HJ 15-2019Technical specifications and test procedures for ultrasonic open channel sewage flowmeter (English PDF)

4.1 Basic composition of the flow meter

The flowmeter generally consists of a primary meter and a secondary meter, as shown in Figure 1.

Figure 1 Schematic diagram of flowmeter composition

Primary instrument. Transmit and receive ultrasonic waves, convert the received ultrasonic signals into time series electrical signals and send them to the secondary meter.

Secondary instrument. Calculate liquid level height through time series electrical signal, calculate flow according to liquid level-flow formula, display, store, Output the measurement results.

4.2 Basic requirements

4.2.1 The identification of the instrument shall meet the requirements specified in GB/T 13306, and the label shall be fixed at an appropriate and obvious position.

Has the following identification.

a) the name and address of the manufacturer;

b) Instrument name, model specifications;

c) factory number;

d) manufacturing date;

e) measurement range;

f) Working conditions.

4.2.2 The surface coating of the flow meter should be sprayed evenly, without peeling, rusting or scratching, and with anti-corrosion function. Probe should Primary instrument secondary instrument

3 Seal is intact. The connecting part should be fastened and reliable. Potentiometers and screws used for adjustment should be varnished after assembly.

The flowmeter should have anti-corrosion function.

4.2.3 When the flowmeter is used in an environment with explosion-proof requirements, it should meet the explosion-proof technical requirements in GB 3836.1.

Obtain the corresponding explosion-proof certification.

4.2.4 The insulation strength of the flow meter should meet the requirement that it can withstand 50 Hz between the power line and the case, and 1500 V AC is effective the voltage is tested continuously for 1 min without flashover and breakdown. The insulation resistance between the power line and the case should be >=20 Mohm.

4.3 Functional requirements

4.3.1 The flow meter shall have the instantaneous liquid level, instantaneous flow rate, cumulative flow rate and the total measurement time of the cumulative flow rate.

(Min or h) function. The flow meter should have data memory and storage functions, and keep the existing data when it is stopped.

The minimum time should be no less than 1 year.

4.3.2 The flow meter should have the function of automatically locking the flow calculation parameters and storing data to prevent artificial changes in the flow calculation of the instrument Parameters and memory data such as accumulated flow and accumulated measurement time.

4.3.3 The flowmeter changes the key parameters such as weir trough, calibration level, calibration time, etc. to be done in the instrument's operation log the corresponding records shall be kept for at least one year.

4.3.4 The flowmeter shall have a digital output interface or an analog output interface.

4.3.5 Relevant requirements of water measuring weirs are implemented with reference to JJG 711.

Canal flow standard verification device verification is given.

4.4 Environmental adaptability requirements

4.4.1 The primary meter of the flow meter should meet the requirements of outdoor places (Class D1) in GB/T 17214.1.

4.4.2 The secondary meter of the flowmeter shall meet the requirements of the sheltered place (Class C1) in GB/T 17214.1.

4.4.3 The flowmeter should work under the condition that there is no foam or other floating substances on the surface of the measured medium.

6.1 Testing equipment

6.1.1 Flowmeter laboratory testing device. by height caliper (measurement range 0 ~ 1000 mm, minimum scale value is less than 0.5 mm, uncertainty is less than 0.5 mm), reflecting plate (flatness does not exceed 0.1 mm, with pointer, can indicate the height of the reflecting plate Degree position) and a meter, as shown in Figure 2.

Flow meter primary meter

Figure 2 Flowmeter laboratory testing device

6.1.2 Open channel flow comparison device. a level gauge (level measurement accuracy <=1 mm) plus a standard flow calculation formula can be used Way for on-site comparison.

6.1.3 Stopwatch.

6.2 Test conditions

Ambient temperature. 5 °C ~ 40 °C;

Relative humidity. 65% ± 20%;

Power supply voltage. AC voltage, 220 V ± 22 V;

Power frequency. 50 Hz ± 0.5 Hz.

