sulfur and high acid resistance has the functions of good sealing performance, small opening torque, small flow resistance coefficient, great flow rate, easy clearing of the pig and long service life, and has the advantages of flexible opening and closing and labor saving operation. According to the needs of the project, there are manual transmission, bevel gear transmission and explosion proof electric transmission for high-pressure slab gate valves. The special high-pressure slab gate valve as a reliable device to control the flow and cut-off of the medium can be widely used in the mining and gathering of high sulfur oil and natural gas, oil and natural gas pipelines.
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