[Abstract] The thermal system of power plant is an organic whole which is connected by thermal equipment, soft water pipelines and various accessories. In this organic whole, soft water pipelines and valves are not only an integral part of the production system but also occupy an important position , Because the power plant production process and the delivery of the working fluid, must be completed through the pipeline, the valve is an important part of the pipeline, only in the piping system to arrange various types of valves, the media movement is controlled, the pipeline facilities to give full play to the utility , To meet the needs of the production process to ensure system security. Valve leakage, leakage, switch does not move and other defects, will bring unsafe system equipment factors, in order to ensure the safety, stability, economy, efficient operation, you need to promptly determine the causes of defects and eliminate methods.
Key words: thermal system, valve defect elimination method, reliability and economy CLC number: TG245 Document code: A Article ID: 1009-914X (2017) 25-0370-01
First, an overview Power plant thermal system is a combination of thermal equipment and soda pipes and various accessories made of organic whole, in this organic whole, soda pipes and valves are not only an integral part of the production system, but also occupy an important position , Because the power plant production process and the delivery of the working fluid, must be completed through the pipeline, the valve is an important part of the pipeline, only in the piping system to arrange various types of valves, the media movement is controlled, the pipeline facilities to give full play to the utility , To meet the needs of the production process to ensure system security.
At present, power generation units are in the direction of large capacity, high parameters, the valve also with the media parameters to improve, continue to the high temperature, high pressure direction; with the media pressure to improve the valve is also constantly improving the sealing structure, the use of New sealing materials to improve the sealing performance; with the continuous improvement of the level of automation of the generator set, the valve drive device and the implementing agencies have been improved, and to facilitate the centralized control and remote control direction.
Second, the valve selection and common failures, causes and elimination methods (A), power plant safety, economic and rational use of the valve is inseparable from the valve on the pipeline can be used according to the type of media and media working parameters (Pressure, temperature and flow) and other factors to choose. When it is chosen, the nominal pressure, nominal diameter, working temperature and operating range of the selected valve should be adapted to the nominal pressure, nominal diameter and medium type in the piping system where the valve is located. At the same time, the ease of installation, operation, maintenance and overhaul should also be taken into account and economically justified.
(B), gate valve , globe valve common faults, causes and elimination methods 1, the valve body leakage:
1.1 Causes: (1). Casting poor manufacturing, with trachoma or cracks, resulting in reduced mechanical strength. (2). Fracture body repair welding.
1.2 Elimination method: (1). On the suspected crack polished, etching with 4% nitric acid solution, if cracks can be displayed. (2) cracked at the cracked wheel with a light metal to crack the cracked layer; processed bevel weld repair, valve body made of alloy steel and bonnet, before welding to be carried out at 250 ℃ ~ 300 ℃ Preheat, after welding to asbestos dust naturally cooled to room temperature. (3) After flange welding, the weld is higher than the original plane, must pass through the flat weld, in order to ensure the formation of concave and convex mouth without deformation after heating.
2, the door rod and the thread with the damaged wire or broken door, bending:
2.1 Causes: (1). Improper operation, excessive force, too much, with a small hook off the valve. (2) Thread fit too loose or too light. (3). Too many operations, the service life is too long.
2.2 Elimination method: (1). Improve the operation, generally do not allow to close the small valve with a large hook. (2) When manufacturing spare parts to meet the tolerance requirements to choose the appropriate material. (3), re-processing replacement parts.
3, the door cover with leakage:
3.1 Causes: (1). Bolt tension is not enough or tight bias. (2) The cover gasket is damaged. (3) with uneven surface or groove cracks.
3.2 Elimination methods: (1). Bolts to deal with the corner tight, tight to ensure consistency, the surface should be consistent with the gap. (2). Change the gasket. (3). Disintegration re-repair the bonding surface, such as the groove with the groove surface cracks deep groove grinding can be processed Bending welding repair, welding flange after welding, the original plane above the weld, must be flat through the turning weld , In order to ensure the formation of flange surface.
