Are You Looking For Dry Screw Vacuum Pump(Oil Free Vacuum Pump)

The clear benefits of dry vacuum pump technology, especially hybrid variable pitch screw pump chemical dry pumps, are evident and tangible in many essential applications. This pump is a well-designed, cost-effective, safe and reliable solution to processing requirements. These are Oil free vacuum pumps. These pumps do not require oil or water for sealing and lubrication of the vacuum stages. These dry vacuum systems are therefore free from pollution and effluent generation.

Oil-Free Vacuum Pump Operation:

• Two parallel, non-contacting, helical screw-shaped rotors (1) or (2) make up a dry screw vacuum pump. Fig. 1. Rotating at high speeds using precision gears (3). They rotate in opposite directions and trap gas at the suction pocket (5), compressing & transporting it to the exhaust port (6) and into the exhaust cavity (7). The gas is transported by the compression chambers, or pockets , which are formed by the walls of the stator (9).
• There are very small gaps between the screws and stators, as well as between intermeshing screws. This ensures that there is less reverse leakage towards the inlet than the forward flow of gas created by the screw pockets.
• The length of the sealing border (i.e. the number of spirals or tight clearances) prevents reverse flow of the pumped gasses. Pumps fitted with compression plates at discharge sometimes experience slight reverse expansion when the outlet valve or port is first exposed. As the screw action reduces the volume of trapped gas, this is quickly expunged.

Thermal Management in Dry Vacuum Pumps:

For reliable operation of a chemical Dry Screw Vacuum Pump, thermal management is crucial.

If the pump is TOO COLD for the process being performed, aggressive vapours can condense. This could lead to corrosion, dilution of oils, and swelling of seals. This is a serious problem that can only be caused if the vapor is allowed to condense into the liquid due to the heavy compression happening inside the pump.

If the operating temperature of the pump is too high for the process being performed, undesirable reactions like polymerization and auto-ignition can occur. To prevent this, high bearing temperatures or thermal seizure may be added as add-on instrumentation.

Although internal coatings can reduce some of the above effects, they should not be relied upon. While coatings are great for protecting the pump during installation and commissioning, they will not last long in the vacuum and temperatures where the pumps spend the majority of their time. Thus Everest has come up with special alloy steel rotors which are ENP plated for longer lifespan. Everest has also developed stainless steel screw rotors that are becoming very popular in corrosive operating environments.

It is important to make sure that process vapours remain in the vapours phase (Green area) as shown in the figure below. There are several ways to make sure this happens: temperature/flow control for the pump coolant; nitrogen purge to increase process dew point; and inlet condensers that remove vapor upstream from the pump.

Additional features can be added to the pump system in order to increase reliability and address system problems. A solvent flush system is one example to ensure that the pumping mechanism remains clean and free from any contaminants. Another example is knock-out pots (KOPs), which are filters that capture liquid and powder slugs, when they are not prevented.