Global one-stop procurement platform for industrial spare parts.
English| Español| عربي
Catalogue

Is there any problem with compressor oil return

Is there any problem with compressor oil return 1. Mechanism analysis of compressor oil shortage During the operation of the system, the lubricating oil is discharged from the compressor along with the refrigerant, and then returned to the compressor after circulation. Then, where there is refrigerant in and out, there is the in and out of lubricating oil. There is an essential difference between the performance of the refrigerant and the performance of the lubricating oil. The refrigerant has two phases in the system circulation process, namely liquid refrigerant and vapor refrigerant, and the lubricating oil is basically in the liquid state. Precipitated in the refrigerant, under the influence of many factors, they are likely to be stored in a certain part or a certain structural point, resulting in the lubricating oil cannot be smoothly returned to the compressor, resulting in a lack of oil in the scroll compressor. If it is not resolved, it will lead to insufficient lubrication of moving parts inside the compressor, dry burning and other failures, which will greatly accelerate the damage of the scroll compressor. 2 Guarantee oil return-installation When the compressor discharges the refrigerant, it also discharges a small amount of refrigerating machine oil. Even if there is only 0.5% oil rate, if the oil cannot be circulated back to the compressor through the system, if 5HP is used as an example, the circulation volume is about 330kg / h under ARI operating conditions, then the compressor can be used in 50 minutes. All the oil is taken out, and the compressor will burn out in about 2 to 5 hours. Therefore, in order to ensure that the compressor does not run short of oil, we should proceed from the following two aspects: 1. Make sure that the refrigerant oil discharged from the compressor returns to the compressor; 2. Reduce the oil rate of the compressor. 1. Make sure that the refrigerant oil discharged from the compressor returns to the compressor 1. The flow rate of the refrigerant in the suction pipe (about 6m / s) should be ensured to return the oil to the compressor, but the maximum flow rate should be less than 15m / s to reduce pressure drop and flow noise. The horizontal pipe should also be along the refrigerant The flow direction has a downward slope, about 0.8cm / m. 2. Prevent the freezing oil from staying in the evaporator. 3. Make sure that the oil return hole of the gas-liquid separator is too large, which will cause wet compression. If it is too small, the oil return will be insufficient, and the stagnation oil will be in the gas-liquid separator. 4. There should be no part of the system where oil stays. 5. Ensure that there is enough refrigeration oil in the compressor under the condition of long piping high drop. Usually, the compressor with oil mirror is used to confirm that the frequent start of the compressor is not conducive to oil return. Second, reduce the oil rate of the compressor 1. Make sure that the refrigerant does not dissolve into the refrigerator oil when the machine is shut down (use crankshaft heater). 2. Avoid over-wet operation, because too much oil will be caused by foaming. 3. An oil separator device is provided inside. 4. Oil bubbling inside the compressor makes the oil easily taken out of the compressor. 3. High drop of long piping When the piping length is larger than the allowable value, the pressure loss in the piping becomes larger, which reduces the amount of refrigerant in the evaporator, resulting in a decrease in capacity. At the same time, when there is oil stagnation in the piping, the compressor is starved of oil, resulting in compressor failure. When the refrigeration oil in the compressor is insufficient, the refrigeration oil of the same brand as the compressor should be added from the high pressure side. 4. Set the necessary oil return bend When the drop exceeds 10m ~ 15m, an oil return elbow should be installed on the side of the trachea. 1. Necessity When shutting down, avoid freezing oil attached to the piping to return to the compressor, causing liquid compression. On the other hand, in order to prevent the poor oil return of the gas pipe, the compressor will run out of oil. 2. Set interval of oil return bend One oil return bend is set for every 10m drop. Fifth, ensure proper viscosity of frozen oil The refrigerating machine oil and the refrigerant are miscible. When the machine is shut down, the refrigerant is almost completely dissolved in the refrigerating machine oil, so a crankshaft heater needs to be installed to prevent dissolution. 1. The refrigerant containing liquid should not be returned to the compressor during operation, that is, to ensure that the compressor suction has superheat. 2. During starting and defrosting, liquid return phenomenon should not occur. 3. Avoid running in an overheated state and avoid oil degradation. 4. The size of the oil return hole of the gas-liquid separator should be appropriate: 1) Over-aperture will cause liquid refrigerant to be sucked and cause over-humid operation; 2) If the pore size is too small, the oil return will not be smooth, and the oil will stay in the gas-liquid separator. 3 Guarantee oil return-equipment First, the choice of lubricating oil Lubricating oil mainly plays the role of lubrication, sealing, cleaning, heat dissipation and rust prevention in scroll compressors. Choosing a good lubricating oil not only helps to improve the reliability of scroll compressors, but also greatly improves the performance of air conditioning systems. 1). Pour point: There are many standards for the selection of lubricating oil. From the perspective of favoring oil return, the lubricating oil is required to have good flow characteristics at low temperatures. Therefore, it is necessary to choose a low pour point to avoid adhesion at low temperatures and cannot return to the compressor The following table shows the pour points of several commonly used lubricants; 2), solubility: When the refrigerant is in the vapor state, the lubricating oil is mixed in the high-pressure and high-speed air flow. When the refrigerant is in the liquid state, the lubricating oil is mixed to flow in it. Lagging will occur. When selecting lubricating oil, it is required that the lubricating oil and the refrigerant have good compatibility. The following figure is a typical dissolution curve of lubricating oil and refrigerant, which brings a lot of convenience in daily analysis. Second, the selection of components in the system Oil separator: The oil separator is generally installed on the exhaust pipe, and realizes gasoline separation through rapid pressure drop, and then returns to the compressor oil storage tank through the oil return