Valves Maintenance Technology
With the continuous development of oil fields, domestic oil fields have entered the middle and late development stage, and oil well maintenance and oil and gas transportation have become the key work of oil fields. In these processes, a wide variety of valves are used. Although the valve was inspected 100% before leaving the factory, and all the performance indexes met the standard requirements, in the process of use, various defects began to appear due to the change in the use environment and time. To avoid safety accidents, it is necessary to stop the use of the valve, and replace it with a new one or use it after the defective valve is repaired and inspected.
According to incomplete statistics, in 2018, the number of valves used was about 30,000 sets, and the annual capital usage reached more than 10 million yuan per year, mainly small and medium-sized valves, medium-pressure valves and high-pressure valves.
Valve maintenance technology
1. Common faults of valves
Common valve failures refer to the phenomenon that the valve can't be opened normally or there is oil leakage, etc. There are four main failures.
(1) Valve leakage inside. The internal leakage of valves mainly includes the damage to the sealing ring; The valve body is damaged and the switch is not in place; Impurities exist between the sealing ring and the valve body; the O-ring of the sealed seat is not sealed.
(2) Valve leakage outside. Valve leakage mainly includes valve stem leakage; Leakage of sewage from the mouth; Leakage at the flange joint.
(3) The switch is difficult. The main reasons for the difficulty in switching are the excessive pressure difference between upstream and downstream; Rust of the sealing ring and the valve core; The pressure difference between DPE valves, valve cavity pressure and downstream are too large; Sealing ring lock or deviation of sealing seat is not correct, and sealing ring groove is blocked; The valve cavity is caused by water freezing; The torque of the rotary seal seat is slightly larger at the last 1/8 of the closing stroke.
(4) Failure of the grease injection system. The main reason for the failure of the grease injection system is the problem of the grease injection nozzle; Internal check valves or check valves fail; The seal is hardened and blocked. In addition to the above basic faults, the valve also has the phenomena of damaged handwheel, broken valve stem, oil leakage at the valve body and lax sealing at the bolt and flange face. Only by analyzing the basic faults of the valve, can the valve be repaired purposefully.
From the above faults, it can be seen that the problems of the valve are mainly reflected in two aspects, namely, the damage to metal parts and soft seals. It needs to be treated differently in the overhaul process.
2. The basic process of valve maintenance
Summarizing the maintenance experience of domestic valve maintenance manufacturers, we can get the basic process of valve maintenance: on-site disassembly, cleaning and disassembly, parts inspection, repair, assembly, testing, painting and packaging, and acceptance. Whether it is metal or non-metal parts maintenance, the above basic procedures should be implemented.
3. Contents of valve maintenance
According to the basic structure of the valve and the fault of the valve, the overhaul contents are as follows.
Faults and maintenance of valves
Internal leakage of the valve: grinding of static sealing surface; replacement of sealing ring, packing and sealing gasket; repair of the T-groove; repair of the gate drop; repair of the gate guide groove.
Leakage of valves: repair of micropores of the valve body by glue infiltration; repair of the valve body by screws of small holes of the valve body; repair of damaged adhesive and lining; flange turning, grinding and repairing; straightening of the valve stem; grinding of the valve stem sealing surface; repair of the valve stem thread; repair of the valve stem head; repair of the bearing position of the valve stem and the shaft; electroplating, nitriding and heat treatment of the valve stem; replacement of the valve stem.
Switch difficulty: sealing surface repair; valve stem repair; cleaning the sundries inside the cavity; cutting off the upstream and opening the downstream valve.
Failure of the grease injection system: replacement of grease injection nozzle; dredging repair of check valves.
Others: maintenance of supports, springs, bolts, valve signs, bearings, etc.
4. Technical difficulties in valve maintenance
Valve grinding
Grinding of valves is suitable for repairing scratches, abrasions, corrosion spots and indentations with unevenness out of tolerance and defect depth within 0.3mm. The grinding process of the valve follows the following points.
(1) The grinding amount should be controlled within 0.3 mm, and the pre-tightening clearance of the static sealing surface should be checked to see if it meets the requirements; The grinding process should be checked while grinding to prevent the occurrence of grinding defects.
