Proper installation of the control valve is just as important as proper selection. Installation quality is related to the operational performance, control quality, safety and cost of the control system, so it should be taken seriously.
The control valve is installed at the site, which puts higher requirements on fire prevention, explosion prevention and leakage prevention. The noise pollution of the control valve is also increasingly valued by relevant departments.
Preparation for installation and construction
In order to strengthen the management of the quality of construction projects, ensure the quality of construction projects, and protect the safety of people's lives and property, the construction organization of construction projects implements a qualification management system.
The construction project construction unit shall undertake the construction business of the construction project within the scope of its qualification permit. It is forbidden to construct construction projects and allow other units or individuals to undertake construction business related to construction projects in the name of their own units. It is forbidden for the construction project construction unit to exceed the business scope of the qualification level of the unit or to undertake the construction business of the construction project in the name of other construction units. In violation of the above provisions, the company shall be ordered to suspend business for rectification and reduce the qualification level until the qualification certificate is revoked.
The construction project construction unit shall be responsible for the construction quality of the construction unit, and the construction business of the construction project shall be completed within the specified time within the specified quality and quantity. The main work is as follows.
1. Establish a construction project quality responsibility system, determine the construction project, technical person in charge and construction management person in charge.
2. Participate in the bidding activities of construction projects in accordance with the principles of openness, fairness, impartiality and good faith.
3. Construction may not be carried out without permission before the construction unit obtains the construction permit or the construction report.
4. The construction projects contracted shall not be subcontracted or subcontracted. In addition to the subcontracts specified in the contract, the subcontractor must agree in writing to carry out the subcontracting or subcontracting of some minor projects in the contracted project. The subcontracting unit shall have the corresponding construction qualification and be subject to the management and coordination of the general contractor.
5. It is not allowed to collude with construction units, project supervision units, etc., to reduce fraud and reduce project quality and safety standards.
6. It must be constructed according to engineering design drawings and construction technical standards. It is not allowed to modify the engineering design without authorization. If there are any errors in the engineering design drawings and documents, it is necessary to make timely comments and suggestions.
7. According to the engineering design requirements, construction technical standards and contractual agreements, the equipment and components used in the construction shall be inspected, and the written records of the inspection signed by a special person shall be completed. Those who fail to pass the inspection or the inspection shall not be used, and shall not cut corners.
8. Adhere to the principle of â€œsafety*, prevention firstâ€, safe construction, civilized construction, and organize construction and safety management.
9. A sound construction inspection system should be established, strict process management should be carried out, and quality inspection and records of concealed works should be done. Concealed works should be quality tested by the relevant quality supervision department before concealing.
10. Establish and improve the education and training system, and strengthen the education and training of employees. Those who are not qualified for education or assessment may not be allowed to work.
11. Review of the construction drawings. Including professional construction drawings, system construction drawings and comprehensive construction drawings.
12. Quality problems arising during construction shall be rectified in a timely manner, and those that fail to pass the inspection shall be reworked.
13. When a problem occurs, for example, if the construction unit or design unit expressly or implies that the construction unit uses unqualified construction materials and equipment, it has the right to report, sue or complain to the construction administrative department or relevant department.
14. Completion of the completion acceptance report and related documents.
15. Support and cooperate with the construction unit and the construction project quality supervision unit to perform their duties according to law.
16. Vigorously advocate the use of advanced science and technology and management methods to continuously improve the quality of construction.
The construction contract is a written document signed between the construction unit and the construction unit. The construction contract shall include: the scope of the project, the construction period, the start and completion time of the intermediate handover project, the project quality, the project cost, the delivery time of the technical data, materials and equipment. Supply responsibility, appropriation and settlement, completion acceptance, quality warranty coverage and warranty period, liability for breach of contract, mutual cooperation, and resolution of disputes.
Division of construction and construction
Installation works can be divided into sub-projects, sub-projects and unit projects. Sub-projects are projects that are classified by purpose, type, and transport of different media and materials and equipment groups. For example, water supply installation engineering, drainage installation engineering, power transformer installation engineering, instrument panel installation engineering, temperature instrument installation engineering, etc. The divisional engineering is a project classified according to the type of installation engineering, such as pipeline installation engineering, electrical installation engineering, automatic instrument installation engineering, and process furnace installation engineering. A unit project is a unit of work. For example, a factory installation of an industrial building is a unit project, and the installation of outdoor water supply, drainage, heat and gas pipes in the plant area is a unit project. A unit project can consist of multiple sub-projects or sub-projects.