4. Spool corrosion damage:
4.1 Causes: (1). Spool material selection improper.
4.2 Elimination method: (1). According to the nature of the media and temperature selection of qualified spool material. (2). Replacement of the valve in line with the requirements, the installation should be consistent with the flow of media.
(C), butterfly valve common faults, causes and elimination methods 1, filler leakage:
1.1 Causes: (1) packing did not compress. (2). Not enough packing circle. (3) filler wear, aging.
1.2 Elimination method: (1). On the suspected crack polished, etching with 4% nitric acid solution, if cracks can be displayed. (2) cracked at the cracked wheel with a light metal to crack the cracked layer; processed bevel weld repair, valve body made of alloy steel and bonnet, before welding to be carried out at 250 ℃ ~ 300 ℃ Preheat, after welding to asbestos dust naturally cooled to room temperature. (3) After flange welding, the weld is higher than the original plane, must pass through the flat weld, in order to ensure the formation of concave and convex mouth without deformation after heating.
2, valve and pipe connections at the leak:
2.1 Causes: (1). Flange nut is not tightened or unevenly fastened. (2) Flange sealing surface or valve end sealing surface damage or dirt. (3) gasket failure.
2.2 Elimination method: (1). Tighten the nut evenly. (2) Repair the sealing surface or clean the dirt. (3). Replace the gasket.
(D), safety valve common fault causes and solutions:
1, pulse gate leakage:
1.1 Causes: (1). Deviation of the door core and door center is too large, because the door core in the door seat cover too much gap, resulting in lax joint surface. (2). Door core combination with the door to eat too narrow, or vaguely broken place. (3) Lever is not horizontal position, inconsistent gate knife edge and the fulcrum blade center to form one-way door force, or two pairs of screws on the door to withstand the hole on both sides of the door core, preventing the ball compensation . (4). Door seat sleeve outer ring of a small narrow gasket is not done, the thickness may not be enough, or over-pressure and fracture. (5) There is dirt in the tube, back seat card action in the combination of the surface of poor contact. (6). Pulsating gate lower strut (formerly referred to as the cushioning piston) over the fingers, against the door core, so that the binding surface can not be combined.
1.2 Elimination method: (1) replace the door core, so that the gap in the seat cover line with the quality standards, to door core 0.17 ~ 0.35mm.
(2). Grind again. (3) Welding repair or file to the lever on the two knife, so that the tip in the lever centerline. Check the stability of the two poles on the door, adjust the position of the door and the ball inside the door core, so that the steady screw cap does not touch the hole in the door core. (4). Switch to forming copper gaskets, when installed first annealed copper mat, a detailed examination of its location. (5). When the valves of the extraction pipe are installed and reprocessed, carefully clean the dirt inside the pipe. (6). After assembly, check strut empty trip, control within 3 ~ 5mm. If there is no free travel, the strut rod should be worn away.
2, pulse door stuck dead, no action or action is not flexible:
2.1 Causes: (1). Hammer the wrong position, will not be fixed after thallium fixed, so that heavy hammer displacement. (2) Leakage of the door core joint interface is too large, or the gasket of the door seat cover leaks, resulting in slow movement. (3) inconsistent leverage knife gate deviation, or lever knife Λ111 °. (4). Clamping plate tightly stuck door lever or door core seat cover gap is too small. (5) Door lever and lever connection Plywood size wrong, lever force is not on the blade. (6). Sliding pole is too short, so that the pulse door slightly open, the door core pressure drops after the spool rises, can not continue to open the pulse gate.
2.2 Elimination method: (1). Maintenance will be heavy hammer fixed screws live, after the fixed wheel tighten the screws. (2). Re-ground door core joint surface to replace the lower gasket. (3). Lever knife to readjust, check knife point angle = 111 °. (4) Adjust the plate nut to eliminate skew, adjust the gap between the door core and the door sleeve, so that they meet the quality standards. (5). Replace the splint to make it the same size as door and lever pin pitch. (6) Keep the strut empty travel at 3 ~ 5mm.
