DL/T 259-2012Calibration regulation for SF6 gas density monitor (English PDF)

3.1 Rating pressure

It refers to the pressure of filling the equipment air chamber with the required

SF6 gas under standard atmospheric conditions, before the equipment is put into operation or during air injection.

3.2 Alarm pressure

It refers to the pressure of giving alarm signals, when the SF6 gas pressure in the equipment air chamber drops to a certain set value.

3.3 Lock pressure

It refers to the pressure of giving lock signals, when the SF6 gas pressure in the equipment air chamber drops to a certain set value.

3.4 Overpressure alarm pressure

It refers to the pressure of giving overpressure alarm signals, when the SF6 gas pressure in the equipment air chamber rises to a certain set value exceeding the rating pressure.

3.5 Absolute pressure type density relay

It refers to the gas density relay indicated with absolute pressure and using absolute vacuum as reference pressure.

3.6 Relative pressure type density relay

It refers to the gas density relay indicated with relative pressure and using environmental atmospheric pressure as reference pressure.

3.7 Relatively mixed pressure type density relay

It refers to the gas density relay indicated with relative pressure and using standard atmospheric pressure as reference pressure.

3.8 Absolutely mixed pressure type density relay

It refers to the gas density relay indicated with absolute pressure and using environmental atmospheric pressure as reference pressure.

3.9 Condition-based maintenance

It refers to a kind of maintenance strategy used for arranging the maintenance reasonably, based on the equipment status and taking the security, reliability, environment, cost and other factors into overall consideration.

[Definition 3.1.1 in DL/T 393-2010]

4.2.1 As for the density relay equipped with a stop pin, whose scale starts from a certain positive pressure value, when the ambient temperature is 20°C and the atmospheric pressure is standard atmospheric pressure, the pointer shall rest against the limit nail under non-pressure working condition, before the pressure-rise calibration and after the pressure-drop calibration. For the specific relationships among reference zero, temperature and atmospheric pressure,

REFER to the instruction manual of this density relay.

4.2.2 As for the density relay whose scale starts from the minimum pressure

value, the pointer zero error under non-pressure working condition, before the pressure-rise calibration and after the pressure-drop calibration, shall comply with the following requirements.

a) For the absolute pressure type density relays, when the ambient temperature is 20°C, the pointers shall point at local atmospheric pressure value. When the ambient temperature is higher than 20°C, the pointers shall point at the pressure which is lower than local atmospheric pressure. When the ambient temperature is lower than 20°C, the pointers shall point at the pressure which is higher than local atmospheric pressure. For the specific relationships among reference zero, temperature and atmospheric pressure, REFER to the instruction manual of the density relays.

b) For the relative pressure type density relays, when the ambient temperature is 20°C, the pointers shall point within the width range of the zero index line.

The width of the zero index line shall not exceed twice the absolute value of the maximum allowable basic error. When the ambient temperature is higher than 20°C, the pointers shall point at the position below the zero. When the ambient temperature is lower than 20°C, the pointers shall point at the position above the zero. For the specific relationship between reference zero and temperature, REFER to the instruction manual of the density relays.

c) For the relatively mixed pressure type density relays, when the ambient temperature is 20°C, the pointers shall point at the difference of local environmental atmospheric pressure minus standard atmospheric pressure.

When the ambient temperature is higher than 20°C, the pointers shall point at the position below this difference. When the ambient temperature is lower than 20°C, the pointers shall point at the position above this difference. For the specific relationship between reference zero and temperature, REFER to the instruction manual of the density relays.

d) For the absolutely mixed pressure type density relays, when the ambient temperature is 20°C, the pointers shall point within the width range of the

0.1MPa index line. The width of the index line shall not exceed twice the absolute value of the maximum allowable basic error. When the ambient temperature is higher than 20°C, the pointers shall point at the position below

Under rating pressure, the hysteresis error shall not be greater than the permissible error specified in Section 5.1.

5.4 Tapping displacement

TAP the case so that the pointer can swing freely. The variation of the pointer’s indicating value shall not be greater than 1/2 of the absolute value of the permissible error specified in Section 5.1.

5.5 Pointer deflection stability

Within the range of measurement, the pointer deflection shall be stable and without obvious jitter and jam faults, except when the pressure-rise pointers pass near the low-pressure lock contacts and low-pressure alarm contacts.

5.6 Switching value error

On the set point of the same signal contact, the difference between the actual pressure values during the signal connection and disconnection or switching of the density relay shall not exceed 3% of the range.

6.1 Environmental conditions

6.1.1 The ambient temperatures shall refer to the temperatures required by the standards and density relays for normal operations. The standards and density relays shall be protected from direct sunlight, and shall not be affected by stronger heat sources. In addition, the ambient temperatures shall be steady.

The periods with larger temperature fluctuations shall be avoided during on-site calibration.

6.1.2 Relative ambient humidity. no greater than 85%.

6.1.3 Ambient pressure. atmospheric pressure.

6.1.4 Before calibration, the density relays shall operate or stand for at least

3h in the calibration environment.

6.2 Standard

6.2.1 The absolute value of the standard’s permissible error shall not be greater than 1/4 of the absolute value of the permissible error of the density relay to be inspected.

6.2.2 The available standards include.

calibration. PAY attention to the connection mode between density relay and equipment body, so as to prevent gas leakage.

6.3.2 During the on-site calibration of the density relays, it is allowed to lead the contact s...

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