The vacuum pump unit gets hot, and the ultimate vacuum level is not high
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The unit has three stages: the first stage consists of 2x-100 double-vane vacuum pumps, the second stage features two ZJP-70 Roots pumps connected in parallel, and the third stage is composed of a ZJP-300 Roots pump. Under normal operation in the past, the pressure across the entire unit was at least 100 Pa, and the pumping speed was stable. Recently, however, the vacuum level in the unit dropped to 900 Pa, and it became evident that the pumping speed was insufficient (during vacuum distillation, the flow rate of the distilled liquid decreased significantly). All three Roots pumps became warm to varying degrees; the current consumption of the ZJP-300 Roots pump increased from 4 A to 6 A. The Roots pumps were inspected, and the bearings as well as the clearance between moving parts were found to be normal. It is suspected that there might be a problem with the rotary vane pump, which was also disassembled for inspection but no issues were detected. I really don’t know what to do anymore; I hope experts can offer some advice
We use water ring Roots pumps; in such cases, assuming air leakage is ruled out, it’s very likely that the preceding pump is the problem
It is likely due to the insufficient basic vacuum level provided by the rotary vane pump. For a single-stage rotary vane pump, is the vacuum level above 0.085 MPa? The motors of the Roots pumps in our factory all have strict current limits, and their power rating is just right. With a unit like your ZJ-300, when the rating goes from 4A to 6A, the thermal relay trips right away. Roths pumps generally function properly; as long as they can be rotated when turned off, they will work correctly. Yesterday, the ZJ-150 in my workshop didn’t work properly, which resulted in insufficient vacuum level when operating the primary pump (water jet pump) alone. It can only reach 0.08 MPa, because the gas stream has to pass through a Roots pump and then a water-jet pump before being discharged from the tank. The Roots pump is not rotating, and exhaust is poor due to that small gap. So the vacuum level just can’t be increased. Of course, when the Roots pump gets stuck, it can’t be started. The problem lies in the fact that vacuum needs to be created in pipes that have not been used for many years, which pulls the solid residues inside the pipes toward the Roots pump and causes it to get stuck. It is recommended to install a filter in front of the Roots pump. If the Roots pump is working properly, is there any air leakage in the pipeline? Is there a leak in your distillation tank? A change from 100 PA to 900 PA can be caused by just a small amount of air leakage. Disconnect the connection to the reactor and check whether the vacuum level of the Roots pump increases; apply nitrogen pressure separately to either the distillation reactor or the recovery reactor to see if the vacuum level decreases.
This post was last edited by Xin Chang Xiao Xu on 2017-7-11 08:28. In the vacuum buffer tank and the exhaust gas condensate receiver, when material is discharged, are there any low-boiling substances present?
Question 1: The principle behind the configuration of vacuum systems is that the pumping capacity of the booster pump (rotary vane pump, diffusion pump) should be greater than or equal to that of the preceding pump (vane pump, slide valve pump, screw pump); the intermediate pump has a pumping capacity of 70 L/S