Professional help needed

[torpedochief]

I don't mean to make mountains out of molehills or be dramatic, however, doing research sometimes leads even us not so bright people into questions.

I Need some help. Any welders, marine engineers, or shipwrights I need your opinion.

Suppose we have a ship 15 years old. Designed for one load line, however, it was decided to increase the load line with no internal work.

During inspection, it was noticed the hull plates and the keel welds were separating, and the keel was hogged.

Repairs were to use steel plates and wedges welded between the keel and the plates.

Would this repair be sufficient for continued loading beyond the designed load line?

[CDR_Ret]

Hi Chief.

 

Don't suppose you have any photos of this situation?

 

Changing the load line of a ship isn't a trivial thing. Either the ship had reserve cargo capacity built in or someone is playing with the stability tables. It would seem that seaworthiness certifications and insurance companies would have something to say about such an act.

 

From my limited familiarity with marine physics, I would think that the main adverse effects to raising the load line would be reducing reserve buoyancy and some effect on the righting moment (the actual effect on stability might either reduce it or increase it, depending on a number of factors).

 

As for the weld issues, I'm having a hard time visualizing the problem. Are there gaps (broken welds) at regular intervals along the keel, that would indicate some relationship to deep frame locations? Does this condition basically flood the keel structure with seawater?

 

Overall, welding plates between the buckles seems to be a band-aid approach to the problem. There is obviously some serious structural issues at work.

 

Terry

[Bob Cleek]

43 minutes ago, CDR_Ret said:

It would seem that seaworthiness certifications and insurance companies would have something to say about such an act.

 

You betcha!

 

"Raising the load line," is simply "overloading the ship" and painting a new load line that hides the fact. There are no free lunches at sea. Overloading a ship places excess stress on the entire hull structure. Something's always got to give.

:

[Jim Rogers]

I read the title “Professional Help Needed” and saw you were also a Chief Torpedoman so I said to self “Well at least he is asking”

[Roger Pellett]

Chief,

 

There are  number of issues to consider-

 

First there are loadline rules established by international agreement.  These rules assign a freeboard to a vessel based on its design, with the ship presumably in good condition.  The Plimsoll mark painted on the side of the hull defines the vessel’s minimum freeboard under different situations:  Winter North Atlantic, Summer, Fresh Water, etc.  Unless the basic design of the ship were to be changed there would be no reason to change the freeboard.  Freeboard could be changed by making what might seem to be minor changes.  For example making a deck previously open to the weather watertight by permanently closing openings might allow the load line to be changed but this would depend entirely on the vessel’s design vs the load line rules.

 

Second, most ships are insured.  To obtain insurance the owner must have the vessel surveyed by a “classification society.”  In the USA the society is ABS, The American Bureau of Shipping.  They will review the vessel’s design and its construction, and will publish a rating.  A less than A-1 rating will cause insurance underwriters to set high rates or possibly refuse to insure the vessel and its cargo.  Each classification society publishes its own rules that would cover the repairs needed to correct the condition you describe to allow it to pass a survey.

 

Third the US Coast Guard is charged with ensuring that vessels sailing in US waters are seaworthy.  They have the authority to enforce rules published by others such as the freeboard organizations plus those that they publish plus those issued by various other governmental agencies.

 

As they say, “it’s complicated,” but the short answer is I don’t see how repairing a vessel can allow its freeboard to be reduced.

 

Roger

Edited April 17, 2019 by Roger Pellett