Watchkeeping on an Irish Steamship
The following engineering notes were taken about what was checked by the engineering watch-keeper while going on watch in the engineroom of the steam turbine powered steamship S.S. Irish Poplar almost 50 years ago.
The incoming engineer was expected to check the machinery spaces before arriving at the maneuvering platform on the hour for the changeover. He could then take any problems up with the departing watch-keeper before accepting responsibility for the watch.
Indeed he could refuse to take over until a particular problem was ironed out. If he was late coming on watch so that there was not time for the pre-watch inspection then if anything was wrong he would not spot it.
Once he took over it became his problem so tough titty in that case.
Details of S.S. Irish Poplar
The Irish Poplar was a single screw steam turbine cargo liner. She was fitted with twin Babcock and Wilcox marine single pass watertube boilers fitted with interdeck superheaters and tubular air heaters. The fuel burned was called Bunker C with a viscosity of about 3,500 seconds Redwood No.1 at 100 degrees F.
This fuel was really the scrapings of the barrel! It had the following properties:
Specific Gravity at 60 deg. F: 0.94 to 0.99
Flashpoint : above 150 deg. F
Viscosity Redwood No. 1 at 100 deg. F: 1,000 to 3,000 seconds
Ash Content: 0.15% Max
Sulphur: 2 to 4 %
Calorific Value BTHU/lb: 18,300 to 18,800
Water & Sediment: 0.5%
Ignition Quality (Cetane Number) : 30 to 35
Conradson Carbon Residue: 10 to 12%
Electrical Power Generation
The electrical power was provided by three Ruston diesel 220 volt DC main generators and one 50kw harbour generator.
Boiler Details S.S. Irish Poplar
Evaporation rate: 32,000 lbs of water per hour
Design Steam Pressure: 505 psi
Safety Valve on steam drum set to blow at 495 psi
Safety Value on Superheater set to blow at 480 psi
Working Pressure at Superheater outlet: 450 psi
Final steam temperature 750 degrees F
Number of oil burners: 3 per boiler
Combustion air temperature at burner: 350 degrees F
Weight of water in boiler at working level: 4.75 tons
Design calorific value of fuel oil 18,500 BThU/lb
Ships daily consumption of 40 tons of fuel oil at normal sea speed and power output of 6,000 bhp
Design and Operation of the Boilers
The Babcock & Wilcox marine single pass boiler had a steam drum but no water drum but did have collector boxes at the bottom of the water-walls. The downtake headers which came down from the steam drum were connected to a mud drum at their lower ends.
Path of water through the rear water-walls is as follows:
From the steam drum down the rear downcomer tubes to the rear collectorbox, up through the uptake headers and back to the steamdrum through the return tubes.
Path of water through the side water-walls is as follows:
From the steam drum down the side downcomer tubes to the sidewall headers, through the sidewall tubes to the upper sidewall headers and back to the steamdrum through the uprisers from side waterwalls.
Path of main water circulation is as follows:
The path of the main circulation was down via the downtake headers through the main generating tubes, up through the uptake headers and returning to the drum via the return tubes.
Gas path in the boiler:
The air was taken from the top of the boiler room by two forced draught fans, one for each boiler. It is carried from the fans through ducts to the airheater side, it could then pass through the air heater tubes to pick up heat from the outgoing exhaust gasses.
If the airheater bypass damper was open the air would not pass through the airheater. After the airheater the combustion air passed down the back of the boiler and along the bottom, picking up heat all the while. It arrived at the front of the boiler from underneath.
The air then passed through the air registers on the burners to mix with the oil sprayed in order to burn it. The air temperature being about 380 deg F at this point. The fans delivered air at a pressure of 2.5 inches of water with all burners in. With only two burners per boiler less pressure was required and with one burner even less.
If one of the fans should suffer a failure there was a flap which allowed the remaining fan to feed air to both boilers. The fireman on watch looked after the burners and kept his own set of burner nozzles which he changed out and cleaned as necessary.
The steam was generated in the boilers and then passed through the main stop valves to join the main steam line at the auxiliary stop valves. It passed through the main steam line to the emergency stop valve. With the ship going ahead the steam passed through the ahead manoeuvring valve into the High Pressure (HP) Turbine.
After the steam gave up some heat and thus work in this turbine it passed to the Low Pressure (LP) Turbine. It passed through this turbine to give up nearly all the remainder of its energy and was condensed back into feed water in the sea-water cooled condenser located beneath the LP turbine.
There was a separate Astern Turbine which was controlled by the astern turbine manoeuvring valve when the ship was entering or leaving port. The LP and Reverse Turbines were on the same shaft and the overspeed trip mechanism also.
