NB/T 20318-2014Pressure transmitter important to safety in nuclear power plants (English PDF)

3.1 Error

The algebraic difference between the measured value and the true value of the measured variable.

Note: When the measured value is greater than the true value, the error is a positive value. The error is usually expressed as a percentage of the corresponding ideal range. [GB/T 18271.1-2000, definition 3.8]

3.8 Repeatability error

The algebraic difference between the limit values obtained by continuously measuring and outputting the same input value for multiple times in a short time when making a full range movement from the same direction under the same working conditions.

Note: Repeatability errors are usually expressed as a percentage of range and do not include hysteresis and drift. [GB/T 17212-1998, P2.2.2.29]

3.9 Span shift

Set the range again according to the measurement needs.

3.10 Zero adjustment

Adjust the zero point of the meter to the specified value.

4.1 Transmitter type

A pressure transmitter is an instrument that converts a pressure variable into a standardized output signal that can be transmitted, meanwhile there is a given continuous functional relationship between the output signal and the pressure variable (usually a linear function).

4.2 Electrical parameters

See Table 1 for detailed electrical parameters of the transmitter.

5.1 Functions important to safety

The pressure transmitters important to safety are mainly used to detect the pressure, flow rate and liquid level of the process system; provide necessary signals for the protection systems and post-accident monitoring systems of nuclear power plant, which is very important for ensuring the safe and reliable operation of nuclear power plants.

6.1 General performance requirements

6.1.1 Basic performance

6.1.1.1 Basic error

The basic error of the transmitter shall include the hysteresis and dead band under certain conditions, which shall be at least grade 0.5. The test method is carried out in accordance with the requirements of 7.3.1.

6.1.1.4 Response time

The response time required by the pressure transmitter shall be determined according to the system function requirements. Except for special requirements from users, it shall not be greater than 1.2s (at 90%).

6.1.2 Electrical performance

6.1.2.1 Insulation resistance

The insulation resistance between the output terminal of the transmitter and the housing shall not be less than 100 Mohm. The test method is carried out in accordance with the requirements of 7.3.12.

6.1.3 Immunity

6.1.3.1 Impact of power changes

When the power supply voltage (DC) changes between 12 V to 45 V, the output signal's change amount shall not be greater than 0.005% / V of the range. The test method is carried out in accordance with the requirements of 7.3.7.

6.1.3.6 Impact of static pressure

When the static pressure of the differential pressure transmitter increases from zero to the maximum working pressure, the static pressure will affect the output signal of the transmitter; the change of the output signal shall not exceed ± 0.25%/6.9 MPa of the range. The test method is carried out according to the requirements of 7.3.9.

6.1.3.10 Impact of output load

When the load resistance changes from the minimum value to the maximum value as specified by the manufacturer, the change of its output signal shall not exceed one half of the basic error. The test method is carried out in accordance with the requirements of 7.3.8.

6.1.3.11 Impact of mechanical vibration

Except for the special requirements of the user, under the mechanical vibration of the frequency range of the transmitter of 10 Hz ~ 60 Hz, the peak amplitude of 0.07 mm, the frequency range of 60 Hz ~ 150 Hz, the acceleration of 9.8 m/s², the change of output signal shall not exceed 1/2 of the basic error.

The test is carried out at 50% of the maximum range according to the requirements of Chapter 7 of GB/T 18271.3-2000.

6.2 Nuclear safety-related performance requirements

6.2.1 Aging impact

The transmitter shall be subjected to aging test according to NB/T 20149-2012.

After the test, it shall be adjusted to meet the basic error requirements.

6.2.2 Irradiation impact

For the transmitters important to safety installed in a containment, they shall be able to withstand a radiation test with a cumulative dose of 6 x 10^5 Gy in an accident environment. Except for the special requirements of the user, the maximum allowable error during and after the test shall not exceed ± 8% of the maximum range.

6.2.3 Resistance to earthquake impact

According to the requirements of GB/T 13625-1992, the transmitter shall be able to withstand three-axis earthquake test, at a vibration frequency of 2 Hz ~ 35 Hz and zero-cycle acceleration of 4 x 9.8 m/s².Except for the special requirements of the user, the maximum allowable error during and after the test shall not exceed ± 1% (grade 0.25) or ± 1.5% (grade 0.5) of the maximum range.

The test method is carried out according to the requirements of NB/T 20149-2012.

7.1 Inspection and test requirements

Inspection and test requirements shall include at least the following. […]

7.2 Test conditions

7.2.1 Environmental conditions

7.2.3 General requirements for testing

7.2.3.1 Except for the test of impact from the installation position, the transmitter shall be in the normal working position during the test, that is, the detection diaphragm is perpendicular to the horizontal plane.

7.2.3.2 Adjustments are allowed before each test; but adjustments are not

allowed during each test.

7.3 Basic performance test

7.3.1 Basic error test

The basic error test shall be carried out within the range. The test points shall be equally distributed and not less than 5 points, but including 2 points equal to or close to the upper and lower limits. Before the test, the transmitter shall move up and down three rounds within the range;

7.4 Type test

7.4.1 Conventional test

For each type of transmitter, at least 3 transmitters of the same product are used as samples to perform the test of the following items. […]

8.1 Marking

The transmitter shall be marked of the following in a prominent position.

8.2 Packaging, transportation and storage

Unless the user has special requirements, the packaging of the transmitter shall comply with the requirements of grade B packaging in 5.2.3 of EJ/T 564-2006.

The transport of the transmitter shall comply with the provisions of 6.1 of EJ/T 564-2006.