Height caliper

Reflective plate

pointer

56.3 Testing methods

6.3.1 Level measurement error Use the flowmeter laboratory detection device to fix the flowmeter primary meter on the bracket above the height caliper to reflect the plate moves to 0 mm height caliper, and the flowmeter level returns to zero. Move the reflector in turn at the maximum scale of the height caliper (1000 mm) at 20%, 50%, and 80%, respectively, and then move the reflector in reverse direction at the height of 80%, 50%, Stop once at 20%. Record the liquid level indication iH of each flowmeter, calculate the liquid level indication and the height caliper scale value iH Stingy the maximum value of the absolute value of the difference is taken as the level measurement error and is calculated according to formula (1).

max

-= ii HH (1)

In the formula. -liquid level measurement error, mm;

iH-Flowmeter liquid level display at the i-th stop, mm;

--the value of the height caliper at the i-th stop, mm;

i--measurement sequence number, i = 1, 2, 3, 4, 5, 6

6.3.2 Flow measurement error Use the flowmeter laboratory testing device to fix the flowmeter primary meter on the bracket above the height caliper, as follows Steps to check flow measurement errors.

a) Set the flowmeter weir groove to a 90 ° triangle weir (p/B is 0.2);

b) Adjust the height caliper to zero and correct the zero level of the flowmeter level;

c) Adjust the height caliper to 20%, 50%, 80% of the maximum liquid level allowed by the weir groove in turn, and wait for the flow meter to show After the value is stable, record the flow display value separately;

d) Set the weir groove of the flowmeter to a rectangular notched thin-wall weir (0.5 m weir width, 1.0 m canal width, 0.25 m p) Repeat steps b and c after completion to record the displayed value of the flow;

e) Set the flowmeter weir trough to No. 4 Parshall trough, repeat steps b and c, and record the flow display value.

Calculate the percentage of the maximum difference between the displayed value and the theoretical value of the flow relative to the range value as the flow measurement error.

Equation (2) is calculated.

nsni

n 100

max x-= (2)

In the formula. nQ-flow measurement error of the nth weir,% niQ-Display value of flow rate at different levels of the nth weir trough, m3/h;

nsQ-Theoretical value of flow at different liquid level heights of the nth weir, m3/h.

6.3.3 Level precision Use the flowmeter laboratory detection device to fix the flowmeter primary meter on the bracket above the height caliper to reflect the board moves to the height caliper of 0 mm, and the flowmeter liquid level returns to zero. Move the reflector to the maximum scale of the height caliper (1000 mm) at 80% of the level, record the level indicator of the flowmeter after the level indicator is stable, then move the reflector to the zero scale of the height caliper, and then Move to 80% of the maximum scale (1000 mm) of the height caliper twice, record the flowmeter liquid level indication after stabilization, and repeat 6 measurements 6 times. Calculate the relative standard deviation of the measured value of the liquid level six times as the liquid level precision, and calculate it according to formula (3).

In the formula. HS-level precision,%;

iH-measured value of the i-th level, mm;

H-the average value of n level measurement values, mm;

n--number of measurements, n = 6;

i--measurement sequence number, i = 1, 2, 3, 4, 5, 6

6.3.4 Flow Precision Using a flowmeter laboratory testing device, verify flow accuracy as follows.

a) Set the type of flowmeter weir groove to No. 4 Parshall groove;

b) Adjust the height caliper to zero and correct the zero level of the flowmeter level;

c) Adjust the height caliper to 400 mm. After the flowmeter indicates a stable value, record the displayed value of the flow rate, and then adjust the height caliper.

Ruler to zero

d) Repeat the measurement 6 times according to the above step c, and record the flow rate display value.

Calculate the relative standard deviation of the 6 measured values as the flow precision, and calculate according to formula (4).

