Relationship between roots pump and pumping speed of front stage pump
Date of issue:2021/8/19 15:28:04 Number of Views:
The relationship between the pumping speed of roots pump and the pumping speed of front stage pump mainly depends on the volumetric efficiency and the allowable pressure difference of roots pump. If the volumetric efficiency is low, the effective pumping speed of roots pump unit will decrease significantly. If the pressure difference of roots pump exceeds the allowable maximum pressure difference, the rotor will overheat and expand due to compression work and will be stuck. Because the pump casing is easy to dissipate heat to the surrounding environment, it is still not too hot.
The maximum allowable pressure difference range of the Luoci pump is 40-100hpa. In the higher pressure range (150hpa), the allowable pressure difference is slightly higher. Thanks for the volume of air pumped, the cooling of the rotor is improved. Due to the increase of differential pressure, the required power will also increase.
A special gas cooler is set at the outlet pipe of roots pump. At this time, the allowable maximum differential pressure can be increased, because the return flow of cooling gas can keep the temperature of rotor within the specified range.
In the range of vacuum and high vacuum, the pumping speed ratio is mostly 10:1. When the inlet pressure changes greatly or the front stage pressure decreases, the compression ratio decreases, so the extraction speed ratio is mostly 5:1.
1) When the roots pump is started at a higher pressure, the pressure drops rapidly and reaches the required pressure. Although the maximum allowable pressure difference is exceeded during startup, the motor of the roots pump will not have problems in a short time overload (within a few minutes).
When the inlet pressure is very low or the air ballast valve of the front stage pump works, the two-stage front stage pump is usually used, otherwise the front stage pressure required by the roots pump is difficult to reach, and the pumping speed of the front stage pump becomes too low under this pressure. The compression ratio will be too high and the volumetric efficiency will be reduced.
2) When the pump inlet pressure is within the coarse vacuum range, this is the maximum allowable pressure difference, which becomes an important factor.
The pumping speed ratio of roots pump and front stage pump is 6:1 for the inlet pressure of 15hpa and 2:1 for the inlet pressure of 75hpa. Within the coarse vacuum range, the pumping speed ratio of roots pump and front stage pump should be determined separately for each case. Generally speaking, it is relatively small. The volumetric efficiency is quite good.
The relationship between the pumping speed of roots pump and the pumping speed of front stage pump mainly depends on the volumetric efficiency and the allowable pressure difference of roots pump. If the volumetric efficiency is low, the effective pumping speed of roots pump unit will decrease significantly. If the pressure difference of roots pump exceeds the allowable maximum pressure difference, the rotor will overheat and expand due to compression work and will be stuck. Because the pump casing is easy to dissipate heat to the surrounding environment, it is still not too hot.
The maximum allowable pressure difference range of the Luoci pump is 40-100hpa. In the higher pressure range (150hpa), the allowable pressure difference is slightly higher. Thanks for the volume of air pumped, the cooling of the rotor is improved. Due to the increase of differential pressure, the required power will also increase.
A special gas cooler is set at the outlet pipe of roots pump. At this time, the allowable maximum differential pressure can be increased, because the return flow of cooling gas can keep the temperature of rotor within the specified range.
In the range of vacuum and high vacuum, the pumping speed ratio is mostly 10:1. When the inlet pressure changes greatly or the front stage pressure decreases, the compression ratio decreases, so the extraction speed ratio is mostly 5:1.
1) When the roots pump is started at a higher pressure, the pressure drops rapidly and reaches the required pressure. Although the maximum allowable pressure difference is exceeded during startup, the motor of the roots pump will not have problems in a short time overload (within a few minutes).
When the inlet pressure is very low or the air ballast valve of the front stage pump works, the two-stage front stage pump is usually used, otherwise the front stage pressure required by the roots pump is difficult to reach, and the pumping speed of the front stage pump becomes too low under this pressure. The compression ratio will be too high and the volumetric efficiency will be reduced.
2) When the pump inlet pressure is within the coarse vacuum range, this is the maximum allowable pressure difference, which becomes an important factor.
The pumping speed ratio of roots pump and front stage pump is 6:1 for the inlet pressure of 15hpa and 2:1 for the inlet pressure of 75hpa. Within the coarse vacuum range, the pumping speed ratio of roots pump and front stage pump should be determined separately for each case. Generally speaking, it is relatively small. The volumetric efficiency is quite good.
