24th August 2008, 13:50
As a mere decky may I ask this question. Why were some turbine ships with water tube boiler so dirty and sooty on the after deck, whilst others were not? My experience of NZSCo Pipiriki and the rest of the "P" class and of course the "Horrible Rata" Horarata all circa 1940s was that they were very sooty abaft the funnel. My later experience of this type of ship, BISNCo Nowshera and other "N"s circa 1955s, was that one did not notice this problem, although I believe BI's Kenya and Uganda made a lot of soot, they even gave Uganda a taller funnel to alleviate this problem.
24th August 2008, 16:58
The soot from boilers landing on the afterdeck during sootblowing operations had more to do with the positioning of the ship during sootblowing. We always informed the bridge watchkeeper prior to starting. Most of them would alter course, if prudent, to minimise depositing the soot on the ship.
As an afterthought, the older LNG tankers very rarely needed to "blow tubes" when burning the cargo boiloff, which was methane. It is a nice clean burning fuel which can be seen in your domestic gas cooker.
24th August 2008, 18:11
Some of Fyffes steam ships had Air Puff sootblowers on Babcock Header Type boilers. These used compressed air instead of steam and normally operated continuosly 24 hours/day by means of a sequencing device.
By this method soot discharges from the funnel were minimised.
This type of sootblowing would probably not suit all types of boiler.
On the general question of dirty, sooty afterdecks the velocity of exhaust from the funnel and the funnel design has a lot to do with where the deposits land. Over the years there have been many weird and wonderful funnel designs some more successful than others. For example the winged funnels on liner France, the fireman's helmet of Canadian Pacific's Empresses, the Thorneycroft smoke deflecting funnel design of P and O's Himalaya and Chusan, Shaw Savill's Gothic. Booth's Hubert and the various stove pipes on Ellerman ships for instance. Albeit on a Scotch Boilered ship Brocklebanks answer to boiler fumes affecting the aft crew accommodation was simply to heighten Maipura's funnel by some 11 feet or so.
25th August 2008, 05:23
I had a few discussions with the Mate on Watch when I had to blow tubes due to high stack temperatures. One was that I could not blow tubes since it was raining outside. I always called the bridge to inform them before blowing tubes since we reduced the speed and increased the boilers draft. It was up to Mate to turn the ship if he did not want the deck department to clean the soot off the deck. I do not remember asking permission just that we were going to blow tubes.
I was Chief on a T2 tanker that wandered into a missile testing range. (The deck department did not read the nav tex on the bridge. No R/O to blame). Walking back toward the house from sounding the fuel tanks (2) for the noon report I saw a missile go over the ship from my position on deck it looked very close followed by a jet then a helicopter that was hovering just behind the house down wind from the stack. At the same time the Second Engineer started to blow tubes the helicopter started to slow down and veer away from the ship and toward the water before the helicopter regained its control and speed. The helicopter left the area at a high rate of speed.