(2) The roughness of the ground static sealing surface should meet the following requirements: the general static sealing surface ≤ 12.5; O-ring groove ≤ 6.3; trapezoidal groove, lens type, conical pad static sealing surface ≤ 3.2; rigid static sealing surface ≤0.40.
(3) After grinding, the unevenness of the static sealing surface should meet the following requirements: generally, the static sealing surface should be printed evenly; Trapezoidal ring, lens pad, conical pad and static sealing surface are evenly distributed and continuous; The static sealing surface is printed with a round shadow and is qualified continuously.
Valve Pressure Test
A Valve pressure test is a key process to check whether the valve is qualified for maintenance, and it is also difficult to maintain. The valve pressure test is mainly carried out according to the standard of the Industrial Valve Pressure Test, in which the test medium, test items, test pressure and holding time of the valve are specified in detail. At present, there are many kinds of valves in China, mainly referring to foreign test equipment. According to the application of valves in Topper Valves, the combination of water pressure test and gas test can be adopted.
Domestic water pressure test equipment can be used for the low-pressure gas test, but the observation mode of the experimental process needs to be improved, so it is necessary to conduct an air pressure test separately, while the high-pressure gas test needs a high-pressure water pressure test first, so the combination of water pressure test and gas test can meet the test requirements.
Maintenance equipment and tools for valves
In order to meet the requirements of valve maintenance, the valve maintenance process needs to be equipped with corresponding equipment, which can be simply configured as follows according to the usage of the valve. Valve maintenance tools mainly include common wrenches, common measuring tools, etc. In the process of maintenance, according to the specific valve needs, some tooling and so on are configured in real-time.
Configuration of valve maintenance equipment: a DN50-DN200 ball grinder, a DN40-DN300 gate grinder, a DN20-DN300 planetary grinder, a DN10-DN100 valve test bench, a DN80-DN300 valve test bench, a DN300-DN600 valve test bench, a gas test bench, an electric welding machine, a cold welding machine and a shot blasting device.
Summary
(1) In the process of valve maintenance, mastering valve grinding technology is the key to valve maintenance. In terms of equipment selection and use, try to refer to foreign portable grinding equipment, which can bring convenience to valve maintenance.
(2) The research of the valve maintenance technology provides technical support for the development of the valve maintenance business in Topper Valves. In the follow-up maintenance process, it is necessary to constantly solve the problems existing in the valve maintenance process and improve the maintenance quality.
According to incomplete statistics, in 2018, the number of valves used was about 30,000 sets, and the annual capital usage reached more than 10 million yuan per year, mainly small and medium-sized valves, medium-pressure valves and high-pressure valves.
Valve maintenance technology
1. Common faults of valves
Common valve failures refer to the phenomenon that the valve can't be opened normally or there is oil leakage, etc. There are four main failures.
(1) Valve leakage inside. The internal leakage of valves mainly includes the damage to the sealing ring; The valve body is damaged and the switch is not in place; Impurities exist between the sealing ring and the valve body; the O-ring of the sealed seat is not sealed.
(2) Valve leakage outside. Valve leakage mainly includes valve stem leakage; Leakage of sewage from the mouth; Leakage at the flange joint.
(3) The switch is difficult. The main reasons for the difficulty in switching are the excessive pressure difference between upstream and downstream; Rust of the sealing ring and the valve core; The pressure difference between DPE valves, valve cavity pressure and downstream are too large; Sealing ring lock or deviation of sealing seat is not correct, and sealing ring groove is blocked; The valve cavity is caused by water freezing; The torque of the rotary seal seat is slightly larger at the last 1/8 of the closing stroke.
(4) Failure of the grease injection system. The main reason for the failure of the grease injection system is the problem of the grease injection nozzle; Internal check valves or check valves fail; The seal is hardened and blocked. In addition to the above basic faults, the valve also has the phenomena of damaged handwheel, broken valve stem, oil leakage at the valve body and lax sealing at the bolt and flange face. Only by analyzing the basic faults of the valve, can the valve be repaired purposefully.
From the above faults, it can be seen that the problems of the valve are mainly reflected in two aspects, namely, the damage to metal parts and soft seals. It needs to be treated differently in the overhaul process.
