Anyone Interested in Ships

[MarkC]

On 08/05/2024 at 17:02, jjb1970 said:

I suspect they may be doing maintenance which needs the bow lifted up, perhaps on the bowthruster as even unladen the ship should be able to keep the bow immersed.

Been there, done that...

 

Best one was on a 78 metre length ship at Las Palmas. Bowthruster stripped its gears. We had a 4.5 metre trim to lift the bow thruster tunnel clear so that dismantling could take place...

 

Mark

[jjb1970]

I was on a (for the time) big containership which did it. We had to flood one of the after holds to get the bow thrusters out of the water. Bit of a pain but a lot less than dry docking.

[chipbury]

Bow thruster repairs are much easier on a jack up!  One of the internal hoses had come off so it went full pitch in one direction and stayed there.

Edited May 11 by chipbury
Typo

[MarkC]

3 hours ago, chipbury said:

Bow thruster repairs are much easier on a jack up!  One of the internal hoses had come off so it went full pitch in one direction and stayed there.

Not quite "Physician, heal thyself", but close!

 

Mark

[johnofwessex]

Heres a question that I have been mulling over for a while.

 

When you shut down a Marine (Or Stationary) Boiler you close the stop valve which is steam tight.

 

So as the boiler cools the steam will condense and the water in the boiler will contract.

 

So, does this create a vacuum on the boiler?

 

If not, why?

 

 

[Ozexpatriate]

7 hours ago, johnofwessex said:

So, does this create a vacuum on the boiler?

 

If not, why?

I would think there's still plenty of air in there. When under steam, pressure increases above atmospheric pressure. As the steam condenses the gas in the pressure vessel (now mostly air) returns to some pressure level - possibly atmospheric, perhaps above. I doubt it would go below atmospheric pressure, and certainly not a "total" vacuum.

[MarkC]

10 hours ago, johnofwessex said:

Heres a question that I have been mulling over for a while.

 

When you shut down a Marine (Or Stationary) Boiler you close the stop valve which is steam tight.

 

So as the boiler cools the steam will condense and the water in the boiler will contract.

 

So, does this create a vacuum on the boiler?

 

If not, why?

 

 

Yes it does - and should be avoided. There's a vent cock at the top which you open once the pressure is very low.

 

When firing up again, this cock remains open until you have a good flow of steam escaping - you don't want any free air in the boiler whilst steaming it - can lead to corrosion issues.

 

Mark

Edited May 12 by MarkC

[MarkC]

2 hours ago, Ozexpatriate said:

I would think there's still plenty of air in there. When under steam, pressure increases above atmospheric pressure. As the steam condenses the gas in the pressure vessel (now mostly air) returns to some pressure level - possibly atmospheric, perhaps above. I doubt it would go below atmospheric pressure, and certainly not a "total" vacuum.

Nope. Per my previous post, you don't want air inside the boiler whilst steaming it, and you certainly can "pull a vacuum" if you shut down a boiler & fail to open the vent. OK, not a full vacuum, but a few mm water gauge, depending on the size of the boiler.

 

Mark

Edited May 12 by MarkC

[jjb1970]

On high pressure systems a lot of effort is made to control oxygen level, things like deaerators and chemical dosing.

 

Usually a full shutdown to atmospheric pressure is unusual in marine and power plant boilers. Some heat and pressure is maintained to make it quicker to bring them back on line and and reduce thermal stress. 

 

The bit where you want a huge vacuum is the condenser. Condenser vacuum is critical to performance and efficiency in a ranking cycle steam plant. They have vacuum breaking valves.

[St Enodoc]

3 hours ago, jjb1970 said:

The bit where you want a huge vacuum is the condenser. Condenser vacuum is critical to performance and efficiency in a ranking cycle steam plant. They have vacuum breaking valves.

You are James Watt and I claim my five pounds.

[johnofwessex]

5 hours ago, jjb1970 said:

On high pressure systems a lot of effort is made to control oxygen level, things like deaerators and chemical dosing.

 

Usually a full shutdown to atmospheric pressure is unusual in marine and power plant boilers. Some heat and pressure is maintained to make it quicker to bring them back on line and and reduce thermal stress. 

 

The bit where you want a huge vacuum is the condenser. Condenser vacuum is critical to performance and efficiency in a ranking cycle steam plant. They have vacuum breaking valves.

 

I havnt worked on anything over 180 psi and the highest pressure boilers I have seen were 415psi

[chipbury]

I used to hate dosing the high pressure boilers (62bar/900psi) with chemicals.  It was done using a device called a 'bomb' - an apt name as it was a small pressure vessel with a funnel on the top that you poured in all the chemicals.  Once you'd closed the funnel valve (double checking to avoid a shower of boiling water/chemicals) feed water pressure at 78bar/1100psi is slowly let in.  As the pressure rises the 'bomb' groans and moans as it gets used to the pressure/temperature.  Once at full pressure you open valves to flow the dodgy chemicals into the appropriate boiler.

