A cascade filling system is a high pressure gas cylinder storage system used for recharging smaller compressed gas cylinders. In some applications, each large cylinder is filled by the compressor, otherwise they can be charged remotely and replaced when the pressure is too low for effective transfer. The cascade system allows small cylinders filled without a compressor. In addition, the cascade system is useful as a reservoir to enable low-capacity compressors to meet the demand for multiple small cylinders in sequence, with longer mid-periods during rechargeable storage cylinders.
Video Cascade filling system
Principle of operation
When the gas contained in the cylinder at high pressure is allowed to flow to another gas-containing cylinder at a lower pressure, the pressure will equal the value between the two initial pressures. The equilibrium pressure is affected by the transfer rate as it will be affected by temperature, but at a constant temperature the equilibrium pressure is explained by Dalton's partial pressure law and Boyle's law for the ideal gas.
The formula for equilibrium pressure is:
- P 3 = (P 1 ÃÆ' â € "V 1 P 2 ÃÆ' â 2 )/(V 1 V 2 )
- where P 1 and V 1 are the initial pressures and volumes of one cylinder
- P 2 and V 2 pressure and other initial cylinder volume
- and P 3 are the equilibrium pressures.
An example can be a 100-liter cylinder (internal volume) (V 1 ) pressurized to 200 bar (P 1 ) filling a 10-liter cylinder (internal volume) (V 2 ) that is not pressed (P 2 = 1 bar) (produces both cylinders equalizing approximately 180 bar (P 3 ). this to 250 bar is then used for the 10 liter "top-up" cylinder, these two cylinders will equalize around 240 bar.However, if the pressure is higher, the first 100 liter cylinder is used first, 10 liter cylinder will equalize about 225 bar and 100 liter cylinder lower pressure can not be used to raise it In a cascade storage system, several large cylinders are used to carry small cylinders to desired pressure, always using the cylinder supply with the lowest possible first pressure, then the next lowest pressure cylinder, and so on.
In practice the theoretical transfer can only be achieved if the gas is allowed to reach the equilibrium temperature before disconnection. This takes significant time, and lower efficiency is acceptable to save time. Actual transfers can be calculated using the general gas equation of the state if the gas temperature in the cylinder is accurately measured.
Maps Cascade filling system
Usage
Breathing set
A cylinder of breathing sets can be charged to its working pressure by decanting from larger cylinders (often 50 liters). (To make this easy the cylinder neck of the rebreather Siebe Gorman Salvus has the same thread as the oxygen storage cylinder, but the opposite sex, for direct decanting.) Storage cylinders are available in various sizes, typically from 50 liter internal capacities up to more than 100 liters.
In a more general case, a high-pressure hose known as a fill whip is used to connect the charging panel or storage cylinder to the receiving cylinder.
Cascade filling is often used for mixing partial pressure of respiratory gas mixture to dive, to save expensive oxygen, for more expensive nitrox, and helium in trimix or heliox blends.
Compressed natural gas fuels
Cascade storage is used in compressed gas refueling stations (CNG). Usually three CNG tanks will be used, and the first vehicle will be driven from one of them, which will result in incomplete charging, possibly up to 2000 PSI for a 3000 PSI tank. The second and third tanks will bring the vehicle tank closer to 3000 PSI. The station usually has a compressor, which recharges the station tank, using natural gas from the utility channel. This prevents accidental accumulation of the tank, which can occur with the system using a single fueling tank at a higher pressure than the target pressure for the vehicle.
Hydrogen storage
In a cascade storage system for hydrogen storage, such as at a hydrogen station, fuel dispenser A pulls hydrogen from tank A while dispenser B pulls fuel from a hydrogen tank B. If dispenser A is used excessively, A tank will become exhausted before tank B On this point of dispenser A is transferred to the tank C. Tank C will then supply the A and B dispensers and the A tank until the A tank is filled to the same pressure as the B tank and dispenser is disconnected, after which the control system will be closed. control valve to switch to its original state.
System settings
The storage cylinder can be used separately sequentially using a portable transfer whip with a pressure gauge and a manual valve, to exchange the receiver cylinder until the appropriate charging pressure has been reached, or the storage cylinder can be connected to the manifold system and fill the control panel with one or more whip fills.
Ideally each storage cylinder has an independent connection to the charging panel with a filler pressure gauge and a dedicated supply valve for the cylinder, and a charging meter connected to the filler whip, so the operator can see at a glance the next higher storage cylinder pressure compared to the receiver's cylinder pressure.
The storage cylinder can be charged remotely and connected to the manifold with a flexible hose when in use, or it can be connected permanently and recharged by the compressor through a special charging system, which may be automatic or manually controlled.
Excess pressure safety valves are usually installed inline between the compressor and the storage unit to protect the cylinder from overfilling, and each cylinder can also be protected by a broken dish.
References
Source of the article : Wikipedia
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