Home > FAQ > Chillers' Troubleshooting >

Why set oil return bend?

Why set oil return bend?
Update Time:2018-08-19

1.Why set oil return bend ?

When there is a large height difference in the piping of the system, in order to prevent the refrigerating oil from effectively returning to the compressor and affecting the service life of the compressor, the oil storage bend must be set on the vertical pipe line.

 

2.When to set the oil return bend

1.When the host is higher than evaporator

There is an ascending riser between the evaporator and the main steam pipe, because the frozen oil will not evaporate and vaporize in the evaporator, so it accumulates at the bottom. When the frozen oil accumulates at the bottom of the evaporator, it will block the steam pipe.

If set the return bend at the bottom of the evaporator, there will not be too much oil stored in the elbow. As long as the elbow is about to be blocked, the pressure difference between the two ends is enough to pump out the limited frozen oil "pump" in the elbow until the horizontal suction pipe at the top is drawn back up the slope by the compressor.

If you are worried that the riser riser is too long to get the pump to the top, you should consider setting up a return bend at every height distance (such as 6-10 m) for the riser segment to gradually return to the main engine.

 

2.When the main engine is lower than the evaporator and the height difference is large

Although the frozen oil can be automatically sloped back to the main engine without oil return bend, it is worried that too much oil return will cause the main engine "liquid hit".Therefore, every time the main steam suction pipe is separated by a certain height distance (such as 6 meters to 10 meters), a return oil bend is set to enable the frozen oil segment to gradually return to the main engine.

 

3.Low load operation

Frozen oil accumulates in the oil return bend. Due to the limitation of flow rate.Frozen oil accumulates in the oil return bend. Due to the limitation of flow rate, it only drives the oil return by "as long as the bend is about to be blocked and the pressure difference at both ends".

 

If the inhalation velocity can be increased to a greater value, then there is no need to increase the oil return bend.the truth is,When small load the internal heat transfer effect increases the output of the press.The output of the press increases too much,Easy to cause low pressure, no excessive heat intake,This means that the air intake velocity is limited, and in the case of large height distance the oil recovery curve must be used to gradually restore oil!

 

3.Principle of set oil return bend

1.When there is a large distance between the system indoor and outdoor machines, the vertical pipe part of the air pipe shall be installed with an oil storage bend every 8 meters or 10 meters from bottom to top.The oil storage bend is made in two "U" or one "O" shape with a height of 3 ~ 5 times of pipe diameter.At the same time, add the oil storage bend and check bend at the bottom and top of the riser.

 

2.The design of the exhaust pipe is the same as that of the return pipe. The pressure drop control must be taken into account in the design to ensure that the exhaust pipe is oily, avoid liquid attack and avoid noise and vibration.

 

Size reference of oil return bend, check return bend

A

B

C

mm

inch

mm

mm

Φ19.05

3/4

34

105

Φ22.2

7/8

31

150

Φ25.4

1/1

45

150

Φ28.6

9/8

45

150

Φ34.9

11/8

60

250

Φ38.1

12/8

60

350

Φ41.3

13/8

80

450

Φ44.45

7/4

80

500

Φ54.1

17/8

90

500

  Lydia