Engineering as it used to be Part 5. Continued

Now where was I………………………………..?

Oh yes I was in the boiler room. It has been pointed out in the comments that I haven’t given a good description of the properties of superheated steam. Most of us think of steam as the wispy stuff emanating from the spout of the kettle. Wrong. The wispy bit is actually water vapour condensing from steam. It’s the bit you can’t see close to the spout that is steam. 

Pure steam is a transparent gas. At standard temperature and pressure, pure steam (unmixed with air, but in equilibrium with liquid water) occupies about 1,600 times the volume of an equal mass of liquid water. In the atmosphere, the partial pressure of water is much lower than 1 atm, therefore gaseous water can exist at temperatures much lower than 100 °C (212 °F) (see water vapour and humidity).

In the above paragraph you’ll note that you can’t see real steam.

The one thing that may save your life is your hearing. Superheated steam at 600 psi (41 bar) and at a temperature of 800 deg F (426 deg C), makes a noise when it is issuing from a small hole or leaking gland. As I said in my last post don’t believe that noise is a drunken motorman whistling. Another valuable aid involves a piece of stick and a captured sea gull. *Now you really think I’m losing my marbles*  It’s really quite simple. Take one feather, attach it to the stick, hold stick in front of you, and when the feather magically disappears you know the rough vicinity of the steam leak.

Technical bit over for now.

Damn. Lost my train of thought.

Anyway the ship set sail for an exotic location. So I thought. I was wrong. Instead we sail across the Indian Ocean till we nearly hit Africa. Then we stopped. What was our purpose you ask? We were to maintain a blockade of the Rhodesian (Zimbabwe)  port of Beira to stop the import of fuel to the then, white Government of Ian Smith who had declared unilateral independence.

All in all we spent months of that coast. Sometimes at a crawl up the coast, sometimes drifting, even sometimes going in large circles just to break the monotony. Occasionally we would meet up with other ships in the task force and competitive sports would be played. deck Hockey being one of them. All to win that most coveted prize. “The Beira Bucket” (Mentioned in my last post).

The trophy for these sporting activities was a battered old metal bucket which at the end of each sporting contest was hung triumphantly from the winning ship’s yardarm. Now housed in the Portsmouth Naval Museum it remains as a reminder to crews and naval personnel of those Indian Ocean patrols in the years 1966 to 1971.

Decorated with ships names and crests, the bent and battered Beira Bucket is an unusual reminder of those years in the Mozambique Channel, and has been the subject of a number of fond reunions in the past years.

After months of patrol I would happily have kicked the sodding thing over the side.

*Technical stuff alert*. Look away now if you hate technology.

The one thing that I had plenty of time do though, was to actually find out how all this strange machinery worked. Right we’ve had the steam in all it’s forms bit so I’ll give you and idea what to do with it.  First it would meander it’s way through large, lagged pipes until it arrived at the throttles in the engine room. (Think huge tap) . The two throttles, one for forward and one for backwards (Even ships need a reverse gear. Especially if someone shouts out “Iceberg ahead”), were controlled by what looked like large steering wheels.

An actual picture of the control station of The Tidereach

The steam (superheated type) would then whiz over and into the turbine which is made up of steam injection nozzles and rows and rows of  rings with blades on them. Pretty much the same as a modern jet engine.

 

Of course this turbine would spin at several thousand RPM which is not a very practical speed to turn a ships propeller. A bit akin to permanent wheel spin. So just like a car you need a gearbox to achieve an output speed somewhere in the region of 100 RPM.

Whilst all this is going on all that steam wizzing out of the boilers causes the water levels to drop therefore it needs to be replenished. This is where those handy little items, condensers and feed pumps come in. The steam leaving the turbine is no longer superheated, as it has given up much of it’s energy to produce motion, and is now a saturated vapour. This vapour is cooled in the condenser by sea water(Plenty of that. The volume of the oceans and their seas is nearly 1.5 × 109 [sic] cubic kilometers"), and then pumped back into the boilers.

Now you know as much as me about steam engineering. After all I’m qualified as a Motor Engineer.

Are you bored yet?

Next time on Lost Fe’s adventures at sea will be Sembewang, voyage on a destroyer, a broken light bulb (You think I’m joking. Oh No), Japan, and  Ladies of the night, and Portland harbour.

