Special filter equipment of nuclear sampling system
Technical Field
The invention belongs to the technical field of medium filtration in a nuclear sampling system, and particularly relates to a special filtering device for the nuclear sampling system.
Background
One of the primary functions of a nuclear sampling system of a nuclear power plant is to acquire media from the secondary circuit of the nuclear power plant, perform chemical analysis and radioactivity monitoring to determine the secondary circuit water chemistry parameters, and monitor possible leakage of the primary side of the evaporator to the secondary side. However, the secondary loop process system of the nuclear power plant generally uses carbon steel materials, corrosion products easily cause the blockage of sampling loop equipment, the flow of a pipeline is low or the pipeline is cut off, the nuclear sampling system is unavailable, and the availability (back-proof) of a unit is influenced. If a common filter is additionally arranged in the nuclear sampling system, the precision and the response speed of the radioactivity monitoring instrument can be influenced, and the functional requirements of the system cannot be met. Therefore, there is a need to develop a new filtering device, which can filter out the corrosion products of the two circuits without affecting the measurement accuracy and response speed of the radioactivity monitoring instrument.
Disclosure of Invention
The invention aims to provide a special filtering device for a nuclear sampling system, which can filter out non-radioactive fixed impurities in the system to avoid the blockage and failure of the system and has no substantial influence on radioactive sampling monitoring.
The technical scheme of the invention is as follows: a special filter device for a nuclear sampling system comprises an end cover, a shell, a filter core assembly and a magnetic rod assembly, wherein the shell is of a cylindrical barrel structure with a flange surface at the upper end, the side wall of the flange surface at the upper end is provided with a channel communicated to a cylindrical groove in the middle of the shell, and the channel is communicated with a downstream pipeline through an outlet valve; the downstream pipeline is communicated with the opening at the bottom end of the shell through a bypass valve and an inlet valve, and the opening at the bottom end of the shell is also connected with the other pipeline through a drain valve; the end cover is fixed on the flange surface of the shell in a sealing way, so that the magnetic rod assembly fixed at the center of the end cover is inserted into the cylindrical groove in the middle of the shell; and a filter element assembly is fixed on the lower end face of the end cover in a sealing manner, and the lower end of the filter element assembly is positioned below the side wall channel of the shell and is sealed with the inner side wall of the shell.
The magnetic rod assembly comprises a magnetic rod and a magnetic rod sleeve, wherein the magnetic rod sleeve is of a cylindrical barrel structure with an opening at the upper end, is arranged in a through hole in the center of the end cover in a matching mode, and is fixed with the end cover.
The filter element assembly comprises a filter screen, an upper connecting ring and a lower connecting ring, wherein the upper end face and the lower end face of the filter screen are respectively fixedly connected with the upper connecting ring and the lower connecting ring, and an upper sealing ring is arranged on the outer side wall of the upper connecting ring, so that the upper connecting ring is sealed with the annular groove on the end cover; the outer diameter of the lower connecting ring is slightly larger than that of the filter screen, the outer diameter of the lower connecting ring is matched with the inner diameter of the middle cylindrical groove of the shell, and the lower connecting ring and the inner wall of the shell are sealed through a lower sealing ring arranged on the outer side of the lower connecting ring.
A metal winding gasket is arranged between the end cover and the shell; the end cover and the shell are fastened through a plurality of bolts circumferentially arranged on the end cover, and an annular metal winding gasket placed on a flange face at the upper end of the shell is compressed tightly, so that the end cover and the shell are sealed.
The filter screen is a cylindrical Johnson pipe, the size of the mesh of the filter screen is determined according to the particle size of impurities to be filtered, and the filter screen is made of corrosion-resistant stainless steel.
The outer wall of the magnetic rod sleeve is smooth, and the thickness of the cylinder body of the magnetic rod sleeve is determined according to the pressure of the system.
The magnetic rod can be inserted into the magnetic rod sleeve in a matching way; the magnetic rod is made of standard high-magnetic-flux materials, is inserted into the magnetic rod sleeve to be not in direct contact with a medium, and impurities on the surface of the magnetic rod sleeve can fall off automatically after the magnetic rod is drawn out.
The blowoff valve is a small-caliber nuclear-grade ball valve.
The inlet valve, the outlet valve and the bypass valve are nuclear grade stop valves.
The invention has the following remarkable effects: according to the special filtering device for the nuclear sampling system, the outer shell and the end cover are connected through the flange, and the shell, the end cover, the flange, the magnetic rod sleeve and other pressure-bearing components can bear design temperature and pressure, so that the design requirements of the nuclear sampling system on nuclear safety level and anti-seismic level are met. The filter device is compact in structural design, adopts a magnetic and Johnson pipe combined filtering form, can meet the requirement of filtering precision, has no influence on radioactive sampling monitoring, and has a selective filtering function. Convenient operation for installation and maintenance and good filtering effect. The back washing operation is simple and convenient, the back washing does not influence the normal operation of the sampling monitoring loop, and the reliability of the nuclear power unit system and the unit availability are improved.