Industrial automation instrumentation engineering is also known as instrumentation engineering. The construction of the instrumentation engineering shall be carried out in accordance with the provisions of the design and construction drawings and the installation and operation instructions of the instrument and other relevant standards. Modification of the design must be approved by the original design unit.
Instrument engineering and other installation projects have a division of labor. described as follows.
1. The installation of the instrument's primary source unit shall be completed by the process and pipeline installation and construction unit. Installation should be done at the same time as the process piping is manufactured or prefabricated and installed. For example, the opening and welding of the source parts should be completed before the process piping or equipment anti-corrosion, lining, purging, pressure testing; the source parts on the high-pressure, alloy steel, non-ferrous metal pipelines should be mechanically processed; The source parts installed on the masonry or concrete cast body shall be buried at the same time during masonry or pouring. The source valve should be inspected before it can be installed, and the card sleeve connection method should not be used.
2. Instruments directly installed on the process piping, such as orifice plates, rotor flowmeters, control valves, etc., shall be installed by the pipeline installation and construction unit after the process piping is purged and before the pressure test. If it is required to be installed at the same time as the process piping, the instrument installation unit shall remove the instrument and install the short pipe when the process pipe is purged. After the purge is completed, the instrument shall be installed by the pipeline installation and construction unit.
3. The support, base or boom required for the installation of control instruments such as control valves and measuring orifices shall be completed by the pipeline installation and construction unit o. The operating platforms, connecting channels and other components required for maintenance of instruments and automation equipment are installed and constructed by equipment and pipeline installation and construction units.
4. Insulation engineering of instruments, automation equipment and pipelines shall be carried out by the installation and construction unit of the insulation layer.
5. The main pipe project of the instrument, automatic equipment for heat preservation, heat tracing and discharge pipelines, and the compressed air and hydraulic pipelines shall be installed and constructed by the pipeline installation and construction unit.
6. The connecting pipelines of the instrument, automation equipment and auxiliary equipment, the branch pipes of the heat preservation, heat tracing and discharge pipelines shall be installed by the instrument engineering installation and construction unit.
7. The installation of special instruments is installed and constructed by professional installation units. For example, the installation of analytical instruments and special instruments introduced with the associated equipment is installed and installed by a professional installation unit designated by the manufacturer.
8. If the instrument and automation equipment not specified in the design are installed, the construction unit and the general contractor shall determine the construction unit and the division of labor.
Control valve installation and construction regulations
General rules for installation and construction
The general provisions for the installation and construction of control valves are described below.
1. Control valve installation should be in accordance with the design drawings and design documents.
2. The installation of control valves shall comply with the relevant national standards, such as the quality inspection and assessment standards for construction and installation engineering, the construction and acceptance specifications of industrial automation instruments, the construction and acceptance specifications of electrical equipment installation works, etc.
3. The equipment, auxiliary equipment and main materials required for the installation of the control valve shall comply with the relevant provisions of the current national or ministerial standards.
Precautions for installation and construction
Precautions for the installation of control valves should be considered for ease of operation, safety and standardization. The details are as follows.
(1) Control valve installation position and orientation According to the design drawings and design documents, the installation position should have sufficient operating space for installation, operation and maintenance; its position should be protected from vibration, humidity and mechanical damage. Where there is strong electromagnetic interference, high temperature, severe temperature change and corrosive gas; the installation should be firm and level; the installation orientation should be such that the actuator of the control valve is in the upper part of the adjustment mechanism, Figure 6-8 shows the straight stroke control valve Various mounting orientations.
Among them, position 1. is the preferred location.
2. It is the location of the second election. If the installation site does not have enough space, the optional installation location 3. and 4. If necessary, there should be measures to prevent leakage. Try not to use the position 5. It is only used when the control valve is installed on the vertical pipe. At this time, the boom or support should be added, as shown in Figure 6-9. The valve shaft of the angular stroke control valve should be horizontal so that the dirt contained in the fluid does not sink to the rotary bearing of the valve shaft. For ease of operation and maintenance, the control valve should be installed close to the floor or floor.
(2) Flow of fluid in the control valve The flow of fluid in the control valve should be consistent with the arrow marked on the valve body of the control valve. Under special circumstances, it is not subject to the provisions of this regulation.
