BLOG 75 - "Marine Musings 20" - 'Nosac Tai Shan' - Sea Trials - A 'Starting' Challenge

15th September was "Engineer's Day" -----------

A revered colleague and friend, Capt Rajkumar sent this in.

BEYOND MIDNIGHT

A train was racing to its destination with a howl in the silence of the night. A man was sleeping with his head on the side window of the train. Suddenly he woke up from his sleep. He jumped from his seat and pulled the chain hanging just over his head. The chain was nothing but the danger chain. The train moved for some more distance and stopped suddenly.

The employees and other passengers in the train rushed to the compartment to know what had happened. Someone even suspected that the man did it in his sleeping mood. So they were angry towards this man. All surrounded the man and asked the reason behind chain pulling.

“There is a crack in the rail after some more meters from here!!! If train goes over it mishaps may occur.” The man said quietly.

“What nonsense are you saying. In this dark night how did you see the crack which is far in front ? Are you mocking us ?” That was the response of the people. “No. I have no need to mock you all and stop the train to disturb all. You just check it and then talk to me ” The man replied very gently.

The railway persons got down to rail. With the help of a torch they checked the railway track. To their surprise they saw a big crack in the rail a few meters away from the stopped train! If train passed over the crack definitely some mishap was obvious in that dark village night.

All persons again gathered around the man who predicted it correctly. He told that he heard the sound from the track while sleeping and it changed at some place . The vibrating sound changed too heavily that the man recognized that it was due to the crack in the railway line. Do you know who was that man who saved many lives from death? It was none other than the best engineer that India ever gave birth to, Mokshagundam Visvesvaraya or M.Visvesvaraya.

Engineer's Day in India is celebrated every year on September 15 to commemorate the birth anniversary of India's first Civil Engineer, Mokshagundam Visvesvaraya, India's greatest Engineer

There is something special about engineers and it is that they can create anything that we can imagine.

Wishing ALL ENGINEERS. Happy Engineers Day!

Marine Musings - 20 Nosac Tai Shan

Chapter 5 - SEA TRIALS

For any new building (ship), probably the most important test is the Sea Trial. Most of it is about the theoretical calculations that have gone into the Specifications, all of which will need to be proved by the Shipyard during an actual demonstration, which is known as the Sea Trials. Since these specifications form part of the Contractual Obligation between the Ship Owner and the Shipyard, the latter are always under tension to prove, practically, all the specified parameters.

Examples

1. Speed : The Ship Owner would have specified that the vessel should be capable of doing X number of knots. This is to be proved during Sea Trials. This is one of the ‘most important’ parameters.

2. Consumption : Fuel Oil consumption of the Main Engine to be maximum of so many grams per kw hour. Normally, this would be well within specifications due to Test Bed Trials.

3. Vibration measurements at various points or specified areas to be within specified limits.

4. First Start Arrangements: Vessel should be capable of being restarted from a cold / dead state, where no power or compressed air is available on board. There are several methods, all of which need to be Class approved.

The first priority is to start the Emergency Generator by one of several methods:

1. Hand operated compressor - fills primary air bottle - which air can start the Emergency Generator - which supplies power to a couple of cooling pumps and one Main Air Compressor - this Compressor is used to ‘press up’ one of the Main Air Receivers - then a Main Generator can be started ……. Most use this method.

2. Hand hydraulic pump to increase pressure in a hydraulic cylinder - which pressure, when released, rotates a small turbine and pushes out a rotating toothed gear - this engages a toothed wheel rim on the flywheel of the Emergency Generator - the Generator starts - power is supplied to specific pumps and one Main Air Compressor. Method is a little off beat, but I have seen this employed on 2 ships. The mechanical action is similar to what happens when a car is started.

3. An explosive device is inserted into a small pocket of one of the cylinders of the Emergency Generator which, on being lit, explodes and the expanding gases starts the engine. Bizarre, but true.

4. A horizontal duplex, 2 man operated hand compressor, to pump up a primary air bottle, large enough to supply air to one Main Generator. (Etaiwi 2). Takes time and a lot of energy.

I am unable to recall what the method was on the ‘Nosac Taishan’.

5. Other Class Required Tests which included

1. Minimum number of starts and reversals of the Main Engine, initially with full Air Bottles, without the Main Air Compressors running. This test, I found, kept the Yard staff under a lot of tension. They all breathed a sigh of relief when successfully competed. I will elaborate later.

2. Crash Stop and Astern Test

3. Turning Circle Tests

4. Black out and Auto Sequential Start up of main machinery - the complete sequence is to be shown working to the Class Surveyor. In the previous months, I had had a clash with the Yard on the actual sequence. Class had to be involved for the approval, so we were going around in circles for almost 3 months, till they got it right.

5. Other performance parameters such as turbocharger speeds, air pressures, efficiency of Main Engine and Generators, Coolers' Efficiency, Purifiers' Efficiency, various trips on the Main Switch Board and much more.

6. Indicator cards, Power and Efficiency calculations

7. Basically proving that the whole plant is as per specifications.

There have been many cases where the Owner finds that specified parameters are not met in performance during Sea Trials, with Owners refusing to take possession.

So, for the Shipyard, the Sea Trials are fraught with tension. They have many ‘experts’, one for each facet of the operational performance.

Most of the trials had been completed. To prove the ‘minimum number of starts’ ClassNk’s rule was (H.2.4) “The total capacity of air receivers is to be sufficient to provide, without their being replenished, not less than 12 consecutive starts alternating between Ahead and Astern of each main engine of the reversible type”.

During this test, the controls were under ‘ECR Control’, which meant that the Main Engine was being started from the Engine Control Room.

I was told that the Shipyard man at the controls was one who was an expert and who was specifically brought on board for this test only.

