Good day all, I am curious about turning rates for azimuthing thrusters. (qualifier-18 yrs DP exp)I have operated some which can spin 360 deg in 20 secs all the way to some taking just over 2 mins. The 1 taking over 2 mins is what I am dealing with now. I am new to this vessel and it is having station holding issues. I have never run across thrusters this slow. It appears that the thrusters just can’t keep up with the demands. I have had to play with gains and whatnot just to do the job. do any of you have some insight as to minumin turning rate requirements for DP vessels???
Ours will do one full rotation in 30 seconds. The thrusters are ulstiens.
We have Ulsteins and do a timed test everytime as an extra check on our system. If it is 24 secs or higher, we change the filters and every other time there are two screens we change. They have a 10,000 hour recommended but we change them early because it can’t hurt.
2 minutes seems a little excessive.
thanks for the quick replies, Yep just what I suspected…They’ve been getting azimuth errors and such but I guess they didn’t think to check demands and feedback to troubleshoot the real issue. The Port Captain asked me what I thought of the problem and I replied to him that I would be suprised if it held at all, maybe in perfect conditions but watch out if something changes on you…
Ours are 40-50 seconds but they are odd to this series of anchor boats. Holds DP great in variable allocation, not at all in free run.
Everyone should be doing DP capability plots on regular basis. All information should be recorded, that is related to the DP system and thrustrs. If you are not doing them, you should have old FMEA reports from the time the vessel was new. Look back to see what the turning time was last year, the year before, and when the vessel was new. Has it always been like this, or did it just start recently? If the turning rate was 50 seconds 2 years ago, the 1 minute 20 seconds the next year, you have mechanical issues some where. Also is it both thrusters doing the same thing or just one side?
Also what type of thruster is it, there are so many different styles it would be hard to say anyone thing for sure without knowing. Some do use hydraulic steering, some use a electric motor run through a planetary, and no hydraulics at all. I have seen one stering motor go out and the system still work, but just have slow steering speed. If the steering demand is calling for a certain rate of turn, and the feedback signal is lagging behind that by a predetermined ratio, you should be getting feed back errors, slow steering speed alarms, or incorrect steering response alarms.
Has the company been doing oil samples on the thrusters. You may very well have to be taking gear box oil samples along with hydraulic steering oil samples. If you are getting contamaniats in either they need to be investagted. You may have a thrust bearing or thrust ring binding up in the lower unit causing the slow steering speeds, even if the steering gear is working correctly. In that case I would think the hydraulic oil temp would be high, or if you don’t have hydraulic steering the amperage should be high on the steering motors. If you have contamanated hydraulic oil find out where it is coming from now. It is only going to cause you more problems down the road. It could be a pump going south, a broken spring in the relief valve, or even a hose coming apart on the inside, along with many other things.
I agree 2 minutes seems very slow for any brand of thruster I have been on.
Everyone should be doing DP capability plots on regular basis. All information should be recorded, that is related to the DP system and thrustrs. If you are not doing them, you should have old FMEA reports from the time the vessel was new. Look back to see what the turning time was last year, the year before, and when the vessel was new. Has it always been like this, or did it just start recently? If the turning rate was 50 seconds 2 years ago, the 1 minute 20 seconds the next year, you have mechanical issues some where. Also is it both thrusters doing the same thing or just one side?
Also what type of thruster is it, there are so many different styles it would be hard to say any one thing for sure without knowing. Some do use hydraulic steering, some use a electric motor run through a planetary, and no hydraulics at all. I have seen one stering motor go out and the system still work, but just have slow steering speed. If the steering demand is calling for a certain rate of turn, and the feedback signal is lagging behind that by a predetermined ratio, you should be getting feed back errors, slow steering speed alarms, or incorrect steering response alarms.
Has the company been doing oil samples on the thrusters. You may very well have to be taking gear box oil samples along with hydraulic steering oil samples. If you are getting contamaniats in either they need to be investagted. You may have a thrust bearing or thrust ring binding up in the lower unit causing the slow steering speeds, even if the steering gear is working correctly. In that case I would think the hydraulic oil temp would be high, or if you don’t have hydraulic steering the amperage should be high on the steering motors. If you have contamanated hydraulic oil find out where it is coming from now. It is only going to cause you more problems down the road. It could be a pump going south, a broken spring in the relief valve, or even a hose coming apart on the inside, along with many other things.
I agree 2 minutes seems very slow for any brand of thruster I have been on.
You can also check the Onboard test method results from the shipyard to give you a good baseline.