Additional requirements

Basically, all class notations related to propulsion, power generation and auxiliary systems (the class notations belonging to DNV-RU-SHIP Pt.6 Ch 2 such as E0, SRtP, Redundant propulsion and alternative fuel solutions) are giving additional requirements for cooling systems. Those are mostly related to required control and monitoring systems, and redundancy of components.
In addition, class notations for cold climate (DNV-RU-SHIP Pt.6 Ch 2) give stricter requirements for sea chest (ice box) design and location to ensure cooling water supply when navigating in ice.

M/S MERSol is arranged with two sea chests in STB pump room serving auxiliary engines, central coolers, fuel oil coolers and evaporator cooler. According to the DNV rules, these sea chests should preferably be on the opposite sides of the vessel, while on MERSol the chests are located next to each other. In addition, there is a separate sea chest in bow thruster room serving fire pump.
The sea chest openings on ship hull are equipped with bolted gratings, with the total grating hole are being three times the total flow area in the sea inlet valves. The sea chests are connected sea water crossover tank through separate strainers, as required by the rules. Further there are two sea water suctions from the crossover tanks, of which one is serving two central coolers for main engines, evaporator and ballast water system and the other one is serving the two auxiliary engines, fuel oil coolers, auxiliary equipment and fire water extinguishing system. The sea chests and crossover tank are vented to atmosphere above upper deck.
Two main engine coolers are served by three frequency-controlled SW cooling pumps. Normally one pump is running, and the center pump is on standby.  Evaporator has its own SW pump. On the other sea water cooling circuit two frequency-controlled SW pumps are serving two central coolers for auxiliary equipment. Normally one pump is running. Cooling system for auxiliary engines is based of sea water and consist of one engine driven SW -cooling pump and heat exchanger. That is acceptable solution by the rules as long as a complete spare pump ready for mounting is available as a spare onboard.
Excluding cooling water pipes for auxiliary engines all sea water pipes are zinc threated class III pipes. The auxiliary engine piping is made of conifer.
Each of the main engines have own LT and HT water circuits cooled by the central coolers for main engines. The system is arranged with one HT circulating pump and one cooling water transfer pump. HT and LT pumps for each of the engines are engine driven. There is one ex-pansion tank for each of the main engines and a common fresh water tank for main engines and auxiliary equipment.
The cooling circuit for auxiliaries has two fresh water cooling pumps, normally one running and one standby. The auxiliary cooling circuit is serving shaft bearings, CPP hydraulic units, AC-compressors, freezer room and space cooling compressor unit, shaft generators, reduction gears, water cooled brake resistors, deck crane power packs and deck hydraulics oil coolers. The auxiliary cooling circuit has its own expansion tank.