Precautions for installation and use of regulator valve
Matters needing attention for installation and use of regulator valve:
New design, installation of the control system, in order to ensure that the regulator valve in the start up can work normally, and make the system safe operation, before the installation of the new valve, should first check whether the nameplate on the valve is consistent with the design requirements. The following projects should also be debugged. Basic error limit; Full stroke deviation; Back to the poor; Dead zone; Leakage volume (in a demanding situation).
If it is the original system control valve overhaul, in addition to the above check, should also old valve stuffing box and joints and other parts of the sealing inspection. Regulator valve in the field of use, many often is not caused by the quality of the regulator itself, but the improper installation of the regulator valve caused by, such as the installation environment, installation position and direction of improper or pipeline is not clean and other reasons. Therefore, the electric control valve should pay attention to the following aspects in the installation and use:
(1) the control valve belongs to the field instrument, the environmental temperature should be in the range of -25 ~ 60℃, relative humidity ≤95%. If it is installed in the open air or high temperature occasions, should take waterproof, cooling measures. In the source of the place to be away from the source of vibration or increase anti-vibration measures.
(2) the regulating valve should be installed vertically in general, under special circumstances can be tilted, such as the tilt Angle is very big or the valve itself weight is too big when the valve should be added support protection.
(3) the pipeline for installing the regulator valve should not be too high from the ground or the floor. When the height of the pipeline is greater than 2 m, the platform should be set as far as possible to facilitate the operation of the handwheel and maintenance. (4) before the installation of the regulator valve, the pipeline shall be cleaned to remove dirt and welding slag. After installation, in order to ensure that impurities do not remain in the body, the valve should be cleaned again, that is, all the valves should be opened when the media is in, so as to avoid impurities stuck. After using the handwheel mechanism, should be restored to the original neutral position.
(5) in order to enable the regulator to continue the production process in the case of failure or maintenance, the regulator shall be provided with a bypass pipeline.
At the same time, special attention should be paid to whether the installation position of the regulator conforms to the requirements of the process.
(6) the electric part of the electric control valve shall be installed according to the construction requirements of the relevant electrical equipment. If the flameproof product is used, it shall be installed according to the requirements of "installation code of electrical equipment in explosive dangerous places". Such as the scene copper-clad SBH type or other six or eight core, the outer diameter is about 11.3 mm Φ rubber cable installation. In the use of maintenance, in the explosive places are prohibited to open the electricity cover maintenance and the explosion-proof surface for pry. At the same time, do not break or scratch the flameproof surface in the process of disassembly and installation, and restore to the original flameproof required state after maintenance.
(7) the reducer of the actuator should pay attention to oil lubrication after repair, low speed motor generally do not
Analysis of common fault locations and causes
The working performance of the regulating valve will directly affect the working quality of the whole regulating system. Because the regulating valve is in direct contact with the adjusted medium on the spot, the working environment is very bad, so it is easy to produce a variety of faults. In the production process, in addition to the troubleshooting at any time, but also must carry out regular maintenance and regular maintenance. Especially for the use of the environment is particularly bad control valve, more attention should be paid to the maintenance and regular maintenance.
Different types of regulator, its failure and its causes are not the same. Taking the direct stroke electric control valve produced by * instrument general factory as an example, the general failure and maintenance method of electric control valve are illustrated.
2.1 servo amplifier
When the servo amplifier works normally:
(1) when there is no input signal, there should be no output voltage.
(2) open loop dead zone current acuities were 160 mu (Ⅱ type is 100 mu).
(3)输入信号＞240 μA(Ⅱ型为150 μA)时，输出负载电压为205～220VAC。
(4) the output voltage is basically symmetrical.
If the servo amplifier is not working properly, the following situations may occur in each part:
(1) magnetic preamplifier
When there is no signal input, the output of the double-beat magnetic amplifier can be adjusted to zero through the potentiometer W101. If it cannot be set to zero, it may be:
A. Transformer W101 is out of welding or damaged.
B, resistors R110, R111 and electrolytic capacitors C101, C102 are welded or unwelded.
C, diode D105 ~ D108 virtual welding or damage.
