I got home last night after one of the most pleasant and unexceptional travel days ever. It was EXACTLY what I needed.
I was pretty refreshed after a few light days in week 3, and week 4 hit us like a hammer, with weather, wind and a lot of strange cargo movements. One of the more trying events that we deal with is when we load cargo for multiple discharges at anywhere from 2 to 5 ships with multiple products... and trying to do so in such a way that we can pump everything off in order.
To explain, I have two large diesel engines on deck that drive a Crisafulli-style screw drive impeller pump on a right-angle gearbox- so the suction point for the pumps is about at the same depth as the bottom of my tanks. However, such a unit is not self-priming at low volumes... in other words, a tank has to be partially filled a fair bit in order for me to be able to pump it out. In my case, there needs to be about 3 feet of product in a given tank in order to fill up the pump to prime it. This is related to the height of my piping in the tanks- the oil has to be able to flow through the pipes to fill up the barrel (sump) of the pumps. One weakness there is that in draining the tank dry, sucking in air will cause the pump to lose suction, so when the tank is almost empty, we need to slow the pump down and slow the feed rate by partially closing the valves to that tank... if we suck air, the pump stops working, and if we suck air, it can be a bitch to reprime the pump unless we have more cargo in another tank to reprime the pump. 'Losing suction' before pumping off all cargo is a no-no, and causes shame and gnashing of teeth and wailing and lamenting from the office, as you become the proud owner of oil that can't be given to that customer now.
Now, the tanks themselves have a suction point (a sump and a pipe to suck out of it) with a valve to open and close it, at the aft end of each tank as close to the centerline of the barge as possible. The tanks are laid out in pairs, so as we work after from the bow we have #1port and #1 Starboard tank, and aft of that are the #2 tanks, etc etc. This is done to that we can pump off cargo from the bow and as it lifts up out of the water as it empties, oil will naturally flow down to the suction point in the tank, and really allow it to be emptied completely... we actually roll the barge slightly to one side or the other to help drain the tanks as empty as possible. except in the after tanks, where the suction point is at the front of the tank. The house on board actually sits partway on top of my aftermost cargo tanks, so there would be no way to put in valves and a suction point in those tanks the same way and have access to it... and so in order to pump off the after tanks, we have to have full tanks up forward somewhere to drive the bow down and the stern up as the stern tanks are pumped off... but after the after tanks are empty, we need to get the bow back up again in order to pump off all the other tanks properly... anyhow, it's not always easy, given that we also have designated tanks for designated products based on the sulfur content of the oil we carry. Some tanks are for Ultra-low sulfur fuel oil (ULSFO), some for Very low sulfur fuel oil (VLSFO) and some for Low or Ultra-Low sulfur marine gasoil (LS-MGO, a type of high-quality diesel fuel).
Now, with all that confusing folderol, we loaded, for example, last Friday, with three grades of fuel in 10 tanks for 3 ships. The first ship was getting some VLSFO and all the LS-MGO, the second ship was getting some ULSFO and the rest of the VLSFO, and the 3rd ship was getting the remainder of the ULSFO. We loaded up, and the peculiarities of where we had to put the fuel made it so that we actually left with a nice 2' of drag- which is to say that the stern was 2 feet lower in the water than the bow, which eases how we handle while underway and doesn't stress the hull with bending forces either. .. but when I woke up 8 hours later, the order in which we had to pump off the cargo had changed... now we had to pump off the product for the second ship first, the 3rd ship second, and then we had to go back to a loading terminal and load more VLSFO, then go to another loading terminal to load more ULSFO, before returning to pump off fuel for what used to be the first ship, and also two more ships after that with the crap we loaded between the second and 3rd ships.
Oh, and the VLSFO and the MGO were owned by one charterer, and the ULSFO was owned by another, that was also fun to deal with. Two different chain-of-custody procedures and paperwork policies... and if there is any remaining fuel in a given tank that we can't pump off, we can't use that tank again until either the original owner gets their fuel back or we load more on top and give it to someone else.
Now, on changing of our orders, my first concern is 'Can we pump this stuff off?' Which tanks we use is based on being able to trim and roll the barge to be able to empty the tanks completely. Changing the order in which we pump off tanks will change the trim of the barge, which may make it impossible to completely empty a tank. As it happened, with the changes, I could manage to get everything off in theory, although we had a strong list to one side and were way down by the bow between the 3rd ship and the 4th, so there was much wailing and gnashing of teeth by our tugboaters, who had to drag us around and did not enjoy doing so with a barge that doesn't want to move well at all... oh, and at this point we had a storm come in again, with gale-force winds, so that was fun for all. And by fun, I mean awful.
So, yesterday, while we were loading the final products, it was time for crew change, and I got relieved by Big E, and had my unusually pleasant flight home, followed by a great evening with my family... and here I am, typing away just before sunup, waiting for the Mrs. to wake up and start the day... not bad at all. It's cool for Florida (65 degrees) but promised to be in the low 80's and sunny today. Can't wait.