Keywords: intelligent valve positioner; adjustment; troubleshooting 0 Introduction Intelligent industrial control and automation is one of the current and future development direction, it has become a field of industrial and automation of various new technologies, new methods, new products Trends and notable signs. Intelligent valve positioner in the control accuracy, environmental adaptability, commissioning, maintenance and operation costs are superior to the conventional valve positioner, its practical application is also increasingly widespread, the problem of on-site adjustment also began to increase . How to deal with these problems and make the intelligent valve positioner get a better application is the problem that our field installation and debugging personnel must face.
1 intelligent valve positioner choice In engineering design, we must carefully select the appropriate smart valve positioner, the specific points to note the following:
1.1 requirements to meet the conditions of the scene to achieve intelligent requirements We use intelligent valve positioner, is to obtain its intelligent features and improve overall control performance. Therefore, to meet the conditions of the scene conditions, intelligent is our important indicator. Intelligence includes its communication capabilities, online or offline troubleshooting capabilities, and more.
1.2 requires on-site operation to be convenient For some intelligent valve positioner products, due to the more complex settings, affecting the product in actual use. Therefore, we prefer to operate convenient products.
1.3 Requirements on-site display Some intelligent valve positioner products, because there is no on-site liquid crystal display, so in the field adjustment must be adjusted by hand terminal. This adds cost. In addition, the LCD liquid crystal display, pay attention to its display at very low ambient temperature.
1.4 Requirements In some cases, to ensure the normal operation of long-distance installation As large petrochemical companies nowadays more and more joint control room, so from the control room to the scene intelligent valve positioner distance may be far, the cable voltage drop The problem must be considered, otherwise the intelligent valve positioner can not work normally.
2 intelligent valve positioner works Intelligent valve positioner generally modular design, its internal module base is a separate, it can easily replace the sub-module in the field without having to demolitions of the scene line or conduit. Some submodules can be installed in this mode field base: I / P converter, electronic and microprocessor unit components, pneumatic relay, position sensor, pressure indicator, etc. Some of the sub-modules such as pressure indicator Optional.
Intelligent valve positioner incorporates a highly integrated micro-controller, the use of electrical balance (digital balance) principle instead of the traditional balance principle, the control system to the input signal through the microprocessor and I / P converter into a pneumatic positioning increment Signal to achieve the valve position control, the use of digital open, stop, close the signal to drive the pneumatic actuator action, the valve position feedback signal directly through the high-precision position sensor into a digital signal input to the microprocessor for feedback comparison, Achieved electrical / gas conversion and valve positioning accuracy of the function. The integrated pressure sensor in the intelligent valve positioner is used to collect the gas pressure signal output by the valve positioner to the valve actuator to further improve the valve positioning accuracy and provide the basis for self-diagnosis of the intelligent positioner.
3 intelligent valve positioner the main features (1) high output force and speed of action;
(2) high regulation accuracy (minimum stroke resolution up to ± 0.05%), to achieve the correct positioning;
(3) simple installation, highly automated adjustment;
(4) almost maintenance-free operation, which means saving time and easy to use;
(5) Manual and automatic calibration function with zero position and travel range;
(6) has optional or programmable output characteristics;
(7) has a strong self-diagnostic function;
(8) Air consumption is much less than the traditional valve positioner;
(9) Setpoint and control variable limits can be set by selection;
(10) can be adjusted valve dead zone settings;
(11) The online adaptation process means high quality control even under harsh environmental conditions.
4 problems during use and solutions In the years of calibration and use of intelligent valve positioner, we encountered some problems and failures, summarized the following some common problems approach:
4.1 Intelligent Valve Positioner can not complete automatic calibration Automatic calibration can not pass the case, first after the manual calibration, then automatic calibration generally no problem.
4.2 Intelligent Valve Positioner can not complete automatic and manual calibration When automatic and manual intelligent positioner calibration can not pass, the main steps should be to check the process:
(1) Confirm there is no problem with the air circuit, the air path of the valve positioner is not blocked;
(2) check whether due to the installation and other issues in the process of switching the valve stuck phenomenon;
(3) check the intelligent positioner set the valve parameters are correct;
(4) Improper installation of the valve positioner feedback lever can also cause the intelligent positioner not to perform automatic and manual calibration. Normally, the lock nut on the intelligent positioner feedback lever is loose, resulting in the valve positioner feedback lever being deviated from the original installation position. In this case, the feedback lever mounting position needs to be adjusted.
4.3 control valve leakage, calibration problem still exists If the valve is still in the automatic calibration problem exists, you can use the following method:
(1) for gas off valve can first input 20mA signal, the valve is completely closed, and then use the two lock nuts on the stem to adjust the valve stem, the valve stem down until you can not make the valve stem to Move down so far. Then enter a signal of about 12mA and use the two lock nuts on the stem to adjust the stem to move 1/4 turn downward.
(2) for the gas valve can be input 4mA signal, the valve is completely closed, and then use the two lock nuts on the stem to adjust the valve stem, the valve stem down until you can not make the valve stem to Move down so far. Then enter a signal of about 12mA and use the two lock nuts on the stem to adjust the stem to move 1/4 turn downward.
4.4 intelligent valve positioner shock intelligent control valve installation problem:
(1) the valve installation problem caused by stem jamming control valve is not installed vertically, resulting in stem jamming, so that may cause the phenomenon of valve turbulence.
(2) gas connection is not correct In the large-diameter intelligent control valve, the valve positioner before the gas source has a gas source amplifier, the gas amplifier exhaust port in the valve during the movement of the insufficient amount of gas, resulting in the valve In the adjustment process of shock phenomenon.
5 Conclusion With the development of time and technological advances, its application will be increasingly widespread. Because it has a strong self-diagnostic function, when the problem is usually given a smart locator in a component of the fault tips, but sometimes these tips will mislead us, which requires us to take the overall system of vision To deal with the problem.
References [1] Pan Rui. Analysis of intelligent valve positioner in the application of chemical plant [J]. Shanxi Building, 2010,36 (34): 346-347.
[2] Jiang Zhiliang. Intelligent valve positioner in chemical plant applications [J]. Petrochemical Automation, 2000, (4): 69-71.
(Author: Henan Energy Chemical Group Coal Gasification Company Yima Gasification Production Management Center)
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