Learn and grow with Shanghai Feihe Compressor every day! Generally speaking, oil leakage is closely related to the following factors: oil separation failure, compressor system failure, improper oil separation installation, and defective oil-gas separation system design. If the compressor leaks oil, it will not only pollute post-processing equipment such as dryers and precision filters, but also affect product quality and cause varying degrees of damage to certain production equipment. Therefore, it is necessary for us to understand the causes and treatment methods of high oil consumption in screw compressors.
In oil-injected screw compressors, a large amount of oil is sprayed into the inter-tooth volume of the compressor while compressing the gas. The oil-gas mixture formed by these oils and the compressed gas is discharged into the oil-gas separator of the unit after undergoing the same compression process. The oil-gas separator is one of the main equipment in the system of oil-injected screw compressor units. In order to reduce the oil content in the exhaust gas of the unit and recycle the lubricating oil in the unit, the oil-gas separator must be used to effectively separate the lubricating oil from the gas. If the oil separator fails, the lubricating oil cannot be separated well, and the lubricating oil will be discharged along with the compressed air. Therefore, the failure of the oil separator and its oil separator core is the main factor for the oil injection screw compressor to consume a lot of oil.
The main causes and hazards of compressor oil separator failure are as follows:
1. Blockage of the oil separator core: When the oil separator core is blocked, it will cause the air compressor motor to have too much current. It is also possible that the oil separator core is deformed due to excessive pressure, and the main engine will be locked when the motor is seriously overloaded. In addition, excessive current will shorten the life of the contactor or burn the contacts, causing major accidents.
2. Damage to the oil separator core. When the oil separator core is damaged, the air compressor will consume a lot of oil, and there will be a lot of oil in the air tank and pipeline. In severe cases, the air compressor oil will be directly discharged when the air tank drain valve is discharged.
The main reasons for this failure are:
The oil separator core was not replaced on time;
An oil separator core of poor quality was selected;
Failure to follow the regulations during the installation process, such as breaking the oil separator core when installing the return oil pipe.
3. The oil separator core is burned. The burning of the oil separator core is not common during the operation of the air compressor, but it occasionally occurs. The main manifestation is that the filter screen of the oil separator core is partially or completely carbonized, and even the metal shell of the oil separator core is burned.
This type of failure mainly occurs because:
The quality of the air compressor oil is poor;
The quality of the oil separator core itself is too poor;
When installing the oil separator core, there is no reliable connection between the oil separator core shell and the oil separator barrel and it cannot be grounded. When there is static electricity, the oil mist is ignited and the oil separator core is burned.
4. The separation effect of the oil separator core is poor. The main manifestation is that the compressed air contains too much oil, which causes damage to the post-processing equipment and user equipment.
The main reasons for this failure are:
The quality of the oil separator core itself is too poor;
The installation was not carried out according to the regulations.
Other reasons
1. Minimum pressure valve failure
The minimum pressure valve is a component that maintains the pressure of the screw compressor system. If there is a leak in the seal of the minimum pressure valve or the minimum pressure valve is opened in advance, the time it takes to establish the oil and gas tank pressure in the early stage of the machine will increase. At this time, the gas oil mist concentration in the low-pressure state is high, and the flow rate is fast when passing through the oil separator, the oil separator load is increased, and the separation effect is reduced, resulting in high oil consumption.
Solution: Repair the minimum pressure valve and replace it if necessary.
2. Use of unqualified compressor lubricant
Currently, the general screw compressors have high temperature protection, and their usual trip temperature is about 110-120℃. Some compressors use unqualified lubricants, and when the exhaust temperature is high, there will be different degrees of oil consumption (based on this, the higher the temperature, the greater the oil consumption). The reason is that at high temperature, after the primary separation of the oil and gas barrel, some oil droplets can have the same order of magnitude as the gas phase molecules, and the molecular diameter is ≤0.01μm. It is difficult for the oil separator to capture and separate them, resulting in excessive oil consumption.
Solution: Find the cause of the high temperature, solve the problem and lower the temperature, and try to use good quality screw compressor lubricating oil.
3. The design of the oil and gas separation tank is not standardized. Some compressor manufacturers design the primary separation system unreasonably when designing the oil and gas separation tank, and the primary separation effect is not ideal, so that the oil mist concentration before entering the oil separator is very high, the oil separator is overloaded, and the processing capacity is insufficient, resulting in excessive oil consumption.
Solution: The manufacturer improves the design to improve the effect of primary separation.
4. Too much oil filling. The amount of oil filling exceeds the normal oil level, and part of the oil is carried away with the air flow, resulting in excessive oil consumption.
Solution: After shutdown, wait until the air pressure in the oil and gas barrel is released to zero, open the oil drain valve, and discharge the oil to the normal oil level.
5. Damage to the oil return check valve
If the oil return check valve is damaged (from one-way to two-way), the internal pressure of the oil separator tank after shutdown will pour a large amount of oil back into the oil separator through the oil return pipe. The next time the machine is running, the oil inside the oil separator will not be sucked back to the machine head in time, causing part of the oil to escape from the compressor with the separated air (this situation is common in machines that are not equipped with oil circuit shut-off valves and machine head exhaust outlet check valves).
Solution: Check the check valve after disassembly. If there is debris stuck on it, just clean the debris. If the check valve is damaged, replace it with a new one.
6. Improper installation of the oil return pipe
When replacing, cleaning, and repairing the compressor, the oil return pipe is not inserted to the bottom of the oil separator (reference: 1 to 2 mm from the arc center of the bottom of the oil separator is better), resulting in the separated oil not being able to return to the machine head in time, and the accumulated oil will escape with the compressed air.
Solution: Stop the machine, wait for the pressure relief to return to zero, and then adjust the oil return pipe to a reasonable height (the oil return pipe is 1~2mm away from the bottom of the oil separator, and the beveled oil return pipe can be inserted to the bottom of the oil separator).
7. Large gas consumption, overload low pressure use (or the oil treatment capacity selected before the machine leaves the factory is too tightly matched with the machine exhaust volume)
Load low pressure use means that when the user uses the compressor, the exhaust pressure does not reach the rated working pressure of the compressor itself, but can basically meet the gas requirements of some corporate users. For example: corporate users have added gas-using equipment, and the gas consumption has increased, so that the compressor exhaust volume and the user's gas consumption cannot be balanced. Assuming that the rated exhaust pressure of the compressor is 8kg/cm2, but the actual pressure is only 5kg/cm2 or even lower during use, the compressor is in a long-term load operation state and cannot reach the rated pressure value of the machine, resulting in increased fuel consumption. The reason is that under the condition of unchanged exhaust volume, the flow rate of the oil-gas mixture increases when passing through the oil separator, and the oil mist concentration is too high, which increases the oil separator load and ultimately leads to large fuel consumption.
Solution: It is recommended to contact the manufacturer to replace an oil separator product that can match low pressure use.
8. Oil return line is blocked
When the oil return line (including the one-way valve and oil return filter on the oil return line) is blocked by foreign matter, the oil condensed at the bottom of the oil separator after separation cannot return to the engine head, and the condensed oil droplets are blown up by the air flow and taken away with the separated air. These foreign objects are usually caused by solid impurities dropped during installation.
Solution: Stop the machine, wait for the oil barrel pressure to be released to zero, remove all pipe fittings of the oil return pipe, and blow out the blocked foreign objects. When installing the built-in oil separator, pay attention to clean the oil and gas barrel cover, and pay attention to whether there are solid particles remaining at the bottom of the oil separator core.