2024年3月16日发(作者：)

大型LNG液货罐的水压和气密试验要求

Hydrostatic Test and Leakage Test of Cargo Tank

1 PURPOSE

The hydraulic and leak test shall be conducted for Cargo Tanks according todrawing and design

requirements to inspect the integral mechanicalproperty and tightness property and verify that the

safety properties of theCargo Tanks conform to requirements.

2 RULES FOR THE HYDRAULIC AND LEAK TEST

GL rules shall be followed, the rules of GB 150-, Chapter 10.9 may beconsidered.

During the test and inspection additional safety regulations have to beobserved.

3 SUPPORTS

3.1 Temporary supports

During hydrostatic test the bullets may be supported by temporary and design of

the temporary supports shall consider the maximumload requirements of the soil.

Drawings of the temporary supports and of their arrangement under theTank shall be submitted to

SMC for approval.

In order to avoid surface damages of the tanks, the top surface of thetemporary supports shall be

equipped with a layer of softwood.

3.2 Settlement

Theodolites shall be used for measuring the foundation settlement. Thereshall be one monitoring

point on each side of the tank above the supports. Atthe start of the test procedure, all monitoring

points shall be in one line withthe accompanying theodolite.

The total number of monitoring points shall be not less than 6.

The settlements shall be recordedbefore start of water filling

at 1/3 water filling

at 2/3 water filling

at complete water filling

during complete water filling every 10 minutes.

The water filling shall be interrupted if the settlement of one monitoring pointis found to exceed 10

mm or if the differential setting of two neighbouredmonitoring points exceeds 5 mm.

4 HYDROSTATIC TEST AND LEAK TEST

4.1 The area for test

The area for hydrostatic test and leak test will be the final assembly site ofcargo tanks. The area

shall be symbolized with safety protection and safetyidentification, and inspected and approved by

chief engineer and safetymanager.

During the complete test procedure, only authorized personnel related to thetests shall be allowed to

stay near the tanks.

4.2 Test water

4.2.1 Water quality

Test water shall have at least industrial water quality. The chloride contentshall not exceed 25 ppm.

In case that harbour water will be used, high pressure fresh water washingof all tank internals and

surfaces shall be carried out straight after the tankshave been discharged from the test water.

Afterwards the tank shall be airdried completely.

4.2.2 Water temperature

The temperature of the water used for the test shall be at least 15 °C duringthe whole test procedure

until all water is drained off.

4.2.3 Ambient conditions

The hydrostatic test shall take place in dry weather condition.

For ambient temperatures below 0 °C it must be ensured that neither thewater inside the vessel, nor

manometers and filling lines can freeze. It isrecommended to carry out the hydrostatic test

procedure at an ambienttemperature above +5 °C.

It is recommended to carry out the hydrostatic test (test pressure) at daytime.

If the natural lighting conditions are not sufficient, extra lighting facilitiesmust be provided to

ensure that coming-out water can be detectedimmediately and that all readings can be done

correctly.

4.3 Test equipment

4.3.1 Pumps

Filling water pumps shall have appropriate capacities in order to fill the tankwithin the shortest

possible time. The soil conditions and the symmetricalsettlement of all supports shall limit the

filling rate.

The pressurizing pump shall have a minimum capacity of 20 m³/h at 3.0Pa(g) with appropriate and

safe hose connections. The pump must beable to maintain the test pressure at Zero flow rate.

4.3.2 Safety valve

On one of the tank nozzles a safety relief valve shall be installed with a setpressure of 1.2 MPa(g).

The size of the safety valve shall be sufficient tolead off the flow of the pressurizing pump.

4.3.3 Temporary blind flanges

Nozzles which are not equipped with their original blind flanges at the time ofthe hydrostatic test

shall be closed with temporary blind flanges. Thetemporary blind flanges shall be provided by

manufacturer.

4.3.4 Temporary gaskets

Flanged connections which are not equipped with their original gaskets atthe time of the hydrostatic

test shall be closed with suitable temporarygaskets. The temporary gaskets shall be provided by

manufacturer

4.3.5 Shut-off valves

All butt-welded nozzles shall be equipped with the original shut-off valves inorder to avoid welding

after hydrostatic test.

4.3.6 Local pressure gauge

Three calibrated and certified local pressure gauges of the same measuringrange shall be placed on

different nozzles:

Measuring range: approx. 6.5 Bar (g) (min. 4.875 Bar(g), max. 13 Bar(g))

Accuracy: 60 kPa over the full range

Minimum dial diameter: 100 mm

4.3.7 Remote controlled pressure indication and recorder

A remote controlled pressure transmitter may be placed on one tank nozzle:

Indicator: Digital

Accuracy: Class 0.1

4.3.8 Temperature indication

The temperature inside and outside the tank shall be measured andrecorded during the hydrostatic