capillary. Currently, there are three widely used oil separators: 1). Oil separator with floating ball, if oil accumulates in the oil separator, the floating ball valve set inside will open to return the oil to the compressor; 2) Manually return the oil to the oil separator of the compressor. The oil accumulates in the oil separator, and the oil return valve needs to be manually opened to return the oil to the compressor; 3). There is no oil separator with float valve inside. Although the structure of this oil separator is simple, the size of the oil return pipe is very strict. Gas-liquid separator The gas-liquid separator is one of the most critical parts that affect the oil return. It is generally installed between the air return port and the compressor; The gas-liquid separator has two key indicators, oil return hole and balance hole. When designing and selecting, it is necessary to select the appropriate gas-liquid separator according to the needs of your system. In the gas-liquid separator of the oil-deficient system, oil is basically stored. At present, there are many manufacturers of gas-liquid separators, and the general air-conditioning manufacturers simply choose them, but do not design a suitable gas-liquid separator according to the needs of their own systems, which is likely to cause oil collection in the gas-liquid separator. And some companies with research and development capabilities will develop gas-liquid separators suitable for the system according to their own needs when developing distinctive products. Another key part is the connecting pipe of the internal and external units. At present, many manufacturers have developed multi-line groups, but as the length of the oil return pipe becomes longer, the difficulty of oil return gradually increases. How to configure a longer connection pipe It is also a question worth thinking about how to return oil well. 3. System Control System Control Mainly involves oil return control and oil equalization control 1), oil return control: In the multi-line system, under partial load operation, oil collection will occur in the unoperated load. The more unoperated load and the longer the operating time, the more oil will collect outside the compressor and return to the compressor. The less lubricant. When the system runs to a certain controlled index (the index can be oil level, running time, temperature, etc.), the oil return system works by adjusting the load, refrigerant flow, working frequency, motor, system air volume and other controllable factors Adjust the flow rate and pressure of the refrigerant in the system to increase the flow rate of the refrigerant in the compressor and drive the lubricating oil back. When the monitoring system detects that the amount of oil satisfies the operation of the compressor, it enters the normal load work, and so on. 2). Oil control: Electronically controlled oil leveling system: Oil equalization occurs in the multi-line group. Similarly, detection points can be designed in the system, such as oil level, etc., when the system detects that a compressor is lean, it can be used from the oil-rich compression compressor system through the oil equalization system Balancing part of the lubricating oil to the lean oil compressor system. If the second compressor also produces lean oil, restart the oil equalization by testing again, and so on, until the oil volume of all compressor systems is balanced. Optimized structure design oil equalization system: Optimized structural design is also conducive to oil return. Currently, gasoline balancing technology is commonly used. In theory, the oil pressure and air pressure in the crankcase of each parallel compressor can be guaranteed, but the actual situation is not very ideal. Due to the influence of factors such as the design and processing of the balance tube, the installation of the unit, and the pump oil volume of each compressor, etc. The oil pressure and pressure of the crankcase will vary, so this oil return method must be well controlled from the above aspects, and do not exceed three compressors when used. Another type of oil return structure uses unbalanced technology, Danfoss' patented structure. The pressure in the system flow path decreases in sequence, so that a pressure gradient is established in the compressor. The lubricating oil first flows into the upstream compressor. When the oil level is higher than the bottom of the communication pipe, it will overflow under the action of air flow and pressure difference. Flow to the next compressor, if the oil volume is normal, each compressor can get enough lubricating oil. 4. The effect of system speed and pressure on oil return Changes in system operating conditions have a great influence on the flow rate, pressure, and phase state of the refrigerant in the scroll compressor system. During the operation of the system, the refrigerant and the lubricant are almost mutually soluble. The greater the flow rate and pressure of the refrigerant in the pipeline, the more favorable it is for the return of lubricating oil. The oil return control generally changes the unit refrigerant flow rate by controlling the unit frequency. When the unit frequency increases, the greater the refrigerant flow through the compressor in unit time, the faster the speed and density of the refrigerant flowing in the pipeline. If it improves, then the speed of lubricating oil return will naturally increase. During the installation of the multi-line group, based on structural requirements, the internal and external connecting pipes may exceed the size recommended by the manufacturer. With the lengthening of the connecting pipes, the pressure loss of the system will increase, and the flow rate of the refrigerant in the system will also slow down. The oil return is extremely unfavorable, the lubricating oil will be precipitated from the slow-flowing refrigerant, and it will be attached to the inner wall of the pipeline. It will cause the accumulation of lubricating oil in some parts that are easy to store oil, so that the lubricating oil cannot be completely returned to the compressor. therefore 1) Use lubricating oil with a lower pour point as much as possible, which is conducive to the flow of lubricating oil in the pipeline; 2) Select the oil separator and gas-liquid separator of the applicable system. The influence of the length of the connecting pipe on the oil return can not be ignored. When the connecting pipe is too long, it should be treated accordingly, such as adding lubrication; 3). Consider the oil return factor as much as possible in the early stage of design and optimize the system oil return through structural design; 4) Frequency plays a vital role in the flow and velocity of refrigerant. With the increase of frequency, the flow and velocity will increase, and the amount of oil returned will also increase.