The maneuvering valves had geared shafts passing down to the maneuvering platform and were operated by large diameter, easily spun, handwheels. The most important items in addition to these valves were a large revolution meter (max revs were 106 at full sea speed) and the telegraph through which the bridge signaled the movements they required.
A very important piece of equipment was the wrong-way alarm. This alarm rang a loud bell if the engineer started the shaft turning the wrong way to that indicated by the telegraph. So if the Captain wanted half astern but the engineer went half ahead instead the alarm prevented catastrophe.
Emergency Stop Valve
The Poplar was fitted with a Cockburn-MacNicoll bulkhead emergency stop valve in the main steam line. This valve was arranged to stop the steam flow to the turbines for three reasons:
A fall in turbine lubricating oil pressure to below 8 psi.
A failure of the vacuum in the condenser, if it became lower than 9 inches of mercury the emergency stop tripped.
If the turbine shaft rpm increased to 15% above normal then the steam flow to the turbine was also interrupted.
An over-speed could be caused by the propeller shaft breaking or by blade damage on the propeller, damage to the gearbox or a shaft coupling or indeed the propeller coming out of the water in severe weather. The latter was unlikely as the engineer would have reduced power already to prevent racing and over-stressing of the machinery in heavy seas. Pressing on in heavy weather got you nowhere, just wasted fuel.
[One instance I came across was where all the bolts which secured the main gearwheel to the output shaft fractured in the main gearbox. The engine was started and the bridge given control. The Captain phoned down "no power" Chief Engineer "well the engine is running". On checking the main gearbox the Engineer of the Watch was astounded to find the input shaft rotating but the output shaft stopped! So a failure could occur which could cause a dangerous over-speed. It was on a variable pitch propeller system]
The emergency stop valve had a manual override so that power could be restored should the safety of the ship require.
It was very important that the watchkeeping engineer established a set routine and journey around the machinery spaces in his watchkeeping checks. The sight, feel and smell of each part of the engineroom had to become an ingrained part of his experience. If this was done correctly then any departure from the normal would automatically trigger his attention. It was uncanny how accurate and instant this could be.
Route around Engine Spaces on S.S. Irish Poplar
Descending into the engineroom the first machinery were the forced draught fans, the bearings and motors were checked for malfunction such as overheating, vibration etc. Next the gland vapour extraction fan. Then the generator cooling water header tank was checked to see there was a level of water in it.
Down to the next level to check the steam to steam generator and the water levels in the distilled water tanks. [The steam-steam generator provided the low pressure auxiliary steam while the main boilers were in service in port the auxiliary boiler provided this steam.] From them to the main switchboard to check the voltages and load on the generators – if the load was too high another generator might be needed for instance. It was important when two generators were connected to the board that the electrical load was evenly shared between them. If the main voltage was too high or low then this also needed to be corrected. The operating position of the various isolating breakers such as for the fore and aft deck machinery to establish where an electrical load might come from.
Down to the maneuvering platform level to check the bearings on the steam turbines and gearboxes. Each bearing had its own temperature which it found rest at for a particular power setting. If it was very different from that normal temperature, particularly higher, then this indicated a potential problem. Through the oil sight glasses on each bearing it was possible to check that the correct supply of lubricating oil at the correct temperature and pressure was reaching the bearing.
Next the temperature of the oil exiting the lube oil cooler was checked, it was normally about 100 deg F and it could be reduced by opening the cooling water outlet valve some more allowing more water to pass through the lube oil cooler.
The temperature and pressure of the lubricating oil were interconnected. If the temperature of the oil rises the thickness of the oil decreases and it becomes more free flowing. If the oil gets colder its density will rise and it will get thicker and harder to get flowing so its pressure will rise. Before any changes were made to the pumping rate it was necessary to check that the temperature had remained correct. There were no thermostats so the engineer manually controlled the various temperatures and pressures.
[This controlling process was continuous ( and tiring) throughout the four hours of the engineering watch. Such hands on experience over thousands of hours of manual control gave great insight into the operation of machinery. Modern automatic controls mask the operating characteristics of machinery so such experience and knowledge is not obtained.]
Down next to the lowest level in the engine room and on this level were the generators, all pumps and condensers. As a general rule two pumps were provided for each important service. One was in use and one on stand-by. The operating pump was changed over regularly to ensure that any fault would be detected and that the stand-by pump would work should a failure of the in use pump occur. This also equalised the wear.
Also located on the lowest level were the main and auxiliary boilers, the main and auxiliary feed and extraction pumps and the main sea water circulation pumps. All these pumps and motors had to be individually checked for correct operation and overheating.
