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DP11 Limitation (Dynamic Positioning system in AHTS Vessel)
24 December 2016
Dear All Experts,, could you please inform is there any swell/wave limitation for using DP 1
system in AHTS vessel? Currently we are having bad weather in our area and the swell is reaching 2.7 to 3.0 meter. Our AHTS Vessel are equipped with DP 1 system however they reject to use the DP 1 system because the swell is already to high (2.7-3.0 meter).
Thank You.

5 answer(s)
Companyrep
Drilling Specialist/Well Engineer/Training Consultant
SPREADAssociates
Total Posts: 339
Join Date: 10/01/05
Safe DP operations document 2006 as attached.

The important factors to this question as stated in other respondents comments, are the knowledge and experience of the personnel managing and controlling the evident conditions presented. Their confidence in the assurance and quality of their equipment (whether it is DP1, 2 or 3) and as stated a fully weighted, risked, and ranked, best practise judgmental assessment of the 'combined conditions' presented for job at hand.

Where neither Anchor handling nor supply can be risked, judged nor decided on one factor alone e.g. sea state. One has to assess, evaluate and determine combined conditions is such situations on a job by job basis.

Documents uploaded by user:
Safe DP operating guidelines.pdf
david.vavasseur
HPHT Drilling Engineering Team Lead
Maersk Oil
Total Posts: 24
Join Date: 22/07/12
Benny

Here in the north sea, we do not work boats when sea is beyond 3m significant wave height. This whatever the doc system (as far as I know most supply boats are still dp1) This is an area Where crews both on rig and boats are used to rough weather. Hence I am not choked by your boat crew reaction!


BradleyPate
Deepwater Drilling Engineering / Su
Afrik Santa Cruz Energy
Total Posts: 5
Join Date: 10/04/09
Christmas Greetings Benny & SPREAD TEAM

My response will be of little immediate value to you . . .  but just i wanted to provide 'some observational' feedback from far far away here in Texas.  

Thus, I will not make an outright judgement as to your specific ongoing situation, as there are a lot of facts in the matrix that you are going thru to make a proper action (weighing Risk / Outcome)

Over my 33 years of managing Marine Vessels in all types of sea state, conditions. . . the majority issue always comes down to  the expertise and professional capability of your Captain and Crew.
I was rarely concerned about the vessel and equipment and much more concerned about the Personnel to understand and control the vessel no matter what the sea state may be.
These things you know.. . .  
DP equipment means little if the Captain / Crew  and the Vessels Technical limits are of insufficient capability. 

If you are satisfied with your Captain/ Crew, then a review of 'optional operational management' (what are viable options to the efforts to move your operation forward effectively).

However, If you are not satisfied with your Captain/ Crew's ability, you should not be held hostage for the duration of your contracted services and thus an appropriate professional review may be in order for replacement of crew or company as justified . .

Best Regards
Respectfully
C. Bradley Pate
(former ExxonMobil) 
 
JDDrouin
QA/QC Subsea Wellhead Specialist
SPREADAssociates
Total Posts: 83
Join Date: 06/05/09
Benny,

In addition to Dave's response, you should verify the exact definition / technical details of the service provider's DP1 system.

In other words, not all DP1 systems are equal.  By extension, not all DP0, -2, or -3 systems equal to other -0, -2, or -3 systems.

Also, you should be aware that the "Z" coordinate (think of that as "altitude" or "height") is always the most problematic to accurately determine.

Best of luck.
admin
Managing Director (rp-squared.com)
Relentless Pursuit Of Perfection Ltd.
Total Posts: 376
Join Date: 10/01/05
Hi Benny

I am sure that all vessels will have an operating limit, which is often covered in the vessel-specific or corporate Marine Operations Manual.  This may be driven by things such as vessel size also.

I do know that DP1 vessels are quite limited and the swells that you mention are quite high. Other factors that will come into consideration are, vessel size, sea and wind direction and the type of activity that you are undertaking.

Sometimes it is possible to review the situation by undertaking a rigorous, documented Risk Assessment (with input from experts) and to operate under permit to work.

If it's purely anchor handling, one of the primary considerations is the safety of the deck crew working with an open-stern vessel.  If it's  cargo lifts there may be crane limitations (Rig Owner to advise) on main-block and fast-line lifts. If it's bunkering operations, there may be limitations based on the type of hose and flotation devices you are using.

The boat owner should be able to advise, by providing their limits.

However, as I know from my time as a DS in the North Sea, the final decision is always made by the vessel master who, like an OIM, is overal responsible for the safety of the vessel and all aboard.

Best wishes

Dave
Posted by

Benny H

Drilling Engineer

Pertamina

Total Posts: 3
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