(3) Control valve connection control valve connection is threaded, flanged and welded. Threaded connections are used for small diameter control valves. When installing a threaded control valve, a removable movable connection must be installed at the same time. The flange connection has two types of flange connection and clamp connection. The nominal diameter of the connection flange should be the same as the diameter of the control valve. Flanges also have different pressure levels, and the pressure rating of the flange should be consistent with the pressure rating of the control valve. The inner diameter of the flange should be equal to the inner diameter of the pipe. The perpendicularity of the flange face to the axis of the pipe allows a deviation of lÂ°. The flange sealing surface should be flush. The coaxiality of the flange to the pipe allows the deviation t to satisfy:
t â‰¤0.015D(1/Î²) (6-27)
Where D is the inner diameter of the pipe; eve is the ratio of the inner diameter of the throttle to the inner diameter of the pipe under working conditions. When the flange is connected, the force should be evenly applied to avoid excessive pressure on the part.
Try to avoid solder joints, and the removable joints must be installed at the same time.
When the control valve is connected, the inside of the connecting pipe should not be led to a new projection. For example, gaskets, welds, etc. should not protrude inside the pipe.
(4) The control valve and the upstream and downstream shut-off valves and bypass valves are connected. The upper and lower shut-off valves and bypass valves should be installed at the same time as the control valve. The length of the pipe section between the upstream and downstream shut-off valves and the control valve should take into account the pipe resistance and the influence on the fluid flow state. The long length of the straight pipe section is conducive to the stability of the fluid after the valve is cut off, the fluid flow can be stabilized, the turbulence effect can be reduced, and the noise can be reduced; the length of the straight pipe section is short, and the fluid enters the control valve after being stabilized by the shut-off valve, so that the noise is enhanced. However, the short length of the pipe section is beneficial to reduce the pipeline resistance, increase the pressure drop across the control valve, and reduce the distortion of the flow characteristics, which is beneficial to the stable operation of the control system. Therefore, we should weigh and consider. Generally, the upstream side should have a straight pipe section of 10D to 20D, and the downstream side has a straight pipe section of 3D to 7D. D is the nominal diameter of the pipe and a rectifying device should be provided if necessary.
1. The choice of connection scheme. There are many ways to connect the control valve to the upstream and downstream shut-off valves. Figure 6-10 shows several common connection options. In the figure, the structure of the scheme A is compact, the floor space is small, the maintenance and operation are easy, and the system is easy to discharge or drain. However, it is often not possible to satisfy enough straight pipe lengths, resulting in increased noise. The structure of the scheme B is large, and the position of the control valve can be installed in the lower part or the upper part, which is easy to adapt to the operation requirements, but the length of the straight pipe section is not easy to guarantee. The structure of the scheme C is suitable for the angle control valve, which can reduce the number of elbows and has a small footprint. For the flow direction of the bottom side, there may be a longer length of the upstream straight pipe section. The structure of scheme D is similar to that of scheme B, and the floor space is large. The structure of the scheme E is suitable for the angle valve. Compared with the scheme C, the length of the straight pipe section on the upstream side is shortened, which is not conducive to the stability of the fluid. The structure of scheme F is a common connection structure of Zui. It has a large footprint and low pipe resistance, but has less space for operation and maintenance.
2. The connection of the relief valve, the vent valve and the drain valve. In order to facilitate the disassembly of the control valve, the pressure before and after the valve should be released before disassembly. The relief valve should be installed in the control valve and the upstream and downstream shut-off valves. between.
The vent valve and the drain valve are used to discharge non-condensable gases and condensate entrained in the fluid. When installing, when the controlled fluid is gas or steam, in order to facilitate the discharge of condensate, the drain valve should be installed at the lower part of the control valve group. When the controlled fluid is a liquid, in order to facilitate the venting of the non-condensable gas, the venting valve should be installed at the high position of the control valve group.
3. Bypass valve. When the control valve is disassembled for maintenance, the bypass valve can be used to operate the production process. When the controlled traffic is too large,
Figure 6-10 Common connection scheme
When the control valve cannot be adjusted normally, as a countermeasure, the bypass valve can also be used as a parallel connection scheme of the control valve to control the process. In order to reduce costs, the large-diameter control valve is equipped with a handwheel actuator that can be operated in place of the bypass valve. The installation of the bypass valve should be easy to operate. It forms a control valve group together with the upstream and downstream shut-off valves of the control valve. Therefore, it should be matched with them during installation and completed at the same time. The nominal diameter of the bypass valve is the same as the nominal diameter of the pipe, and the pressure rating is also consistent with the process withstand voltage rating.
