10.1.2 The additional requirements contained within this Section are applicable
to semi-submersible and self-elevating units only.
10.1.3 Normally, each separate overboard discharge from an enclosed space is to
be fitted with an automatic non-return valve at the shell boundary. Where the
inboard end of a discharge is situated below the worst damage water line, the
non-return valve is to be of a type which is effective at the worst expected
inclination after damage, whatever the orientation, and is to have a positive means
of closing, operable from a readily accessible position above the damage water line.
An indicator is to be fitted at the control position showing whether the valve is
open or closed.
10.1.4 The requirements for non-return valves are applicable only to those
discharges which remain open while the unit is afloat during normal operation. For
discharges which are closed while the unit is afloat, such as gravity drains from
tanks, a single screw-down valve operated from the freeboard deck is considered to
provide sufficient protection. An indicator is to be fitted at the control position
showing whether the valve is open or closed.
10.1.6 Discharge piping, situated between the sea level and the bottom of the
upper hull of semi-submersible units and below the bottom shell of the
self-elevating units when in the elevated position, is to be of substantial
construction, well secured and protected.