LC OVAL GEAR FLOWMETER
E: flowmeter error (generally total error), two effective numbers.
Vm: flow meter’s measuring value (displaying value).
V: after adjusted, flowmeter standard set measuring value (actual value).
It is known by basic error calculation that when Vm is larger than V, meter basic error is “+”
value ,which means that meter is fast, when Vm is smaller than V , meter basic error is “—”
value ,which means that meter is slow.
Flowmeter error may need to be adjusted and stay in basic error by replacing a standard gear set of the counter. That is to change mechanic transmitting ratio, which can make displaying value adjusted. Adjusting error can’t change flow meter’s flow characters, but it can make the error curve stay in the new coordinates system.
Usually, the actual flow range’s basic error of Max. &Min. tested dots is not able to surpass definitive basic error. Flowmeter used generally is tested by adjusting intrinsic gear wheel set and then adjust error again according to idiographic condition.
Vortex street flowmeter common faults
Q Using the Ann explosion-proof vortex flow time, the safety of the flameproof vortex flowmeter points is what?
A When using the Ann explosion-proof type of vortex flow sensors and flow display the flow measurement system, and between them must be equipped with explosion-proof electrical parameter matching of explosion-proof safety gate type sensor, and explosion-proof safety barrier and display must be installed in the safety zone (non explosive environment).
When using the flameproof vortex flow timing, should strictly abide by the “current state, not allowed to open the flame-proof electric shell”?Regulation, in the case of electricity, open the flame-proof shell electric adjustment is very dangerous and absolutely not allowed.
What is Metal Tube Rotameter?
Metal tube rotameter, characterized by high strength, safety, and durability, is designed to measure the flow of such medium as liquid, gas, and vapor etc. It is especially suitable for measuring the corrosive and turbid liquid as a result of its fine characteristics of high pressure and temperature resistance. Metal tube rotameter is able to not only ensure high measurement accuracy but also enhance safety and dependability. Thanks to its nicely unique appearance design, it has the finest explosion proof performance.
The rotameter adopts variable area measuring principle. The measuring device is composed of one taper measuring pipe and floater. The floater can move freely up and down in the taper measuring pipe to change the flow area in the pipe. When the flow changes, the vertical position of the floater inside the measuring pipe changes correspondingly. Through magnetic transmitting system, the position of the floater is transmitted to the dial scale of the indicator to indicate the flow.
Rotameter uses magnetic sensor and chip process technology, which allows the LCD to express instantaneous flow, accumulated flow, and percentage flow, and also provides twowire current signals output 4~20mA, compatible with HART communication protocol. Equipped with the indicator and alarm switch on the setpoint, metal tube rotameter gives high precession indicating and alarm signals output.
How to choose a right model for electromagnetic flowmeter?
The flowmeter model selection is very important in the application of instrument. The related information shows that in the practical application of instruments,2/3 failures are caused by incorrect selection of model and incorrect installation of instrument to which the special attention shall be paid.
1. Data Collection
1> Name of measured liquid and its chemical substance.
2> Maximum flux and minimum flux Normal flux.
3> Maximum working pressure.
4> Maximum and minimum temperatures.
2. The measured liquid shall have certain conductivity, with conductivity t>5 μS/cm.
3. The Miximum flux and the minimum flux shall meet the values specified in the following page.
4. The actual maximum working pressure shall be less than the rated working pressure of the flowmeter.
5. The maximum and minimum working temperatures shall meet the temperature requirement stipulated for flowmeter.
6. Whether negative pressure exists or not shall be confirmed.
You may choose a corresponding electromagnetic flowmeter according to the fluxes in the above table, and if the inside diameter of the selected electromagnetic is different from that of the tube under existing process, the tube reduction or expansion shall be considered.
1. In case of tube reduction, whether the pressure loss caused by tube reduction will affect the process flow or not shall be considered.
2. If the price of the product is considered, the electromagnetic flowmeter with smaller diameter maybe selected to reduce investment relatively.
3. When the uncontaminated water is measured, the economic velocity is 2-3m/s, and when the solution which is easy to crystallize is measured, the velocity shall be increased appropriately to common velocity of no less than 2 m/s. so as to prevent the electrode of electromagnetic flowmeter from being covered.
Prev:How to use the instrument correctly?
Ultrasonic level transmitter Measuring principle: Time-of-flight method
The sensor of the meter pulses in the direction of the product surface. There, they are reflected back and received by the sensor. The meter measures the time t between pulse transmission and reception. The meter uses the time t (and the velocity of sound c) to calculate the distance D between the sensor membrane and the product surface: D=c*t/2. As the device knows the empty distance H from a user entry, it can calculate the level as follows: L= H- D.
An integrated temperature sensor compensates for changes in the velocity of sound caused by temperature changes. Calibration Enter the empty distance H and the span F to calibrate the device.
Blanking distance: Span F may not extend into the blanking distance B. Level echo from the blanking distance cannot be evaluated due to the transient characteristics of the sensor.
Ultrasonic flow meter Measuring principle
When the ultrasonic beam is transmitted through the flowing liquid, there will be a difference between the
upstream and downstream transit time (travel time or time of flight), which is proportional to flow velocity,when
fluid is flowing,counterflow transit time is more than direct flow transit time. the formula as below.
θ :The angle between the ultrasonic
beam and the flow
M :Transit times of the ultrasonic beam
D :The internal diameter of the pipe
Tup: Transit time in the forward direction
Tdown Transit time in the reverse direction
F is instant flow rate(unit:m³/hour)
D is inside pipe diameter(unit:m)
V is flow velocity(unit:m/s)
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