DP II Question

I recently had a conference call from a co-worker asking me a question about DP II operational parameters in the USA Gulf of Mexico OSV industry, he couldn’t seem to get an answer from the companies he called and ABS was not immediately forthcoming so I offered to put the question to gCaptain members as I don’t know either.
As we know DP II is supposed to mean the failure of any one system will not result in an immediate loss of control of the vessels position. Depending on sea state etc., one may be able to maintain position indefinitely but as a practical matter it means the failure of one system allows the vessels crew to safely cease operations, move themselves and their equipment out of harms way until such time as the system or equipment is repaired.
All vessels we have previously audited also have weather parameters. Example; if the seas are 12’ and the wind over 30 knots you must cease DP operations because you are approaching the limits of the systems capability and once exceeded you are no longer practically DP II. These limits are established by the company along with input from the class society, insurance company, manufacturer’s reps and whoever else they can come up with. There is usually a safety factor built in also.
The problem my co-worker has is that during a recent incident review he was told operational limits were at the discretion of the captain and there were no established limits by the company. While the captain’s discretion is always the overriding factor in all operations it seems that IF this is the case the company is setting up a trial by error DP II operational limit with as many parameters as there are masters AND all the responsibility then falls on the master.
So, the question is this: Are there established rules for the maximum safe weather operational limits of the DP II system for vessels in the OSV industry?


On drillships we have well specific operating criteria (WSOC) to provide the guidelines you are describing. These are generated for each well and account for a variety of weather conditions, environment, and hardware issues. They are reviewed by our shorebase management and client and give the master and DPO’s clear guidance on when to suspend operations or perform an emergency disconnect. IMCA provides guidelines that are pretty widely used in the industry. I’m at the house so I don’t have the books with me but you can check out their website for ordering info and basic data.

Here’s a link to IMCA’s site: http://www.imca-int.com/divisions/marine/publications/103.html

Thanks CaptMRB. We are aware of the drillship rules as we audit them, MODUs, MSVs and others. We thought OSVs had them same sort of operational rules, perhaps they do but the information is hard to come by. Hopefully some of the OSV members of this forum will enlighten us.

Our DP ops manual is based on the guidelines given by the IMCA along with the manufacturers operation manuals. But, the number 1 priority is the safety of the personnel, equipment & the environment. If any one of the those are at risk, the operation ceases until it can resume safely again. Hopefully I answered the question or shed a little more light without being to vague.

TEngineer - If, you’re co-worker is operating aboard a “Classed DP-2” vessel, there should be a few things that should be present aboard the vessel -

  1. The FMEA (Failure Mode and Effects Analysis) report from when the vessel was put on trials prior to delivery. A stamped copy of that report should reside aboard the vessel.

  2. The Certificate of Class, that should annotate class’ acceptance of the vessel as “DP-2”, based upon their own observations and surveys, and the above FMEA that was done by third party.

  3. An addendum to the Company’s SMS system as per the ISM DOC and SMC, which in this case would pertain to this particular vessel, IF, it was truly classed as DP-2. I say this, because there are plenty of vessels out there that were “built” to DP-2 spec., but never FMEA trialed, and never accepted by Class as such.

Now, that being said, where does your friends current assignment stand? If all of the above is true, there should be a clearly defined set of parameters that the vessel should take caution about exceeding, and these are usually set around the percentage of power being utilized by any one thruster, or propulsion unit to maintain the vessel on station. Dependent on the type of vessel, two “limit” points that are generally used are 50% for critical operations (such as an operation that requires a DOI, or a personnel transfer, operating on the upwind side of an installation), and 70% for non-critical operations (such as cargo ops on the downwind side of an installation).

Most all of these points discussed can be found here, in it’s entirety, in .pdf form (if you click on this link it is going to download the pub) -[B] International Guidelines for the Safe Operation of DP Offshore Supply Vessels

[/B]These are the guidelines that have been accepted by most members of the IACS, hence, Lloyd’s, DNV, and ABS [B][I]should[/I][/B] be following these points when accepting a vessel into class.

Here’s part of the problem that I’ve found in the GOM - Most managers of the oil majors in the GOM have no idea about any of the Codes of Safe Work Practices, or about IMCA guidelines, as have been utilized everywhere else in the world for last two decades, and especially in the North Sea since all those practices have been accepted by UKOOA (United Kingdom Offshore Operator’s Association).

So, TEngineer [U][B][/B][/U]- What kind of vessel is your colleague on, and is the vessel classed as “DP-2” by the vessels classification society? Do they have a FMEA report aboard for the DP system? Do they have a DP annex, or addendum to their SMS system? What type of service is the vessel in? With those questions answered, we might be able to point your friend in the right direction to find the answers to his questions.

Meanwhile, yes, I’m 100% in agreement with your line of thought as to this seeming to be the introduction of “human error” very early on into system that should have had “clear” parameters to guide by long before the Master would have had to utilize his “discretion”, and “overriding authority”. If I had to guess, I would say that you’re co-worker will find that the vessel is lacking in something along the certification path of this particular vessel / operator. I would review the documentation with a slightly more discerning eye.