Third, the conclusion In short, quickly and correctly determine the causes of valve defects, and promptly take the correct way to eliminate, to ensure the safety of power plant units, stable, economical and efficient operation, can provide better protection.
References [1] Wang Hao. Power plant valve leakage form and factors and pressure plugging method [J]. Science and Technology of Communications, 2014, (10): 149 + 147.
Key words: thermal system, valve defect elimination method, reliability and economy CLC number: TG245 Document code: A Article ID: 1009-914X (2017) 25-0370-01
First, an overview Power plant thermal system is a combination of thermal equipment and soda pipes and various accessories made of organic whole, in this organic whole, soda pipes and valves are not only an integral part of the production system, but also occupy an important position , Because the power plant production process and the delivery of the working fluid, must be completed through the pipeline, the valve is an important part of the pipeline, only in the piping system to arrange various types of valves, the media movement is controlled, the pipeline facilities to give full play to the utility , To meet the needs of the production process to ensure system security.
At present, power generation units are in the direction of large capacity, high parameters, the valve also with the media parameters to improve, continue to the high temperature, high pressure direction; with the media pressure to improve the valve is also constantly improving the sealing structure, the use of New sealing materials to improve the sealing performance; with the continuous improvement of the level of automation of the generator set, the valve drive device and the implementing agencies have been improved, and to facilitate the centralized control and remote control direction.
Second, the valve selection and common failures, causes and elimination methods (A), power plant safety, economic and rational use of the valve is inseparable from the valve on the pipeline can be used according to the type of media and media working parameters (Pressure, temperature and flow) and other factors to choose. When it is chosen, the nominal pressure, nominal diameter, working temperature and operating range of the selected valve should be adapted to the nominal pressure, nominal diameter and medium type in the piping system where the valve is located. At the same time, the ease of installation, operation, maintenance and overhaul should also be taken into account and economically justified.
(B), gate valve , globe valve common faults, causes and elimination methods 1, the valve body leakage:
1.1 Causes: (1). Casting poor manufacturing, with trachoma or cracks, resulting in reduced mechanical strength. (2). Fracture body repair welding.
1.2 Elimination method: (1). On the suspected crack polished, etching with 4% nitric acid solution, if cracks can be displayed. (2) cracked at the cracked wheel with a light metal to crack the cracked layer; processed bevel weld repair, valve body made of alloy steel and bonnet, before welding to be carried out at 250 ℃ ~ 300 ℃ Preheat, after welding to asbestos dust naturally cooled to room temperature. (3) After flange welding, the weld is higher than the original plane, must pass through the flat weld, in order to ensure the formation of concave and convex mouth without deformation after heating.
2, the door rod and the thread with the damaged wire or broken door, bending:
2.1 Causes: (1). Improper operation, excessive force, too much, with a small hook off the valve. (2) Thread fit too loose or too light. (3). Too many operations, the service life is too long.
2.2 Elimination method: (1). Improve the operation, generally do not allow to close the small valve with a large hook. (2) When manufacturing spare parts to meet the tolerance requirements to choose the appropriate material. (3), re-processing replacement parts.
3, the door cover with leakage:
3.1 Causes: (1). Bolt tension is not enough or tight bias. (2) The cover gasket is damaged. (3) with uneven surface or groove cracks.
3.2 Elimination methods: (1). Bolts to deal with the corner tight, tight to ensure consistency, the surface should be consistent with the gap. (2). Change the gasket. (3). Disintegration re-repair the bonding surface, such as the groove with the groove surface cracks deep groove grinding can be processed Bending welding repair, welding flange after welding, the original plane above the weld, must be flat through the turning weld , In order to ensure the formation of flange surface.
4. Spool corrosion damage:
4.1 Causes: (1). Spool material selection improper.
4.2 Elimination method: (1). According to the nature of the media and temperature selection of qualified spool material. (2). Replacement of the valve in line with the requirements, the installation should be consistent with the flow of media.
