CJ/T 477-2015Ultrasonic gas meter (English PDF)

3.1 Terms and definitions

3.1.1

A gas meter that uses ultrasonic technology to measure, record and display the volume of gas passed.

3.1.2

Ultrasonic transducer A device used to transmit and receive ultrasonic signals in a gas meter.

3.1.3

Base condition

The specified conditions for gas volume conversion (ie, the reference gas temperature is 20°C, and the reference gas pressure is 101.325kPa).

3.1.4

Communication port

Interface for data exchange.

3.1.5

Electrical signal interface Gas meter serial or pulse output interface.

3.1.6

Indication error

The percentage of the difference between the volume displayed by the gas meter and the volume actually passed through the gas meter and the volume actually passed through the gas meter.

3.1.7

Prompt information

Visual signals, characters and letters that prompt important events during the operation of the gas meter or (and) the operation of the gas meter.

3.1.8

Maximum error offset the maximum average error change at any test flow point.

3.1.9

Working pressure

The upper limit of the working pressure of the gas meter is the same as that declared and marked by the manufacturer on the display window or nameplate.

3.1.10

average error

The arithmetic mean of the indication error of multiple measurements for the same flow.

3.1.11

Measuring unit

A gas meter component that generates an electrical signal proportional to the gas flow.

3.1.12

level of accuracy

The gas meter meets the level required by this standard, such as level 1.5 or 1.0.

3.1.13

Normal working conditions Conditions when the gas meter works.

---Do not exceed the maximum working pressure (regardless of whether there is gas flowing through);

---In the flow range;

---In the range of ambient temperature and working medium temperature.

3.1.14

Operating mode

The measurement method to obtain the gas volume is divided into standard mode and test mode.

3.1.15

Optical interface

Use serial data interface such as infrared transmission and reception.

3.1.16

Pressure loss

The pressure difference between the inlet and outlet of the gas meter when it is working.

3.1.17

Pressure port

The measurement point at the outlet of the gas meter can directly measure the outlet pressure of the gas meter.

3.1.18

Average error range

The difference between the minimum average error and the maximum average error within a specific flow range.

3.1.19

Error curve

Curve graph of average indication error and corresponding actual flow.

3.1.20

Recorder

It consists of two parts. memory and display, used to record and display information.

3.1.21

Starting flow

The lowest flow rate that the gas meter can display.

3.1.22

Temperature conversion device A converter that converts the measured gas volume to the volume under the reference temperature condition.

3.1.23

Thermal shut-off valve when the ambient temperature around the gas meter exceeds a predetermined temperature, shut off the gas valve.

4.1 Flow rate range

4.1.1 The specification and model of the gas meter and the corresponding flow value should meet the requirements of Table 2.

4.1.2 The minimum flow value of the gas meter can be smaller than the minimum flow upper limit listed in Table 2, but the value should be a certain value in the table, or a decimal value of a certain value.

4.2 Maximum working pressure

The manufacturer shall declare the maximum working pressure of the gas meter. This value shall be marked in the display or on the nameplate of the gas meter.

4.3 Temperature range

4.3.1 The test temperature in this standard is 20°C±2°C.

4.3.2 The minimum operating temperature range of the gas meter is -10°C~ 40°C, and the minimum storage temperature range is -20°C~ 60°C.

4.3.3 The manufacturer can declare a wider operating temperature range, from -10°C, -25°C or -40°C to 40°C, 55°C or 70°C, or more Wide storage temperature range. The gas meter shall comply with the corresponding regulations of the declared temperature range.

4.4 Gas range

4.4.1 The manufacturer shall specify the gas categories suitable for gas meters, see Table 3.

4.4.2 When testing the gas meter.

---Natural gas should be carried out with air or 99.5% methane;

---Liquefied petroleum gas should be carried out with air or 99.5% propane and (or) 99.5% butane.

4.4.3 According to the agreement with the testing organization, any other test gas should be included and should be marked on the gas meter in accordance with 14.1.

See Appendix A for more test gas information.

5.1 General requirements

5.1.1 The gas meter should be able to connect to the detection device through the communication interface, and the start and end of the test should be able to be synchronized.

