What are regulations for Inert Gas System on Tankers as per SOLAS ?

1. a positive pressure in excess of the test pressure of the cargo tank if the cargo were to be loaded at the maximum rated capacity and all other outlets were left shut; and 
2. a negative pressure in excess of 700 milimetres water gauge if cargo were to be discharged at the maximum rated capacity of the cargo pumps and the inert gas blower were to fail.  Such devices shall be installed on the inert gas main unless they are installed in the venting system required by rule 66 of the Merchant Shipping (Cargo Ship Construction and Survey) Rules 1988 or on individual cargo tanks. 

(b) The location and design of the devices referred to in sub-para (a) of this para shall be in accordance with rule 66 of the Merchant Shipping (Cargo Ship Construction and Survey) Rules, 1988.