(C), butterfly valve common faults, causes and elimination methods 1, filler leakage:
1.1 Causes: (1) packing did not compress. (2). Not enough packing circle. (3) filler wear, aging.
1.2 Elimination method: (1). On the suspected crack polished, etching with 4% nitric acid solution, if cracks can be displayed. (2) cracked at the cracked wheel with a light metal to crack the cracked layer; processed bevel weld repair, valve body made of alloy steel and bonnet, before welding to be carried out at 250 ℃ ~ 300 ℃ Preheat, after welding to asbestos dust naturally cooled to room temperature. (3) After flange welding, the weld is higher than the original plane, must pass through the flat weld, in order to ensure the formation of concave and convex mouth without deformation after heating.
2, valve and pipe connections at the leak:
2.1 Causes: (1). Flange nut is not tightened or unevenly fastened. (2) Flange sealing surface or valve end sealing surface damage or dirt. (3) gasket failure.
2.2 Elimination method: (1). Tighten the nut evenly. (2) Repair the sealing surface or clean the dirt. (3). Replace the gasket.
(D), safety valve common fault causes and solutions:
1, pulse gate leakage:
1.1 Causes: (1). Deviation of the door core and door center is too large, because the door core in the door seat cover too much gap, resulting in lax joint surface. (2). Door core combination with the door to eat too narrow, or vaguely broken place. (3) Lever is not horizontal position, inconsistent gate knife edge and the fulcrum blade center to form one-way door force, or two pairs of screws on the door to withstand the hole on both sides of the door core, preventing the ball compensation . (4). Door seat sleeve outer ring of a small narrow gasket is not done, the thickness may not be enough, or over-pressure and fracture. (5) There is dirt in the tube, back seat card action in the combination of the surface of poor contact. (6). Pulsating gate lower strut (formerly referred to as the cushioning piston) over the fingers, against the door core, so that the binding surface can not be combined.
1.2 Elimination method: (1) replace the door core, so that the gap in the seat cover line with the quality standards, to door core 0.17 ~ 0.35mm.
(2). Grind again. (3) Welding repair or file to the lever on the two knife, so that the tip in the lever centerline. Check the stability of the two poles on the door, adjust the position of the door and the ball inside the door core, so that the steady screw cap does not touch the hole in the door core. (4). Switch to forming copper gaskets, when installed first annealed copper mat, a detailed examination of its location. (5). When the valves of the extraction pipe are installed and reprocessed, carefully clean the dirt inside the pipe. (6). After assembly, check strut empty trip, control within 3 ~ 5mm. If there is no free travel, the strut rod should be worn away.
2, pulse door stuck dead, no action or action is not flexible:
2.1 Causes: (1). Hammer the wrong position, will not be fixed after thallium fixed, so that heavy hammer displacement. (2) Leakage of the door core joint interface is too large, or the gasket of the door seat cover leaks, resulting in slow movement. (3) inconsistent leverage knife gate deviation, or lever knife Λ111 °. (4). Clamping plate tightly stuck door lever or door core seat cover gap is too small. (5) Door lever and lever connection Plywood size wrong, lever force is not on the blade. (6). Sliding pole is too short, so that the pulse door slightly open, the door core pressure drops after the spool rises, can not continue to open the pulse gate.
2.2 Elimination method: (1). Maintenance will be heavy hammer fixed screws live, after the fixed wheel tighten the screws. (2). Re-ground door core joint surface to replace the lower gasket. (3). Lever knife to readjust, check knife point angle = 111 °. (4) Adjust the plate nut to eliminate skew, adjust the gap between the door core and the door sleeve, so that they meet the quality standards. (5). Replace the splint to make it the same size as door and lever pin pitch. (6) Keep the strut empty travel at 3 ~ 5mm.
Third, the conclusion In short, quickly and correctly determine the causes of valve defects, and promptly take the correct way to eliminate, to ensure the safety of power plant units, stable, economical and efficient operation, can provide better protection.
References [1] Wang Hao. Power plant valve leakage form and factors and pressure plugging method [J]. Science and Technology of Communications, 2014, (10): 149 + 147.
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