5.1.2 The start test signal should be generated by the detection device. The response (volume reading) of the gas meter test should be synchronized with the sampling time, and the gas meter should Delay its test response until it receives the next sampling period of the start command.

5.1.3 The sampling time should be synchronized with the start of the data transmission string. The timer should have sufficient resolution to meet the requirements for measuring time.

5.2 Measurement principle

Refer to Appendix B for the measurement principle of ultrasonic gas meters.

5.3 Working mode

The gas meter should have a standard mode (normal sampling) and a test mode (fast sampling), and different sampling modes should not affect the measurement of the gas meter performance. The difference between the average error between the standard mode and the test mode should not exceed 0.3% (qt<=q<=qmax) and 0.6% (qmin<=q \u003cqt)。

5.4 Indication error

5.4.1 Gas meters of different grades should meet the maximum allowable error requirements specified in Table 4, and the error curve should meet the requirements of Table 5.

5.4.2 In the flow range of qt<=q<=qmax, when the signs of the indication error value of each flow point are the same, the indication error value of the 1.5-level gas meter must be absolute.

The value should not exceed 1%; the absolute value of the indication error of the 1.0-level gas meter should not exceed 0.5%.

5.4.3 When the manufacturer declares a wider ambient temperature range, the declared limit temperature should replace -10°C and 40°C.

5.5 Gas-air relationship

When the indication error of all test gases (including air) meets the requirements of Table 4 and Table 5, air can be used as a test in subsequent tests medium.

5.6 Repeatability error

Within the flow range of qmin<=q<=qmax for gas meters, the repeatability error should not exceed 1/3 of the absolute value of the maximum allowable error specified by the corresponding accuracy level.

5.7 Pressure loss

When air with a density of 1.2kg/m3 flows through the tested gas meter at qmax, the pressure loss should meet the requirements of Table 6.

5.8 Zero flow

When the flow is zero, neither the gas meter display nor the accumulated flow stored in the internal storage should change.

5.9 Starting flow

The starting flow qstart of the gas meter should not be greater than 0.25qmin.

5.10 Overload flow

After experiencing the overload flow of qr, the indication error should still meet the MPE specified in Table 4.

5.11 Pulsating flow

The sampling period of the gas meter in the standard mode should not exceed 2s. When using a longer sampling period, the manufacturer should ensure that the the measurement performance of the gas meter should not be affected in the case of constant flow.

5.12 Environmental adaptability

5.12.1 Installation impact

Under the installation impact test, the average error of all flow points should meet the requirements of Table 4, and the difference of the average error of each flow point should not exceed 1/3 of the MPE.

5.12.2 Temperature influence

Within the allowable operating temperature range, the gas indication value error should meet the requirements of Table 4, and the error curve should meet the requirements of Table 5.

5.12.3 Impact of pollutants

After the pollutant influence test, the pressure loss of the gas meter should not exceed 275Pa. The average error of a class 1.5 gas meter should not exceed ±3%, the error deviation should not exceed ±2%; the average error of the 1.0-level gas meter should not exceed ±1%, and the error deviation should not exceed 1/3 of the MPE in Table 4.

5.13 Durability

During and after the durability test, the error of the indicated value of all tested gas should meet the requirements of Table 4, and the pressure loss should meet 5.7 the airtightness should meet the requirements of 6.3.2.

6.1 General requirements

6.1.1 The gas meter casing should be made of metal materials.

6.1.2 Any device for adjusting the performance and characteristic parameters of the gas meter shall be protected against external interference.

6.1.3 The electronic seal shall meet the following requirements.

---You can only enter through a password or an updateable start code, or with a specific device;

---At least the last operation should be recorded in the memory, including the date and time of the operation and the special elements to confirm the operation;

---Operation records should be kept in the memory for at least 24 months.

The seal pattern should be part of the type approval document, and the seal pattern should include a metering seal and other tamper-proof seals.

6.2 Protection performance

The protective performance of the gas meter's casing and communication interface should comply with the IP65 rating specified in GB 4208.

6.3 Robustness

6.3.1 General requirements

6.3.1.1 The part of the gas meter that directly contacts the external ambient air and internal fuel gas shall have sufficient strength.

