Air Inleakage into System

Few vacuum systems are completely airtight, although some may have extremely low leakage rates. For the ideal system the only load for the ejector is the non-condensables of the process (absorbed gases, air, etc.) plus the saturated vapor pressure equivalent of the process fluid. Practice has proven that allowance must be made for air leakage. Considering the air and non-condensables. For base ejector capacity determine inert gases only by  

For design of a new system, it is recommended that the results of the summation above be multiplied by 2 or 3 to establish the jet system inert (noncondensables) capacity, and add to this the non-condensed process vapors that are released into the jet suction system. 

Since the determination of air inleakage involves considerable knowledge of vacuum systems and judgment, no empirical method can be expected to yield exact and correct values. Most manufacturers use one of the methods presented here, together with a factor to account for 

Vacuum Pump Capacities From Steam Surface Condensers 

Maximum Steam Condensed, Lb. Per Hr. Serving Turbines Serving Engines  

---