Cat Steering

[steve123]

Hi,
Reading a spec for new build quote and this baffles me..
This 35m Aluminium Cat has inboards with conventional rudders and the basic spec ask for the following;

A POWER ASSISTED ELECTRO-HYDRAULIC STEERING SYSTEM SHALL BE FITTED TO PORT SIDE. MAIN STEERING POWER IS SUPPLIED VIA A DEDICATED HYDRAULIC FITTED WITH 2 X 415V PUMPS. THE SYSTEM TO RUN ON 1 PUMP WITH THE SECOND AS BACK UP HOWEVER BOTH PUMPS MUST BE CAPABLE OF OPERATING CONCURRENTLY TO IMPROVE VESSEL MANOEUVRABILITY.
EMERGENCY STEERING IS TO BE PROVIDED BY AN INDEPENDENT 24V HYDRAULIC POWER PACK. A SWITCH LOCATED IN THE WHEELHOUSE SHALL SUPPLY FROM AC TO DC POWER PACKS.
THE SYSTEM SHALL INCLUDE REMOTE RUDDER REALIGNMENT.

Baffled as to how to acheive this request any idea's ????

 

[gonzo]

Are you looking to sub-contract the job?

 

[steve123]

No...just looking for advice.
Thought this site was about giving and gaining advice on a subject we all have in common.

 

[PAR]

What is baffling about the request? Seems they want a standard system, with a redundant backup, as well as an alternative emergency system? I wouldn't let the client dictate the parts (they should be appropriately sized and designed), though the system requirements are indicated. This requirement does show a serious desire, for multiple redundant steering properties. You may need to discuss this perception with the client, as most steering systems are pretty stable and reliable. I can understand a backup, but triple and quadruple redundancy seems the work of an inexperienced spec writer or a inexperienced owner, just trying to cover things that will never exist.

 

[steve123]

PAR,
It's the "BOTH PUMPS MUST BE CAPABLE OF OPERATING CONCURRENTLY TO IMPROVE VESSEL MANOEUVRABILITY" that baffles me.
Is he asking for rudders that move seperately ?

 

[PAR]

It sounds like he wants a duel pump setup, which is odd, but not undoable. They will not "improve vessel maneuverability", just simply add to the complication of the arrangement, so I question the need. This happens fairly frequently and the designer must "gain control" of the situation.

This is best approached by reminding the client that they came to you, because you where the expert in these maters and your advise should trump most of the unreasonable requests. I usually just pin down the client and ask why they feel the need for this arrangement. If it sounds reasonable, I might change my mind, but if not, I'll strongly object and list the reasons why I do. Most of the time, reasonable discussion resolves these types of issues.

 

[steve123]

PAR,
Thank you...your comments and advice are greatly appreciated.

 

[philSweet]

Steve, it is nearly impossible to help you based on little excerpts of documents. These things might make more sense if you could post a link to the entire spec. It is obvious that the spec writer is struggling to work in English. Is the spec in English, or are you translating it for us?

What the spec should describe is to what extent they want a dual, independent, redundant steering system, which might include separate rams, pipes, electrical power supply feeds and electric sources. Then they should describe any crossover requirements that permit normally independent parts of the system to be linked; and describe how the linking is to be accomplished and by whom. The user should provide a table of what requirements need to be met for each mode of operation.

Unless there are regulations that cover the specific system design and they are called out in the spec, there should be a design review process for something like this before the final RFP and award (two step procurement).

 

[steve123]

Phil,
This is the request on basic requirements and no its not translated.

 

[PAR]

This is the part both I and Steve are eluding to and you opportunity to get some control over the project. Talk to the client and/or spec writer and find out what they need (not what they want) and address the need, with the appropriate recommendations or revision to the spec.