6.3.1.2 The design and installation of the gas meter shall ensure that any non-permanent deformation shall not affect the normal operation of the gas meter.

6.3.1.3 The gas meter should have a seal. The internal parts can only be accessed after the metering seal is disassembled or there is obvious permanent damage.

6.3.2 Tightness

The gas meter should not leak after normal use and pressure strength test.

6.3.3 Compressive strength

After the pressure of the gas meter compressive strength test is relieved, the residual deformation of the casing shall not affect its measurement performance.

6.3.4 Vibration resistance

After the vibration test of the gas meter, the tightness should meet the requirements of 6.3.2, and the average error should meet the requirements of Table 4.

6.3.5 Impact resistance

After the gas meter has undergone an impact test, its tightness shall meet the requirements of 6.3.2.

6.3.6 Drop resistance

After the drop test of the gas meter, the tightness should meet the requirements of 6.3.2.

6.4 Anti-corrosion

The anti-corrosion performance of the gas meter should meet the requirements of 6.3 of GB/T 6968-2011.

6.5 Anti-aging

6.5.1 Anti-aging performance of non-metallic materials

After the aging test, the tightness should meet the requirements of 6.3.2.

6.5.2 Anti-aging performance of the outer surface (including the display window and its accessories) After the test, the following requirements should be met.

a) Damage to the outer surface of the gas meter should not affect the function of the gas meter;

b) The display window should not fall off, cracks and blisters, and the display content should still be clearly visible within 15° of the normal line of the display window;

c) The gas meter should continue to record the volume of gas.

6.6 Solar radiation protection

After the test, the appearance of the gas meter should not be changed, and the display should be clear and easy to read.

6.7 Flame-retardant external surface

All outer surfaces (including the observation window) of the gas meter and the materials contacting the gas components should be flame-retardant, and the flammability level of these materials should meet Comply with V-0 in GB/T 11020.

6.8 Storage temperature range

After the test, the average error of the gas meter should meet the maximum allowable error range specified in Table 5.

6.9 Appearance

The gas meter should have a good surface treatment, and there should be no defects such as blistering, shedding, scratches, dents, stains, etc. The display content and logo should be clear and easy to read, and the mechanical seal should be intact and reliable.

6.10 Explosion-proof performance

When the manufacturer declares that the gas meter is suitable for use in the hazardous area defined by GB 3836.14, the design, construction and identification of the gas meter shall be Comply with GB 3836.1 and GB 3836.2 or GB 3836.4 and GB 3836.8.

6.11 Gas meters installed in open spaces

The additional requirements and tests applicable to gas meters installed in open spaces shall meet the requirements of Appendix C.

7.1 Recording and storage

The recorded cumulative volume should be displayed on the display and stored in non-volatile memory for at least 24 months. The manufacturer should specify the memory retention time.

7.2 Display

7.2.1 In addition to the alphabetic logo characters, the display should have at least 8 numeric characters, and the qmax should not be greater than 6m3/h. The numeric characters should be displayed to cubic meters.

3 digits after the decimal point, qmax is greater than 6m3/h and not greater than 60m3/h. Numeric characters should be displayed to 2 digits after the decimal point of cubic meters.

The numeric characters of qmax greater than 60m3/h should be displayed to 1 digit after the decimal point of the cubic meter.

7.2.2 Any selected alphabetic logo characters should not be confused with numbers, and there should be enough digits to show that the qmax flow rate is running 8000h the displayed value should not return to zero.

7.2.3 The displayed value should be easy to read, and the minimum height of the displayed character is 4mm, and the measurement unit (m3) should be clearly and clearly displayed in the displayed value.

7.2.4 The number showing the submultiple of cubic meters should be clearly distinguished from other numbers, and there should be an obvious symbol to distinguish the two numbers.

7.2.5 The following gas meter operating status can be read from the display screen through icons or codes.

a) Failure of the ultrasonic transducer;

b) The supply voltage is too low;

c) Data error in non-volatile memory.

7.3 Non-volatile memory

7.3.1 The contents of the non-volatile memory shall be refreshed at least every 1h, and shall meet the following requirements.

a) It should be able to be read and written within the extreme ambient temperature range;

b) In the case of power failure, the data should be stored within the storage temperature range.

