Reasons and Measures for Excessive Fuel Consumption of Roots Oil Pump and Performance Evaluation Indicators

Firstly, the reasons and measures for excessive oil consumption in Roots pumps

It is reported that once the Roots pump consumes too much lubricating oil during operation, it indicates that there is a serious problem inside the equipment. This requires us to stop the machine and conduct maintenance in a timely manner to avoid internal faults causing huge wear and tear on the equipment and causing more serious consequences.

. So we need to understand the reasons and solutions that cause excessive fuel consumption in the equipment

1. Oil leakage

Roots pump oil leakage is generally the main cause of excessive fuel consumption. Maintenance personnel need to quickly identify the location of the oil leakage and repair it as needed.

. It should be emphasized that pump oil leakage can cause oil to accumulate in the machine and other areas. To reduce pollution, it is recommended to use specialized cleaning agents for maintenance and repair

2. Too much oil in the valve chamber

It may be due to wear on the valve guide, piston rings and cylinder liners, and damaged sealing rings of the turbocharger, which can also cause excessive oil consumption in the Roots pump.

3. The oil temperature is too high

Roots pump users should check the operation of the oil cooler after stopping for a period of time, replace with new parts, and clean the oil cooler core.

4. Excessive oil in the engine

Maintenance personnel should remove excess oil, identify the source of this oil, use appropriate oil in the engine, and do not add too much oil for oil leakage.

So once you find that the Roots pump you are using consumes too much oil during operation, you can carry out maintenance according to the above aspects to quickly identify the cause of the excessive oil consumption of the equipment and take targeted measures to solve it. After dealing with the fault problem, you can also perform relevant maintenance work on the equipment to avoid the recurrence of the fault

Secondly, the performance evaluation index of Roots pump

The use of pumping speed as the main performance evaluation index of Roots pump is not accurate enough, and it cannot truly reflect the quality level of Roots pump. It is recommended to use zero flow compression ratio as the performance index to evaluate the pumping capacity of Roots pump.

From the surface, the pumping speed and zero flow compression ratio of Roots pumps are two completely different concepts, seemingly unrelated performance indicators. But in reality, they are not only performance indicators that represent the pumping capacity of Roots pumps, but also closely related to each other. Compared with pumping speed, zero flow compression ratio can truly reflect the design and manufacturing quality of Roots pumps, and has unparalleled advantages in testing and application. Therefore, we believe that zero flow compression ratio should be used as an evaluation index for pumping capacity

Generally, Roots pumps can only work when matched with the front stage pump, so their pumping speed is closely related to the front stage pump. Roots pump, liquid ring pump, rotary vane pump, slide valve pump, piston pump, etc. can form various types of vacuum units, and various ratios can be used according to different needs, so the vacuum units formed have different pressures and pumping speeds. Therefore, the so-called Roots pump pumping speed is actually the pumping speed of the vacuum unit. It largely depends on the type and size of the front stage pump, that is, the pressure and pumping speed of the front stage pump. Although the "Roots Pump Product Quality Classification" standard specifies the model of the front stage pump, due to the standard for the front stage pump (rotary vane pump, slide valve pump), the geometric pumping speed of the pump is (1.1-1.2) nominal pumping speed, so the measurement error of pumping speed alone reaches 2%

The change in ambient temperature will inevitably have an impact on pumping speed measurement, especially when the vacuum degree is high. It indirectly affects pumping speed by affecting the vacuum degree of the preceding pump. This point was elaborated on in the author's previous article "Performance Evaluation Indicators for Roots Pumps - Discussion of Pressure". The "Roots Pump Product Quality Grading" standard specifies the use of the pre stage pump recommended in the "Roots Pump" standard when assessing pumping speed. This is not a big problem for Roots pumps below ZJ-300, but a big problem for Roots pumps above ZJ-600. One of them is the pre stage pump recommended by the standard, which includes both Roots pump and rotary vane (slide valve) pump. It is not necessarily required by the user, but is only designed and manufactured for measuring pumping speed, specifically for a vacuum unit, or even a very complex unit. For example, when testing a ZJ-10000 Roots pump, it is equipped with front stage pumps such as ZJ-2500, ZJ-600, and H-150 pumps. On the other hand, such a matched unit can only test pressure and pumping speed, and cannot measure large allowable pressure differences and zero flow compression ratio curves, because the Roots pump as the front stage pump cannot withstand the pressure differences generated during testing. In this way, in order to test the larger allowable pressure difference and zero flow compression ratio curve, and to equip a front stage pump, another set of units is manufactured, which is less desirable for Roots pump manufacturers