Recent related posts

Customers frequently viewed

New In stock for sale, IWAYA DENKI Water Pump 25CJT0752

IWAYA DENKI Water Pump 25CJT0752
US$2307.69
New In stock for sale, Panasonic Servo Motor MHMF022L1V2M

Panasonic Servo Motor MHMF022L1V2M
US$653.85
New In stock for sale, Honeywell Solenoid Valve VE4025B1045

Honeywell Solenoid Valve VE4025B1045
US$334.62
New In stock for sale, ROTEN Mechanical Seal 8E5K-22-X

ROTEN Mechanical Seal 8E5K-22-X
US$384.62
New In stock for sale, DIODES IC Integrated Circuit Chip AP62300WU-7

DIODES IC Integrated Circuit Chip AP62300WU-7
US$1.35
New In stock for sale, SBC Linear Guideway SBI15SL-C-K1

SBC Linear Guideway SBI15SL-C-K1
US$56.92
New In stock for sale, GUOMAO Reduction Drive Gearbox Speed Reducer B0-1.1KW

GUOMAO Reduction Drive Gearbox Speed Reducer B0-1.1KW
US$326.63
New In stock for sale, ASCO Solenoid Valve B220A23

ASCO Solenoid Valve B220A23
Contact Us
New In stock for sale, BLAUBERG FAN Iso-Mix 125

BLAUBERG FAN Iso-Mix 125
Contact Us
New In stock for sale, Rexroth Piston Pump A4FO71/10R-PPB25N00

Rexroth Piston Pump A4FO71/10R-PPB25N00
US$6250.00
New In stock for sale, PALL Filter HC8400FKS16H

PALL Filter HC8400FKS16H
US$138.46
New In stock for sale, Omron PLC ZEN-10C1AR-A-V2

Omron PLC ZEN-10C1AR-A-V2
US$327.75
New In stock for sale, BANDO Belt T2.5-540-26

BANDO Belt T2.5-540-26
US$73.08
New In stock for sale, Schneider Circuit Breaker NSC400K4320K

Schneider Circuit Breaker NSC400K4320K
US$5000.00
Submitted Successfully
Submission Failed
© eCommerce. 2017-2024. All Rights Reserved
Press and drag the mouse to start taking a screenshot