GB/T 4213-2024Pneumatic control valves (English PDF)

4.8 Gas Source

4.8.1 Maximum gas source pressure The maximum values of the gas source pressure are as follows:

a) Pneumatic diaphragm control valve. 600 kPa;

b) Pneumatic piston control valve. 1,000 kPa. NOTE. special gas source pressure is allowed to be used upon agreement between the user (buyer) and the manufacturer.

4.8.2 Humidity of gas source The dew point of the gas source at operating pressure shall be at least 10 °C lower than the working environment temperature of the control valve.

4.8.3 Quality of gas source The quality requirements of the gas source are as follows:

a) The gas source shall be free of obvious oils (liquid oil, suspended oil, oil vapor) and other liquids, the oil concentration shall not exceed 5 mg/m3, and the liquid water concentration shall not exceed 10 g/m3;

b) The gas source should not contain corrosive gases, vapor and solvents;

c) Explosive gas shall not be used as the gas source;

d) The solid particle concentration in the gas source of the control valve with a positioner shall not exceed 5 mg/m3, and the particle diameter shall not exceed 5 m.

4.9 Normal Working Conditions Unless otherwise specified, the control valve shall be able to normally operate in the following atmospheric conditions.

a) Temperature. 25 C ~ +55 C, 40 C ~ +70 C or 30 C ~ +80 C; special working temperature ranges may be used, but the temperature value shall be an integral multiple of 5 C.

b) Relative humidity. 5% ~ 100%.

5.3 Leakage

5.3.1 The leakage of the control valve under the specified test conditions shall comply with the provisions of Table 1.

5.3.2 The leakage level I of the control valve is required to be determined by the user (buyer) and the manufacturer. However, the leakage level of the control valve with a single-seat valve structure shall not be lower than Level IV, and the leakage level of the control valve with a double-seat valve structure shall not be lower than Level II. Level VI is applicable to control valves with elastic sealing valve seats.

5.3.3 When the leakage is greater than 5 103 the rated capacity of the valve, it shall be ensured by the structural design, and the product can be exempted from testing.

5.3.4 Leakage shall be specified by the following codes.

5.3.5 When calculating and determining the allowable value of leakage, the rated capacity of the control valve shall be calculated in accordance with the method specified in GB/T 17213.2- 2017 (see Table 3).

5.5 Intrinsic Error The intrinsic error of the control valve shall not exceed the intrinsic error limit specified in Table

4.The intrinsic error is expressed as a percentage of the rated stroke. The switching type control valves are exempted from testing.

5.6 Hysteresis Plus Dead Band The hysteresis plus dead band of the control valve shall not exceed the hysteresis plus deadband limit specified in Table

4.The hysteresis plus dead band is expressed as a percentage of the rated stroke. Control valves without positioners and the switching type control valves are exempted from testing.

5.7 Start and End Point Deviation When the input signal in the pneumatic actuator is at the upper and lower limit values, the end point deviation of the air-to-close control valves and the start point deviation of the air-to-open control valves shall not exceed the provisions of Table

4.The start and end point deviation is expressed as a percentage of the rated stroke. The switching type control valves are exempted from testing.

5.8 Dead Band The dead band of the control valve shall not exceed the dead band limit specified in Table 4. The dead band is expressed as a percentage of the input signal range. The switching type control valves are exempted from testing.

5.9 Rated Stroke Deviation The rated stroke deviation of the air-to-close control valves shall comply with the provisions of Table

4.The rated stroke deviation of the control valves is expressed as a percentage of the rated stroke.

6.1 Test Conditions and Instructions

6.1.1 Reference working conditions Except for surface quality inspection and other provisions in the clauses, the test shall be carried out under the following reference conditions.

6.1.2 Recommended atmospheric conditions Tests which are not necessary or impossible to be carried out under reference working conditions should be carried out under the following atmospheric conditions.

6.1.3 Recommended test sequence The recommended test sequence is specified in Table 7.

6.3 Sealing of Packing Boxes and Other Joints Procedure A. the test medium is room temperature water (which may contain water-soluble oil or rust inhibitor), which is injected into the valve body of the control valve in the specified inlet direction, and the other end is closed. The test pressure is

1.1 times the maximum allowable working pressure at 38 °C. At the same time, make the valve stem (shaft) reciprocate 1 ~ 3 times per minute for a duration of not less than 3 minutes. Observe the control valve packing NOTE. for nominal diameters or nominal pressures (pressure classes) not listed, the test time shall be the higher-class value.

