[CaptBones]

Let me take a shot at answering this; having been Engineer Officer (often incorrectly called “Chief Engineer”) of two USN oil-fired steam ships (USS KIRK and USS TARAWA), a member of the Pacific Fleet Propulsion Examining Board, and the Director of Propulsion Engineering “A” Schools at Great Lakes, I have an idea of how it worked.

Regardless of whether it’s a battleship, an aircraft carrier, a cruiser, a destroyer, or any other type of “conventional” (oil-fired) steam ship, the propulsion plant works essentially the same way. And BTW, there is never ever seawater used, deliberately, in a steam propulsion boiler. Next to the propulsion engines and electrical generators, one of the biggest “consumers” of the steam produced in the boilers is the distilling plant, to provide distilled water for the boilers.

Before the introduction of automatic boiler controls and automatic combustion controls, changes to the firing rate of the boilers had to be done manually. The firemen (or Boiler Tenders in the WWII USN) would cut burners in or out and adjust the flow rate of feedwater and combustion air to the boiler as the steam demand changed. In older ships, like the TEXAS, that had to be done before the throttles were changed, opened or closed, in the engineroom. In ships built during or just before WWII, the throttles could be opened or closed at the same time as the burners, air registers, feedwater valves, feedwater pumps, and forcer draft blowers were being adjusted. Boilers of that era were called “Express Boilers” because of the high flow rates and the speed with which adjustments could be made.

When the engine order telegraph signaled a change, the throttlemen would begin turning the valve wheels, slowly, to increase or decrease the flow of steam to the high-pressure turbine nozzles. At the same time, the BTs would either cut additional burners in or shut them off, as needed, adjust the air registers, the feedwater supply valves and adjust the feedwater pumps and forced draft blowers, if necessary. Depending on the type of boiler, the BTs might have to cut burners in or out for both the main furnace and the superheater; some designs only required one or the other set of burners to be cut in or out, the other set had a range of adjustments for the fuel oil flow and air flow (called the “turn-down” range) that could accommodate the normal changes in steam flow rate.

One of the tricks to controlling the water flow to the boilers is that the water level in the steam drum will change immediately in reaction to the change in steam pressure in the drum and compensating for that change is exactly the opposite of what the final adjustment needs to be. That is, when the throttles are opened, the drum pressure decreases and the water level in the drum rises. The feedwater flow has to be reduced to keep the water level from rising too high (bad things will occur if that happens). After that, when the water level begins to drop, the feedwater valves need to be opened to admit the increased flow of feedwater that the higher steam demand requires. The opposite is true when the throttles are closed.

Now, all of this can be nicely “tempered” by an experienced and considerate Officer of the Deck (OOD) or a Commanding Officer who puts an appropriate note in his Standing Orders. A good OOD or conning officer will advise the Engineering Watch of expected speed changes or a forthcoming evolution that will require frequent speed changes. The engineers can make preparations for that.

As for starting up a steam plant…that is a fairly straightforward evolution, but can be dependent on a lot of outside influences and variables. Prior to and during WWII most large ships would never be “cold iron” in port. Being in the engineering department in those days meant frequent weekend duty, but at least you didn’t have to stand Deck Watches. The reason the NEVADA was able to get underway during the attack on Pearl Harbor, is because the Engineering Watch was preparing to change over the inport steaming boiler and had two boilers available to answer maneuvering bells within minutes.

Here’s a somewhat condensed and simplified explanation. If you were “cold iron”, the plant startup would begin several hours before the ship was scheduled to get underway. Small ships (with small boilers) could do it in two or three hours, big ships would need six to eight hours. Preparation could require activities a day or so earlier, depending on the circumstances and condition of the plant; including such things as whether or not sufficient shore steam and water are available or if the ship’s feedwater tanks and de-aerating feed tanks are filled or not…water is the key.

With those older boilers, when everything was ready the actual light-off was fairly simple, but almost comical. You opened a burner assembly and put in a couple of oil-soaked rags and scrap pieces of wood and set a match to it; then closed the burner, opened the air register and cut-in the fuel oil…whooosh! “Fires lit in (number) boiler!” Memory lapse here! That really applied to boilers prior to the mid-1920's and early 30's; mostly ships converted from coal to oil...almost all marine boilers since the late 20's were equipped with light-off ports in one or more of the burner assembly front plates. We actually had to do it that way once during Casualty Control Drills in Tarawa...talk about a "Keystone Cops" evolution! In more modern boilers, you have the pleasure of being able to light off by inserting a torch through a special aperture in the burner air register front plate. I've had the excitement of getting a "blow-back" in the face during that evolution...lost every hair on my head...young enough then for it all to grow back though!

As the heat in the furnace built up and it began to produce steam, the auxiliary steam stops would be opened to supply the forced draft blowers and feed pumps. Once those were rolling and supplying more air and water to the boiler, the steam pressure would build rapidly and then you could open the main steam stops and begin rolling the generators. Once the generators were supplying correct voltage, you could shift the electrical load from shore power to ship’s power and shift any motor-driven pumps in the plant to steam driven pumps. After that, it was a short time until full steam pressure was available to answer all bells.

Hope this helps…