Sinocean robust liquid CO2 storage tanks operation manual

一.Sinocean thanks every customer who order our liquid co2 storage tank. We kindly remind you operate our product properly in case of any accident. Please read our manual carefully before you use co2 storage tank.

二.Liquid co2 storage tank is widely used in industry, agriculture, national defense, and science research department in different sectors. Compared with gas cylinders, co2 storage tank is more convenient on transportation and keep liquid co2 safe and reliable inside.


  About horizontal 10 m3 co2 storage tank

  Capacity: 10 m3

  Vessel type: 3 class

  Design pressure: 2.27 MPa

  Max working pressure: 2.16 MPa

  Design temperature: -40to 50

  Medium: liquid co2

  Main materials: 16MnDR

  Insulation type: perlite vacuum insulated


Main structure: double layer cylinder structure: inner vessel is made of 16MnDR, outer vessel is made of Q235-B/Q345R, interlayer is filled with pearlite sand and vacuumed, and we also use specially treated absorbent to extend the tanks life.


三.Operation and maintenance


Warning: the liquid co2 storage tank should be operated by trained professionals who wear protective clothes and masks because the liquid co2 is deep cold and danger may happen due to wrong operation.


Preparation: customer should do air tight test, blow treatment and instrument & valves check works before use co2 storage tank.


3.1. Air tight test: after the tank is installed on foundation or the inner vessel has normal temperature, please do air tight test before filling liquid co2. Test pressure is max working pressure of this tank and test air is oil free air or dry nitrogen gas. Test time should be at least 4 hours.


3.2. Blow treatment: after air tight test, customer should use dry and oil free air to blow inner vessel of tank to remove moist air.


After blow by dry air or dry nitrogen, customer should use product gas blow inner vessel and discharge air till purity is meeting requirement.

3.3. Check valves and instrument: before filling liquid co2, customer should check if valves are in right on/off state and instruments direction right or not and give adjust if necessary.



4.Filling liquid co2: first liquid filling and add liquid

4.1 first time liquid filling (inner vessel is normal temperature):

a.connect liquid filling pipe, co2 tanks gas phase balance valve and liquid inlet valve should be connected co2 tank cars gas phase balance valve and liquid outlet valve.

b.Slowly open co2 tank s liquid outlet valve and co2 tank cars liquid inlet valve, and open co2 tanks air release valve to discharge air. Turn off release valve when air purity is meeting requirement.

c.Open co2 tank and co2 tank cars gas phase balance valve and turn on liquid level meter(full on L1, L3 valve and off L2 valve), turn on co2 tank cars transfer pump when pressure inside co2 tank and co2 tank car is balanced. Then co2 tank car fill liquid into co2 tank.

d.Observe pressure inside co2 tank car and the pressure should be at least 1.3 MPa, otherwise pressure should be increased in case there is dry ice in co2 tank car to make pipe jam.

e.Observe liquid level meter on co2 tank and stop filling when the number reaches 95% of tank capacity or when there is liquid overflow from measuring full valve.

f.After filling co2, turn off co2 tanks liquid inlet valve and gas phase balance valve and off co2 tank cars liquid outlet valve and gas phase balance valve.

g.When filling co2 is over, remove liquid filling pipe.


4.2. Add liquid co2(when there is some liquid co2 inside vessel)

Remark: add liquid co2 process is basically same as first time liquid filling and the difference is there is no need to open air discharge valve so the process is more simple: connect liquid filling pipe, co2 tanks gas phase balance valve and liquid inlet valve should be connected co2 tank cars gas phase balance valve and liquid outlet valve. turn on co2 tank cars transfer pump Then co2 tank car fill liquid into co2 tank.


5. Boost pressure


The minimum pressure inside co2 storage tank is 1.3 MPa. And if it is less than 1.3 MPa, pressure should be increased to keep co2 tank stable.


The way is to connect vaporizer to co2 tank. Liquid co2 discharged from tank and become gas when flow through vaporizer and then back into storage tank to increase pressure. There is liquid outlet valve and air return inlet on co2 tank for spare use.

6. Liquid co2 discharge:

a.discharge liquid co2 to vaporizer or low temperature liquid pump: open liquid outlet valve when pressure inside co2 tank is meeting requirement.

b.Discharge liquid co2 by liquid co2 inlet valve: supply liquid co2 for co2 tank car or bigger co2 tank by liquid soft pipe. This operation way is similar to filling liquid.


7. Liquid co2 storage

When liquid co2 is stored in co2 storage tank, the pressure should be min. 1.3 MPa otherwise pressure boost is necessary. During storage, air release valve should be off. The pressure inside inner vessel will rise due to natural co2 evaporation and the air release valve should be open when the pressure reaches working pressure.


Warning: the co2 storage tank pressure should not exceed max working pressure during operation. Otherwise it may reduce tank life or cause accident.


The co2 storage tank pressure should not lower than 1.3 MPa. Otherwise it may bring dry ice and damage tank.


It means an accident and shorten tank life when safety valve releases. It is forbidden that safety valve release outlet towards human or equipment.


