# DP2 class question **URL:** \ **Category:** Dynamic Positioning\ **Created:** [December 14, 2019, 10:06am UTC](https://forum.gcaptain.com/t/dp2-class-question/53576 "2019-12-14T10:06:46Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Mat\_Bouv](https://sea2.discourse-cdn.com/flex016/user_avatar/forum.gcaptain.com/mat_bouv/32/11326_2.png) [@Mat\_Bouv](https://forum.gcaptain.com/u/Mat_Bouv)\ **Post date:** [December 14, 2019, 10:06am UTC](https://forum.gcaptain.com/t/dp2-class-question/53576/1 "2019-12-14T10:06:46Z")
Good morning gents, I please have a ‘technical’ question that I’m trying to clarify. On a DP2 vessel, in case one of our 4 DGs is not available (engine failure) , do we keep DP class 2? For information we normallly (before failure) have 4x1360kw DGs (two per bus) , 2x 1000kw bow thrusters, and 2x 2000kw azimuth thrusters. Also do we keep Class2 when working with only one DGPS and one cyscan PRS? Thank you very much for your eventual assistance on this question, I’ve read a lot of documentation on that point, but still I have a small doubt on it. ---
**Author:** ![Capt\_Phoenix](https://sea2.discourse-cdn.com/flex016/user_avatar/forum.gcaptain.com/capt_phoenix/32/281_2.png) [@Capt\_Phoenix](https://forum.gcaptain.com/u/Capt_Phoenix)\ **Post date:** [December 14, 2019, 8:30pm UTC](https://forum.gcaptain.com/t/dp2-class-question/53576/2 "2019-12-14T20:30:41Z")
> [@Mat\_Bouv](#): > > On a DP2 vessel, in case one of our 4 DGs is not available (engine failure) , do we keep DP class 2? No. > [@Mat\_Bouv](#): > > do we keep Class2 when working with only one DGPS I don’t think so. ---
**Author:** ![powerabout](https://avatars.discourse-cdn.com/v4/letter/p/43a26b/32.png) [@powerabout](https://forum.gcaptain.com/u/powerabout)\ **Post date:** [December 15, 2019, 12:56am UTC](https://forum.gcaptain.com/t/dp2-class-question/53576/3 "2019-12-15T00:56:13Z")
DP2 only requires 2 gen sets as does DP3 as a minimum under the rules 3 pos ref are a min for dp2 with one working with different technology than the others ---
**Author:** ![airmann](https://avatars.discourse-cdn.com/v4/letter/a/9fc29f/32.png) [@airmann](https://forum.gcaptain.com/u/airmann)\ **Post date:** [December 15, 2019, 2:45am UTC](https://forum.gcaptain.com/t/dp2-class-question/53576/4 "2019-12-15T02:45:47Z")
you need 3 PRS. Generators are a bit more complicated, are you the DPO on the vessel? Maybe ask the master. ---
**Author:** ![powerabout](https://avatars.discourse-cdn.com/v4/letter/p/43a26b/32.png) [@powerabout](https://forum.gcaptain.com/u/powerabout)\ **Post date:** [December 15, 2019, 10:26am UTC](https://forum.gcaptain.com/t/dp2-class-question/53576/5 "2019-12-15T10:26:58Z")
you should be looking at the vessel documentation ---
**Author:** ![Quimby](https://sea2.discourse-cdn.com/flex016/user_avatar/forum.gcaptain.com/quimby/32/3448_2.png) [@Quimby](https://forum.gcaptain.com/u/Quimby)\ **Post date:** [December 15, 2019, 11:51pm UTC](https://forum.gcaptain.com/t/dp2-class-question/53576/6 "2019-12-15T23:51:59Z")
Here’s the ABS DPS guide if you’re interested. Company specific information should be on the ASOG. Unless you are making one? [dps-guide-nov19.pdf](https://forum.gcaptain.com/uploads/short-url/yXavrjmrkzwjv5l8AK8nR3Zgfwt.pdf) (1.3 MB) ---
**Author:** ![Capt\_Phoenix](https://sea2.discourse-cdn.com/flex016/user_avatar/forum.gcaptain.com/capt_phoenix/32/281_2.png) [@Capt\_Phoenix](https://forum.gcaptain.com/u/Capt_Phoenix)\ **Post date:** [December 16, 2019, 8:26pm UTC](https://forum.gcaptain.com/t/dp2-class-question/53576/7 "2019-12-16T20:26:32Z")
> [@powerabout](#): > > DP2 only requires 2 gen sets as does DP3 as a minimum under the rules It’s a diesel electric boat so it would require all 4 generators, 2 per bus, to have redundancy. ---
**Author:** ![CaptainBulkhead](https://avatars.discourse-cdn.com/v4/letter/c/82dd89/32.png) [@CaptainBulkhead](https://forum.gcaptain.com/u/CaptainBulkhead)\ **Post date:** [December 17, 2019, 12:31am UTC](https://forum.gcaptain.com/t/dp2-class-question/53576/8 "2019-12-17T00:31:29Z")
Most likely yes you are still DP 2. There are plenty of twin engine (likely the majority of sub 300’ vessels) of DP 2 vessels that are conventional or hybrid twin engine. They are DP 2 with just 2. You may have reduced capability due to a reduction in available thrust. But if that 1 gen can run the required thrusters on that bus it should be fine. Your worst case failure will change. The redundancy is the other bus. ---
**Author:** ![Capt\_Phoenix](https://sea2.discourse-cdn.com/flex016/user_avatar/forum.gcaptain.com/capt_phoenix/32/281_2.png) [@Capt\_Phoenix](https://forum.gcaptain.com/u/Capt_Phoenix)\ **Post date:** [December 17, 2019, 12:51am UTC](https://forum.gcaptain.com/t/dp2-class-question/53576/9 "2019-12-17T00:51:47Z")
> [@CaptainBulkhead](#): > > But if that 1 gen can run the required thrusters on that bus it should be fine. Your worst case failure will change. The redundancy is the other bus. That’s a good point. Assuming it can hold position with one main azi and one bow thruster it should still be DP2. ---
**Author:** ![powerabout](https://avatars.discourse-cdn.com/v4/letter/p/43a26b/32.png) [@powerabout](https://forum.gcaptain.com/u/powerabout)\ **Post date:** [December 17, 2019, 5:03am UTC](https://forum.gcaptain.com/t/dp2-class-question/53576/10 "2019-12-17T05:03:13Z")
no, dp2 rules say hold position with a single failure so once you are down to a single stern azi and a bow thruster your DP2 vessel is in dp1 mode as another failure you are drifting ---
**Author:** ![powerabout](https://avatars.discourse-cdn.com/v4/letter/p/43a26b/32.png) [@powerabout](https://forum.gcaptain.com/u/powerabout)\ **Post date:** [December 17, 2019, 5:06am UTC](https://forum.gcaptain.com/t/dp2-class-question/53576/11 "2019-12-17T05:06:53Z")
are we talking class rules here or having enough gear to support a single failure and still be in DP 2 mode which is an owners choice and not defined under any rules? A full DE boat with 2 gen sets and 4 thrusters is Dp2, lose a gen set its in dp1 mode.