1. Corrosive Suction media:
Corrosive Suction media can corrode the internals of a vacuum pump to a large extent. In order to tackle the corrosion, the pump will have to be made in a corrosion resistant material of construction which will increase the capital costs greatly.
In case of a liquid ring vacuum pump the corrosive vapours can dissolve in the sealing liquid inside the pump and this can convert the sealing liquid into a dilute acid. This will aggravate the corrosion problems not only inside the pump but in the entire sealing fluid loop. This will require the entire sealing fluid line in corrosion resistant materials along with the pump.
This will make the entire system highly expensive and the increased complexity will increase maintenance costs and downtime period.
Ejectors systems provide a solution in such cases in a cost-effective way.
Ejectors can be easily manufactured with a corrosion resistant material of construction. Ejectors do not require sealing fluids or cooling media hence the auxiliary fluid loops are eliminated.
The high reliability of ejector systems and minimalistic maintenance requirement can decrease downtime drastically and enhance production.
2. Non-continuous operation:
In case your process requires the vacuum system to operate for a limited period during the day, the high operational costs of an ejector over a vacuum pump can be offsetted by the saving in the capital cost of an ejector system over a vacuum pump.
Also the high reliability of ejector systems and minimalistic maintenance requirement can make the ejector more suitable than the vacuum pump in the long run.
3. Remote installation location:
An ejector system weighs much less compared to a vacuum pump of comparable capacity, can be installed in any orientation, doesn't feature lots of connection points which all relates to easy installation.
This combined with the high reliability of ejector systems and minimalistic maintenance requirement enable the ejector systems to be installed into remote locations in a plant and in difficult to access areas.
This helps the vacuum system to be placed near your process, eliminating the leakage losses and problems to a large extent.
Installation close to application also cuts down on piping costs and enables the system to achieve the required vacuum in short period of time.
4. High Temperature Process Streams:
High temperature process fluids occupy a huge volume which requires a considerably larger size of the mechanical vacuum pump system.
The high temperature of the process media can also increase the corrosive activity which requires a more corrosion resistant material of construction for the pumps, thus increasing the cost.
In case of liquid ring pumps, it also reduces the capacity and the maximum obtainable vacuum drastically.
The high temperature process streams also lead to thermal stresses which increases the maintenance of the system.
An ejector can be designed to operate with such suction conditions without any of the above problems. Also the ejector can direct induct high temperature gases into it thus eliminating a cooling heat exchanger in the suction line
The temperature at exhaust can also be lowered by selecting the right type of motive media.
For Eg: If compressed air is used as a motive medium, the temperature at exhaust is lowered due to the mixing of the cool expanded air with the high temperature process.