El Capitan, thanks for your input. Of course the first thing checked is the FMEA and class which says DP II. In my experience the drilling or oil companies know of IASC but don’t fully examine the contracted OSV company certification other than, “You are DP II aren’t you? Good send us a copy” If the OSV owner can get a vessel DP II certified with minimal hp he will do so as all he needs is the DP II class in order to get the contract. One can be perfectly DP II capable in Mobile Bay but not in the real world. A SMS program saying you don’t use over 75% of your available power is useless if for example; your total horsepower is 1000 but one of those thrusters is 750 and the other is 250. Couple this with an ISM maintenance program that is poorly enforced and rarely audited one can get into trouble. But the contractor usually covers this making the master responsible for stopping work if he feels it’s unsafe blah, blah, blah. Unfortunately with a lousy maintenance program the master never gets a warning that his world is getting ready to fall apart and when it does he may at times discover his equipment really isn’t DP II as advertised. BUT he is responsible. Happily most male masters have two balls, sadly neither of them are crystal.

I have only been exposed to the DP world a short period of time but what El Capitan said is spot on. THe company I work for provides a DP Manual as part of their ISM program. In that manual are guidelines or minimums that we are expected to follow with regard to operational limitations. For example, if working the windward or up current side of the installation, when 1 thruster is at 60% just to maintain position you better be thinking about calling it quits.

Bottom line, in addition to the vessels capability plots for various environmental conditions and thruster configuations, the company should have a policy in place dictating guidelines regarding the safe operation of the vessel while on DP. But nothing will override or take the place of experience and sound judgement! IF you are not comfortable, don’t do it!

I think the original question had to do with max environment that a DP2 vessel was required to be capable to hold station with any single point failure. To the very best of my knowledge nowhere has there been a minimum stationkeeping ability codified in any of the existing regulations. I do think that both IMCA and IADC have guidelines but because every vessel has different propulsor/thrustor/generator configurations as well as hull size and form differences, there is no way to perform exactly to some predetermined standard.

One other thing is that all DP2 and 3 systems have what is called “consequence analysis” which when enabled is always calculating the resultant condition of thruster/generator loads in the present environment should there be any single point failure. If it determines that any single point failure will cause the vessel to either go into overload condtion or to not be able to hold station it will give the DPO a warning. It is then up to vessel policy if operations are suspended should that warning be received.

Lastly, the station keeping ability of an DP vessel is a matter of considerable concern to charters who often have a third party audit the vessel’s ability to maintain the charterer’s minimum environment requirements. I know of one particular case where a vessel was rejected by Petrobras because its bow thrusters did not have enough HP for the current encountered in Brazil (which can be just as wicked as any loop current in the GoM)

My DPII question is:
How can you really be DPII and only have one DPO in the Bridge. All the redundancy in the world is great… But the most important part of the DP system is the operator right ? If there is only one at any given time, how can you really be DPII? Put that on top of the fact that, most OSV DPO’s may sit in that chair looking at the legs of a platform for twelve hours straight, it makes me wonder even more at the validity of a OSV classed DPII with only one DPO on watch. No company want’s to pay any more than they have to for vessel personal, but you would think that the client would demand a two DPO watch at all times for safety.

but wouldn’t that also require two licensed engineers be on watch as well?

I like a two man DP watch but have also done it as a one man watch 4 on 8 off and that proved to be quite enjoyable.

they also have deadman alarms so if an operator keeled over the other DPOs can be alerted and come to the bridge to take over

ultimately what are the odds of having the DP system fail and an operator collapse simultaneously?

C. Captain,
I agree that the possibility of the DPO dropping dead and the DP system going out at the same time might be a slim; however that does not satisfy my question about how everything must be redundant BUT the operator.
And THEY may have dead-man alarms but WE do not have this function on my vessel.
Never mind being able to use the head while your on DP at the rig. Nothing says professionalism like the master of a 30 million dollar deepwater OSV pissing in a Rouses milk jug at the console.

The answer to your Question is NO. There is no set or written guidelines for the GOM or Offshore Industry. Most Companies Make there own rules on when you should cut DP work short. If your friend was told that the captain sets the standard on when to shut it down that would be an isolated situation. I have been DP ing for 10 years now and I shut it down when I feel it is no longer safe most often that is very close to the company policy. Most limits like you said are based on the boats capabilities. If the company that your friend represents dosen’t set guidelines they are asking for a law suite.

Interesting question. The company I work with now has 2 DPO’s on watch at all times. Some of this was generated from the Client (Shell, BP). I really helps out for those long times sitting at the rig.

This is true about shell and bp wanting 2 dp operators on the bridge at the same time, I have worked with shell on a dp vessel for 4 years and also bp. But my company only supplied three bridge watch standers on the vessel at a time, this makes it impossiable to have 2 in the wheelhouse on watch at the same time for more the a day.

[quote=salman22;8576]This is a TEST Comment
Salman Khan
Salman Khan

You failed. It said absolutely nothing!!!

So, the question is this: Are there established rules for the maximum safe weather operational limits of the DP II system for vessels in the OSV industry?[/QUOTE]

As far as being a set in stone wind & current value that stops the job, No.
All vessels will react differently so use should be made of the Capability Plot to determine where the limits of redundancy are in case of a Worst Case Failure.

Has anybody here experienced the Loop Current in the Gulf while on DP? We have had to stop the job in less than 10kts of wind, but the current was ripping!
Try explaining [I]that[/I] to a client with no DP knowledge…

LOL thanks anchorman!