Thursday, February 28, 2008

Making Steam the Navy Way

A while back, a friend of mine asked me what happens if there is a loss of steam pressure in an operating naval boiler. Short answer: The generating tubes melt. The boiler could blow up.

Long answer: Take a look at the schematic of a 1200psi naval plant. look at the boiler on the upper left corner. See the circle in the boiler labelled "SD" and one labelled "WD" and the two curved lines between them? Those are the steam drum and the water drum. (Click on it to enlarge it)

Naval boilers do not have circulation pumps. There is a steam drum at the top, the water level is kept at the half-full mark. The water drum is at the bottom, it's also called the mud drum. The two drums are connected by the steam generating tubes and the downcomers. The generating tubes are in the firebox, the downcomers run between the boiler and the air casing. (There are also screenwall tubes, which protect the sides and rear wall of the boiler casing. Those tubes also generate steam, but not a significant amount.)

If you've ever closely watched a pot of water boil on a gas burner, you'll see there is a point where bubbles are coming off the bottom of the pot where the flames are hitting the underside of the pot. The cooler water goes down to where the flames aren't hitting the other side to replace the steam bubbles coming up, you are watching natural circulation. That's how a naval boiler keeps water circulating; slightly cooler water goes down the downcomers to the mud drum and then it replenishes the water in the generating tubes that has turned to steam.

Look again at the pot of water. When the little bubbles are coming off the bottom, that's called "nucleate boiling".

So let's start with a cold boiler and light fires. As the water heats, you get nucleate boiling off the sides of the tubes. The little bubbles go up the center of the tubes and rise to the steam drum. This is "bubble flow", the tubes are about 5% quality (5% steam) . As the water has more heat applied, the bubbles become larger and now you have slug flow. More heat and the center of the generating tubes is just steam with a ring of water around the inner wall of the tubes, which keeps the tubes cooled. This is annular flow and it's about 30% quality; you still have nucleate boiling going on and water is being replenished by natural circulation. The steam coming out of the generating tubes into the steam drum is heavily saturated with moisture.

This is as far as you can fire a boiler at normal pressures of 1,200psi, you will reach the "endpoint of combustion", you can't get any more fuel through the burner nozzles.

Now, say you lower the boiler's operating pressure below the operating set point. The water boils at lower levels of heat, so you can get more steam generated in the tubes. Then you can get to spray flow, where you still have nucleate boiling but the tubes are only just wetted on the inside and the steam is about 60% quality.

Lower the pressure a little more and you get to DNB or "departure from nucleate boiling", where there is no longer any water on the inside of the tubes. The steam is 100% quality or even slightly superheated, no moisture is carried over to the steam drum ("endpoint of carryover"). This is, to quote Rod Machado, A Bad Thing, for the generating tubes are designed to be cooled by the water inside of them. The tubes will start to melt.

If you can push it even hotter, you will generate so much steam that the downcomers will not be able to supply water to the water drum. This the endpoint of circulation and at this point, the damn thing may very well blow up. This is like having the water level in an old steam locomotive or traction engine drop below the crown sheet over the firebox.

So, to prevent that from happening, if the main steam pressure drops below 1080psi, the fireroom crew will call out a low pressure casualty and they will wrap up the boiler.

Monday, February 25, 2008

Beans, Bullets and Black Oil

Black Oil, also known as "Bunker C", was the fuel that powered the Navy from the days that the Navy converted its ships from coal-fired up through World War II. Then it was replaced with Navy Special Fuel Oil, which was a blend of Bunker C and somewhat lighter fuels.

Both Bunker C and NSFO were heavy fuels. They were hard to pump unless they were warm. So ships back in the day had steam lines running through their fuel tanks so the fuel could be warmed up prior to being transferred. The fuel was also hard to burn; the boilers had to have steam lines running to their burners, for the steam would be used to atomize the fuel in order for it to be burned. NSFO was not suitable for use by marine diesel engines; the Navy had to supply its new diesel LSTs with a different fuel, known as "Distillate Fuel, Marine" or DFM. DFM was also needed as the construction of gas turbine warships was on the horizon and NSFO was unsuitable for gas turbines.