8. Maintenance

8.1 Protect insulation function

Good insulation function is very important for low temperature cryogenic storage tank. And good vacuum degree is key for insulation. The pearlites thermal conductivity coefficient is 0.05W/.k under nomral pressure and normal temperature condition. If during vacuum 66.71.33pa, The pearlites thermal conductivity coefficient is 0.0026W/.k. Therefore, we should protect the co2 storage tanks good vacuum degree. The co2 storage tanks outer vessels explosion proof equipment and evacuation valve are directly connecting to vacuum interlayer. And it is not allowed to take down the equipment and valve when the vacuum is not broken or no need to re-vacuum the interlayer. Evacuation valve is aluminum sealed when leaving factory and it shouldnt be moved otherwise it will damage the vacuum.


The outer vessel of co2 storage tank is external pressure vessel Under atmospheric pressure. It is forbidden knot, strike and expose to 50℃ higher environment. Otherwise it will damage vacuum and insulation function.





8.2 Vacuum check and re-vacuum.

Please check vacuum degree every 6 months. Screw cover on Metal thermocouple gauge and plug in  thermocouple vacuum gauge and it can measure interlayer vacuum. And specific operation is up to vacuum gauge instructions.


After co2 storage tank is used for some years, the vacuum may be down 66.7Pa or lower. And it needs re vacuum. First discharge liquid inside and blow by 80100℃ oil free dry air or nitrogen gas till inner vessel back to normal temperature. Then connect vacuum pipe, pump moist out inside pipe and open vacuum valve.


9. Normal check and fault solution

9.1 Normal check

a.check if valve is in right on/off position

b.Check if pressure gauge, level gauge measurement correct

c.Check if equipment pipe, valve any block

d.Should calibaration safety valve offline pressure when safety valve doesnt work if the tank pressure reaching safety valve offline pressure.

e. Pressure gauge should calibrate once a year

f. Safety valve action should calibrate once a year

g. Measure vacuum degree half a year


9.2 fault solution: refer to table below:


Table 4-1 fault solution




Inner vessel pressure rise abnormally

pressure rise adjust valve can’t close tightly

Take down valve, clean

pressure boost valve can’t close tight. Leakage inside


Repair pressure boost valve or replace sealings

pressure gauge indicates wrong number

Repair or replace pressure gauge

Liquid level gauge shows wrong num

liquid level gauge doesn’t work

Repair liquid level gauge

up and down pipe leakage

Check and repair

joint leakage

Check and repair

Evaporation rate higher and the top is frosting

V1 valve cant close tightly, inner leakage

Repair valve

vacuum valve damage


pearlite not filled fully

Supplement pearlite and re-vacuum

Liquid or gas leakage from valve hat or joint

sealing filler not compact

Compact filler

sealing rings damage

Replace rings

sealing surface damage

Repair or replace

welding line leakage



Transport and installation


a.when co2 storage tank arrives at site, customer should make a proper discharge plan with workers.

b.It is forbidden to roll co2 storage tank and the saddle for installing co2 tank can only be removed after it is fixed on site.


Installation is not allowed to knot or strike co2 storage tank during installation. And pay special attention to explosion proof equipment and vacuum valve outside.

b.Perpendicularity error range within 1/1000

c.Fill dry air or dry nitrogen to inner vessel till the pressure reaches working pressure and do air tight rest, check valves, pipes, flanges and make sure no leakage.

d.Should set water drain around co2 tank, pressure booster, vaporizer to discharge frost water.

e.Foundation weight bearing capacity should be determined by civil engineer based on co2 tank weight filling full.


Co2 Storage Tank Stop Use and Reuse

a.please dont drain up liquid if stop use co2 tank for a short time

b.If stop tank use for long term not due to maintenance, then use product gas to keep the inside pressure0.02MPa.

c.If due to maintenance and drain up liquid co2 and reuse the tank, should do air tight test, blow treatment and check the tank is qualified to fill high purity low temperature liquid.(vacuum leakage can be done if allowed)


Safety requirement and notice requirement

Safety operation for co2 storage tank should consider gas, low temperature and pressure vessel.


Liquid co2 features:





Element symbol

Gas density0.101MPa     



Saturated vapor pressure 1.005MPatemperature

1 ton liquid co2 at 0℃0.101MPagas volumem3





Carbon dioxide











b.Place requirement for installation co2 storage tank

l Installed outside with good ventilation

l There is no open way for basement, cellar etc within 5 meters around  co2 storage tank.

l Distance from crowd people should not less than 7.5 meters.

l Storage tank should not installed in basement. If so, it must be good ventilated and absolute safety for discharge air or liquid.

l Discharged air or liquid should be flowed to safe area.


c. Filling rate should be less than 95% at any circumstance under any working pressure. requirement on operation and maintenance

Should slowly turn on or off valves. Too fast may occur spark

Safety equipment should be reliable when co2 liquid storage with pressure

Replace new valve after clean oil pollution

First drain up liquid and dry it by oil free nitrogen before repair and welding equipment

Vent and blow before enter rooms with high concentration co2

Dont contact liquid with skin and should wear suitable clothes and masks.




Close pressure boost valve tightly when there is no need to boost pressure to avoid inner leakage.


Please dont drain up liquid co2 inside when you stop the tank use for short time. And if you really think it is more economic to drain up the tank, then pls drain up liquid and turn off all valves and keep inner vessel 0.002 MPa in case moist air or dust going into inside and block pipes.


Our co2 storage tank will be filled with 0.02 MPa dry nitrogen when eaving factory and please dont discharge it before put the tank into real use.


Hits: 【Print】