2. The basic process of valve maintenance
Summarizing the maintenance experience of domestic valve maintenance manufacturers, we can get the basic process of valve maintenance: on-site disassembly, cleaning and disassembly, parts inspection, repair, assembly, testing, painting and packaging, and acceptance. Whether it is metal or non-metal parts maintenance, the above basic procedures should be implemented.
3. Contents of valve maintenance
According to the basic structure of the valve and the fault of the valve, the overhaul contents are as follows.
Faults and maintenance of valves
Internal leakage of the valve: grinding of static sealing surface; replacement of sealing ring, packing and sealing gasket; repair of the T-groove; repair of the gate drop; repair of the gate guide groove.
Leakage of valves: repair of micropores of the valve body by glue infiltration; repair of the valve body by screws of small holes of the valve body; repair of damaged adhesive and lining; flange turning, grinding and repairing; straightening of the valve stem; grinding of the valve stem sealing surface; repair of the valve stem thread; repair of the valve stem head; repair of the bearing position of the valve stem and the shaft; electroplating, nitriding and heat treatment of the valve stem; replacement of the valve stem.
Switch difficulty: sealing surface repair; valve stem repair; cleaning the sundries inside the cavity; cutting off the upstream and opening the downstream valve.
Failure of the grease injection system: replacement of grease injection nozzle; dredging repair of check valves.
Others: maintenance of supports, springs, bolts, valve signs, bearings, etc.
4. Technical difficulties in valve maintenance
Valve grinding
Grinding of valves is suitable for repairing scratches, abrasions, corrosion spots and indentations with unevenness out of tolerance and defect depth within 0.3mm. The grinding process of the valve follows the following points.
(1) The grinding amount should be controlled within 0.3 mm, and the pre-tightening clearance of the static sealing surface should be checked to see if it meets the requirements; The grinding process should be checked while grinding to prevent the occurrence of grinding defects.
(2) The roughness of the ground static sealing surface should meet the following requirements: the general static sealing surface ≤ 12.5; O-ring groove ≤ 6.3; trapezoidal groove, lens type, conical pad static sealing surface ≤ 3.2; rigid static sealing surface ≤0.40.
(3) After grinding, the unevenness of the static sealing surface should meet the following requirements: generally, the static sealing surface should be printed evenly; Trapezoidal ring, lens pad, conical pad and static sealing surface are evenly distributed and continuous; The static sealing surface is printed with a round shadow and is qualified continuously.
Valve Pressure Test
A Valve pressure test is a key process to check whether the valve is qualified for maintenance, and it is also difficult to maintain. The valve pressure test is mainly carried out according to the standard of the Industrial Valve Pressure Test, in which the test medium, test items, test pressure and holding time of the valve are specified in detail. At present, there are many kinds of valves in China, mainly referring to foreign test equipment. According to the application of valves in Topper Valves, the combination of water pressure test and gas test can be adopted.
Domestic water pressure test equipment can be used for the low-pressure gas test, but the observation mode of the experimental process needs to be improved, so it is necessary to conduct an air pressure test separately, while the high-pressure gas test needs a high-pressure water pressure test first, so the combination of water pressure test and gas test can meet the test requirements.
Maintenance equipment and tools for valves
In order to meet the requirements of valve maintenance, the valve maintenance process needs to be equipped with corresponding equipment, which can be simply configured as follows according to the usage of the valve. Valve maintenance tools mainly include common wrenches, common measuring tools, etc. In the process of maintenance, according to the specific valve needs, some tooling and so on are configured in real-time.
Configuration of valve maintenance equipment: a DN50-DN200 ball grinder, a DN40-DN300 gate grinder, a DN20-DN300 planetary grinder, a DN10-DN100 valve test bench, a DN80-DN300 valve test bench, a DN300-DN600 valve test bench, a gas test bench, an electric welding machine, a cold welding machine and a shot blasting device.
Summary
(1) In the process of valve maintenance, mastering valve grinding technology is the key to valve maintenance. In terms of equipment selection and use, try to refer to foreign portable grinding equipment, which can bring convenience to valve maintenance.
(2) The research of the valve maintenance technology provides technical support for the development of the valve maintenance business in Topper Valves. In the follow-up maintenance process, it is necessary to constantly solve the problems existing in the valve maintenance process and improve the maintenance quality.