In the 1960s, naval oilers had to be able to supply four types of fuel: Aviation gasoline for the A-1s, S-2s and E-1s, jet fuel (JP-5) for the rest of the airplanes and helicopters, NSFO and DFM. The S-2s were replaced by the S-3s and gasoline was also phased out, much to the relief of everyone who had to deal with it. The decision was made to phase out NSFO, and, if JP-5 jet fuel wasn't significantly more expensive, DFM probably would have also gone away. DFM didn't need to be heated, so the steam lines in the fuel oil tanks were capped off. It didn't require steam atomization, which saved on steam losses. DFM basically wasn't a heck of a lot different from the diesel fuel that came out of a truck station's pump. Gas turbine ships were more finicky about contaminants in the fuel; they had large fuel purifiers whereas the only purification done on steam ships was to make sure any water in the fuel tanks from ballasting operations had settled out and then had been stripped out.

The steam heating lines in the tanks, as I mentioned, were capped off. This had tragic consequences in 1983 aboard the USS Ranger, when a fire broke out in one of the engineering spaces. The fuel for the fire came from an old steam line in the fuel tanks that had corroded away from the inside. In essence, several fuel tanks were linked together by the rusted-out steam line, which fed fuel into the fire. Six sailors were killed in the fire and it became a priority to remove the steam lines during overhauls.

DFM is still in use.

In a future post, I will write about what it took to get a steam-powered warship ready to sail.

Saturday, February 23, 2008

What I am Doing On This Here Blog

I am blogging about military matters, other than the Chimperor's Wars. For that topic, you'll have to check out my other blog. I don't profess to being any great expert. I didn't go to any of the war colleges and I stopped reading the professional journals a long time ago.

What I am going to do is read the news and set down my thoughts. I might throw a few stories in now and then. I won't plan on being anywhere near as prolific as I am on my home blog. I may limit the snark, but not too much.

(If you link to me, drop a comment and I'll reciprocate.)

B-2 Crash

A B-2 has crashed in Guam.

21 of the aircraft were built
. At over a billion a copy, only a crack-smoker (or an Air Force general) would have ever thought that the Air Force would get to build the 132 that they originally wanted. Yet the B-52s are still flying and probably will be still in service for another 35 or 40 years. The pilots then may have had a great-great-grandfather who flew them in the 1950s.

If the Air Force is going to survive in any size, they have to get over their addiction to platinum-plated toys.

UPDATE: Jeff Huber thinks that the flyaway price of a B-2 is $2 billion/copy. So the choice is a single bomber or a single submarine. It's been close to 40 years since the Navy last lost a sub.

Friday, February 22, 2008

USS Virginia vs. F-22

In an article in today's New London Day, the Chief of Naval Operations, Admiral Gary Roughead, called on Electric Boat and Newport News shipbuilding to reduce the cost of Virginia class submarines from $2.5 billion to $2 billion, and that is in 2005 dollars.

Think about that number for a minute. At $2.5 billion, a Virginia class nuclear attack submarine caries 38 21" diameter weapons, be they torpedoes or missiles. It has 4 torpedo tubes and 12 vertical launching tubes. It has a nuclear reactor, sensors, and it carries a crew of 113, which means it has the berthing for them and the food and stores to operate over great distances.

And for all of that, at $2.5 billion a copy, you could instead buy 10 F-22s (or 14.5 F-35s). If the costs get shaved, as the CNO wants, then that's 8 F-22s (or 10 F-35s). The idea that a nuclear attack submarine costs as much as a handful of fighters seems a little whacked to me.

F-22 Musings

Two F-15s collided and crashed over the Gulf of Mexico on Wednesday. One pilot was killed.

The F-22 has a 20mm gun
, as does the F-15. That means that the F-22 pilots are going to train in air combat maneuvering and they are going to have to practice it. That is the "up close and personal" form of air combat, the "get behind the other guy and shoot him" type, not the "fire a missile at a blip on the scope" type. They will be mixing it up in training. And shit will happen, like it did to those two F-15s.

