The SELECTION AND CALIBRATION MAINTENANCE OF THE SAFETY valve of LECCO. Lecco Valve specialist answers how to verify the pilot safety valve correctly and quickly

The SELECTION AND CALIBRATION MAINTENANCE OF THE SAFETY valve of LECCO. Lecco Valve specialist answers how to verify the pilot safety valve correctly and quickly

The control pressure determines the nominal pressure of the safety valve, the operating temperature determines the use temperature range of the safety valve, the calculated constant pressure value of the safety valve determines the constant pressure range of the spring or lever, and then decides the material and structure of the safety valve according to the use of the medium, and then calculates the throat diameter of the safety valve according to the release of the safety valve. The following are the general rules for safety valve selection.
(l) Hot water boilers generally use unclosed micro open safety valve with wrench.
(2) Steam boiler or steam pipeline is generally used not closed with a wrench full open safety valve.
(3) Water and other liquid incompressible media generally with closed micro open safety valve, or with a safety relief valve.
(4) High pressure water supply is generally used closed full opening safety valve, such as high pressure water supply heater, heat exchanger and so on.
(5) Gas and other compressible media generally use closed full-opening safety valve, such as gas storage tanks, gas pipelines, etc.
(6)E class steam boiler generally with static weight safety valve.
(7) large diameter, large displacement and high pressure system with the general pulse safety valve, such as temperature reduction and decompression device, power plant boiler, etc.
(8) Built-in safety valve is generally used for transporting liquefied gas, such as train tankers, truck tankers and storage tanks.
(9) The top of the tank is generally used with hydraulic safety valve, which needs to be used with the breathing valve.
(10) The pilot safety valve is generally used for underground drainage or natural gas pipelines.
(11) Safety return valve is generally used on the liquid phase return pipeline at the outlet of tank pump of liquefied petroleum gas station.
(12) Negative pressure or negative pressure may be generated in the process of operation, the system is the same as the general vacuum negative pressure safety valve.
(13) the container or pipeline with large back pressure fluctuation and toxic and flammable is the same as the general bellows safety valve.
(14) the low freezing point of the medium is the same as the general selection of thermal insulation jacket type safety valve.
Safety valve calibration and maintenance
To test the safety valve’s technical performance indicators must be a full performance test, test the most basic requirement is to have the actual running state, even more than the actual running state. In addition to high temperature and high pressure vessels and other equipment, this test device should also be equipped with a variety of rapid determination of parameters, and ensure a large flow of high temperature and high pressure steam source, the cost is huge.
Check is a part of the safety valve test and is the main item of the factory’s factory test. Before leaving the factory, the safety valve check table at room temperature is generally used for opening pressure adjustment and sealing test of air medium. Safety valve room temperature check table can only do open pressure adjustment and sealing test.
(1) Under what circumstances does the safety valve need to be checked
1) Before long-term storage or * use
2) Regular verification
3) Severely damaged and corroded valves
4) Valves with missing valve nameplates
5) Valve with damaged lead seal
(2) The significance and method of adjusting the seat pressure
National standard of the definition of back pressure refers to the relief valve to discharge, medium pressure dropped to a certain value, the disc to contact with the seat, i.e. open height is zero, the valve inlet of the static pressure, back pressure is too low, too much is bad, too low will cause medium and energy loss, is too high, short of emissions, caused the valve frequency jump, The principle is to adjust the back seat pressure as much as possible to reduce the loss of medium and energy in the case of achieving emissions.
(3) Adjustment method
The back seat pressure is adjusted by adjusting the ring, the principle of adjustment is the gap principle, the smaller the gap, the greater the resistance when ejecting, the greater the force holding the spool down, the more difficult it is to return to the seat, on the contrary, the larger the gap, the more easy the spool to fall back, the higher the back seat pressure.
