General classification requirements
Sea water cooling systems for main and auxiliary machinery shall be connected to at least two separate sea water inlets (typically sea chests), preferably on opposite sides of the vessel. Sea chest openings in the shell plating shall be equipped with strums, with the total area of strum holes being at least twice the total flow area in the sea inlet valves. When sea water is used to cool main or auxiliary engines, suction lines need to be fitted with strainers, which can be cleaned without interrupting sea water cooling. Air pipes from sea chests shall lead to open air above bulkhead deck. //DNV-RU-SHIP Pt.4 Ch.6 Sec.4.10.1 and Pt.4 Ch.6 Sec.5.2.3
Centrifugal cooling pumps shall be installed as low as possible to avoid that the pumps loose water in a seaway. Both sea and freshwater cooling pumps for propulsion drivers shall have product certificates. //DNV-RU-SHIP Pt.4 Ch.6 Sec.1.3 and Pt.4 Ch.6 Sec.5.2.1
All heat exchangers shall be provided with a vent and a drain and shut-off valves at inlets and outlets. //DNV-RU-SHIP Pt.4 Ch.6 Sec.5.2.1
Control system functional description for sea water valves and pumps, together with arrangement of sea water inlets and discharges are subject for classification approval. Steel pipes can be used for sea water systems with required corrosion allowance of 3 mm. Typically, sea water pipes are efficiently protected against corrosion by zinc coating or rubber, which may reduce the corrosion allowance by 50%. //DNV-RU-SHIP Pt.4 Ch.6 Sec.1.3 and Sec.9.1