What Should Be Pay Attention to When Installing the Cold Storage Pipeline?

The most troublesome thing in the refrigeration system is the oil return problem. When the system is running normally, a small amount of oil will continue to leave the compressor with the exhaust gas. When the system piping is well designed, the oil will return to the compressor and the compressor can be fully lubricated.

If there is too much oil in the system, it will have a negative impact on the efficiency of the condenser and evaporator; the oil returning to the compressor is less than the oil leaving the compressor, which will eventually damage the compressor; refueling the compressor can only be maintained the oil level for a short time ; only the correct pipeline design can maintain a good oil balance in the system, and then achieve the safe operation of the system.

A. Design of suction pipe

1. The horizontal suction pipe must have an inclination greater than 0.5% along the direction of refrigerant flow;

2. The cross section of the horizontal suction pipe must ensure that the gas velocity is not less than 3.6m/s;

3. In the vertical suction pipeline, the gas flow rate must be not less than 7.6-12m/s;

4. At the bottom of each vertical suction pipe, a U-shaped oil return bend must be established;

5. If the height of the vertical suction pipe exceeds 5m, a U-shaped return bend must be set up;

6. The length of the U-shaped return bend should be as short as possible to avoid excessive oil accumulation.

7. The gas flow rate greater than 12m/s cannot significantly improve the oil return, it will produce high noise and cause a higher pressure drop in the suction line;

B. Design of evaporator suction pipe

1. When the system does not use the pump-down cycle, a U-shaped interception bend should be set at the outlet of each evaporator. To prevent the liquid refrigerant from flowing into the compressor under the action of gravity during shutdown;

2. When the suction riser pipe is connected to the evaporator, there should be a section of horizontal pipe and interception bend in the middle to install the temperature sensor; prevent the expansion valve from malfunctioning.

C.Design of exhaust pipe

When the condenser is installed higher than the compressor, a U-shaped bend is required at the inlet pipe of the condenser to prevent oil  returning to the exhaust side of the compressor during shutdown, and also helps prevent liquid refrigerant flowing back from the condenser to the compressor.

D.Design of liquid pipeline

1. Liquid pipelines usually have no special restrictions on the flow rate of refrigerant. When solenoid valves are used, the flow rate of refrigerant should be less than 1.5m/s;

2. Ensure that the refrigerant entering the expansion valve is supercooled liquid;

3. When the pressure of the liquid refrigerant drops to its saturation pressure, a part of the refrigerant will flash into gas.