(5) Installation of the actuator Generally, the actuator is directly connected to the valve body of the control valve. However, when the actuators such as the hydraulic actuator and the long stroke actuator are separated from the valve body of the control valve, attention should be paid to the installation of the actuator. The connecting rod and mechanical moving parts should be flexible, without looseness or squeaking. The length of the connecting rod should be stable, flexible and reliable in the full stroke range. When connecting to the control valve body with thermal displacement of the process piping, the relative position between the actuator and the control valve body should be kept constant. There are two types of handwheel actuators, side and top. There should be room for operation during installation. Handwheel operation should be flexible and there is no jamming or twisting. There should be a label indicating the relationship between the direction of rotation of the handwheel and the degree of valve opening. The limit device should be adjusted to protect it. The hydraulic actuator should be installed below the controller. If it must be higher than the controller, the height difference should not exceed 1.0m, and the exhaust valve should be installed at the pipeline gas collector, and the check valve should be installed near the controller. Automatic shut off valve.
(6) Valve positioner installation The valve position detection device of the valve positioner is directly connected with the valve stem or valve shaft of the control valve. Therefore, the feedback signal should ensure that the valve position signal and change can be correctly and timely reflected during installation. Typically, the valve positioner is supplied with the control valve and the manufacturer completes the connection. When the production process control needs to add a valve positioner, the correctness, reliability and flexibility of the valve positioner detection device should be ensured. The mechanical clearance of the feedback rod fulcrum should be as small as possible. The signal line of the valve positioner should be properly connected. The gas source line and output line and input line should be marked with the nameplate. The valve position display signal of the valve positioner should be useful for observation by operating and maintenance personnel.
(7) Installation of other accessories Other accessories include valve position sensor, solenoid valve, limit switch, relay, electrical converter, etc. The installation shall comply with the relevant provisions of the product manual. The small flow control valve should be fitted with a filter upstream. When the turbulence is severe, the rectifier should be installed on the upstream side.
(8) Installation of the connecting pipeline Installation of the connecting pipeline should pay attention to the following matters.
1. Signal gas pipe and gas source pipeline are generally made of PVC sheathed copper pipe cable with diameter sL6Xl or g18Xl
2. The air supply line should be close to the control valve.
3. Signal lines and hydraulic lines should be as short as possible to reduce signal skew and system time constants.
4. The pipeline should have sufficient expansion allowance and should not interfere with actuator operation.
5. The welding slag should not fall into the pipe when welding the pipeline. The connecting line should be cleaned before installation to remove dirt, water and rust. The piping connecting the pipelines should be neat and beautiful.
6. The hydraulic oil pipeline should be kept away from high temperature equipment and pipelines, and the distance from the hot surface should be greater than 150mm.
7. Before installation, the drain valve and vent valve connected to the pipeline should be cleaned, oil is removed, and inspection and testing are carried out.
8. The hydraulic and pneumatic piping systems shall be pressure tested and comply with the regulations.
9. The wires and cables connecting the signals should be laid through the pipe and connected with metal hoses on the equipment side. Equipment that requires explosion protection shall be subject to appropriate explosion-proof measures and shall be sealed for all protected systems.
10. The laying of pipelines shall not impede the operation of the operators and the maintenance of maintenance personnel.
11. The connected pipeline should be marked with a nameplate. If necessary, the pipeline can be fixedly connected by the support frame to prevent the connection pipeline from being fixed after the control valve is removed.
12. The connecting line should avoid the immersion and corrosion of water and liquid or the intrusion of harmful gases.
(9) Installation of additional pipe fittings The additional pipe fittings have a reduced diameter pipe and an enlarged diameter pipe. The installation of additional fittings increases the pressure loss of the piping and affects the flow coefficient of the control valve. When installing additional fittings, there should be room for operation at the joints to facilitate removal of the connecting bolts during maintenance. When installing the pipe fittings, install the support frame or support, and if necessary, add anti-vibration washers or anti-vibration springs.
(10) Control valves and other accessories for control valves and other accessories that require degreasing treatment must be degreased according to design regulations. The control valve and pipeline after degreasing should be naturally ventilated or dry with dry air or nitrogen. After passing the inspection, it should be closed and stored. It should be kept clean and free of oil during installation. Control valves and other accessories that require adiabatic and heat treatment should be insulated and heat treated. The laying of steam lines or heating cables for heat tracing shall comply with the relevant installation and construction regulations. The insulation material and thickness of the insulation shall comply with the design regulations. The various support brackets, supports and connecting lines for the installation of control valves and accessories are painted. Remove rust, weld slag, burrs and dirt from the surface to be painted before painting. The color and thickness of the paint, the conditions of the painting operation, etc. shall comply with the relevant regulations.