Only when it happens to F-22s, a collision between two of them will result in half-a-billion dollars worth of airplanes falling out of the sky.

Thursday, February 21, 2008

Lookit All the Pretty Barges; Part II

As I understood the scenarios, assuming that the Red Army invaded West Germany, the very first thing that probably would have happened would have been a coordinated missile strike against either the NATO navies or anything else floating around. The Soviet Navy had a lot of long-range missile carriers, including Echo-class submarines and the Bear and Backfire bombers. They fired some missiles that were, at least on paper, to be feared. The AS-4 "Kitchen" was one that scared the shit out of me; it cruised at over 75,000' (probably a lot higher) at SR-71 speeds before it would go into a very steep terminal dive with a 2,200lb HE warhead or a nuke.

As an aside, if you look at the size of the warheads on Soviet/Russian anti-ship missiles and compare them to the size of warheads of Western anti-ship missiles, the only reasonable conclusion was that the Soviet designers were trying to kill much larger ships.

The weakness they all shared was targeting information. After the first exchange of fire, any hostiles within contact range would have been killed. One of the reasons the US was interested in developing anti-satellite weapons was to shoot down the Soviet RORSATs. I suspect that the main reason the Phoenix missile was developed for the F-14s was to keep the Bear reconnaissance aircraft far away from the carrier groups, so they could not obtain targeting information to pass along. But that would be a problem only until the Bears had to land; for after that, they would have had to get past the land-based fighters flying out of Iceland and Scotland.

The upshot of it was that the first few hours and days of the war would have been extremely bloody at sea. Most folks who were on the ships and who looked at this probably concluded that if they were alive 72 hours after the war began, they would have been very lucky.

After that initial blood-letting at sea, the survivors would have one real job: Make sure the resupply convoys made it to French ports to keep the Red Army from conquering the rest of Europe.

Lookit All of the Pretty Barges

This is about the US Navy's surface fleet. I should offer a disclaimer, which is that I was a surface warfare officer in the Navy for awhile.

Back in the day, the mission was pretty clear. Besides all of the "show the flag, project power" peacetime stuff, the real mission of the surface Navy was to get the convoys across the Atlantic in the event that the Red Army rolled across the border into West Germany.

Life was kind of different back in the Cold War, when the planners were contemplating casualties that were rather horrendous. First, there was the garrison of British, French and American soldiers in Berlin, whose mission statement upon the beginning of a conventional war with the Warsaw Pact boiled down to two words: Die bravely. The job of the Americans in Europe was to keep the Russians from rolling all the way to the English Channel before reinforcements arrived.

It was the job of the Navy to get the heavy reinforcements there, in the face of the opposition of the Soviet Naval Aviation and the Soviet Navy. By "Soviet Navy," I mean the submarines. They had a lot of surface ships, but most people seemed to think they'd have been converted into artificial reefs pretty damn fast.

(More later)

Origin of the Name

Navy Warships have a secondary mission, or at least they used to, back in the Cold War. The mission was called "Naval Gunfire Support", or "NGFS." That is using the guns on a warship to act as artillery support for the Marines ashore. The Navy used to train at doing NGFS at the gunnery range at Vieques, until the Navy was forced to close the range. The only USN ships in the Atlantic Fleet that never made a visit to Vieques were those without guns or airplanes.

The Navy also did procedures training, where data lines would be hooked up to a van alongside the pier. The crews in the Combat Information Center and in Gun Plot would then run drills, receiving radio and radar inputs from the instructors running the simulation in the van. Other than not rolling as the ship turned and not shuddering as the guns fired, the simulations were pretty much what one would see when shooting for real.

Except, that is, for the targets that were called in. Besides the standard ones of "trucks/troops/tanks in open", one of the goofy targets used was "babies in open." It was just sick humor, and the shells called for, unsurprisingly, would be Willy Peter, also known as White Phosphorous. Which is nasty stuff (look it up).

That's the reason for the name of this blog.

The majority of the posts will be a look back to the Cold War Navy.

Yeah, I Know. I Did it Again

I started another blog with no idea what to do with it, other than the name occurred to me.