7.3.2 If it is consistent with the manufacturer's declaration, when testing according to 12.3.3a), the non-volatile memory should be within the extreme ambient temperature range.

It can be read and written; when the test is carried out according to 12.3.3b), there should be no difference between 3) and 6).

7.4 Display reset

The cumulative gas volume of the gas meter should not be reset during use.

8.1 General requirements

8.1.1 The gas meter should provide the data communication interface to read and write memory information, and the data communication should comply with GB/T 26831 (all parts) Regulations.

8.1.2 The communication interface of the gas meter should not affect the measurement performance of the gas meter.

8.1.3 The manufacturer shall provide a mechanism to clear the battery replacement mark after the battery is replaced.

8.2 Data

8.2.1 General requirements

The information provided through the data communication interface should include at least.

a) The current volume of the gas meter (volatile and non-volatile memory);

b) The volume and time stamp of the past 24 months recorded by the gas meter (non-volatile memory);

c) The serial number of the gas meter;

d) The status prompt information of the gas meter.

8.2.2 Status prompt message

The status prompt information of the gas meter should include at least.

a) The gas meter is working normally without any abnormal state;

b) The gas meter works at a flow rate higher than qmax;

c) The gas meter works at a flow rate lower than qmin;

d) The gas meter works outside the temperature range declared by the manufacturer;

e) Unable to measure normally due to ultrasonic testing failure;

f) Normal measurement cannot be performed due to data errors in non-volatile memory;

g) The power supply voltage is too low and the battery needs to be replaced.

8.3 Test mode

8.3.1 The gas meter should be able to switch between standard mode and test mode.

8.3.2 The gas meter in the test mode should be able to provide high-resolution current cumulative flow data, and the number of characters should not be less than the display words of the indicating device.

The number of characters, qmax is not greater than 6m3/h, the character resolution should be 6 digits after the decimal point of cubic meters, and qmax is greater than 6m3/h and not greater than 60m3/h the character resolution should be 5 digits after the decimal point of cubic meters, and the character resolution should be 4 digits after the decimal point of cubic meters if the qmax is greater than 60m3/h.

9.1 General requirements

9.1.1 The gas meter allows the use of built-in battery power supply, and also allows the use of external power supply auxiliary power.

9.1.2 When the battery is replaceable, the battery box should be able to be operated from the front of the gas meter, and its design should be such that authorized personnel do not need to move the meter.

Complete the battery replacement at the installation position. The battery replacement should be completed within 2 minutes.

9.1.4 The battery should meet the requirements of GB/T 8897.1, and the lithium battery should meet the requirements of GB/T 8897.4.

9.1.5 The design of the gas meter should not affect the structure of the gas meter when the battery leaks.

9.2 Power failure

After the test, the gas meter data should remain unchanged.

9.3 Battery life

When the gas meter uses non-replaceable batteries, the battery life stated by the manufacturer shall not be less than 10 years.

9.4 Minimum operating voltage

After the test, the indication error should meet the requirements of Table 4.

9.5 Undervoltage prompt

When the battery voltage of the gas meter is lower than the minimum operating voltage declared by the manufacturer, it should be able to give prompt information through the indicating device and communication.

9.6 Power fluctuation

When the gas meter uses a DC power supply, the manufacturer's declared power supply voltage V 10%-15% range of indication error should meet the requirements of Table 4.

When the gas meter uses AC power supply, the manufacturer's declared power supply voltage V 10%-15%, frequency f 2%-2% range of indication error should meet the requirements of Table 4.

10.1 Electrostatic discharge

After the test, the gas meter should work normally.

10.2 Radio Frequency Electromagnetic Field

After the test, the gas meter should work normally.

10.3 Electromagnetic induction (power frequency magnetic field)

After the test, the gas meter should work normally.

10.4 Electromagnetic induction (pulsed magnetic field)

After the test, the gas meter should work normally.

10.5 Electrical fast transient/burst

After the test, the gas meter should work normally.

10.6 Electrical surge (surge immunity)

After the test, the gas meter should work normally.

10.7 Radio frequency interference suppression

The gas meter should not produce radiated noise that interferes with other equipment.

11.1 Pressure tap

When the gas meter is equipped with a pressure tap...