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The rotameter measuring method and instrument: rotameter, also called rotor flowmeter, a variable area flowmeter, vertical cone expansion upward in a pipe under the circular cross-section, the float is powered by a liquid under gravity, can float freely up and down in the cone tube in. In the motion velocity and buoyancy, and the weight of the float balance, the magnetic coupling and the dial indicator to flow. Generally divided into glass and metal rotor flow meter. Metal rotameter is the most commonly used in industry, for small diameter corrosive medium, usually with glass material, because of its fragility of glass material, key control points are also useful for full of precious metals such as titanium material for rotor flowmeter.
The rotor flow meter (rotameter) features: rotor flowmeter is industrial and laboratory a flowmeter is the most commonly used. It has the characteristics of simple structure, intuitive, small pressure loss, convenient maintenance and so on. The rotor flow meter is suitable for measuring the flow rate of corrosive medium, which can be measured by the small flow rate of 150mm and d< of the pipe diameter. The flow meter must be installed in the vertical direction of the pipe segment, the fluid medium from the bottom through the rotor flow meter.
The rotor flow meter (rotameter) working principle: the rotor flowmeter consists of two components, one is from the conical rotor flowmeter to gradually expand the tube; the other one is the rotor rotor flowmeter in conical tube can move along the center line of the pipe under the free. When the rotor flowmeter measurement of fluid flow, fluid flows from the lower end of the measured cone tube, fluid flow impact on the rotor, and a force exerted on it (the magnitude of this force varies with the size of the flow); when the flow is large enough, the force generated by the rotor bracket, and the increase of. At the same time, the measured fluid flows through the annular section between the rotor and the conical pipe wall, and flows out from the upper end of the rotor.
When the force of the rotor is measured when the fluid flow is measured, it is equal to the weight of the rotor in the fluid (known as the weight), the rotor is in a state of equilibrium and stays at a certain height. The analysis shows that the position of the rotor in the conical tube is highly related to the flow rate. Therefore, the observation of the position of the rotor in the cone tube height, you can obtain the corresponding flow value.
In order to make the movement of the rotor in the center line in the conical pipe without touch tube wall, usually two ways: one is a guide rod is arranged in the center of the rotor, the rotor to keep moving up and down in the center line of the conical pipe, the other is on the rotor disc edge is provided with a chute road when the fluid flows through the rotor, from top to bottom, side around the rotor, but also through the chute to produce a reverse thrust, the rotor spins around the center line, you can keep the rotor do not hit the wall at work. Rotor flow meter can be made of stainless steel, aluminum, bronze and so on.
The rotor flow meter (rotameter) of the common problems
Pointer jitter: slight pointer jitter: generally due to the media caused by fluctuations. Can be used to increase the damping of the way to overcome. Moderate pointer jitter: in general, due to the state of the media flow. For gas in general due to the operation of the medium pressure instability caused by. The regulator or stabilizer to overcome or increase the damping gas rotameter. Severe pointer jitter: mainly due to medium gas pressure pulsation, the operating state of instability or the user is given the pressure, temperature, flow rate and the actual state of the rotameter is inconsistent, there are large differences caused by excessive rotameter.
Two, the pointer to a fixed location: the main reason is the death card float float flowmeter. Because of rotameter when used to open the valve too fast, so fast float upward impact on the stopper, causing the stopper deformation will float stuck. But do not rule out the float guiding rod and the stop ring is not concentric, causing the float stuck. Treatment can be removed meter deformation stopper remove plastic, and check with the guide rod is concentric, concentric can be corrected if not, then the float installed, hand feeling under the float, float on unimpeded card, in addition, the flowmeter must be installed vertically or horizontally. The installation can not tilt, otherwise it is easy to cause the card table and bring error to the measurement.
Three, measurement error
The installation does not meet the requirements of installation: vertical rotameter to keep vertical angle less than 20 degrees; the level of installation of rotameter to maintain the level, angle less than 20 degrees; 100mm space around the rotameter may not have ferromagnetic objects. The installation location must be away from the valve port, the pump outlet diameter, pipeline corner etc.. To maintain the requirements of 250mm straight pipe section before 5d.
The density change of liquid medium is also one of the reasons that lead to large errors. The instrument in the calibration, will give users according to the conversion of medium density, converted into the calibration condition of water flow calibration, so if the density change of medium large, will cause great error on the measurement. Solution can be changed after the medium density into the formula, converted into error correction factor, and then the flow meter measured flow multiplied by the coefficient for the real flow. Because of the great influence of temperature and pressure, the temperature and pressure compensation method is recommended to get the real flow.
Due to many factors and long-term use of pipe vibration caused by float flowmeter sensor magnet, a pointer, a counterweight, a rotary magnetic activities such as loose parts, resulting in large errors. Solution: first hand pointer to verify the way. First of all, according to the pointer in the RP position, see whether the output is 4mA, the flow rate is 0%, and then in accordance with the scale to verify. If it is found that does not match, the parts can be adjusted to the position. General requirements of professional adjustment, or will result in loss of position, the need to return to the manufacturer for correction.
Four, no current output: first look at the wiring is correct. Liquid crystal display, if there is no output, and more for the output tube is bad, need to replace the circuit board. Missing calibration value. Due to E2PROM failure, resulting in loss of instrument calibration data, it will cause no output current, the current will remain unchanged. Solution: available data recovery operation, if not work, you can set the password 2000 in the data, and then set the password 4011 data, the method is to manually push the pointer calibration data from RP to 100%.
Five, no site display: check wiring is correct. Check whether the power supply is correct. Re install the LCD module, check the contact is not real. For multi wire system power supply inspection 12, 13 terminal is connected with the current meter or short circuit.
Six, the alarm is not correct: check the deviation set D value can not be too large. Fun function, the logic function is correct. A - ha represents the upper bound of positive logic. A - La represents the lower bound of positive logic. Check the alarm value setting size in su. If the LCD bar code is correct, the output has no action, can check the external power supply and the external power of the negative electrode is connected with the instrument power supply. Circuit board fault, replace the circuit board.
Seven, the total field of liquid crystal display 0 or full range: check the 2000 password set range, zero parameters. Requires zero to be less than the value of span, two values can not be equal. Check whether the sampling data to come up, hand push pointer to see the sample value change, if no change, the general circuit board sampling circuit failure, the need to replace the circuit board.
Eight, the cumulative pulse output is not correct: check the cumulative pulse output of the alarm value is set to zero. Circuit board fault, replace the circuit board.