In the formula. QS-flow precision,%;

iQ-measured value of the i-th flow, m3/h;

Q-- average of n measured values, m3/h;

n--number of measurements, n = 6;

i--measurement sequence number, i = 1,2,3,4,5,6.

6.3.5 Period Drift

Set the flowmeter weir groove to No. 4 Parshall groove, fix the primary instrument at a certain height, and calibrate the liquid level to 400 mm.

After stabilizing for 10 minutes, record the initial display value of the flow rate. The flow meter is continuously powered on and no maintenance is allowed during this period.

Calibration, record the final display value of the flow after 168 h, and the absolute value of the relative deviation between the final display value and the initial display value is used as the period Drift, calculated according to formula (5).

100% x-=

In the formula. Q-period drift,%;

aQ-initial display value of flow, m3/h;

bQ --Final flow display value, m3/h.

76.3.6 Voltage stability

Set the flowmeter weir groove to No. 4 Parshall groove, fix the primary instrument at a certain height, and calibrate the liquid level to 400 mm.

Adjust the input voltage to 220 V and record the displayed value of the flow rate as the initial value; adjust the power supply voltage of the flow meter to 242 V and display Record the display value of the flow rate after stabilization; adjust the power supply voltage of the flowmeter to 198 V, record the display value of the flow rate after the display is stable;

The following formula calculates the relative error caused by voltage changes, and takes the larger value of the relative error at two voltages as the voltage stability of the flowmeter.

The qualitative judgment value is calculated according to formula (6).

V 100

max x-= (6)

In the formula. VdeltaQ-voltage stability error,%;

sQ --220 V flow display value, m3/h;

iQ --242 V and 198 V flow display value, m3/h.

6.3.7 Level comparison error Use the open channel flow comparison device and the measured flowmeter to measure the liquid level at the same water level observation section and perform on-site comparison.

For the test, read the data 6 times per minute and continuously read for 30 minutes, and calculate the open channel flow comparison device and the measured flowmeter respectively.

The average value of the liquid level is calculated according to formula (7).

sxi HHH -= (7)

In the formula. iH-liquid level comparison error, mm;

xH-the average value of the liquid level measured by the measured flowmeter, mm;

sH-Mean value of measured liquid level of open channel flow comparison device, mm;

6.3.8 Flow comparison error Use the open channel flow comparison device and the measured flowmeter to measure the instantaneous flow at the same water level observation section and carry out the site.

Compare and detect. After the data is stable, start timing. The timing is 30 minutes (or the accumulated flow is greater than 100 m3).

Channel flow comparison device cumulative flow during this period and measured flow meter cumulative flow during this period, according to formula (8) Calculation.

Si 100max x-= (8)

In the formula. deltaQ--flow comparison error,%;

sQ-Display value of cumulative flow of open channel flow comparison device, m3;

iQ-Displayed value of the accumulated flow of the measured flowmeter, m3.

6.3.9 Timing error

Under the normal working conditions of the flowmeter, read and record the display time T0 of the flowmeter as the starting time, and start at the same time the stopwatch starts timing. After the flowmeter runs continuously for 48 hours, read and record the flowmeter display time T1 and the stopwatch display.

Time T2, calculate the timing error according to formula (9).

8 per mille 1000

201 x--=

TTT

In the formula. deltaT-timing error, per mille;

0T-the initial display time of the flow meter;

1T --The time displayed by the flow meter at the end of the timing;

2T --The stopwatch displays the time at the end of the time.

6.3.10 Minimum maintenance interval Within 168 hours of the flowmeter test, no maintenance can be performed on the flowmeter, and the flowmeter must not affect the flow operation and any failure of the measurement, if the failure occurs, the inspection fails.

7 Random data

The random information such as the instrument manual should include at least the following. the principle of the instrument, the structural drawing of the instrument, and the installation conditions on site and methods, instrument operation methods, component identification and precautions, instrument calibration and use methods, common fault handling, daily routine Maintenance instructions, etc.