One of the first items to check was the main thrust block, this had to take all the many tons thrust from the propeller and transmit it to the ships hull. Then down the shaft tunnel which carried the propeller shaft from the engine room located midships to the stern gland located at the aft peak tank at the back of the ship. The shaft tunnel ran under No. 5 and N0. 6 cargo holds. [So called because they "hold" cargo]. The plumber block bearings which carried the propeller shaft had to be checked and importantly the stern gland where the shaft entered the stern tube. This gland kept the sea from flowing into the engine room while allowing the stern shaft to emerge from the ships hull. This had to be greased once per watch and a good drop of sea water managed to leak in to fill the bilge well here and had to be pumped out regularly.
Traveling back from the stern tube through the shaft tunnel back into the engine room the next item to check was the current going through the lube oil pump motor and the lube oil pump itself. This pump took lube oil from the lube oil drain tank located below the main gearbox and thrust-block and pumped it through filters and up into the sea-water cooled lube oil cooler. Out through the main stop valve on the lube oil cooler the lubricating oil entered two ring mains through a stop valve for each. One ring main supplied oil for the turbine and gearbox bearings the second one supplied the gearbox sprayers which sprayed oil onto the main gears in the gearbox. The used lube oil drained back into the drain tank from the main gearbox and from the turbine bearings through a return pipe to the lube oil drain tank.
Next No. 3 Generator was checked. The generators were cooled by fresh water supplied from the generator header tank. The fresh water was pumped by a chain driven pump on the generator through the FW cooler then through the engine liners and cylinder heads and back to the pump suction. The temperature was controlled by adjusting the outlet sea-water valve on the cooler. Similarly the lube oil was pumped by an engine driven pump and cooled by sea-water in the lube oil cooler.
The cooling pump had to be inspected and the temperatures of the fresh water and lube oil into and out of the coolers were checked and adjusted if necessary. The pressures of the lube oil and fresh water cooling were checked on the engine gauge panel. On each cylinder head was located a cooling water outlet temperature gauge and an exhaust gas outlet temperature gauge. These were noted, for instance, if one of the exhaust temperatures was lower than normal while the rest were higher than normal then it lead one to suspect that that cylinder was not firing. The other side of the generator was checked and the end bearing. The DC generator was checked to see everything was normal. A quick check was made that all the push-rods were free to rotate and that none of the valve-gear holding down bolts had become slack. The lubricators for the rocker gear were topped up with oil and the main sump oil level was checked and oil put in if necessary.
These Ruston generators were fitted with Streamline filters which took a portion of lube oil and finely filtered it back into the sump on a bypass line. The oil flow, pressure and temperature through the Streamline filter was checked.
The next machinery to be checked priming and overheating , if they are running, were the bilge and ballast pumps. The the main sea water circulation pump which supplied water for cooling the main condenser. The motor current and temperature was checked. The greasers on these pumps was turned once each watch.
If frozen meat was being carried as part of the cargo then the main fridge circulating pump was checked, this supplied cooling water to the main fridge condensers.
The next pump to check was the main turbo-feed pump which supplied feed water to the main boilers. This pump was driven by a steam turbine. The bearings and glands were checked for overheating – the glands were water cooled. The feed pressure from the feed pump was checked. The bearings were checked for water in the lubricating oil and if necessary this was drained off and the oil replenished to the correct level.
The condensate extraction pump was checked next – this removed the condensed steam from the main condenser.
Onto the stoke-hold to check the main boilers. Normally the water level was on automatic control and the steam pressure was also on automatic being controlled by the “Baily Board” this was a pneumatic boiler pressure controller. Never the less the boiler water level, fuel oil pressure and boiler steam pressure was checked to ensure all was under control. The oil temperature at the burners on the boiler front was checked.
The same things were checked on the auxiliary boiler with its steam and electric feed water pumps. After the boilers pass onto the oil fuel unit checking the motor, gearbox, pump and pump gland. Then the domestic fridge sea water circulating pump, the general service pump (if it was running) and the auxiliary boiler blower.
If the evaporator was running it was checked for water level and shell pressure. This produced distilled water from sea water. The boilers had to be supplied with distilled water ordinary drinking water contained too much impurities to be used. The brine in the evaporator was checked with a salinometer and if it was getting too salty then the blow-down rate was increased. The distilled water from the evaporator was monitored by a salinity alarm.
Next if either No. 1 or No. 2 Generators were running they were checked out. Next were the domestic freshwater and sea water pumps. The freshwater pump supplied washing water for hot and cold taps. The sea water pump supplied water for flushing the toilets.
The final machinery to check was the generator sea water circulating pump and the main air compressor. A separate compressor for control air to the Bailey Board was also inspected.
Return then to the maneuvering platform to take over the watch.
After Watch Inspections
Several machinery areas outside the main engine rooms were visited by the engineer going off watch. The most important of these was the steering gear located at the stern of the vessel and one had to go along the after deck to reach this as the engine-room and accommodation were located midships. Another important one was the main fridge compressor room.