6.4 Leakage

6.4.1 The test medium shall be clean gas or room temperature water.

6.4.2 Test medium pressure.

6.4.3 Test gas source signal pressure. the pneumatic actuator shall be adjusted to the specified working state. In Test Procedure 1, the input gas source pressure of the air-to-open control valve actuator shall be zero; the input gas source pressure of the air-to-close control valve actuator shall not exceed

1.2 times the upper limit of the spring pressure range; the input gas source pressure of the switching type control valve actuator shall be the rated gas source pressure. In Test Procedure 2, the gas source pressure of the actuator shall be the same as in Test Procedure 1. When testing a valve that has not yet been equipped with a pneumatic actuator, a thrust device shall be added to the test, and the force applied shall not exceed the maximum valve seat sealing force specified by the manufacturer.

6.4.4 Test medium flow direction. the test medium shall be injected into the valve in accordance with the specified direction. The control valve outlet shall be directly connected to the atmosphere or connected to a low-pressure head loss measurement device whose outlet is connected to the atmosphere. Only after it is confirmed that the valve and all downstream connecting pipelines are completely filled with the medium and the leakage is stable can the leakage be measured.

6.4.5 Measurement error. the measurement error of leakage and pressure shall be less than 10% of the reading value. Appendix B gives examples of leakage calculation.

6.5 Sealing of Air Chamber Introduce a gas source with the rated pressure specified in the design into the sealed air chamber, cut off the gas source, and observe the pressure drop in the diaphragm air chamber or each air chamber in the cylinder within 5 minutes. For actuator air chambers with no possibility of internal leakage, soapy water can be applied to the seals of the air chamber to check for leakage. For small-sized actuators, they can also be directly immersed in water to check for leakage.

6.6 Intrinsic error When conducting the test of intrinsic error, it shall be ensured that the packing is compacted and satisfies the requirements of 5.2. Smoothly input the specified input signal into the actuator air chamber (or positioner) in the increasing or decreasing direction and measure the stroke value corresponding to each point. In accordance with Formula (1), calculate the error at each point between the actual "signalstroke" relations and the theoretical relations. The maximum value is the intrinsic error.

6.7 Hysteresis Plus Dead Band When conducting the test of hysteresis plus dead band, it shall be ensured that the packing is compacted and satisfies the requirements of 5.2. The test procedures are the same as that in 6.6.The ratio of the absolute value of the maximum difference between the positive and negative strokes measured on the same input signal to the rated stroke is the hysteresis plus dead band.

6.8 Start and End Point Deviation When conducting the test of start and end point deviation, it shall be ensured that the packing is compacted and satisfies the requirements of 5.2. The test procedures are the same as that in 6.6.In accordance with Formula (1), calculate the start and end point deviation.

6.9 Dead Band When conducting the test of dead band, it shall be ensured that the packing is compacted and satisfies the requirements of 5.2.

a) Starting from 0% or 100% of the control valve input signal, change the input signal (by 25%, 50% and 75% of the input signal range), until the valve stem (shaft) stroke stabilizes.

b) In the same direction, slowly change the input signal, until a perceptible change in stroke is observed, and record the input signal value (A) at this time.

c) Continue to slowly change the input signal in the opposite direction, until a perceptible change in stroke is observed, and record the input signal value (B) at this time.

8.1 Marking

8.1.1 Valve body marking NOTE. M stands for mandatory and S stands for supplementary. The valve body marking should include but not be limited to the following contents. For valve bodies smaller than DN50 (NPS2) and other valve bodies without sufficient space, the marking is allowed to be installed on the valve body or valve cover in the form of metal marking plates.

a) Manufacturer's name or trademark (M);

b) Nominal pressure (M);

c) Nominal diameter (M);

d) Medium flow direction (except where no flow direction requirement is specified) (M);

e) Valve body material (M);

f) Valve body material batch number (casting furnace number or forging batch number) (M);

g) Product production serial number (S);

h) Thread or flange marking (S).

8.1.2 Nameplate marking A nameplate shall be fixed at an appropriate position on the pneumatic actuator and shall at least indicate.

a) Manufacturer's name or trademark (M);

b) Product model (M);

c) Nominal diameter (M);

d) Nominal pressure (M);