 

I see to recall one of the chemicals being hydrazine?

 

I'm glad I don't do that anymore!

[J. S. Bach]

13 hours ago, jjb1970 said:

 ...snip... The bit where you want a huge vacuum is the condenser. Condenser vacuum is critical to performance and efficiency in a ranking cycle steam plant. They have vacuum breaking valves.

Do you mean Rankine? I like to use the Rankine scale when giving the local temperature; as of this moment, it is only 528°R.

[jjb1970]

18 hours ago, J. S. Bach said:

Do you mean Rankine? I like to use the Rankine scale when giving the local temperature; as of this moment, it is only 528°R.

 

Sorry, spellcheck!

[jjb1970]

The only steam turbine ship I sailed on had two Foster Wheeler ESDiii boilers and a Stal Laval AP steam turbine of 32,450SHP. Pressure was 65Bar if I remember right (it's a long time ago....) which is about 940PSI. I had much more experience with steam plant after leaving the sea when I went into electricity generation, some of the plant I worked with there was 250Bar super critical, about 3600PSI. That's quite a lot of pressure. I liked steam plant, the engine room on the turbine container ship I sailed on was clean and quiet, utterly reliable and there was a tiny little lube oil purifier which was cleaned once a week. Splendid.

[jjb1970]

I don't want to be judgemental, but I can't help feeling these two ships this morning could do with a wash and a lick of paint.

 

[jjb1970]

A China Navigation boat, China Navigation is the shipping company of the Swire Group of Cathay Pacific and HK investments fame, one of the old colonial era HK companies.

 

[KeithMacdonald]

1 hour ago, jjb1970 said:

I don't want to be judgemental, but I can't help feeling these two ships this morning could do with a wash and a lick of paint.

 

Are they British ships?

[Mol_PMB]

On the topic of Swire Shipping, here's my photo of sister ship 'Coral Chief':

The service is still marketed as Swire in the Pacific islands.

[jjb1970]

When I  worked for P&O Containers they had two joint ventures with Swire. AJCL which operated the containerships Ariake and Arafura between Australia and Japan,  and CSCS which operated the Aotea between New Zealand and Japan.  At that time the liner services operated by Swire were marketed under that name and China Navigation was the name for their general cargo and bulk activities. 

 

In a sign of the times, China Navigation is now based in Singapore. Although that's probably less of a catch for Singapore than ONE. ONE is a merger of the container operations of the big three Japanese lines (NYK, K and MOL) and is a Singaporean registered company headquartered in the PSA building near Pasir Panjang. Interestingly their CEO is British. 

[jjb1970]

This is the steam turbine container ship I worked on. The mighty TS Flinders Bay. The first shot is from MV Encounter Bay, departing Jeddah as Flinders was arriving. The second is returning from a run ashore. Encounter Bay was originally a sister ship but re-engined with a Mitsui-B&W diesel. The bottom pic is Encounter Bay in Port Chalmers from the Scott monument. Taken over 30 years ago, these days they would be modest size feeder ships.

 

[Erichill16]

Another ship needing a lick of paint. 
I’ve never worked in a maritime environment but if I turned up for my first job and realised that was it I think I’d change my career! Colombo Sri Lanka 
Im hoping that the external condition of a ship is not an indication as to its seaworthiness.

 

[62613]

On 10/05/2024 at 17:12, jjb1970 said:

I was on a (for the time) big containership which did it. We had to flood one of the after holds to get the bow thrusters out of the water. Bit of a pain but a lot less than dry docking.

On a similar note, on my first trip, we were coming out of Sundsvall and a floating log hit the prop. So reduced speed to Stockholm, where she was trimmed by the bow enough to bring the top of the prop out of the water., It was turned using the turning gear, while the mate examined it from a lifeboat.

Three years later, had the water - lubricated stern gland start leaking, going up the Red Sea, on another ship which my company had just taken over. The ship was trimmed quite heavily by the bow so that it could be repacked.

Edited May 14 by 62613

[Mol_PMB]

Encounter Bay (and sister ships) were quite significant historically if I recall correctly. Whilst my library is mostly railway-themed, there is a corner of it containing books on containers and container ships and I do have an unhealthy fascination with the developments in the 1960s. 

[Mol_PMB]

For ships in need of a lick of paint, I can offer the ‘Aliki Force’ seen here approaching Liverpool: