Zero Speed Operating Limitation

[dalebirrell]

Hi,

I am looking to create an operability model for an offshore wind turbine access vessel and become stuck in looking for rules/regs regarding operational limitations at zero speed. (i.e. when the vessel is alongside a turbine performing personnel transfer.)

DNV are the first to provide rule specifically for wind turbine access vessels which were released in jan 2011 but there is nothing to do with personnel transfer or operational limitations. Infact much of the rules refers to HSC Code 2000 but again there is little on operational limits and nothing considering zero speed.

Has anyone know of any rules/regs that could be similar to what I'm looking for? I've spent the last 2 days trawling through DNV, MCA, SOLAS and HSC Code rules and I'm at the verge of giving up on this project entirely.

Cheers

Dale Birrell

[Ad Hoc]

Dale

DNV is Class. As such Class only have rules governing the safety of the vessel at sea. Is the boat strong enough...is the engine built to correct standards etc. As such Class do ntr provide guidelines to operation of personnel. That is a flag issue, ie MCA etc

There are currently nor formal guidelines for this function. The usual way is by HAZOPS and since each operator has their own method of performing this task, it is dealt with on a case by case basis.

[dalebirrell]

Thanks for the snappy reply, do you think curent access vessel builders/designers would divulge any of their HAZOPS or HAZZID info, or is this something people tend to treat as sensitive information?

Thanks

Dale

[gonzo]

Colregs. They state that you must maintain enough speed for steerage. If you have multiple thrusters or Zpods, that may be zero.

[jehardiman]

As Ad Hoc pointed out, the rules/regs only address the strength and/or physical requirements of the ship system; i.e. ABS man-rated lift stystems will be designed with a given minimum FoS or OSHA regulatons will specificy a minimum rail height. It is important to remember that the class society rules, unlike the SOLAS agreements, are not to protect life per se, but to provide confidence to investors, shipping agents, and insurance parties that there is no undue risk associated with the vessel.

What you are looking to do is to write a specific Concept of Operations (CONOPS) for the vessel/system. This will lead you to a set of Top Level Requirements (TLRs) specific to the overall operations. In making the TLRs certain things will fall out; like a platform needs to be re-supplied weekly, and in the winter the Sea State is 5+ 80% of the time at the site so either you will need to transfer in SS 5 or you will need to extend re-supply period or be able to wait out the weather. Once you have the TLRs you can apportion functions to specific system, creating System Level Specs (SLS). SLSs will also have trade-offs between them such as using a SWATH hull form to minimize motion or put fast over-hauling constant tension winches on the platform (be very careful here when working with different contractors being responsible for different aspects of the systems...many fences and many flying pigs). Once you have all the SLSs you can then write the Ship Spec which the rules apply to; i.e. strength, motions, FoS, etc. From the TLR's and the Ship Specs you can then do a Hazard Analysis which will lead to a Safety Plan. Once through the classification analysis and with Safety Plan in hand you can get insurance and flag approval.

Check the UK Department for Transportation, Maritime and Coast Guard Agency for Safety Plan Requirements.

[Ad Hoc]

Originally Posted by jehardiman

What you are looking to do is to write a specific Concept of Operations (CONOPS) for the vessel/system.

Ah, there you go..learnt something new today

In the UK we call this HAZOPS; Hazard & Operability studies.

[Ad Hoc]

Originally Posted by dalebirrell

Thanks for the snappy reply, do you think curent access vessel builders/designers would divulge any of their HAZOPS or HAZZID info, or is this something people tend to treat as sensitive information?

Thanks

Dale

Dale, you can ask. But each HAZOPS is type specific and may not yield everything you are looking for, there is no one stop shop!

We have done just such studies for just such operations. Is there anything in particular you wish to know? JEH gave a good outline above.

[jehardiman]

Originally Posted by Ad Hoc

Ah, there you go..learnt something new today

In the UK we call this HAZOPS; Hazard & Operability studies.

Yes, now that I look it up, it seems that IMO has gotten into the hazard analysis business also. Hazard and Operability Study (HAZOP), Process Hazard Analysis (PHA), Failure Mode and Effects Analysis (FMEA), are all listed in the sections about alternative SOLAS compliance.

[jehardiman]

Oh I also just remembered:

A vessel can only have 4 states...Moored/anchored, underway (possibly with restrictions on navigation), not under command, and aground/stranded. In this case, PersTrans, is a navigation restriction and the COREGS acknowledge this in 3g(iii) so giving her privilege in Rule 18.

"Back deck" operations are generaly limited by ships motions, i.e. it is very had to accomplish work in +/- 0.5 G motions. This is a probablistic function of sea state so you will need to work the spectral RAO's based on the TLRs worked out for the site. It is important to keep in mind that the Master really has the last say if the operation occurs. As Admiral Nimitz once said "the Commander in Chief, Pacific Fleet wishes to emphasize that to insure safety at sea, the best that science can devise and that naval organization can provide must be regarded only as an aid, and never as a substitute for the good seamanship, self- reliance, and sense of ultimate responsibility which are the first requisites in a seaman and naval officer."

[yipster]

aground/stranded

these legged ships place the mills but is not exactly a service vessel isnt it

[yipster]

remember the ampelmann witch when i first saw it seemed far fedged
yet it had possitive reviews but dont know about those rules

[dalebirrell]

Ad Hoc,

It's a university project where we are planning analysing vessel RAO's with seat state data for specific farm sites. The idea being that a client could come with a proposed vessel design, or existing vessel and the we'd be able to tell him how efficient their vessel would be. Probabilities of being able to perform personnel transfer combined with probabilities of turbine breakdown in different months will give some degree of how efficient the vessel is, compairing this data to financial aspects can give an indication of whether or not the vessel is a worthy invesment.

We're trying to define some sort of criteria for maximum vessel motion before transfer is too dangerous (i.e. jumping onto a ladder), I know it'll be variable dependent upon which vessel but at the minute I've no idea how big or small heave and vertical accelerartions can be before jumping off the front of a boat is pretty dodgey. Personally I reckon i'd be up to the task in meters of heave but I'm not sure that'll satisfy health and safety!

[gonzo]

The problem is acceleration and not simply height. There are many studies in sports, space programs and the military relating to that.

[powerabout]

like the offshore industry, what happens when you go inside the 500m zone the insurance liability moves to the platform, hence they make the rules that you need to follow and have the vessel with a capability that they demand.
I notice in Asia operators are even asking for crew boats to have DP capability
The operator wil also have rules about max wave height and wind speed etc.
There is Dp 1 , 2 and 3 that basically ups the redundancy for these sort of vessels.