(11) Self-operated control valve The installation of the self-operated pressure and differential pressure control valve for the source component is carried out with reference to the installation regulations of the pressure source component. The source component of the self-operated temperature control valve can be constructed according to the temperature package installation regulations.
Control valve before installation
Part of the performance test should be performed before the control valve is installed. Before leaving the factory to the installation, the control valve and accessories are transported, stored, etc., and different environmental conditions cause changes in the performance of the control valve and accessories. Therefore, pre-installation inspection is required.
During the transportation process, the instrumentation equipment is subjected to random vibrations excited by the transportation tools and various shocks during loading and unloading. In addition, during the transportation process, the ambient temperature, humidity, etc. and climatic conditions will change. Therefore, during the transportation process, the instrumentation equipment Performance has changed.
Instrumentation equipment changes in the performance of the instrument due to changes in the climate, biological and chemical environmental parameters of the storage environment during storage.
The instrumentation equipment is subjected to mechanical stress caused by handling or assembly during the installation process, and also changes the performance of the instrumentation equipment. However, since the installation process is generally short-lived, the installation environment has less impact.
Environmental conditions for pre-installation control of control valves
Similar to the environmental conditions of other instrument inspections, the environmental conditions of the inspection site prior to installation of the control valve are as follows.
a. Temperature: 10 to 35 Â° C.
b. Humidity: The relative humidity of the air is not more than 85%.å·³No corrosive gas.
d. Good working lighting, clean, quiet and well lit.
e. It should not be inspected in places with high vibration, high noise, humidity, dust and strong magnetic field interference.
f. There should be inspection equipment such as power supply, gas source and hydraulic pump, and water supply and drainage equipment.
g. Power requirements: 50Hz, 220VAC or 48VDCil0%, 24VDCi 5%.
h. Air source requirements: clean, dry, dew point 10 Â° C lower than the low ambient temperature of zui, in line with the instrument compressed air quality standards,
The pressure is 0.5-0.7 MPa, the pressure is stable, and the fluctuation does not exceed Â±10% of the rated value.
Inspection content before control valve installation
The inspection before the installation of the control valve mainly includes the following contents:
a. Static characteristics test of the control valve;
b, air tightness test;
c. Sealing test, reinstall the stuffing box if necessary;
d. Leakage test
e. No-load full travel time test;
f. insulation performance test;
g, pressure strength test.
Before the actual installation, the tests that must be carried out include appearance test, compressive strength test, starting point error, dead zone, hysteresis, basic error test, leakage test, and no-load full travel time test.
Air supply requirements for control valves
Control valve accessories, such as electrical converters, electric valve positioners, pneumatic amplifiers, and retaining valves, are all pneumatic components. Therefore, the quality of the air supply to the control valve can be based on the requirements of the instrument to purify the air (HG/T20510-2000). )
1. Dew point temperature. The dew point is the temperature at which water vapor begins to condense under a certain pressure. The use of dew point to limit the moisture content in the gas source is a common method of engineering design. The moisture content of the instrument air source is not controlled by condensation at the operating pressure. Therefore, the dew point temperature under normal operating pressure should be at least 10 Â° C lower than the ambient temperature. For example, if the air dryer outlet pressure is 0.7 MPa and the ambient temperature is 15 Â° C, the operating pressure has a dew point of at least 25 Â° C. For example, in Shanghai, the dew point temperature at atmospheric pressure is 40 Â°C. Figure 6-11 shows the relationship between the dew point at atmospheric pressure and the dew point at operating pressure.
2. Dust content. The dust particle diameter at the outlet of the filter is not more than 3 Î¼m, and the dust content is less than 1 mg/m 3 . Inhalation of industrial dust and atmospheric dust, flammable, explosive, toxic and corrosive gases (or steam) should be avoided.
3. Oil content. The oil content at the outlet of the filter is not more than 10 mg/m3 [or 8 ppm (W)]. When using oil-lubricated air compressor or direct process air compressor as instrument air source, it must be equipped with high-efficiency degreaser to control the oil content in compressed air below the specified value, and with corresponding filtering and drying device and Alternate storage tank.