I had been watching the starting of the Engine on Bridge Control, listening to the sequence of sounds and the pick up in rpm. Now it was being started from the Engine Control Room itself.

To pass the Classification requirement, 6 reversals were to be made, starting with air receivers full and Main Air Compressors shut off. There was tension in the air as, with each reversal and start, air receivers’ pressures kept going down. The 12 starts - or 6 reversals - were achieved and the pressure had come down to 12 bar from 30 bar. The engine would not start any more below this pressure.

Everyone from the Shipyard breathed a sigh of relief that the test was (barely) passed and crowded around to congratulate their ‘expert’, with a lot of bowing back and forth.

I should have kept my mouth shut. Instead I told their Senior Manager, who was next to me, that I can do better and extract more number of reversals from the engine, with the same initial pressures.

There was a sudden silence when the Senior Manager translated what I had said. After nearly 3 months, all of them were very friendly with me and we had mutual respect for each other. But my statement was a bit too much for them. It was a loss of face for them, hence I was challenged.

The Class NK Surveyor said that, as far as Class was concerned, the test was successful and he was going to sign off on it. He also had worked closely with me during those three months and had realised that, behind the mild exterior, there was steel. He also knew that I wouldn’t say things lightly. I saw him talking to the Senior Manager and I think he was telling him to call off the challenge. But the Japanese, around 25 in number (in the ECR), were adamant.

So the air receivers were again filled to 30 bar and I started manning the controls.

But, before starting, I did something that was strange to them - I kept the door between the Control Room and the Engine Room propped open.

Having stood outside the Engine Control Room during the numerous starts and stops of the previous few hours, I was instinctively aware of the sequence of sounds during starts, with the Main Engine on Bridge Control.

During the ‘Minimum Starts’ tests from the Engine Control Room, I had realised that their starting expert was using too much air, pausing too long at the ‘start’ position of the lever and completely relying on what the RPM Indicator was telling him, before moving the lever to fuel.

A few more ‘asides’ before I get to the crux of the ‘challenge’.

If the ship were to be moving in an ‘ahead’ direction, it will take less amount of air to start the engine in the ‘ahead’ direction and more amount of air to start the engine in the ‘astern’ direction.

And vice versa.

If the ship was completely stopped, it would take slightly more amount of air for reversing and starting the engine than starting the engine in the same direction.

The below image of the Starting Lever is similar in many respects to what we had on the ‘Nosac Taishan’, but not exactly the same.

Here, the lever is at the ‘Stop’ position and the lever cannot be moved, as the lock is in a slot. To move it up, one has to hold the lever handle and simultaneously press the ‘feathered’ lever (adjacent to the handle) inwards, which releases the lock on the lever movement. Further up the curved surface is another slot for another (temporary) lock, at which point air is supplied to reverse and / or start the engine. Beyond that is the curved, toothed, surface for fuel regulation.

Although this was a Sulzer RTA Main Engine, the Starting Unit in the Engine Control Room was similar in many ways to the Starting Unit on the B&W Main Engines I had worked on and was very familiar with.

I used to operate this unit as follows:

I would put my palm against the handle and my fingers around the feathered locking lever, gently pressing the latter inwards. The lock would release and lift from the slot. I would move the handle an inch or so on the curved surface and release my fingers from the feathered lock and, using the palm of my hand, gently keep pushing the handle circumferentially in an arc upwards till the lock engages at the next slot, which is the slot for air release to the Main Engine for reversing / starting which would initiate the mechanical links or microswitches below the Starting Unit. One can, then, hear the engine start, see the RPM tachometer move, the turbochargers’ RPM Indicator starting to move up. That is when I would again put my fingers against the feathered lever, unlock the handle and move it towards giving fuel to the engine, by which movement the starting air to the engine is cut off.

A combination of listening to the sound of venting of pneumatic valves, various other engine sounds that indicate that the shaft is rotating and the indication on the tachometers would mean that enough revolutions are now available for combustion, so I would move the handle to ‘fuel’ position and then move it up or down - along the curved surface - to obtain the required rpm. It is more of an instinctive ‘feel’ of the sequence of events and is pretty difficult to explain. The whole sequence takes less than 5 seconds.

Fig 1 - Starting Unit in Engine Control Room

What the Shipyard ‘expert’ was doing wrong was - he was holding on to the handle and the feathered locking lever when he reached the ‘start’ slot and would hover over that spot. Because his hand was not absolutely still at the ‘start’ slot, the mechanical links below would be activated and deactivated a couple of times, causing air to be delivered, cut off and redelivered to the Engine, thereby using more air per start.

By the time I was able to give 12 starts - 6 reversals - the air pressure had fallen to 18 bar only. I kept going and was able to give a total of 24 starts - 12 reversals - with the engine failing to start with air pressure of 5.8 bar. As the air pressure keeps falling with each start and after the Air Receiver pressure goes below 14 bar, the trick to continue giving starts is to pause that small ‘tick’ longer at the ‘start’ position, before moving on to fuel.

Fig 2 - (Copied from Marine Engineering Knowledge) showing the Starting Arrangement

Fig 3 - (Copied from Marine Engineering Knowledge) showing sequence of events

On my completing the sequence of starts, there was silence from them for a minute and then they all started clapping. Their ‘expert’ spent the next few hours going through the whole process with me again and again. Of course, a Sun Tory Black came into view for the evening.

In later years, microswitches, solenoid valves, rpm sensors, electronic timers and servomotors eliminated the need for such ‘instincts’. A robot was born.

Fig 4 - Copied from Dieselship - shows the modern system in comparison to the old one in Fig 2 and 3.

There were some minor glitches, but all-in-all the two day Sea Trials were successful and we returned to Oppama shipyard.

====== Continued in Blog 76 =====