For the safety valve with only the lower regulating ring, the regulating ring is up, the back seat pressure is down, the regulating ring is down, the back seat pressure is up; For the safety valve with the up and down regulating ring, the distance of the up and down regulating ring decreases, the back seat pressure decreases, the distance of the up and down regulating ring increases, the back seat pressure increases.
(4) check method and its advantages and disadvantages
Safety valve check has the field check (online check) and check table check two means, conditions allow should try to check in the field, because the field check is more suitable for the actual operating conditions, so can be better.
The advantages of field check: easy to check the welding safety valve, can be measured back pressure, accurate measurement.
The disadvantage is that the calibration time is long, the system should be repeatedly boosted, not economic, more dangerous, can not do the sealing test.
Advantages and disadvantages of safety valve room temperature check table:
A. Solve the adjustment and leak detection of the safety valve of normal temperature medium and operating temperature below 250C.
B. Determine the small error range of the opening pressure of the safety valve, save the adjustment time of the newly installed safety valve, reduce the labor intensity, reduce the energy consumption and reduce the work risk.
C. There is an error between the operating temperature and normal temperature (the spring becomes soft at high temperature), and the pressure of the back seat cannot be verified.
(5) the medium used for normal temperature verification
Air, nitrogen and water are generally used for normal temperature verification (the pressure is above 20Mpa). Oxygen, hydrogen, acetylene gas and other flammable, combustion-supporting or toxic and harmful media can not be used as the medium source verification. Kerosene, gasoline, diesel, etc., can not be used as a medium source. Although carbon dioxide gas is non-toxic and non-combustible, it is easy to freeze and block the pipeline.
(6) safety valve calibration principle
The medium with pressure is passed into the inlet of the checked safety valve. When the medium pressure rises to the open state of the safety valve, the pressure at this time is measured, and the opening pressure is placed and adjusted to the specified opening value to complete the opening pressure verification. Then when the pressure drops to the specified value (90% of the opening pressure), the pressure gauge or other legal methods are used to check for medium leakage, that is, sealing check.
How to verify the pilot safety valve correctly and quickly
Pilot safety valve is a kind of safety valve with novel structure. It IS mainly used in petroleum and NATURAL gas, chemical industry, electric power, metallurgy and city gas and other fields. It is the best overpressure protection device for pressurized equipment, containers or pipelines. Its main advantage is become spring direct action for the pilot indirect effect, enhances the sensitivity of action, and the sleeve is used in the main valve piston, double seal seat structure, high precision, good repeatability, back to move fast, can not leak, take high back pressure discharge, long working life, work stable and reliable, it can also be online calibration, and jump again and again after discharge, still can automatically return, Close tightly, easy to operate and maintain.
Pilot type safety valve
The pilot safety valve is on the basis of the ordinary spring safety valve, adding the pilot mechanism, so that the safety valve has the pilot safety valve and the double role of the ordinary safety valve. Its characteristics are: accurate and reliable action; The sealing performance is fundamentally improved; The opening and closing pressure difference is easy to meet the requirements; Sensitive action, large emissions. So do you know how the pilot safety valve should be calibrated? Our Leco valve specialist will organize this knowledge for you.
Spring type safety valve
Pilot safety valve verification procedure:
First, the pilot safety valve check is generally sent to the check station check by the user, in special cases can be used in the field check, the site check user should provide the necessary conditions for check.
Two, the user should provide the pilot safety valve factory information, the design pressure and use pressure of the equipment pipeline, the last calibration report or the calibration opinion issued by the equipment inspector.
Three, check the data submitted for review, determine the setting pressure.
4. Check the newly installed pilot safety valve with complete data. Under normal circumstances, two working days are desirable; For the pilot safety valve in large quantities or in need of maintenance, the completion time shall be determined according to the actual situation through consultation with the user.
Five, according to the calibration content, fill in the calibration record, issue the inspection report.
Six, after the verification, the tester will inform the user to get the pilot safety valve and the inspection report.