Valve internal leakage criteria? Valve operation precautions? Specifications for valve painting and marking
1, determine the valve internal leakage method after the valve is closed for 4-6 hours, use infrared thermometer to measure the stem (near the valve body) or 150mm downstream of the valve body metal temperature, such as greater than 70℃, it is identified as “internal leakage”. This method is applicable to most internal leak valves. But in the actual work, we encountered the following special cases 
1) due to the installation position of the pipeline, there are some valves before and after the disturbance of high temperature steam, such as connected to the pressure of the drain, the drain of the jellyfish tube
First, the valve leakage determination standard
1, determine the valve leakage method
After 4-6 hours of valve closure, use an infrared thermometer to measure the metal temperature at the stem (near the body) or 150mm downstream of the body, if greater than 70 ° c, it is considered as “internal leakage”. This method is applicable to most internal leak valves.
However, in our practical work, we encountered the following special cases:
(1) Due to the installation position of the pipeline, there are some valves before and after the disturbance of high temperature steam, such as connected to a pressure drain, jellyfish pipe trap or drain door, these valves even if tight leakage, the valve stem temperature will be more than 70℃.
(2) Side by side access the trap door or drain door of the trap and jellyfish pipe. When the position of a valve is close to the master pipe, as long as any branch valve in the pipeline leaks, the temperature of other valves will rise to more than 70℃, such as the boiler drain valve, superheated steam drain, etc. Therefore, THE DETERMINATION OF INTERNAL LEAKAGE IN THESE VALVES SHOULD ALSO BE MADE BY OTHER MEANS, SUCH AS MEASURING DOOR WALL TEMPERATURE OR PRIMARY DOOR STEM TEMPERATURE TO DETERMINE INTERNAL LEAKAGE.
Two, the valve operation matters needing attention
1. For the manual doors of the drainage water of the thermal system, they should be tightened again half an hour after the completion of operation to eliminate the valve gap caused by thermal expansion and cold contraction.
2. For the heat pipe with one or two doors, the operation sequence of the valve is as follows: open the door once before opening the door twice; When closing, you should first close the door twice and then close the door again.
3, for the operation of gate valve, can only be fully closed or fully open, do not allow half open half closed state, in order to reduce the blow damage to the valve.
Three, the valve management matters needing attention
Unit 1, before the start of each electric, pneumatic valve test, test process, should be the specialist in situ monitoring of the valve and damper movement situation, check the actuator connecting rod and the pin should be no looseness, bending and fall off, check the directions of the opening of the DCS and the in situ should be consistent, there are intermediate stop electric door to test intermediate stop is normal. Adjust the door switch direction is correct, flexible action, with interlocking loop to the relevant professional interlocking test, test pneumatic adjustment device should be flexible, no leakage and abnormal phenomenon, the test should stop the test when abnormal, timely notify maintenance personnel to deal with.
Unit 2, each time you start should be in strict accordance with the provisions of the corresponding operation, the water gate ShuFang should check shut down by the regulation, each ShuFang watergate is turned off (10 hours) after 6 hours, after the water gate of hydrophobic temperature indicator, should be based on the valve pipe after analyze and judge whether the valve leakage, temperature indicating there is no temperature indicating to thin after watergate, The infrared thermometer is used to measure the temperature of the front and rear pipe walls of the valve or feel to determine whether the valve is leaking. Such as electric or pneumatic valve leakage, should be closed hydrophobic electric door or pneumatic door manual isolation door, for hydrophobic electric door, pneumatic door without manual isolation door, such as leakage, should be shaken to close the electric door, and missing and contact maintenance treatment. Such as manual door leakage, the missing and contact maintenance treatment.
3, each time before the unit shutdown, the valve defects (leakage) should be checked, the leakage valve should be boarded and inform the relevant maintenance department.
4. In the opening and stopping process or with pressure drainage process, after the drainage (discharge) water gate is opened, check whether there is a temperature after the valve or throttle hole (trap), to ensure that it can play the role of drainage (release) water, to prevent corrosion caused by the heat pipe water caused by the blockage of the valve or pipeline or throttle hole (trap).
The VALVE PAINTING AND MARKING STIPULATE THAT THE VALVE MATERIAL IDENTIFICATION SHALL BE PAINTED ON THE NON-MACHINED SURFACE OF THE VALVE BODY AND BONNET, AND THE SEALING SURFACE IDENTIFICATION SHALL BE PAINTED ON THE TRANSMISSION HANDWHEEL, HANDLE OR WRENCH, AND THE PAINT COLOR SHALL BE AS SPECIFIED IN THE TABLE BELOW. The paint color of the transmission mechanism is specified as follows: electric device, ordinary type painted medium gray; Three in one (outdoor, explosion-proof, anti-corrosion) type painted sky blue; Pneumatic, hydraulic, gear transmission and other transmission mechanism with the valve product color.
1. Identification of valve parts
On the shell of the valve valve, there is a horizontal line with an arrow. The numbers above the horizontal line indicate the nominal pressure level, and some indicate the temperature parameter and working pressure. For example, PNl0 and PT510 are used under the operating parameters of 10MPa and 510℃. The number below the horizontal line indicates the nominal diameter of the connecting pipe.
→ indicates that the valve is straight through, medium inlet and outlet flow direction, in the same or parallel center line.
Chrysene > indicates that the valve part is right-angle type, the medium acts on the closing part.
Indicates that the valve is three-way and the medium has several flow directions.
Post time: Aug-20-2022
