Calculation of head loss or pressure loss in chemical industry hoses
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Experts, I have a question for you. Our company operates commercial oil storage facilities, and our dock has a capacity of 20,000 tons. A common pipeline is used to connect the dock to the storage tanks. To meet efficiency requirements, it is necessary to unload cargo in large quantities by using DN300 pipelines; however, the pipelines at our dock are all DN150 in diameter. To improve efficiency, we use two DN150 hoses to transfer the cargo onto the ship, and then those two DN150 pipelines are connected to the DN300 pipeline. Now the boss is asking why, since you’re using DN300 public pipelines, you don’t use DN300 hoses on board. But in my understanding, using two DN150 hoses or one DN300 and one DN250 hose gives roughly the same results, as the length of these pipes is relatively short – the hoses are 24 meters long while the rigid pipes are about 150 meters long. Logically, the loss in head pressure or compression should be low; in fact, the losses should occur along the main pipelines. So I hope to explain to the boss the differences in head pressure losses associated with hoses, but I can’t find any method for calculating such losses for composite hoses. I’d like to ask if anyone here knows a method for calculating head pressure losses or pressure drops in hoses?
The 150-meter rigid pipe is the common DN300 main pipe, and what the boss is concerned about is the combination of the joint of this main pipe and the 24-meter DN150 flexible pipe on the ship – is that correct?
The boss is concerned about more than just pressure loss, right? Two questions that come to mind: 1. Investment: Which is more cost-effective, a 24-meter-long DN300 hose or two 24-meter-long DN150 hoses? I don’t know, haha; it’s just an idea. 2. Pressure drop: I haven’t done specific calculations for hoses; the simplest way is to treat them as rigid pipes – calculate it as Q/2 through a DN150 pipe and Q through a DN300 pipe. Which one results in a greater pressure drop? (I haven’t done the calculations; based on experience, DN300 should be smaller – you can calculate it yourself). It’s only 24 meters; if the head requirement isn’t particularly high, there’s no need to worry about it.
I haven’t done the calculations; it’s just an idea for reference only
First of all, I’m just an ordinary guy, not an expert. For unloading or loading, there are two types of pipes, namely hoses and rigid pipes. Hoses are used to ensure a sealed connection even as the hull moves with the water flow. Under normal circumstances, the hard pipes and valve assemblies are installed above the highest water level (i.e., at the end of the dock), and then connected via flexible hoses. The DN300 rigid pipe mentioned in the description was likely determined during the design phase by converting it based on the annual throughput. If the current volume is relatively small, two DN150 pipes will suffice; I believe their performance will be similar to that of DN300 pipes. According to Darcy’s formula, to carry out an accurate calculation, it is necessary to provide the specific flow rate, as the friction in the pipe takes into account the flow pattern. In short, a hose over 20 meters in length has little impact on transmission, so there’s no need to worry. As for the frictional losses of the hose, you can look up the absolute equivalent roughness of the hose, take into account the friction coefficient of curved pipes, and then make a decision based on that. Flexible hoses are not used for long-distance transportation.