D. abnormal deviation current.
E. Asymmetric ac winding.
(2) there is an input signal, but no output or output asymmetry may be:
A. The voltage at the secondary end of the ac winding current supplied by transformer B301 is asymmetric.
The resistance values of B and R110 and R111 have changed, and the electrolytic capacitor C110 and C111 are damaged.
C. Ac excitation winding short circuit.
D, diode D105 ~ D108 have individual tube damage or virtual welding.
(2) when the flip-flop has input, one side of the flip-flop should have an impulse signal on the oscilloscope screen. If the polarity of the input signal is changed, the other side of the flip-flop should have an impulse signal. The number and amplitude of the two sets of trigger pulses should be basically the same. Otherwise, there are several situations.
There is no input signal (the pre-magnetic amplifier is in normal working state), and there is a trigger pulse at the output end, which may be:
A. The triode on the side with triggered pulse output is damaged, or it is extremely virtual welding of c and e.
B, resistance R204, R205, R208, R209 resistance values changed.
There is an input signal and no trigger pulse at the output terminal, which may be:
A. The triode on the side without output pulse and the single-junction tube are damaged.
B. Primary or secondary circuit failure or short circuit of the pulse transformer on the side without output pulse.
C. The diode (D207 or D208) on the side without output pulse is short-circuited.
(3) abnormal output trigger pulse has the following phenomena:
A. When there is no signal, the two sets of triggers have pulse output, which is normal after the signal is added, which may be the virtual welding of electrolytic capacitor C202 or C203.
B. The output of both sides of the trigger is normal at the beginning. After working for a period of time, the output pulse gradually disappears.
C. Positive and negative pulses appear in the output, which may be the breakdown or virtual welding of diode D207 and D208.
(3) after the above inspection and maintenance, the servo amplifier should work normally when the control circuit is fault-free. Otherwise, there are two situations:
When there is no input signal, the output voltage (the voltage is close to 220VAC) may be:
A. SCR SCR1 and SCR2 are damaged.
B. Capacitors C301 and C302 are broken down.
When there is an input signal, there is no output signal or the output voltage is too low, then it may be:
A, diode D301 ~ D308 have been broken.
B. SCR SCR1 and SCR2 are damaged.
2.2 the regulator
When 4 ~ 20 mA signal is input, the regulating valve stem can move up and down freely in the rated stroke with the change of signal. If normal operation is not possible, the following faults may occur:
Operating handwheel paresthesia
A. It feels too light, maybe the handwheel pin has fallen off or broken.
B. It feels too heavy or can't swing. There is a foreign body stuck in the reducer; Spool and bushing or stuck with seat; The stem is severely bent.
Input 4 ~ 20 mA signal, the regulating valve does not work.
A. wrong connection of the system.
B. CD of motor splitter capacitor is damaged.
C. Open motor wiring.
D. Spool falls off or stem breaks (at this time, actuator has action)
Input 4 ~ 20 mA signal, the regulator valve can not complete the rated stroke.
A. the position of the differential transformer is not adjusted.
B, diode D701 ~ D712 has individual damage.
C. Triode BG701 is damaged.
(4) other faults in field use.
Valve vibration, call.
A. If the sensitivity is adjusted too high, the actuator will oscillate.
B. The fluid pressure changes too much and the actuator lacks thrust.
C, the choice of the regulating valve is large, the valve often in a small opening work.
D. The flow direction of the medium is consistent with the closing direction of the valve.
E, nearby other source impact, support instability.
F, spool and bushing wear seriously.
The valve is slow.
A. The viscosity of the medium is too large, resulting in blockage or coking.
B, the packing aging, packing pressure is too tight.
Large amount of leakage.
A. Valve core or seat is corroded and worn.
B. Loose seat or corroded thread.
C. There is a foreign body on the seat and spool.
D. The starting point (electric open type) or ending point (electric closed type) of the valve is not adjusted.
(4) packing and upper and lower cover joints leakage.
A. The packing gland is not pressed tight.
B. teflon packing aging and deterioration.
C. Stem damage.
D. the tightening nut is loose.
E. damaged gasket.The correct use and maintenance of the electric control valve can not only improve the adjustability of the process control, but also increase the service life of the electric control valve, which has considerable economic benefits to the energy saving and consumption reduction of enterprises.