IP Creep on DA - New Seat

[pclarke1]

Hi team,
I am in the process of my DA rebuild, which so far seems to be going well. The reg inside was extremely clean with no residues of any kind. I have put my 1st stage back together and installed the new HPR. I put this on a tank last night with an IP gauge for the first time and want to understand what I am seeing.

Ok, so by way of full disclosure, this tank is sitting at 2600 PSI as I was not planning to bleed it down until the weekend. I understand that there are 2 ways of setting the IP on from the US Divers manual and the other the 300 psi method here at VDH. So my 2600 psi tank is clearly outside of guidelines and if the answer is just follow the instructions, then all is well.

So having said that I still wanted to see where I was so I hooked up my DA to the tank and tried to set the IP to 110 psi as specified in the manual. I got it close, but am seeing some creep over the course of 5-10 minutes of around 10-15 psi. I am assuming this is because my new HP seat is not seated properly.

Is this something that I can resolve by bleeding my tank down to the right pressure and cycling the HPR or is this a case of dissembling the 1st stage and starting again. I am ok with the latter as I am in no hurry and want to get this 100% right (even if it takes quite a few tries).

Apart from that I see no issues in completing my rebuild. It all seems (to my ignorant, untrained and inexperienced eyes) rather straightforward. What am I missing, if I can get a reliable IP and am using the HPR, is it more complex than just putting it all back together?

[Herman]

Until you are ready to set IP to it's final value, there is no need to bleed the tank down, just use the extra pressure to give the seat time to set up by keeping the reg pressurized and cycling the second stage from time to time. What the IP is now is of little concern, just that it is stable...within reason, more on that in a minute. If the IP will not settle down you can dissemble the nozzle and polish the nozzle edge some to remove any dings or scratches it may have. That may solve your problem but there is a down side, polish it too much and it is harder to get it to seal...which may be what you are already dealing with. And once its polished too far, there is no going back.

Now for a reality check.
The DA being an unbalanced diaphragm stage is going to have an IP shift of around 20 PSI over a 300 to 3000 PSI tank pressure range and that IP is going up as tank pressure decreases, counter intuitive I know. If you set the IP to 130 @ 300 PSI tank pressure (I use 130) then at 3000 psi you should expect to see an IP of around 20 psi less.... 300 tank =130 IP and 3000 tank = 110 IP. So if your IP is creeping up by 10-15 psi over a span of 10 to 15 minutes and stabilizes, is that really an problem, IMO no. If you set the IP to 130 at 300 psi, you should expect to see an IP of around 110psi with a full tank , If it does creep up another 10-15 psi and stops, the IP is still less than the 130 that you set it up for and the second stage will not freeflow. In addition, since the creep is over a 10 to 15 minute span, in operation it will not have the chance to creep up as your breathing rate is going to be much higher than that.

So, it worth trying to remove that amount of creep from a DA, as long it does stabilize out I don’t think so. The creep does not have a real impact on the regs operation or performance and there is a real chance you can do more damage than good if you try to fix the problem. If it bothers you to the point you just have to do something, your best option is to upgrade to a Phoenix or Cyclone. They are much more stable than the old DA’s and if you mess up the volcano, it is replaceable.

[pclarke1]

Wow thanks Herman, amazing answer. I appreciate the help.

[swimjim]

What Herman said. The short version in my opinion is that the seat is new and hasn't been cycled enough yet to take a good "set". Scuba Tools sells a machine that does nothing but cycle regs for just this reason. I'm not saying you need one, just cycle the reg more and I think your problem will resolve itself.

[Bryan]

From the Technical section of the forum

Regulator Hard and Soft seating 101

[pclarke1]

Scuba Tools sells a machine that does nothing but cycle regs for just this reason. I'm not saying you need one, just cycle the reg more and I think your problem will resolve itself.

I would love one (you can never have too many tools) , but it is a bit rich for my blood.

http://www.scubatools.com/p-599-quick-s ... xture.aspx