8.1 Pressure Test
8.1.1 Before pressure test, the spherical tank shall have following conditions:
(1) The welding of the spherical tank and the connection with parts and components have been completed and they are qualified after inspection;
(2) The strength of secondary grouting of the foundation is up to the requirements for the strength;
(3) Post weld heat treatment has been done to spherical tank, which needs post weld heat treatment. The product welding test plate is qualified after inspection;
(4) The welds of reinforcing rings have been leakage tested with compressed air of 0.4 ~ 0.5 Mpa and qualified;
(5) The alignment of the supports and the adjustment of the tie rods have been completed.
8.1.2 Gases must not be used to replace the liquid in pressure test, unless it is specified in
design drawings.
8.1.3 During pressure, a pressure gauge of same scale and qualified after calibration shall be
installed respectively at the top and bottom of the spherical tank. The accuracy shall not be less than 1.5 grade. The range of scale of pressure gauges should be 2 times of test pressure, and shall not be < 1.5 times of and not be > 4 times of test pressure. The diameter of the pressure gauge should not be < 150mm.
8.1.4 During pressure test, it is strictly prohibited to impact or strike the spherical tank. 8.1.5 Hydraulic test shall meet following stipulations:
8.1.5.1 For hydraulic test, clean water shall be used as the medium;
8.1.5.2 For hydraulic test of spherical tank of carbon steel, 16MnR steel and normalized
15MnVR steel, the temperature of water used in the test shall not be lower than 5℃. For spherical tank of other low alloy steel (except low temperature spherical tank) the temperature of water used in the test shall not be lower than 15℃. In case the temperature is risen due to the lacking of ductility of material caused by the thickness of the plate, the temperature of water used in the test shall also be raised correspondingly.
8.1.5.3 The test pressure in hydraulic test shall be specified by the design drawings, and not
lower than 1.25 times of design pressure of the spherical tank. For the reading of the test pressure, the one of the pressure gauge at the top of the spherical tank shall apply.
(1) During test, a vent port shall be provided at the top of the spherical tank. Air in the spherical tank shall be completely vented when filling the liquid. During the test, the outer surface of the spherical tank shall be dry;
(2) During test, the pressure shall be risen slowly. Keep the pressure for 15 minutes when the pressure is up to 50% of test pressure. Check all welds and connection places of the spherical tank. Continue the pressure rising after confirming that there isn’t any leakage; (3) Keep the pressure for 15 minutes when the pressure is up to 90% of test pressure. Check
it again and continue the pressure rising after confirming there isn’t any leakage;
(4) Keep the pressure for 30 minutes when the pressure is up to the test pressure. Then fall the pressure to 80% of test pressure and check. If there isn’t any leakage or abnormal, it is qualified;
(5) On completion of the hydraulic test, water shall be drained completely. Water shall not be drained to the ground locally.
8.1.6 Air pressure test shall meet following stipulations:
8.1.6.1 Safety measures shall be taken for air pressure test, which shall be approved by the
person in charge of safety work of the organization. The test shall be supervised and checked by the safety department of the organization. Two or more safety valves and emergency vent valves shall be provided in air pressure test.
8.1.6.2 The test pressure of the air pressure test shall meet what specified in design drawings. 8.1.6.3 Air or nitrogen shall be used as the medium of the air pressure test. The temperature
of the medium shall not be less than 15℃.
8.1.6.4 The air pressure test shall be done in accordance with following steps:
(1) Keep the pressure for 5 ~ 10 minutes when the pressure is up to 10% of test pressure. A preliminary check for leakage shall be made to all welds and connection places of spherical tank. Continue the pressure rising after confirming there isn’t any leakage; (2) Keep the pressure for 10 minutes when the pressure is up to 50% of test pressure. When it
is confirmed that there isn’t any abnormal, the test pressure shall be risen stage by stage at a pressure of 10% of test pressure for each stage. Keep it for 10 ~ 30 minutes. Then fall to design pressure to check. If there isn’t any leakage or abnormal, it is qualified; (3) The pressure shall be unloaded slowly.
8.1.6.5 In air pressure test, the fluctuation of the environment temperature shall be monitored
as well as the reading of the pressure gauge. No over pressure shall happen.
8.1.6.6 The safety valves used in the air pressure test shall meet following requirements:
(1) Safety valves shall be the products manufactured by the manufacturer having manufacturing license and the products are up to technical standard;
(2) The safety valves must be calibrated and qualified;
(3) The begin-to-open pressure of the safety valves shall be set at 0.05Mpa of the test pressure.
shall be observed and actually recorded and it shall meet following stipulations:
8.1.7.1 The settlement observation shall be done at following stages:
(1) Before water filling;
(2) At the time when water is filled up to 1/3 of ID of the tank shell; (3) At the time when water is filled up to 2/3 of ID of the tank shell; (4) At the time when water it fully filled;
(5) 24 hours after fully water filling; (6) After water is drained.
8.1.7.2 Settlement of each foundation of support shall be measured. Permanent plate for
measuring level shall be welded to supports as specified.
8.1.7.3 The settlement of foundation shall be even. After water draining, the uneven
settlement shall not be > 1/1000 of center circle of the foundation. The difference of the settlement of adjoining supports shall not be > 2mm.
8.1.7.4 In case the uneven settlement is > above requirement, measures shall be taken to
handle it.
8.2 Airtight Test
8.2.1 Airtight test shall be done when the hydraulic test is done and qualified to those
spherical tank requiring airtight test.
8.2.2 Air or nitrogen shall be used as the medium of the airtight test. The temperature of the
medium shall not be lowered than 5℃.
8.2.3 The pressure gauges and safety valves used in the test shall be calibrated. The
requirements for pressure gauges and valves shall meet what specified in 8.1.3 and 8.1.6.6 of this Code.
8.2.4 The test pressure of the airtight test shall meet what specified in design drawing. 8.2.5 The airtight test shall be done in accordance with following steps:
8.2.5.1 Keep the pressure for 10 minutes when the pressure is up to 50% of test pressure.
Check all welds and connection places of the spherical tank. Continue pressure rising after confirming there isn’t any leakage.
8.2.5.2 Keep the pressure for 10 minutes when the pressure is up to the test pressure. Check
all welds and connection places of the spherical tank. If there isn’t any leakage, it is qualified. In case there is leakage, re-airtight test it after the leakage is handled.
8.2.5.3 Pressure shall be unloaded slowly.
8.2.6 During airtight test, the fluctuation of the environment temperature shall be monitored
as well as the reading of the pressure gauge. No over pressure shall happen.
8.2.7 For the spherical tank requiring air pressure test specified by the design drawings, the