4. Air source pressure. Should be considered in accordance with the requirements of the end of the zui end instrument gas. The general limit pressure range is 500 to 800 kPa (G) and
300 to 500 kPa (G) two grades. For cylinder actuators, 0.7 MPa is recommended. The upper pressure limit is the delivery pressure under normal operating conditions of the air supply. The specified lower pressure limit is the low pressure of the Zui sent by the air source device. If it is lower than the specified value, there should be an audible and visual alarm and should be processed as soon as possible.
5. Air consumption. The steady-state air consumption of a single control valve is 1~2m3 (standard)/h, and the steady-state air consumption of the low-power positioner is
0.8 to 1.3 m3 (standard) / h estimate. The on-off valve is estimated to be 3 to 5 times the air consumption of the control valve according to the cylinder size and the operating frequency. It should be noted that the air consumption provided by the instrument manual is the air consumption of the air supply pressure of 140 kPa and the state of 20 Â° C. It should be converted to the air consumption under the standard state, and a leakage coefficient of 0.1 to 0.3 should be added.
6. The volume of the gas tank is determined. A gas storage tank with sufficient capacity should be set in the gas source device, and its volume is calculated according to the following formula.
V = QstPo / (P1 - P2)
Where V is a tank volume, m3;
Qs a gas source device gas supply design capacity, m3 (standard) / min;
P1 a normal operating pressure, kPa (A);
P2-zui low delivery pressure, kPa (A);
T-atmospheric pressure, usually, Po = 101.33 kPa (A);
Hold time, min, specific time from the process, the general retention time is 5 ~ u20min.
Control valve on-site commissioning
After the control valve is installed, the on-site commissioning of the control valve should be performed before the production process starts. On-site debugging is divided into line debugging and system debugging.
Line commissioning <br> Line commissioning is used to check that the signal line, air supply line or hydraulic line connecting the control valve is properly connected.
1. Control valve input signal connection. Usually, check with the valve positioner. The control valve input signal comes from the controller, so a start signal is output from the controller to check if the control valve is at the starting position; an end signal is output to check if the control valve is at the end position. To this end, check whether the supply air supply pressure is normal; whether the filter pressure reducer works normally; whether the hydraulic pressure supplied by the hydraulic system is normal; whether the power supply is normal; whether the output signal is correct, etc., and check at least 5 points within the measurement range. Whether the desired relationship is satisfied between the input signal and the valve position. It should be checked whether the air opening and air closing mode of action is correct and whether the safety production requirements of the process production process are met.
2. The connection of the control valve output signal. The control valve output signal is a valve position signal, which can be an analog signal or a digital signal. Check that the valve position signal is correct while checking the control valve input signal. When using a HART or intelligent electric valve positioner, check that the valve status information is correctly transmitted. During the full stroke operation of the control valve, the control valve spool and seat should be monitored for mechanical vibration and abnormal noise.
3. Handwheel mechanism debugging. Check if the handwheel mechanism can rotate and move correctly, and the limit and locking device are easy to use.
4. When the deviation exceeds the allowable deviation limit, the corresponding debugging should be carried out. For example, change the position of the position switch and check for leaks in the wiring or piping.
System Commissioning <br> The control valve is the final component of the control system. Therefore, the system must be commissioned before the control valve is operated. System commissioning should be coordinated with process operations.
1. Negative feedback debugging. The control system should meet the negative feedback requirements. Therefore, the controller, the detection transmitter and the control valve (including the valve positioner) should be considered together with the controlled object, and the positive and negative effects of the controller should be set. The negative feedback criterion is that the total open-loop gain of the control system is positive. After setting the positive and negative modes of the controller, the input signal can be simulated at the measuring end of the controller to increase or decrease, observe whether the output change of the controller meets the requirements of the action mode, and check whether the action direction of the control valve is correct. The controlled variable can be changed in a decreasing direction.
2. Control valve pressure drop check. The control valve pressure drop check is performed during the clean water simulation commissioning. During the full stroke operation of the control valve, check the pressure drop across the control valve, whether there is noise caused by cavitation or flashing, how the flow changes, and whether it meets the designed flow characteristics.
3. Response time check. When some control systems require a response time to the control valve, the response time of the control valve should be checked. When the controller output signal changes, the time required for the control valve position to reach 63% of the final steady state position of Zui is the response time, which should meet the operational requirements of the process.
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