Drawings
FIG. 1 is a schematic structural diagram of a filtering apparatus dedicated for a nuclear sampling system according to the present invention;
FIG. 2 is a schematic view of the end cap and the magnetic rod sleeve of FIG. 1;
FIG. 3 is a schematic diagram of the filter element assembly of FIG. 1;
in the figure: 1. bolts, 2, nuts; 3. a flat washer; 4. an end cap; 5. a metal wound gasket; 6. a housing; 7. a filter element assembly; 8. a magnetic bar; 9. a blowoff valve; 10. an outlet valve; 11. a downstream conduit; 12. an inlet valve; 13. a bypass valve; 14. a magnetic rod sleeve; 15. an upper seal ring; 16. an upper connecting ring; 17. a filter screen; 18. a lower connecting ring; 19. a lower sealing ring.
Detailed Description
The invention is described in further detail below with reference to the figures and the embodiments.
As shown in fig. 1 to 3, a special filtering device for a nuclear sampling system comprises an end cover 4, a shell 6, a filter element assembly 7 and a magnetic rod 8, wherein the shell 6 is of a cylinder structure with a flange surface at the upper end, a cylindrical groove structure with a certain depth is arranged in the middle of the shell 6, a channel is formed in the side wall of the flange surface at the upper end of the shell 6 and communicated with the cylindrical groove in the middle of the shell 6, and the port of the channel is communicated with a downstream pipeline 11 through an outlet valve 10; the downstream pipe 11 is connected to the opening at the bottom end of the housing 6 through a bypass valve 13 and an inlet valve 12, and the opening at the bottom end of the housing 6 is also connected to another pipe through a blow-down valve 9; wherein, the blowoff valve 9 is a small-bore nuclear grade ball valve, and the inlet valve 12, the outlet valve 10 and the bypass valve 13 are nuclear grade stop valves; the end cover 4 is a disc cover-shaped structure, a through hole is formed in the center of the end cover, the magnetic rod sleeve 14 of the cylindrical structure is installed in the through hole in the center of the end cover 4 in a matching mode, the upper end face of the magnetic rod sleeve 14 is flush with the upper end face of the end cover 4 and is fixed through welding, and a magnetic rod 8 can be inserted into the magnetic rod sleeve 14; the outer wall of the magnetic rod sleeve 14 is smooth, and the corresponding thickness is designed according to the corresponding pressure of the system; the magnetic rod 8 is made of standard high-magnetic-flux materials, is inserted into the magnetic rod sleeve 14 and is not in direct contact with a medium, and impurities on the surface of the magnetic rod sleeve 14 can fall off automatically after the magnetic rod 8 is drawn out; an annular bulge is arranged on the lower end face of the end cover 4 close to the central hole, and an annular groove is formed in the annular bulge; the upper end part of a filter element assembly 7 with a cylindrical tubular structure with two open ends can be matched and arranged in an annular groove on the lower end surface of the end cover 4, wherein the filter element assembly 7 comprises a filter screen 17, an upper connecting ring 16 and a lower connecting ring 18, the filter screen 17 is a cylindrical Johnson pipe, the size of the mesh of the filter screen is determined according to the particle size of impurities to be filtered, and the filter screen is made of corrosion-resistant stainless steel; the upper end face and the lower end face of the filter screen 17 are respectively fixedly connected with an upper connecting ring 16 and a lower connecting ring 18, and an upper sealing ring 15 is arranged on the outer side wall of the upper connecting ring 16, so that the upper connecting ring 16 is sealed with an annular groove on the end cover 4; the outer diameter of the lower connecting ring 18 is slightly larger than that of the filter screen 17, the outer diameter of the lower connecting ring 18 is matched with the inner diameter of a middle cylindrical groove of the shell 6, and the lower connecting ring 18 is sealed with the inner wall of the shell 6 through a lower sealing ring 19 arranged on the outer side of the lower connecting ring 18; the end cover 4 is matched and covered on the flange face at the upper end of the shell 6, the magnetic rod sleeve 14 is inserted into a cylindrical groove in the middle of the shell 6, and the filter element assembly 7 is in sealing fit with the inner wall of the shell 6; the end cover 4 and the shell 6 are fixedly connected by a plurality of circumferentially arranged bolts 1, nuts 2 and flat washers 3 on the flange surfaces of the end cover 4 and the shell 6, and an annular metal winding gasket 5 placed on the flange surface at the upper end of the shell 6 is pressed tightly, so that the end cover 4 and the shell 6 are sealed.
The specific working process of the special filtering device for the nuclear sampling system comprises the following steps: when the filter element assembly is in normal operation, the blow-down valve 9 and the bypass valve 13 are closed, the medium in the flow channel passes through the fluid inlet valve 12 of the shell, impurities are adsorbed by the magnetic rod 8 through the shell 6, then are intercepted by the filter element assembly filter screen 7, and enter the downstream pipeline 11 through the flow channel outlet valve 10, so that the influence of the impurities on downstream users is avoided. When a downstream pressure gauge or a downstream flowmeter monitors that the pressure or the flow in a flow passage of the system is reduced to a value which does not meet the operation requirement of the system, the situation that impurities in the filter net are accumulated too much is indicated, and the filter net needs to be cleaned. At the moment, the bypass valve 13 can be opened, the inlet valve 12 is closed, the blow-down valve 9 is slowly opened according to the pressure monitoring after the filter, the magnetic rod is drawn out from the magnetic rod sleeve 8, the medium in the cylinder flow passage can discharge the cleaned impurities through the blow-down valve 9, the condition of the medium discharged by the blow-down valve 9 is observed, the blow-down valve 9 can be closed after the condition that no impurities exist is confirmed, the inlet valve 12 is opened, the bypass valve 13 is closed, and the normal operation state is recovered; the above actions can be performed when the system is running without disassembling the filter.