GB/T 38599-2020Safety valves and bursting disc safety devices in combination (English PDF)

3.1 combination device

A bursting disc safety device is a safety relief device installed in 5 pipe diameters on the inlet side of the safety valve (from the outlet side of the bursting disc holder to the inlet side of the safety valve).

3.2 combination device discharge capacity factor; Kd

The ratio of the measured actual emissions of the combination device to the theoretically calculated emissions.

3.3 adjusted factor of combination device discharge capacity; Fd

The factor used to correct the discharge capacity of the combination device.

4.2 The discharge capacity of the combination device shall be such that the pressure of

the protected equipment does not exceed the allowable limit pressure specified in the corresponding standard.

4.3 The safety valve shall meet the requirements of GB/T 12241.

4.4 The bursting disc safety device shall meet the requirements of GB/T 567.1.

4.5 The maximum burst pressure of the bursting disc safety device shall not be greater

than 110% of the set pressure of the safety valve or 0.01MPa (whichever is the larger value between the two). The minimum burst pressure shall not be less than 90% of the set pressure of the safety valve. The designer shall determine the design burst pressure of the bursting disc safety device according to the design pressure of the protected system.

4.6 The minimum net relief area of the bursting disc in the combination device shall be

larger than the flow passage area of the safety valve.

4.7 Bursting discs shall not be made of brittle materials. The bursting disc shall not

produce fragments or fall off when it bursts.

4.8 When the combination device is used for liquid medium, the type of bursting disc

safety device and safety valve shall be determined by the manufacturer.

4.9 The cavity between the bursting disc safety device and the safety valve shall be

provided with an exhaust valve, a pressure gauge or other alarm indicators. It is used to

6 Determination of adjusted factor of discharge capacity

6.1 Test requirements

6.1.1 When the combination device is used for compressible fluids, the test shall use superheated steam, air or other compressible fluids with known properties whose superheat degree is not more than 10°C.

6.1.2 When the combination device is used for liquids, the test medium is water or other liquids of known properties.

6.1.3 It shall use the safety valve with the largest flow area for that model and size to test.

6.1.4 It shall use the bursting disc safety device with the minimum burst pressure of this model and size to test.

6.1.5 The measured adjusted factor of discharge capacity applies to the combination device of the same design as tested. However, the external shape of the holder may be disregarded.

6.2 Test device The test device shall meet the requirements of GB/T 12242.

6.3 Test methods

6.3.1 Single specification method The single specification method requires the following:

a) It is used to test the combination device of specific design (specification and model are known);

b) Select three bursting discs with the same design bursting pressure to test the combination device separately according to the steps in 6.4;

c) The test results obtained by the above test methods can be used in the three-specification method.

6.3.2 Three-specification method The three-specification method requires the following:

a) It is used to test the combination device that requires serialized mass production.

The Fd value measured by this method can cover the entire type of product range (including different specifications, different pressures);

b) It shall test the combination device of three consecutive specifications;

c) For each of the three specifications of bursting disc safety devices, take three bursting discs with the same design bursting pressure to test the combination device according to the steps in 6.4 (9 pieces in total). The same pair of grippers are allowed to be tested for each size of bursting disc.

6.4 Test steps

6.4.1 According to the relevant requirements of GB/T 12242, in the absence of a bursting disc safety device, conduct tests to determine the discharge capacity factor of the individual safety valve.

6.4.2 Install the bursting disc safety device on the inlet side of the safety valve. Blast the bursting disc according to the requirements of 6.4.3. Then actuate the safety valve.

6.4.3 The combination device shall be tested as follows:

a) Mount the combination device on the test device. The pressure on the inlet side is increased to 90% of the expected minimum burst pressure. Hold the pressure not less than 5s. After that, boost the pressure steadily and continuously. When boosting pressure, it shall be able to accurately read the minimum indication value of the pressure gauge until the bursting disc bursts. Correctly record the burst pressure;

b) The discharge capacity of the combination device shall be tested when it exceeds the set pressure of the safety valve by 10% or 0.01MPa (whichever is the larger value between the two). When the flow rate, temperature and pressure are stable, record the corresponding data;

c) The ratio of the measured discharge of the combination device to the theoretical flow rate is combination device discharge capacity factor Kd;

d) Use the bursting disc safety device of the same specification to repeat a), b), and c).

6.5 Acceptance determination

6.5.1 General requirements Only the combination device discharge capacity factor that meets the requirements of 6.5.2~6.5.4 and passes the test can be accepted.

tests. Calculate a new average Kd value.

c) When the obtained Kd value (excluding the rejected test results), including the replacement test for b), is within +/-5% of the new arithmetic mean, and the burst pressure of the replacement bursting disc is consistent with 6.5.3.2, then the results obtained from this batch of combination devices can be determined as acceptable.

6.6 Calculation of adjusted factor of discharge capacity

6.6.1 The adjusted factor of combination device discharge capacity is determined by the ratio of the average value of the discharge capacity factor determined by the combination device test to the discharge capacity factor of the single safety valve used in the test.

6.6.2 When the Fd value is greater than 1, Fd=1 shall be used. When the Fd value is less than 0.97, this Fd cannot be used unless there are special considerations.

6.7 Certification of adjusted factor of discharge capacity

6.7.1 Only if the requirements of 6.1~6.6 are met, the test results can be accepted and the certified Fd value can be given.

6.7.2 The certified adjusted factor of discharge capacity shall be the average value of the adjusted factors of combination device discharge capacity obtained by the test and shall not be greater than 1.0.

6.8 Other methods to determine adjusted factor of discharge capacity A default value of 0.9 is allowed as the adjusted factor of combination device discharge capacity. However, the pressure drop of the safety valve and the reaction force during discharge shall be recalculated according to this value.

7 Application of adjusted factor of discharge capacity

7.1 The adjusted factor of combination device discharge capacity multiplied by the rated discharge capacity of the safety valve is the rated discharge capacity of the combination device.

7.2 The adjusted factor of combination device discharge capacity can be used to determine the combination device discharge area (corresponding to the size of the safety valve or bursting disc safety device).

7.3 The Fd value obtained by the single specification method is applicable to the combination of safety valve and bursting disc safety device with the same design as the test.

7.4 The Fd value obtained by the three-specification method is applicable to all combination devices not less than the minimum size at the time of testing and the burst pressure is not less than the minimum burst pressure of the specification.

7.5 Under subcritical conditions, the single specification method shall be used to determine the Fd value.

NOTE: For the determination of critical and subcritical flow, see GB/T 36588.

8 Marks

8.1 Bursting disc safety device The nameplate marks of bursting discs, holders and auxiliary components shall meet the requirements of GB/T 567.1.

8.2 Safety valve The nameplate marks of the safety valve shall meet the requirements of GB/T 12243.

8.3 Combination device The combination device shall be marked on the nameplate according to the following requirements:

a) Product serial number;

b) Manufacturer;

c) Manufacturing standard;

d) Adjusted factor of combination device discharge capacity Fd;

e) Nominal size (DN or NPS);

f) Date of manufacture.

9 Quality certificate When providing a combination device, it is necessary to provide a quality certificate with at least the following contents: