Code of Federal Regulations Title 46. Shipping § 46.153.254 Cargo tank access

(a) A cargo tank must have at least one covered manhole opening into the vapor space described in § 153.354.

(b) An access through a vertical cargo tank surface must be at least 60 cm by 80 cm (approx. 23.6x31.5 in.) and no more than 60 cm above a foothold grating, or surface on both sides of the access way.

(c) An access through a horizontal cargo tank surface must be at least 60 cm by 60 cm (approx. 23.6x23.6 in.).

(d) An access trunk must be no less than 76 cm (approx. 29.9 in.) in diameter.