Valves are indispensable components in petrochemical and other engineering projects, and they play a vital role in the connection and installation of process pipelines and mechanical equipment. The quality control of the valve is not only related to the construction progress and quality standards of the project, but also directly affects the smooth progress of the production linkage test and the safe and stable operation of the device.
The quality control of the valve should follow strict specifications and standards to ensure that the valve meets the requirements of the project in order to ensure the smooth completion of the project and the long-term stable operation of the device. This article will briefly introduce the installation and construction technology of petrochemical valves from the following aspects. First, the valve construction process flow chart
On the premise of meeting the requirements of the project specification, the corresponding plan can be formulated according to the type of valve, whether the coating has been completed when the valve arrives, and the results of the valve tightness test. 
2. Valve tightness test
Valve tightness test refers to the process of inspecting the sealing performance of the valve before the valve is installed, so as to ensure that the valve does not leak during use, and to ensure production safety and environmental protection. 
2.1 Classification of tightness tests
According to the provisions of "GB T 13927-2022 Pressure Test of Industrial Valves", the tightness test of general valves in the pressure pipeline industry is divided into the following four categories:
Housing test
It is used to verify the strength and sealing performance of the valve housing and seat. The test pressure is 1 of the design pressure of the valve housing5 times, the test medium is water or air.
Upper seal test
It is used to check the sealing performance of the connection between the valve actuator and the valve stem. The test pressure is 1 of the design pressure of the valve housing1 times, the test medium is water or air.
Low-pressure seal test
It is used to verify the sealing performance between the valve closure and the valve seat. The test pressure is 06 MPa with water or air as the test medium.
High pressure seal test
It is used to verify the sealing performance between the valve closure and the valve seat. The test pressure is the sealing test pressure of the valve, and the test medium is water or air.
The overall requirements of the tightness test
1.Test medium
Water should be used as the medium for strength test and high-pressure sealing test, and the water temperature should not be lower than 5 and not higher than 50.
The low-pressure seal test should use air or nitrogen as the medium, and the gas temperature should not be lower than 5 and not higher than 50.
Unless otherwise specified, vapors, oils, or other corrosive media should not be used as test media.
2.Test pressure and its control
The test pressure of the strength test should be 15 times the nominal pressure pn or the specified housing design pressure ps.
The test pressure of the high-pressure seal test should be 11 times the nominal pressure pn or the specified housing design pressure ps.
The test pressure of the low-pressure seal test should be 06MPa or the specified value.
Unless otherwise specified, each type of tightness test should be gradually ramped up from zero to the specified test pressure and held for at least 2 minutes.
3.Blocking method
During the strength test and high-pressure seal test, both ends of the valve should be completely blocked, and the exhaust hole should be opened in the appropriate position.
During the low-pressure seal test, one end of the valve should be completely blocked, and the other end should be connected to the air source.
4.Detection method
At the time of the strength testThe pressure-bearing parts such as the valve body and bonnet should be comprehensively observed to check whether there are abnormal phenomena such as deformation, cracks, and leakage. •High pressure seal test, the sealing parts such as the seat and stem should be fully observed to check whether there is any leakage. There are several ways to determine a leak:
Visual method: that is, to observe with the naked eye whether there are water droplets or water columns overflowing from the sealing part.
Auditory method: that is, use your ears to hear whether there is a sound of water flowing from the sealing area.
Sensory method: that is, touch your fingers to see if there is any water flowing out of the sealing area.
Coloring method: that is, a layer of liquid with obvious color, such as paint, ink, etc., is applied to the sealing part to observe whether there is color change or flow. •Low pressure seal test, the sealing parts such as the seat and stem should be fully observed to check whether there is any leakage. There are several ways to determine a leak:
Bubble method: that is, apply a layer of soapy water or other foaming agent to the sealing part to observe whether there are bubbles produced or increased.
Pressure gauge method: that is, the pressure gauge is connected at one end of the valve, and the pointer of the pressure gauge is observed to see if there is a drop or fluctuation.
Sound method: that is, use an earpiece or other sound amplifier to listen for the sound of gas escaping from the sealed part.
5.Maintenance
After the tightness test, the medium in the valve should be discharged in time, and the surface and inner cavity of the valve should be cleaned to prevent the medium from corroding or blocking the valve. After the tightness test, the valve should be inspected, and after confirming that there is no damage, the valve should be closed, and the valve should be affixed with a qualified label or record sheet for installation and use.
3. Valve coating
Valve coating is an important step in the production and maintenance of valves, ensuring that the surface of the valve has good anti-corrosion properties and prolonging its service life. Here are the general painting requirements:End and stem protection
The end of the valve and the stem should be protected before blasting. This is to prevent damage to these areas during the blasting process and to ensure that the coating adheres evenly to the valve surface.
Paint requirements
The paint applied must meet the requirements of the project specifications. This includes specifications for color, thickness, adhesion, etc., to ensure that the coating quality meets standards. Listing distinction
After the painting is completed, it is necessary to tag the type of valve and the valve number. This is to clearly identify the valve during installation and maintenance, improving the accuracy of the operation. Water streak protection
During the hoisting process, special attention needs to be paid to the protection of the water surface of the valve. The water ripple surface is the key part of the valve, and its effective protection can prevent scratches, damage, etc., and ensure the sealing performance and normal operation of the valve. Fourth, valve installation and later maintenance
4.1. Large valve hoistingBefore carrying out large-scale valve lifting, it is necessary to prepare a valve lifting plan, which includes valve turning over and valve side entry or formal installation. It is necessary to fully consider the details such as the first method, the way of hooking, the paint protection, the capacity requirements of the tools and the crane, the way of standing and the hoisting path. For instrument valves with pneumatic or electric actuators, a special lifting scheme should be provided by the valve manufacturer. 4.2 Installation of valves
1.Cleaning and end corrosion inspection
Cleaning Check:Before the valve is in place, the inside of the valve should be carefully cleaned and inspected to ensure that there is no debris or dirt.
Corrosion Situation:Check the end of the valve for corrosion, if corrosion is found, it needs to be rectified in time.
2.Hoisting and bolt piercing
Bolt perforation:For flanged valves, make sure to thread at least one bolt through each bolt hole after hoisting in place.
Locating bolts:If the valve has locating bolts, make sure the valve is aligned before wearing the locating bolts.
3.Centering installation
Alignment check:Before the valve is officially installed, it is important to carry out a alignment check.
4.3. Commissioning and trial operation of the valveThe commissioning and trial operation of the valve refers to the process of inspecting and adjusting the performance and function of the valve after the installation of the valve, so as to ensure the normal operation and use of the valve. 4.4. Later maintenance of valves
The later maintenance of the valve refers to the process of regular inspection, cleaning, lubrication, replacement and other operations on the valve after the valve is put into use, with the purpose of prolonging the service life of the valve and keeping the valve in good condition. The installation and construction process of the valve is an important part of ensuring the performance and service life of the valve, and it needs to be operated in accordance with the specifications and requirements to avoid quality problems and potential safety hazards. At the same time, the later maintenance of the valve is also a necessary measure to prolong the life of the valve and keep the valve in good condition, and it is necessary to carry out regular inspections to find and solve problems in time to ensure the smooth progress of petrochemical production.