Double seals for screw compressors

[loribadeaux]

We are completing the design for a compressing unit;
the fluid is sour gas with about 5% H2S;
We have been chosen screw compressors for our application; small capacity (1000m3/h of gas) at 9barg discharge.

Vendor is proposing double seals with fuel gas in the first seal chamber as purge gas and nitrogen as a barier gas and back-up as well.

We've been surprised to hear that for this 'toy' we will need 200m3/h of fuel gas to the seals and another 100m3/h of nitrogen.

Are these expected flow rates for seals? It looks very high for us.

Thanks

Lori