Special Topic on Offshore Drilling Rigs: Seawater Cooling Systems

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The seawater cooling system is used on our platform, as many of the machines generate a large amount of heat while operating. For example, in a diesel engine, diesel is burned to drive the piston and generate power, with the energy being transmitted through the crankshaft. During this process, friction and the heat generated by combustion can cause fatigue in the metal, or they can trigger the machine’s overheat protection mechanism, causing the machine to stop. The above is just an example; there are many mechanical devices on the platform that need to be cooled. Such as hydraulic units, generator sets, frequency converters, air compressors, high-pressure mud pumps, winches, propeller brake pads, propeller hydraulic units, etc. The most readily available cooling medium at sea is seawater, with almost zero cost. The function of the seawater cooling system is to use seawater as a cooling medium for heat exchange, thereby ensuring that our systems and equipment operate under normal, stable conditions. I forgot to mention that seawater is corrosive; if it comes into direct contact with cooling equipment, it can easily cause mechanical corrosion. On modern platforms, including in ship design, centralized cooling systems are the most widely used. This system includes: 1, seawater cooling pump, a high-capacity centrifugal pump. 2. Pipelines and fittings: HDG hot-dip galvanized steel pipes. 3. Heat exchangers, or coolers, come in plate-type and tube-type versions; the plate-type type offers better cooling performance, which is why it is used more frequently. To explain what a cooler is, let’s use an example: if you place a cup filled with boiling water into cold water, after some time, the temperature of the water in the cup will drop, while the temperature of the water outside will rise. It’s just that on one side of the heat exchanger, low-temperature seawater flows, while on the other side, relatively high-temperature fresh water flows, thereby averaging out the temperatures. Hehe, that’s all there is to it. Schematic diagram of the seawater cooling system: Let’s talk about calculations now: We need to know the total power and flow rate of the equipment on the entire platform that requires fresh water for cooling. If there are multiple cooling systems, it is necessary to determine the total power and flow rate of the equipment in that system that requires fresh water for cooling. Q*T = q1*t1 + q2*t2 + q3*t3 + q4*t4 + q5*t5 + …; P = m*c*dt. Moreover, P = Q*1000*4.2*dt/3600 (KW), where: t = temperature, c0*dt = temperature difference, P = power in KW, Q = flow rate in m3/h, c = specific heat capacity in J/kg·K, and m = mass in kg. The total flow rate obtained by adding these values represents the flow rate of the fresh water cooling pump, while the total power obtained in this way represents the total power of the fresh water cooling pump. Finally, by using the power balance relationship and the formula P = Q*1000*4.2*dt/3600, it is possible to calculate the flow rate of the seawater cooling pump. The head is determined by the design pressure of the fresh water system; the pressure in a seawater cooling system is lower than that in a fresh water cooling system. Why is this the case? It’s easy to understand: once the cooler is damaged, it allows fresh water to leak into the seawater system, but it prevents seawater from leaking into the fresh water system, in order to avoid damaging and contaminating the entire fresh water system. This article is from: Bo Yan