RDP Table exercise

[carloslzn]

Hello people

I'm having trouble with one excersie of the OWD

6. After a surface interval my pressure gruop is D. I want to do a repetitive dive to 12m for 32 min. What will be my new PG when I reach the surface?

The answered is N.

¿Any explanation to get that PG? As i cant my the solution on the table to get it.

Thanks

 

[ElGaucho]

So you start in pressure group D, so you need to start at the backside of the RDP (it is a repetitive dive).

Find where 12m and column D intercept: it gives two numbers. Being a repetitive dive, we want to find the RNT (residual nitrogen time) so we can add it to the next calculation. That would be 26 minutes.



Flip the rdp to the front side and now look up 12m, but you need to add the RNT, so instead of looking for 32minutes you look for:

32 + 26 (rnt) = 58

Being no 58 on the table, you go to the next higher value (conservative) and end up in 62.

That's group N



Somebody has not explained RNT properly to you. If you are doing this thru e-learning, you might want to give the RDP handbook another go.

 

[Nirvana]

I don't know the table you are using, so I cannot comment on the exact parameters of the exercise. However, speaking generally, a pressure group translates into "residual nitrogen time" (at least PADI calls it that), that is, some time you add to the time actually spent at depth to account for the inert gas present at the start of the dive. So, you have to look up at the appropriate table how much time corresponds to your initial pressure group.

In your exercise, you should look up how much time corresponds to letter group D at 12m. Then you add this time to the 32 actual bottom time to find the total dive time. This total bottom time at 12m should then get you to group N, per what you said.