Total Capacity at Ejector Suction

The total capacity is the sum of all the expected condensables and non-condensable flow quantities (in 

Applied Process Design for Chemical and Petrochemical Plants 

Non-condensable gases released from gases originally injected into the process for purge, products of reaction, etc. 

Non-condensable gases, usually air, released from direct contact water injection. 

Reasonable factors of safety should be applied to the various loads in order to insure adequate capacity. Excess ejector capacity can be handled by pressure control and some adjustment in steam flow and pressure, but insufficient capacity may require ejector replacement. Factors of 2.0 to 3.0 are not uncommon, depending upon the particular type of system and knowledge of similar system operations. 

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