Mind you I might just blog about the local elections or the Royal wedding. Your choice. You have been warned. Don’t blame me if it ends in tears.

Engineering as it used to be–part 5

I hope that you’re all sitting comfortably with your popcorn and drinks for my next instalment of how young and inexperienced I was in my younger days.

When I left you last I was on the motor ship, RFA Retainer. I spent approximately four months on that greyhound of the seas (If you can call 13kts, speed, then you’ll be under the impression that a tortoise can win the National,), and learnt all the essential engineering skills of drinking, drinking, and more drinking. Engineers were always warned that because of the high engine room temperatures, we should always ensure we kept up a high fluid intake. Of course we followed the leadership of the ship’s doctor, who not having anything to do, spent most of his time in the bar. He was our Role model in all things healthy.

I digress. This is not a post on drinking prowess. Oi. wake up at the back.

As I said, having settled in nicely, and really still hadn’t learnt the difference between a pump and a compressor, I received a shock that shocked me to the core.

I was going to be subjected to a “pier head jump”.

You can imagine what went through this callow youth’s mind. What had I done that was so terrible that I was going to have to undergo some sort of “walking the plank” punishment? Of course, if I’d bothered to read my terms and conditions, I would have realised that I was to serve on different types of ships in this phase of my cadetship. (Then again, how many teenagers read the bold print in their T & C’s, let alone the small print). A pier head jump just means a swift transfer.

God, I really am rambling now

I went whistling up the gangplank of RFA Tidereach……………………

Not. As before I struggled up an even steeper gangway than the Retainer due to the Tidereach being low in fuel and therefore high in the water. Did I mention the heat and humidity in Singapore? Oh I did. OK.

This time I found my cabin slightly easier than the last ship. It was only hours, not days. However for some strange reason the cabin I was sharing with another cadet was in the forward accommodation, a deck below the bridge (That’s the bit that has the steering wheel). Strange seeing as my workplace, the engine room, was at the other end of the ship and at the bottom.

Eventually I was let loose into the machinery spaces………

What a contrast. It was quiet compared with the last ship’s engine room. Why may you ask? Because this ship had a different means of propelling itself through the water. It was steam powered. No big main Diesel Engine thumping away and diesel generators clattering like a horde of metallic banshees. No, just the hiss of superheated steam (800 deg F), and the whirring of the ventilation fans.

The Engine room was split into  two spaces, the boiler room and the turbine  room. The Boiler room (I’m adding a little bit of detail here as requested by a commentor on my last post), was filled with three large main high pressure boilers used for propulsion. These were Babcock Wilcox sinuous header boilers producing the steam for propulsion and steam to the steam steam generators which converted energy from superheated steam into non superheated steam to supply essential steam services whilst underway.

The remaining boiler was a scotch boiler which was a very worrying thing I learnt later. Not because it was tartan clad or anything, they just had a habit of blowing up if not watched carefully. Why you ask?

There are two types of boilers in use. Water tube boilers where the water flows inside the tubes are pretty safe, insofar that if a tube was to split very little water in comparison would fall into the furnace.

Not so with a fire tube boiler such as the Scotch boiler. In this type of boiler the fire goes through the tubes which are surrounded with several tons of water.

It was not uncommon for the water level dangerously falling, causing those tons of water to end up in the red hot furnace with catastrophic results. Usually turning those who were unlucky enough to be in the same space, into deep boiled lobster look- a -likes.

One novel side effect is that the the force of the steam generated in the furnace had a habit of propelling the boiler through the ship’s side at Mach 1 or more. This was not popular with ship’s captains as the big hole caused, usually meant the ship would sink. Captains hate that, as it is universally expected that the captain should go down with their ship. (Bugger being the Captain, I would just clamber over the wimmin and cheeldren and get in the first available life boat. After all I’m young and my parents love me, etc, etc).

Am I being to technical or alarmist?

Then again those other boiling machines were not with out their downside. Steam at 800 deg F and at  a pressure of 600 Psi can hurt you slightly. It was a case that if you heard a whistling noise in front of you, you didn’t assume it was a stoker in a good mood. More likely that if you continued you were likely to have some part of you expertly amputated by the steam leak you were too stupid to avoid. (The wound was well cauterised, therefore the ship’s doctor might be able to save your life. If he wasn’t too pissed).

To be continued………………………………

I know that you’re just waiting for the smutty bit. You’ll just have to wait.